how does tourism damage coral reefs

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Coral Reefs and the Unintended Impact of Tourism

The choices we make as tourists can affect the health of Costa Rica’s renowned coral reefs.

By Camila Cossio  /  International Program

This page was published 8 years ago. Find the latest on Earthjustice’s work.

One day, during my internship in Costa Rica with the Interamerican Association for Environmental Defense (AIDA), I met up with a friend of mine who was visiting from the U.S. She told me about her trips to the gorgeous local beaches. Everything she described sounded beautiful: the clear blue water, hermit crabs that left their shells to eat breakfast in the early morning hours, sweet fruits that fell onto the smooth sand and the lush trees that offered shade from the hot Costa Rican sun.

But her mood changed suddenly from bliss to concern when she told me about how her co-worker swam too close to a coral reef one afternoon and badly cut his thigh. She was concerned by how unprepared their tour guide was to handle the medical situation, and by how irresponsible it seemed that tourists with no diving experience were allowed to swim so close to the reef.

In addition to the physical danger to humans, accidents like these can have a severe impact on sensitive marine ecosystems like coral reefs. Coral reefs are unique and complex systems, vital to the health of the world’s oceans. But 93 percent of the reefs in Costa Rica are in danger , and tourism is a significant factor in their degradation.

How Tourism Threatens Corals

When tourists accidently touch, pollute or break off parts of the reef, corals experience stress. The coral organisms try to fight off the intrusion, but this process often leads to coral bleaching — when corals expel the brightly colored algae that live in them and become completely white. Once corals are bleached, they die and can no longer contribute to the biodiversity of the reef community. And since the disruption of one ocean system impacts all the others, sea grass and mangroves — shallow-water plant species vital to the health of the marine ecosystem — are also threatened by coral stress.

Another significant problem facing coral reefs is sedimentation. When dirt and debris are deposited into the ocean, they pollute marine ecosystems and block the sunlight algae need for photosynthesis. When light is blocked, the immobile coral reefs bleach and die.

In Costa Rica, sources of sedimentation include dredging, logging, agriculture and coastal development driven by the tourism industry.  A study by biologist Jorge Cortés documents a decade of negative impacts from tourism on coral reefs in the Cauhita region of Costa Rica. Sedimentation will continue to devastate Pacific reefs if better management principles are not enacted.

Scientists predict that 50 percent of all coral reefs in Latin America are at risk of degradation in the next five to 10 years. Studies show that globally, 30 percent of coral reefs are already seriously damaged. Seventy percent of all reefs are expected to disappear by 2030 if we don’t take corrective action to stop the negative human impacts of climate change on coral reef communities.

Rebuilding a Future for Coral Reefs

Sustainable tourism is a great concept on paper, but hard to enforce in reality. Construction of coastal properties requires dredging. It creates polluted runoff from roads and parking lots and airports. Sewage is dumped into the ocean, and more intensive agriculture to support all the new people increases sedimentation.

Although it’s difficult for an individual to stop massive projects like these, it’s easy to take small but powerful steps in the right direction. Don’t touch living coral and don’t pick up wildlife for souvenirs, including shells, coral rubble and plants. Be conscious of what you bring with you, for example reusable water bottles instead of plastic bottles and a backpack for your trash in case there isn’t an area nearby to dispose of waste properly. Take the bus instead of a car, and if possible, do your research on the hotels or hostels where you stay. Many coastal hotels dump their graywater — wastewater from laundry, cooking and household sinks — into the ocean, contributing to sedimentation and the contamination of coral reefs.

It’s important to be aware of the fact that many land-based activities may directly harm the marine ecosystem. Being an environmentally friendly tourist is not about being perfect, but individual actions, though they may seem small, really can make a big impact.

AIDA provides much-needed recommendations for effective laws and practices to preserve and protect coral reefs in Latin America.

Earthjustice is a founding partner of AIDA , an organization that uses the law to protect the right to a healthy environment in the Americas, with a focus on Latin America. AIDA has documented International Regulatory Best Practices for Coral Reef Protection and is advocating for Costa Rica and Mexico , in particular, to strengthen protections for coral reefs.

Camila Cossio

Camila Cossio is a former intern with the Interamerican Association for Environmental Defense.

International Program

The International Program partners with organizations and communities around the world to establish, strengthen, and enforce national and international legal protections for the environment and public health.

“The National Environmental Policy Act is an environmental law, but it is also a tool to fight for worker safety, immigrant rights, and human rights.”

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How Does Tourism Affect Coral Reefs?

We are drawn to coral reefs. They are colorful, beautiful, and filled with vast amounts of biodiversity that we love to watch and observe. Coral reefs exist in warm tropical regions around the equator that we love to visit when we travel [1] . Unfortunately, our love affair with coral reefs is causing them to be “loved to death”. 

While ecotourism has the potential to be a sustainable way to support coastal communities and economies in reef regions without negatively impacting natural resources, in many cases, tourism has caused a great deal of damage to coral reef habitats. 

Today, it is estimated that 25% of the world’s coral reefs are damaged beyond repair, with another two-thirds being seriously threatened [2] .

Tourist activities that negatively impact coral reefs

Scuba diving and snorkeling.

While most diving and snorkeling activities have little physical impact on coral reefs, physical damages to corals can and do occur when people stand on, walk on, kick, touch, trample, and when their equipment contacts corals. 

Coral colonies can be broken and coral tissues can be damaged when such activities occur. Divers and snorkelers can also kick up sediment that is damaging to coral reefs. 

Boating and anchors

Boats grounding in coral reef habitat can damage corals, as can anchors. Anchors can cause a great deal of coral breakage and fragmentation, particularly from large boats like freighters and cruise ships. Heavy chains from large ships can break or dislodge corals. These damages to corals can last for many years.

Anchoring can also damage the habitats near reefs such as seagrasses that serve as nurseries and habitats for the juveniles of different coral reef organisms.

Marinas may inappropriately dispose of oils and paint residues, polluting local waters, and additional pollution may occur during fueling [3] .

Fishing and seafood consumption

An abundance of tourist fishing and consumption of local fish stocks may lead to overexploitation and competition with local fishers. 

Inappropriate fishing techniques such as bottom trawling can cause physical damage to reefs.

Cruises and tour boats

These vessels can cause physical damage to reefs through anchoring and grounding, as well as through the release of grey water and human waste into coral reef habitat. 

Chemicals added to paint used on boats and fishnets that are intended to discourage the growth of marine organisms can also cause pollution in coral reef waters.

Coastal development

Coastline development and artificial beach creation can result in runoff and sedimentation that washes into ocean waters. This sediment load increases the turbidity in coral reef waters, decreasing the amount of sunlight that can penetrate through the water to reach the corals.

This in turn causes the corals to become stressed, and can eventually lead to bleaching, suffocation, and even coral death. Heavy sedimentation can also lead to decreased coral growth rates, decreased productivity and decreased recruitment.

Demand for souvenirs from the sea

Direct harvesting of coral and other products from the sea by tourists is not very common, but there can be local shops that sell such products in tourist areas. The harvesting of such products can lead to the exploitation of vulnerable marine species.

Pollution from sewage, waste, and chemicals

Sewage or other wastes may be released into the local waters surrounding coral reefs from boats, hotels, or resorts. 

Such sewage pollution leads to nutrient enrichment in ocean water, which favors algal growth at the expense of coral organisms.

Inappropriate solid waste disposal can lead to the leaching of toxic chemicals into local waters, and litter ( including plastic litter ) and debris can blow and wash into coral reef waters [3] .

Human encounters with marine life

Fish feeding and encounters with charismatic or rare species can alter the natural behavior of coral reef species, such as foraging behavior, changes in home range size, population density, migration patterns, and reproductive activities. 

Changes in the distribution of species may occur, as the more aggressive species will tend to dominate in areas where fish feeding is common. Decreases in overall species abundance have also been observed in some high-use areas.

Invasive species

Invasive marine species can be transported and released into new marine habitats through ballast water and through the washing of ship decks, motors and equipment, water lines, and fishing gear.

How can we reduce negative impacts of tourism on coral reef habitats?

Human behavior change is critical to reduce the negative impacts of tourism on coral reefs.

Tourists must be educated about the negative impacts of destructive activities , the ecological importance of coral reef ecosystems and organisms, and how they can help to preserve coral resources when they travel to these regions. 

The level of activity at sites should be reduced through restricted access, and effective and practical regulations that prohibit detrimental actions must also be put in place and properly enforced to prevent pollution and conserve the natural resources of these regions.

Ecotourism activities in these regions should be emphasized and promoted by local communities and the tourism industry as a fun and environmentally-friendly way to vacation in these regions and support the preservation of coral reef ecosystems .

References [1] http://www.coral-reef-info.com/where-are-coral-reefs-located.html [2] http://goo.gl/sv0rD6 [3] http://goo.gl/Cf5R52

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The Unintended Impacts of Tourism on Coral Reefs

Coral reefs are some of the world’s most biodiverse habitats, typically found in tropical areas within 30 degrees of the equator. Thousands of people come from all over the world to see their color and beauty. Reef networks provide thousands of jobs and billions of dollars in revenue for diving tours, fishing trips, hotels, restaurants, and other businesses. The tourism industry has recently collapsed as a result of the safety measures placed in place to protect communities from the COVID-19 outbreak. This seemed like an ideal opportunity to consider the effect of tourism on coral reefs.

While sustainable ecotourism can help provide alternative lifestyles for coastal communities, over-exploitation of the industry can endanger the reefs that have already been destroyed. Increased coastal tourism has put more strain on coral reef resources, either directly on the reefs or indirectly through increased coastal construction, sewage discharge, and vessel traffic.

Tourists must make educated decisions and act responsibly, as their activities can have a negative effect on the conservation of these fragile ecosystems. Many people are also unaware of the consequences of their decisions. What are the threats to coral reefs, and how can coral reef etiquette assist you in being a more knowledgeable tourist?

How Tourism Threatens Corals

Corals are stressed when visitors accidentally touch, pollute, or break off sections of the reef. The coral organisms attempt to repel the invaders, but this also results in coral bleaching, which occurs when corals expel the brightly colored algae that live inside them and become fully white. Corals that have been bleached die and will no longer contribute to the reef community’s biodiversity. Seagrass and mangroves—shallow-water plant species important to the survival of the marine ecosystem—are often endangered by coral stress because the destruction of one ocean system affects all others.

Sedimentation is another major issue that coral reefs face. When dirt and debris end up in the water, they pollute aquatic habitats and prevent algae from getting the sunlight they need to photosynthesize. The immobile coral reefs bleach and die when light is blocked.

Dredging, logging, irrigation, and tourism-driven coastal growth are all causes of sedimentation in Costa Rica, for example. In the Cauhita region of Costa Rica, research by biologist Jorge Cortés records a decade of detrimental impacts from tourism on coral reefs. If better management principles are not implemented, sedimentation will continue to devastate Pacific reefs.

In the next five to ten years, scientists expect that half of all coral reefs in Latin America will be degraded. According to studies, 30% of coral reefs around the world are now severely affected. If we don’t take steps to mitigate the negative human impacts of climate change on coral reef ecosystems, 70% of all reefs are projected to vanish by 2030.

Let’s break these threats down further.

Vessels grounding and colliding with shallow coral reefs may cause significant habitat damage. In nearshore environments, propeller scarring, anchoring, and other physical impacts are becoming increasingly problematic. In Florida alone, 136 manatees died last year after being hit by speeding watercraft. Anchors can dislodge, crush, and fragment the benthic ecosystem, displacing resident fish and obliterating critically significant topographic complexity and habitat structure that takes hundreds of years to recover.

What you can do:

• Use mooring buoys to secure your vessel.
• Inquire about diving and snorkeling operations that practice reef-safe boating.
• If you must use an anchor, do so in areas with a sandy bottom to avoid harming the marine life, corals, or other marine ecosystems in the region.

Scuba Diving Swimming And Snorkelling

Corals may be harmed by uninformed and careless divers, snorkelers, and swimmers touching and standing on them. The coral polyps can be suffocated by kicking up sand. Corals, despite their rock-like nature, are extremely vulnerable to injury and disease. Eating, chasing, and touching marine life can change their behavior, the frequency with which they visit the area, and even their home range.

• Avoid standing on, touching, or kicking coral.
• Practice good buoyancy and keep a safe distance from the action. When diving or snorkeling, make sure you’re not dragging any equipment, such as depth gauges or cameras.
• Avoid diving activities that don’t have a crew member on board.

Invasive Species

Invasive species can spread through tourism and recreational activities such as ballast water transportation, cruise ship hull fouling, and recreational boat fouling (e.g., from hulls, outboard motors, live wells, water lines, fishing gear and debris).

Reducing the degree of use at such sites (e.g., by limiting access) and reducing the impacts of use by changes in human behavior are the two primary approaches to controlling recreational activities in coral reef areas (e.g., educating reef users to discourage destructive actions, and imposing regulations prohibiting certain destructive actions).

Coastal Development 

Coral reefs and the coastal structures that link them provide protection from erosion and storm damage. Coastal growth poses a major threat to marine resources because mangrove forests defend against wave action and serve as a storm surge buffer. Beachfront construction of houses, hotels, restaurants, highways, sea walls, and nourishment are all examples of coastal development.

Coastal construction is putting a lot of pressure on turtles. Turtles mate and lay their eggs on the same beaches where they were born. Sea walls can prevent female nesting turtles from laying eggs and cause unnatural beach erosion. Furthermore, beachfront lighting from resorts, highways, and buildings can harm turtle hatchlings. The juvenile turtles are led to the ocean by light as they emerge from their nests. Artificial lighting can cause hatchling turtles to become disoriented, leading them away from the sea and toward paths, obstacles, and predators.

Sedimentation

Coastal development and construction projects can alter natural drainage patterns, resulting in runoff into nearby reefs, especially where mangroves and plant anchorage have been removed. When soil, dirt, and debris are deposited in the ocean, particularly after heavy rains, sedimentation occurs. Sediment pollutes marine environments by obstructing light and suffocating corals and seagrass. To photosynthesize, seagrass beds require clear shallow water. Corals also rely on zooxanthellae for photosynthesis, which means that light deprivation can cause them to starve, bleach, and die.

Efficient planning and land use policies can help to reduce coastal growth and sedimentation. Visit areas with strict planning and development laws in place to protect the aquatic and terrestrial ecosystems wherever possible. Mangrove conservation, minimum shoreline construction distances, and wastewater collection can all help to reduce local stress on coral reefs and improve tourism’s long-term viability.

The Big Picture

Ocean protection needs education and knowledge. Being mindful of your environment can have a huge impact on the ecosystem’s health. When planning a holiday, prioritize sustainability and do research on the hotels you will stay in and the events you will participate in. Your decisions have the potential to have a significant effect on how the tourism industry grows in the future.

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MIT Science Policy Review

Coral reefs are critical for our food supply, tourism, and ocean health. We can protect them from climate change

Hanny E. Rivera * , Andrea N. Chan, and Victoria Luu

Edited by Alexandra Churikova and Anthony Tabet

Full Report | Aug. 20, 2020

* Email: [email protected]

DOI: 10.38105/spr.7vn798jnsk

• Coral reefs provide ecosystem services worth $11 trillion dollars annually by protecting coasts, sustaining fisheries, generating tourism, and creating jobs across the tropics.
• Ocean warming is the most widespread and immediate threat to coral reefs globally, followed by disease, and local stressors.
• Management efforts help address local stressors, however, the root cause of global coral decline – increasing temperatures caused by greenhouse gas emissions – must be addressed to ensure the survival of the ocean’s most diverse habitats through the 21st century.
• International climate agreements that aim to continually reduce emissions are our best hope for the survival of reefs.

Article Summary

As many as 1 billion people across the planet depend on coral reefs for food, coastal protection, cultural practices,and income [1, 2]. Corals, the animals that create these immensely biodiverse habitats, are particularly vulnerable to climate change and inadequately protected. Increasing ocean temperatures leave corals starved as they lose their primary source of food: the photosynthetic algae that live within their tissue. Ocean warming has been impacting coral reefs around the globe for decades, with the latest 2014-2016 heat stress event affecting more than 75% of the world’s corals [3, 4]. Here, we discuss the benefits humans derive from healthy reefs, the threats corals face,and review current policies and management efforts. We also identify management and policy gaps in preserving coral habitats. The gain and urgency of protecting coral reefs is evident from their vast economic and ecological value. Management and restoration efforts are growing across the globe, and many of these have been influential in mitigating local stressors to reefs such as overfishing, nutrient inputs,and water quality. However, the current trajectory of ocean temperatures requires sweeping global efforts to reduce greenhouse gas emissions in order to effectively safeguard the future of coral reefs. The U.S. should stand as a world leader in addressing climate change and in preserving one of the planet’s most valuable ecosystems.

Coral reefs are one of our planet’s most biodiverse and economically valuable ecosystems [5], yet they have been declining worldwide due to warming ocean temperatures and other stressors [6]. Many major tropical cities are adjacent to coral reef environments (Figure 1A), with nearly 1 billion people worldwide residing in areas influenced or sustained by coral reefs [1, 2]. Coral reefs provide a myriad of ecosystem services that benefit our economies, our shorelines, as well as our plates and medicine cabinets (Figure 2). Throughout, we discuss the valuable benefits provided by corals, explain the stressors harming coral reef ecosystems across global and local scales, review management and conservation efforts, and identify gaps in current policies.

Why corals matter: A wealth of ecosystem services

Coral reefs are dynamic, vibrant ecosystems, formed by over 800 different species of corals. Corals are animals, closely related to anemones and jellyfish, although considering them rocks or plants would not be entirely off base. Their tripartite nature stems from their ability to create the limestone skeleton in which they live, and from the single-celled algae (marine plants) that live inside their tissues in a mutualistic symbiosis (Figure 3A). These algae provide corals with the vast majority of their energetic needs, by providing sugars they produce via photosynthesis to their coral hosts. In addition, corals also harbor a diverse bacterial flora that contributes to their overall health [7], much like the gut microbiome does in humans [8]. These associations allow corals to thrive and build reefs large enough to be seen from space, such as the Great Barrier Reef or the Florida Reef Tract (Figure 1B, 1C).

Coastal Protection: These massive reefs structures can function as seawalls against storms, hurricanes, and sea level rise by protecting coasts from waves and surge [9]. In fact, coral reefs provide the equivalent of $\$$94 million in coastal protection to the U.S. each year [10]. During severe storms, like category 5 hurricanes, that value increases to $\$$272 billion [10]. Worldwide, the total value of coastal protection provided by reefs is estimated at over $\$$4 billion in averted damages during usual storms [10]. For more extreme events such as one-in-25-year or one-in-a-100-year level storms, corals can prevent $\$$36 billion to $\$$130 billion dollars’ worth of damages, respectively [10]. For comparison, the Port of Miami and Port Everglades (Ft. Lauderdale, FL) collectively represent over 3% of all U.S. seaport trade and are worth over $\$$50 billion dollars each year; while the Miami International Airport comprises over 5% of U.S. airport trade, worth nearly $\$$60 billion per year [11]. Corals can provide equivalent amounts of value during mild storms and much more value during severe storms. Coastal protection by coral reefs not only benefits immediately adjacent cities and residents, but can also prevent downstream economic impacts to trade and commerce. In addition, the presence of coral reefs is often used to define maritime boundaries and jurisdictions (see section on UN Convention on the Law of the Sea), such that deterioration and loss of coral reef habitat can lead to loss of jurisdiction over marine territories. 

Biodiversity and Natural Products: The reef structures created by corals provide habitat for thousands of marine species, in a manner that is highly disproportionate to their total area. While comprising only a small fraction of seafloor (0.2%) [12], coral reefs are home to an estimated 830,000 species of organisms [13]. The number of species living per unit area on coral reefs is one of the highest on the planet, with biodiversity that rivals rainforests. 

This biodiversity is crucial for the health our oceans, and it can also be harnessed for natural product and drug development. For instance, the antiviral drug Vira-A, which is used to treat herpes simplex infections, as well as AZT, which is used to treat HIV, were derived from a compound (Ara-A) isolated from a Caribbean sponge that lives on coral reefs [14]. Another compound (Ara-C) was isolated from the same sponge and developed into the anti-cancer medication Cytarabine [14]. The drug Ziconotide for the treatment of chronic pain was isolated from cone snails found on coral reefs [15]. In addition, several new antibiotic compounds effective against antibiotic-resistance bacteria have been isolated from soft corals that live in coral reefs [16]. The skeletons of hard corals can even be used as bone regeneration materials for humans [17] Overall, the oceans represent a highly unexplored source of products for human medicine. The drug discovery potential in marine environments, and coral reefs in particular, should be considered an invaluable resource [18, 19]. 

Fisheries and Tourism: The biodiversity of corals reefs also includes fish and seafood species that form part of a 143 billion dollar global fisheries trade industry, such as groupers, lobsters, and snappers [20]. In the U.S., recreational fisheries on coral reefs are worth over $\$$100 million each year. In addition, nearly half of all U.S. fisheries depend on healthy coral reefs ecosystems for sustainable stocks [21]. Excessive fishing on reefs can cause considerable damage and threaten the stability of the ecosystem (see fishing pressure section below). As such, coral reef fisheries benefit from strong management plans that limit the risk of overfishing important species. 

Coral reefs also form the foundation of many tourism industries in coastal areas across the globe. In Australia, the Great Barrier Reef received over 26 million visitors in 2016, and tourism to the Queensaland area generates around $\$$6.4 billion (AUD) annually [22]. In the U.S., reef-based tourism in the states of Hawai’i and Florida alone are estimated at over $\$$2 billion dollars annually [23]; and at nearly $\$$240 million in Puerto Rico [21]. ¹

¹Values adjusted for 2020 dollars from the 2007 values reported in [21]

Figure 2: Coral reef ecosystem services (blue) and threats (red). Reefs offer valuable services to humans. Unfortunately, corals are impacted by multiple threats, many of which act to compound each other. Image was created on biorender.com. Icon credits to Lluisa Iborra (skyline), Ifki Rianto (small fishing boat and fisherman), Ruliani (wave), Nikita Kozin (diver), and Luis Prado (large fishing boats), all available from The Noun Project. Reef and associated fish are original artwork by author H.E.R.

What’s killing all the corals: Global and local threats to reefs  

Despite their vast ecological, economical, and pharmaceutical importance, coral reefs are one of the planet’s most rapidly degrading ecosystems [6]. On a global scale, corals are most severely impacted by increasing temperatures, coral diseases, and declining pH levels. At regional and local scales, stressors such as overfishing, run-off from land, and coastal development lead to coral mortality and reef degradation [24]. We discuss the causes, effects, and prevalence of different stressors below. While we have organized this section into global and local stressors, reefs are complex ecosystems and are often subjected to multiple stressors simultaneously. It should also be noted that this is not a comprehensive list. For instance, we do not discuss light and noise pollution, ship groundings, invasive species, or tourism pressure. We have focused on the stressors that we consider the most pressing to address given the magnitude of their impact.

Global Stressors

Temperature: Corals can suffer severe stress if water temperatures rise by just 1◦C above their usual summer maximum [25]. While this change in temperature may seem trivial at first, consider the impacts of a fever on human health, where only a 1-2◦C increase can quickly become life threatening. At higher temperatures, corals lose the symbiotic algae that live inside their tissues, and which provide the coral with the majority of their daily food requirements [25, 26] (Figure 3A). This process is called ‘bleaching,’ as the symbionts are also the main source of color in coral tissue (Figure 3B). Bleaching is often fatal to the coral animal, as they can starve to death without their symbionts. If temperatures return to normal within a few days or weeks, the coral can re-establish their community of symbionts and may survive; but this time window is becoming more elusive as heat stress events are becoming both more prolonged and more severe [27].

Since the 1980s, episodes of bleaching have reached reefs around the world, and even iconic and well-protected areas, like the Great Barrier Reef have lost up to 50% of their live coral [6]. Such bleaching events have increased in both frequency and intensity over the last two decades, and it is projected that by 2050 almost all reefs will experience bleaching level temperatures on an annual basis [27, 28]. The most recent global bleaching event (between 2014-2016) caused devastation across the globe [3]. For instance, this event caused 100% bleaching and nearly 95% coral mortality on Jarvis Island, a U.S. territory in the central Pacific [29]. This island had previously been rated as the healthiest and most robust coral ecosystem on the planet [30], and lacks any other sources of coral stress, underscoring the pervasive impact climate change can have on even the most remote and pristine ecosystems. The Great Barrier Reef in particular, has continued to experience bleaching events every year since 2014, and is seeing its most widespread bleaching event this year [31]. On a smaller scale, other stressors can also prompt a bleaching response in corals, including cold temperature, pollution, high UV, and pathogens [16]. However, heat-induced mass bleaching remains the primary cause of coral decline on a global scale [4, 28, 32, 33]. These declines emphasize the desperate need to curtail the carbon emissions that are responsible for increasing ocean temperatures. 

Disease: Corals have also been affected by disease outbreaks, especially in the Atlantic/Caribbean, where they have been one of the main sources of decline from the mid 1970’s to today [34]. In the late 1970’s, an outbreak of white band disease decimated the three major Caribbean coral species (Acropora cervicornis, palmata, and prolifera) that were the dominant reef builders in the region [35]. In 2014, a new disease, now called Stony Coral Tissue Loss Disease (SCTLD), began in Miami-Dade County, and has since spread throughout the Caribbean [36]. The disease impacts more species than any other known coral diseases, and also kills corals more quickly [36]. In Florida alone, more than 30% of corals have died from the disease over the last few years [36]. Despite much investigation, scientists have yet to isolate the pathogen that causes the disease. 

Disease prevalence in corals has also been increasing over time and is sometimes exacerbated by increased temperatures [37]. Combined, disease and bleaching are major causes of coral mortality, and both are predicted to worsen as climate change progresses [33, 37]. Diseases can also be triggered by local stressors such as coastal human inputs. For instance, in Guam, prevalence of white syndrome was linked to increased nitrogen from sewage outfalls [38]. In Florida, the outbreak of SCTLD also coincided with the dredging of Port Miami, which led to substantial sedimentation and coral mortality [39] [40]. An overall increase in nutrients has also been linked to higher disease prevalence in the both field and experimental studies [41]. Given these synergies, outbreaks of coral diseases are expected to increase [42]. Management efforts that aim to limit sources of coral disease should be high priority especially in the Atlantic/Caribbean, where they have already caused substantial decline. 

Ocean acidification (declining ocean pH): In addition to warming our planet, carbon dioxide emitted into the atmosphere dissolves into our oceans, triggering chemical reactions that increase the acidity of the water (lower the pH level) [43]. Some studies indicate that pH levels in reef water are declining more rapidly than in the open ocean [44]. At lower pH, the process that corals use to build their skeletons (calcification) and which creates the reef structure requires more energy, meaning coral growth slows and they build less reef [45]. The chemical dissolution of older reef structures, as well as erosion of live corals by live organisms, like encrusting mussels or worms, is also easier at lower pH [46, 47]. 

Ocean acidification also negatively impacts the many shell-building organisms that reside on reefs, such as mussels, clams, urchins, and other calcifying organisms [48]. Even fish growth and metabolism can be impacted under low pH, especially during larval stages [49] In addition, pH often interacts negatively with warmer temperatures, hindering growth and survival of corals [50]. As with mitigating the effects of warming, addressing the root cause – rising CO2 levels – is the best course of action to prevent further damage.

Local Stressors

Coastal Development and Nutrient Enrichment: Coastal development can generate sedimentation from poor-land use practices and new development, or nutrient run-off from agriculture and wastewater discharge. The construction of new resorts may involve overwater bungalows, built directly on reef structures, or the creation of artificial beaches that change coastline dynamics and increase sedimentation to nearby reefs. The expansion of ports to accommodate cruise liners or large container ships, often requires dredging of the surrounding reef flats in smaller tropical islands [51, 52], or even larger cities like Miami [40]. On a more dramatic scale, territorial conflicts in Spratly Islands in the South China Sea, have led to land reclamation techniques by China in which reefs are filled to create land that can be claimed [53]. Such efforts destroyed an estimated 6 square miles (3,000 football fields) of coral reef habitat in 2015 [54]. Coastal development represents a severe a direct physical risk to coral reef survival. The environmental impacts of development projects should be thoroughly assessed by independent parties prior to permitting to help alleviate such pressures. 

Nutrient influx to reefs is primarily driven by human activity. Coastal development, sewage and water treatment effluents, agricultural runoff, and discharges from shipping can all increase nutrient levels on reefs. Macroalgae (different from the microalgae that live inside coral tissues) compete with corals for space on reef environments [55]. Normally, macroalgal growth is limited by nutrient availability, but with an influx of nutrients algae can grow more quickly and begin to grow over the coral [55]. This often results in a shift from a coral-dominated reef to an algal-dominated ecosystem [56] (Figure 3B). These patterns can also be exacerbated if there is overfishing of herbivorous fish, which help keep macroalgal populations in check (see Fishing Pressure).

Algal-dominated habitats quickly begin to lose fish species that relied on corals for shelter [56]. Algae can also trap sediments, leading to negative feedback loops that further stress the remaining corals [57]. Algal-dominated reefs lose their value as protective barriers to shorelines, as dead corals can no longer create additional reef structure. In addition, nitrogen and carbon inputs from land can alter the pH of coastal waters, exacerbating ocean acidification in those areas [58]. Policies that limit the environmental impact of coastal development projects and ensure that coastal infrastructure (e.g. sewage pipes and water treatment plants) is well-maintained can significantly limit continued damage to coral reefs locally.

Fishing Pressure: Corals rely on healthy populations of herbivorous fish and invertebrates to keep macroalgal populations from outcompeting them [59]. Overfishing of herbivores like parrotfish and rabbitfish can result in algal population spikes [60, 61]. In 1990, Bermuda banned pot fishing, a practice that mainly impacted herbivorous fish species. As a result, populations of herbivores rebounded [62]. Other fishing practices like dynamite (also called blast fishing) or cyanide fishing can directly destroy reef habitats and kill coral reef organisms. While these methods are not practiced in the U.S., they still represent a significant threat to reefs in the Indo-Pacific, where many U.S. and international non-profits dedicate efforts to reef conservation. Dynamite and cyanide fishing are often practiced by smaller-scale fishermen, harvesting coral reef fish for the aquarium trade (most of which is sent to U.S.) or direct consumption. In Tanzania, for example, dynamite fishing was outlawed in the 1970s, but has continued essentially unchecked [63]. Cyanide fishing allows for the live capture of fish by temporarily anesthetizing them [64]. The concentrations of cyanide used to target the desired fish, however, can be quickly detrimental to coral reef organisms, such as smaller fish and invertebrates [64]. Efficient enforcement against both these practices in the Indo-Pacific would be a substantial relief to local coral reefs; as would limiting overfishing of herbivorous species across coral habitats.

Figure 3: Overview of coral biology. (A) Coral symbiosis. Corals form massive reef structures made of calcium carbonate (limestone) as their skeleton. The live coral tissue is at the surface of this rock, where colonies of polyps (middle inset) cover the skeleton. Inside the polyps, single-celled algal symbionts (left inset) live in specialized tissues. In addition, a diverse microbial community (right inset) lives on and within corals. (B) Coral bleaching and algal overgrowth. A healthy reef (left) undergoes bleaching due to high temperatures (middle). The coral is unable to recover and dark brown macroalgae now grows over the dead coral skeleton (right) causing a shift from a coral-dominated ecosystem to an algae-dominated one. (C) Coral life cycle. Corals can reproduce sexually to create larvae that then float and swim until finding a new home, where they settle down and attach to the seafloor. Corals can also reproduce asexually via fragmentation, whereby a piece of an adult colony breaks but then reattaches elsewhere on the seafloor and continues growing to form another colony. Photo credits: Coral images in A and B are from the Coral Image Bank (Ocean Agency/Caitlin XL Survey: CC license). Symbiont image in panel A was taken by T. LaJeunesse and is reproduced with permission. Polyp image was taken by author H.E.R. Diagram in panel C is original artwork by Nicola G. Kriefall and is reproduced with permission.

What’s protected: U.S. policies addressing coral reefs  

Reducing human access to reefs can mitigate the impact of local stressors on corals – buying them time to become more tolerant of global stressors [65]. Marine Protected Areas (MPAs) are defined as: “[an] area of the marine environment that has been reserved by federal, state, territorial, tribal, or local laws or regulations to provide lasting protection for part or all of the natural and cultural resources therein” (Executive Order 13158, 2000). MPAs may differ in their level of restrictions depending on the conservation goals surrounding their designation. Two specific classes of MPAs are sanctuaries and monuments. The National Oceanic and Atmospheric Administration (NOAA) and Congress may both designate sanctuaries under the National Marine Sanctuaries Act (16 U.S.C. §§ 1431 et seq., 1972), while the President can establish marine national monuments under the Antiquities Act of 1906 (54 U.S.C. §§ 320301-320303, 1906). A number of MPAs include coral reef habitats within U.S. jurisdiction:

• Papahānaumokuākea National Marine Monument in the Northwestern Hawaiian Islands was established in 2006 and is the largest contiguous marine conservation area under U.S. jurisdiction (Proclamation 8031, 2006). A proclamation by President Obama expanded the monument to cover the entire U.S. exclusive economic zone west of 163 West Longitude, providing greater protection for the region’s coral reefs (Proclamation 9478, 2016). • Pacific Remote Islands Marine National Monument includes Wake, Baker, Howland, and Jarvis Islands, Johnston and Palmyra Atolls, and Kingman Reef. Protecting the high coral diversity and endemic coral species in these areas was a major justification for its establishment (Proclamation 8336, 2009). • Florida Keys National Marine Sanctuary protects the largest coral barrier reef in the United States (15 C.F.R. part 922, subpart P; Pub. L. 101–605, 1990). • Flower Garden Banks National Marine Sanctuary was established to protect the northernmost living coral reefs on the U.S. continental shelf (56 F.R. 63634, 1991). • Marianas Trench Marine National Monument protects one of the most diverse coral ecosystems in the Western Pacific and the deepest part of our world’s ocean (Proclamation 8335, 2009). • National Marine Sanctuary of American Samoa (formerly Fagatele Bay National Marine Sanctuary) was designated in response to a proposal from the government of American Samoa, in part to preserve a pristine coral reef terrace ecosystem (51 F.R. 15878, 1986). • Virgin Islands Coral Reef National Monument protects coral reefs as essential habitat for sustaining the fragile biological communities in this region (Proclamation 7399, 2001). • Red Hind Spawning Aggregation Areas west of Puerto Rico are federally managed. All three areas prohibit fishing during the spawning season by implementing area closures from December to February (50 C.F.R. § 622, 1996). A later amendment to this rule established a marine conservation district east of Puerto Rico, in which fishing activity and anchoring by fishing vessels are banned to protect its coral reef habitat (50 C.F.R. § 622, 1999)

Which groups manage and enforce MPAs?  

Through related domestic legislation and international trade law (Table 1), several U.S. federal agencies play important roles in the protection of coral reef environments, among their other duties. In 1998, Presidential Executive Order 13089 (Coral Reef Protection) established the United States Coral Reef Task Force (U.S.CRTF), which includes representatives from the Department of the Interior, the Department of Commerce, NOAA, the Environmental Protection Agency (EPA), the Department of Defense, the National Science Foundation, the Department of Transportation, the Department of Agriculture, the Department of State, the Agency for International Development, and the National Aeronautics and Space Administration (Executive Order 13089, 1998). The U.S.CRTF is charged with leading U.S. stewardship of coral reef ecosystems by supporting scientific research, mapping, monitoring, restoration, international cooperation, and the reduction of threats to reefs in coordination with other stakeholder groups. 

The groundbreaking Coral Reef Conservation Act of 2000 authorized major contributions to the research, mapping, monitoring, conservation, and management of coral reefs, in large part through the development of a National Action Strategy in consultation with USCRFT and the establishment of NOAA’s Coral Reef Conservation Program (CRCP) (Coral Reef Conservation Act of 2000, 2000). The CRCP is one of few federal programs whose direct mission is to address coral reef conservation efforts and the only one with a legislative mandate. In addition to supporting the USCRTF, the CRCP’s multifaceted work involves funding coral research, delivering sound scientific information and tools for management, establishing core partnerships with various stakeholders, and capacity building to help local staff members implement projects that address threats and restore habitats, among other functions. The monumental work of this program relies on federal funds appropriated by Congress. In addition, the U.S. Fish and Wildlife Service manages 10 coral reef National Wildlife Refuges in the Pacific and enforces international trade laws, which regulate the import and export of corals for jewelry or the aquarium trade. The Environmental Protection Agency protects coral reefs by implementing Clean Water Act programs that maintain water quality in watersheds and coastal zones of coral reef areas. While these functions are important, their pertinence to coral reefs is not congressionally mandated. 

A summary of other key domestic policies and the primary agencies responsible for them is shown in Table 1. There are also several international policies that impact coral reefs, though the U.S. is notably absent from several (see gaps section below). The U.S. is contracting party of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES, 1973), which serves to regulate international trade of animal and plant samples in order to promote conservation and reduce the risk of overexploitation and extinction. All hard coral species (Scleractinia spp.) are listed in the CITES Appendix II, and transport of live specimens or products of these species requires a CITES permit (Resolution Conf. 9.24 Rev. CoP17, 1994).

What’s missing: Management and policy gaps in coral reef conservation

  The U.S. stance on ocean policy has varied across administrations. Mostly recently it has shifted from an emphasis on conservation and climate to a focus on economic and security concerns (Executive Order No. 13840, 2018). While the stringency of coral reef conservation has fluctuated, it remains indisputable, as described above, that coral reefs provide substantial economic benefits to many U.S. sectors, in addition to their contributions to biological diversity and ecosystem health. Executive Order 13840, Regarding the Ocean Policy to Advance the Economic, Security, and Environmental Interests of the United States, calls to “facilitate the economic growth of coastal communities and promote ocean industries”, among other priorities (Executive Order 13840, 2018). It is clear from the lengthy list of ecosystem services that preservation of coral reefs is necessary for economic growth and security of many coastal communities.

While there are legal mechanisms (e.g., MPAs) to protect coral reefs under U.S. jurisdiction, gaps often remain in implementation and enforcement. For instance, many MPAs are in remote places where enforcement is difficult, even for countries with substantial resources [66, 67]. When properly enforced, protection can help alleviate some, though not all, stressors. An evaluation of the ecological performance of MPAs in the U.S. Virgin Islands revealed that coral reefs outside MPAs showed larger declines in ecosystem performance, such as lower density of fish including adult snappers [68]. Notably, the amount of live coral cover decreased both inside and outside MPAs during the study period due to bleaching events and hurricane damage, pointing to the importance of global stressors in driving community structure [68]. Table 2 details additional policy tools to tackle local stressors and provides some examples of gaps in implementation at the municipal, state, and national level. 

Key coral reef legislation also requires immediate attention. The Coral Reef Conservation Act of 2000 expired 15 years ago. Reauthorization attempts thus far have either failed or remained stagnant in Congress. Most recently, the Restoring Resilient Reefs Act of 2019 was introduced in both the House of Representatives (H.R. 4160) and the Senate (S. 2429) is a bipartisan and bicameral bill to reauthorize and modernize the Coral Reef Conservation Act of 2000. This bill, however, has not yet proceed past the introduction stage. This legislation would a provide a strong base for coordinated national efforts as well as provides $\$$160 million of federal funding for the next five years for domestic reef management, conservation, and restoration. Such increases in funding are desperately needed. For instance, the budget for CRCP has held steady around $\$$27 million per year over the past ten years [69]. This stagnant budget supports work that is becoming increasingly demanding and urgent. Given the vast monetary value that coral reefs represent to the U.S., increasing this and other program budgets would expand their capacity and impact. 

On a global geopolitical level, the U.S. has the potential to influence coral reef management in other regions, as well. The USCRTF has active working groups that address specific issues and produce incredibly detailed global, regional, and local recommendations based on science that need to be considered in national policy. For example, 60% of the aquarium fish trade is imported into the U.S., with almost 90% originating from Pacific regions [70, 71]. While the U.S.AID’s program in the Philippines and Indonesia are working to improve problems around both overfishing and destructive fishing (e.g. cyanide or dynamite fishing), the program’s limited geographic scope and jurisdiction makes it difficult to coordinate and enforce the larger-scale regional efforts that are needed. To address this, the USCRTF has recommended leveraging work with the Asian Pacific Economic Cooperation (APEC) forum and building a strategic partnership with the South Pacific Region Environmental Program [72]. 

More broadly, however, the U.S. is not party to some major international conventions that would benefit coral reef ecosystems:

• The United Nations Convention on the Law of the Sea (1982) defines the rights and responsibilities of countries with respect to ocean use in order to maintain peaceful relations between governments (U.N. Convention on the Law of the Sea, 1982). Currently, the U.S. has signed but not ratified the agreement, a move that may jeopardize future claims to ocean resources [73]. Within the agreement, the extent of coral reefs is used to help define the limits of territorial seas, and thus the continued loss of reefs has strong implications for future designations of maritime boundaries.

• The United Nations Convention on Biological Diversity (1992) is a comprehensive agreement between 196 parties dedicated to the conservation and sustainable use of biodiversity. Although President Clinton signed the agreement in 1993 and had support from the Senate Foreign Relations Committee, a Senate vote to ratify it was never held (U.S. Senate Committee on Foreign Relations Activities & Reports). The U.S. is party to smaller scale agreements, like the Inter-American Convention for the Protection and Conservation of Sea Turtles and the Specially Protected Areas and Wildlife Protocol.

Saving corals: Restoration, conservation, and research efforts

Despite legislative protections against local impacts, coral reefs have continued to deteriorate mainly due to increasing global temperatures and disease [6, 74]–[76]. This widespread loss has prompted large-scale restoration efforts, involving government programs (e.g. NOAA Coral Reef Conservation Program), non-governmental organizations (e.g. The Nature Conservancy, SECORE International, etc.), academic institutions, and community groups. The Coral Restoration Consortium, which includes international leaders of multiple coral stakeholder groups, provides a collaborative framework that is crucial for successful coral reef restoration on a global scale (crc.reefresilience.org). 

Coral restoration aims to increase the number of healthy adult corals on reefs. However, as corals may reproduce asexually (usually via fragmentation) or sexually, restoration also involves promoting asexual and sexual reproductive processes on reefs to increase coral abundance (Figure 3C) [77, 78]. In the U.S., the largest restoration efforts are in Florida, for the fast-growing staghorn and elkhorn Acropora coral species (the same ones that nearly died out across the Caribbean in 1970s). The Coral Restoration Foundation has led this effort since 2007. To date, the foundation has transplanted over 100,000 coral fragments onto the Florida Reef Tract (www.coralrestoration.org). Coral nurseries in Puerto Rico and the Virgin Islands have also successfully transplanted tens of thousands of coral fragments [79]. Mote Marine Laboratory and Aquarium (www.mote.org), in addition to managing their own underwater coral nursery, has built upon this effort in recent years by developing a method to micro-fragment and fuse typically slower growing corals, thereby speeding up the cultivation process for other species [80].

While increasing asexual reproduction on reefs can help maintain coral populations, only sexual reproduction can generate new genetic diversity. SECORE International (www.secore.org) is leading global coral restoration efforts by regularly producing millions of coral offspring from naturally released eggs and sperm. Once these newborn corals attach to tiles, they are transplanted onto a natural reef, where in time they can mature and contribute to the next generation [81, 82]. However, restoration success (having transplanted colonies grow and sexually reproduce) is contingent upon the environmental conditions being suitable for corals, since stressors such as poor water quality can significantly reduce fertilization [83, 84] and subsequent bleaching can kill transplanted colonies. Increasing the efficiency of coral restoration, e.g. by transplanting coral colonies that are mostly likely to survive and reproduce, in conjunction with improving local environmental conditions will help managers meet the challenges of continued coral population declines [85].

Despite the benefits restoration can offer at a local scale, the pace of climate change is beyond what most corals can handle. Novel research initiatives exploring the possibilities of assisted evolution in corals and their algal symbionts (Figure 3A), such as selective breeding for heat tolerance, continue to gain traction within science and management communities [2, 95]. Other efforts to save coral diversity include genetic repositories (where live corals are maintained in aquaria or nurseries) and coral sperm banks through cryopreservation [96].

Recent initiatives have shifted focus from individual species to restoring and protecting entire reef ecosystems. NOAA recently launched Mission: Iconic Reefs, which targets seven reefs in the Florida Keys National Marine Sanctuary for multi-phased, active restoration. This will involve removing invasive species and algae, transplanting both fast and slow-growing coral species, and increasing the population of other beneficial species like sea urchins and Caribbean king crabs. Another unprecedented coral conservation project is the 50 Reefs Initiative (led by The Ocean Agency), which identified reefs likely to survive climate change and repopulate nearby reefs once the climate stabilizes [97]. The approach developed by the 50 Reefs Initiative will allow managers to maximize long term conservation benefits while reducing the risks of devoting limited resources to reefs that are unlikely to withstand projected warming and wave damage  from increasingly intense cyclones [97].

Saving corals for the long term: Addressing climate change is our largest policy gap

Even with these monumental restoration and conservation efforts, the predictions for climate change-driven coral reef loss are grim. The 2018 IPCC report warned that 1.5◦C increase in global temperatures would correspond to 70-90% coral reef decline, and a 2◦C rise could result in the loss of greater than 99% of reefs [98]. Aggressive international and domestic commitments to reduce greenhouse gas emissions are necessary if coral reefs are to remain functional ecosystems for the benefit of future generations. We, therefore, find it critical to highlight major policies and agreements surrounding greenhouse gas emissions.

The Clean Air Act (42 U.S.C. § 7401, 1963) and the jurisdiction of the Environmental Protection Agency

• 2007 – Massachusetts vs. EPA, the U.S. Supreme Court ruled that greenhouse gases are pollutants under The Clean Air Act, and should be regulated as such. • 2010 – Tailoring Rule by EPA establishes emission thresholds and a process for permitting carbon dioxide equivalent emissions for large, stationary emitters like power plants (75 F.R. 31513, 2010). • 2014 – Utility Air Regulatory Group v. EPA, the U.S. Supreme Court confirmed the jurisdiction of the EPA to regulate greenhouse gas emissions. • 2015 – Clean Power Plan by EPA established final emission guidelines for states to use in limiting greenhouse gas emissions from power generators (80 F.R. 64661, 2015). • 2017 – Executive Order 13783 by President Trump prompts the EPA to review the Clean Power Plan as a potential burden to the development of domestic energy resources. The formal process to repeal the plan was initiated that year (Executive Order 13783, 2017). • 2019 – Affordable Clean Energy Rule by the EPA replaces the Clean Power Plan, stating that the Clean Power Plan overstepped the authority attributed to the EPA under the Clean Air Act (84 F.R. 32520, 2019). Instead, the Affordable Clean Energy Rule places the responsibility of developing standards for CO2 emissions from existing coal-fired power plants on the states. The rule also points to heat rate improvement measures as the best strategy for reducing emissions, rather than shifting some power generation to renewable energy sources.

The move from the Clean Power Plan (CPP) to the Affordable Clean Energy Rule (ACE) demonstrated a clear shift away from federal regulation of greenhouse gas emissions, and federal promotion of renewable energy use. The CPP was enacted to reduce greenhouse gas emissions from power generation by 32% compared from 2005 levels by 2030 (U.S. Environmental Protection Agency 2015). In contrast, the ACE does not set limits on carbon emissions, and instead relies on individual states to take the initiative to regulate greenhouse gas emissions from power plants. The emission reductions projected under the CPP totaled around 870 million tons, compared to 11 million tons under the ACE (U.S. Environmental Protection Agency 2015, 2019). Given the sensitivity of corals to bleaching under increasing global temperatures caused by elevated greenhouse gas emissions [98] this change in legislation undermines efforts to protect and restore coral reefs.

The lack U.S. leadership in reducing global greenhouse gas emissions is further demonstrated by its absence from several international agreements:

• 2012 – Kyoto Protocol operationalizes the United Nations Framework Convention on Climate Change by holding industrialized countries to their committed target reductions in greenhouse gas emissions. The U.S. signed but never ratified the agreement. The Doha Amendment to the Kyoto Protocol includes assigned percentage reductions of greenhouse gas emissions by 2020 for individual countries (not including the U.S.), but has not yet entered into force due to the lack of ratification (United Nations, 2012).

• 2015 – The United Nations Framework Convention on Climate Change Paris Agreement strives to limit average global warming to well below 2◦C relative to preindustrial measurements, with an overall goal to keep the temperature increase to a maximum of 1.5◦C (United Nations, 2015). The U.S. president announced the U.S. withdrawal from this agreement in 2017, due to the negative impact it would have on the U.S. economy (Trump, 2017). However, withdrawing from the Paris Agreement takes four years given the start date of November 4, 2016 (United Nations, 2015), so the earliest possible official withdrawal date is not until November 4, 2020.

Progress towards the global reduction of greenhouse gas emissions continues with the carbon market systems established by other parties to the Paris Agreement. The European Union (EU) Emissions Trading System was the first, and continues to be the largest. The EU system functions by setting a cap on the total amount of specific greenhouse gases emitted, which is lowered over time. Individual companies are then assigned emission allowances for free or purchase allowances via auctions, which they can trade amongst each other [99]. The EU is actively supporting China – the country with the highest annual emissions [100] – in the development of a nationwide carbon emissions trading system [101]. Similar carbon markets already exist in the U.S., but only a small minority of states participate [102, 103], limiting realized emission reductions due to the transfer of electricity generation to unregulated sectors [104].

Despite these federal decisions to abstain from strong action against the root cause of climate change, many states have made their own commitments to reduce greenhouse gas emissions consistent with the Paris Agreement. The United States Climate Alliance was formed in response to the impending U.S. withdrawal from the agreement, and includes 24 states and Puerto Rico. The U.S. governors in the alliance have promised to enact policies that reduce emissions 26-28% below 2005 levels by 2025, track and report progress to the international community, and promote clean energy within their states.

Coral reefs are one of our planet’s most valuable ecosystems [5]. The coastal protection, tourism revenue, biodiversity services, and drug discovery potential of coral reefs are worth trillions of dollars annually [105]. The continued loss of coral reef habitat will represent a significant economic cost to many countries around the world, including the U.S.. The recent actions taken by the U.S. government in national and international policy arenas fall short of an effective strategy to address the greatest global threat to reefs: climate change resulting from increased greenhouse gas emissions. As a country with the second highest annual emissions and the highest cumulative emissions since 1751 [100], the U.S. should take a leading role in the battle against climate change, thereby helping preserve coral reefs for current and future generations. Local management efforts should prioritize the protection of coral reef habitats and strive to mitigate local stressors as much as possible. However, a national and international effort to limit the main source of coral death – increasing global temperatures – is imperative for the future survival of these vibrant marine ecosystems.

Rivera H. E., Chan A. N. & Luu V. Coral reefs are critical for our food supply, tourism, and ocean health. We can protect them from climate change. MIT Science Policy Review 1 , 18-33 (2020).

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Legislation Cited (in order of appearance in text, then tables)

• Executive Order 13158, Marine Protected Areas, 65 F.R. 34909 (May 26, 2000). https://www. federalregister.gov/documents/2000/05/ 31/00-13830/marine-protected-areas

• National Marine Sanctuaries Act, 16 U.S.C. §§ 1431 et seq. (1972).

• Antiquities Act, 54 U.S.C. §§ 320301-320303 (1906).

• Proclamation 8031, Establishment of the Northwestern Hawaiian Islands Marine National Monument, 71 F.R. 36441 (June 15, 2006). https://www. federalregister.gov/documents/2006/ 06/26/06-5725/establishment-of-thenorthwestern-hawaiian-islands-marinenational-monument

• Proclamation 9478, Papahanaumoku ¯ akea Marine ¯ National Monument Expansion 81 FR 60225 (August 31, 2016). https://www.federalregister. gov/documents/2016/08/31/2016-21138/ papahamacrnaumokuamacrkea-marinenational-monument-expansion

• Proclamation 8336, Establishment of the Pacific Remote Islands Marine National Monument, 74 F.R. 1565 (January 6, 2009). https://www. federalregister.gov/documents/2009/01/ 12/E9-500/establishment-of-the-pacificremote-islands-marine-national-monument

• Florida Keys National Marine Sanctuary, 15 C.F.R. part 922, subpart P; Pub. L. 101–605, Nov. 16, 1990, 104 Stat. 3089, as amended by Pub. L. 102–587, title II, §§2206, 2209, Nov. 4, 1992, 106 Stat. 5053 , 5054.

• Flower Garden Banks National Marine Sanctuary, 56 F.R. 63634, Dec. 5, 1991; 60 F.R. 10312, Feb. 24, 1995; 15 C.F.R. part 922, subpart L; Pub. L. 100–627, title II, §205(a)(2), Nov. 7, 1988, 102 Stat. 3217 ; Pub. L. 102–251, title I, §101, Mar. 9, 1992, 106 Stat. 60 ; Pub. L. 104–283, §8, Oct. 11, 1996, 110 Stat. 3366 .

• Proclamation 8335, Establishment of the Marianas Trench Marine National Monument, 74 F.R. 1555 (January 6, 2009). https://www. federalregister.gov/documents/2009/01/ 12/E9-496/establishment-of-the-marianastrench-marine-national-monument

• National Marine Sanctuary of American Samoa (former Fagatele Bay National Marine Sanctuary), 51 F.R. 15878, Apr. 29, 1986; 15 C.F.R. part 922, subpart J; 77 F.R. 43942, July 26, 2012, effective Oct. 15, 2012 (see 77 F.R. 65815).

• Proclamation 7399, Establishment of the Virgin Islands Coral Reef National Monument, 3 C.F.R. 7399 (January 17, 2001). https://www.govinfo.gov/content/ pkg/WCPD-2001-01-22/pdf/WCPD-2001-01-22- Pg156.pdf

• Fisheries of the Caribbean, Gulf of Mexico, and South Atlantic; Reef Fish Fishery of Puerto Rico and the U.S. Virgin Islands; Red Hind Spawning Aggregations, 50 C.F.R. § 622 (1996).

• Fisheries of the Caribbean, Gulf of Mexico, and South Atlantic; Coral Reef Resources of Puerto Rico and the U.S. Virgin Islands; Amendment 1, 50 C.F.R. § 622 (1999).

• Executive Order 13089, Coral Reef Protection, 63 F.R. 32701 (June 11, 1998). https://www.govinfo. gov/content/pkg/FR-1998-06-16/pdf/98- 16161.pdf

• Coral Reef Conservation Act, 16 U.S.C. §§ 6401 et seq. (2000).

• Convention on International Trade in Endangered Species of Wild Fauna and Flora, March 3rd, 1973, 993 U.N.T.S. 243 [hereinafter CITES].

• Criteria for Amendment of Appendices I and II, Resolution Conf. 9.24 (Rev. CoP17), Fort Lauderdale (1994). https://cites.org/sites/default/files/ document/E-Res-09-24-R17.pdf

• Executive Order 13840, Ocean Policy To Advance the Economic, Security, and Environmental Interests of the United States, 83 FR 29431 (June 22, 2018). https: //www.federalregister.gov/documents/2018/ 06/22/2018-13640/ocean-policy-to-advancethe-economic-security-and-environmentalinterests-of-the-united-states

• Restoring Resilient Reefs Act of 2019. 116 U.S.C. §§ H.R. 4160 et seq. (2019).

• Restoring Resilient Reefs Act of 2019. 116 U.S.C. §§ S.2429 et seq. (2019).

• United Nations Convention on the Law of the Sea, December 10, 1982, 1833 U.N.T.S. 397.

• United Nations Convention on on Biological Diversity, June 5, 1992, 1760 U.N.T.S. 69.

• The Clean Air Act of 1963, 42 U.S.C. § 7401 (1963).

• Massachusetts et al. v. Environmental Protection Agency et al., 549 U.S. 497 (2007).

• Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring Rule, 40 C.F.R. §§ 51-52 and 40 C.F.R. §§ 70-71, 75 F.R. 31513 (August 2, 2010). https://www.federalregister.gov/documents/ 2010/06/03/2010-11974/prevention-ofsignificant-deterioration-and-title-vgreenhouse-gas-tailoring-rule

• Utility Air Regulatory Group v. Environmental Protection Agency et al., 573 U.S. 302 (2014).

• Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units (Clean Power Plan), 40 C.F.R. § 60, 80 F.R. 64661 (December 22, 2015). https://www. federalregister.gov/documents/2015/10/23/ 2015-22842/carbon-pollution-emissionguidelines-for-existing-stationarysources-electric-utility-generating

• Executive Order 13783, Promoting Energy Independence and Economic Growth, 82 F.R. 16093 (March 28, 2017). https://www.federalregister.gov/documents/ 2017/03/31/2017-06576/promoting-energyindependence-and-economic-growth

• Repeal of the Clean Power Plan; Emission Guidelines for Greenhouse Gas Emissions From Existing Electric Utility Generating Units; Revisions to Emission Guidelines Implementing Regulations (Affordable Clean Energy Rule), 40 C.F.R. § 60, 84 F.R. 32520 (September 6, 2019). https://www.federalregister.gov/ documents/2019/07/08/2019-13507/repealof-the-clean-power-plan-emissionguidelines-for-greenhouse-gas-emissionsfrom-existing

• US Environmental Protection Agency (EPA) 2015, Regulatory Impact Analysis for the Clean Power Plan Final Rule https://epa.gov/ttnecas1/docs/ ria/utilities_ria_final-clean-power-planexisting-units_2015-08.pdf

• US Environmental Protection Agency (EPA) 2019, Regulatory Impact Analysis for the Repeal of the Clean Power Plan, and the Emission Guidelines for Greenhouse Gas Emissions from Existing Electric Utility Generating Units https://www.epa.gov/sites/production/files/2019-06/documents/utilities_ria_ final_cpp_repeal_and_ace_2019-06.pdf

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Hanny E. Rivera

Department of Biology, Boston University, Boston, MA

Andrea N. Chan

Department of Biology, Pennsylvania State University, University Park, PA

Victoria Luu

Department of Geosciences, Princeton University, Princeton, NJ

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Healthy coral reefs, like this one in Swains Island in American Samoa, support an impressive array of marine life. (Image credit: NOAA)

Coral reefs: Essential and threatened

Coral reefs: one of earth’s most diverse ecosystems, healthy reefs are valuable to you, challenges for coral reefs are both local and global, a hands-on approach to reef conservation.

Healthy coral reefs are one of the most valuable ecosystems on Earth. They provide billions of dollars in economic and environmental services, such as food, coastal protection and tourism. However, coral ecosystems face serious threats, mainly from the effects of global climate change, unsustainable fishing and land-based pollution.

Hidden beneath the ocean waters, coral reefs teem with life. Fish, corals, lobsters, clams, seahorses, sponges and sea turtles are only a few of the thousands of creatures that rely on reefs for their survival.

Corals are animals, even though they may exhibit some of the characteristics of plants and are often mistaken for rocks. In scientific classification, corals fall under the phylum Cnidaria and the class Anthozoa . They are relatives of jellyfish and anemones. There are more than 800 known species of reef-building coral worldwide and hundreds of species of soft corals and  deep-sea corals.

Coral reefs are also living museums and reflect thousands of years of history. Many U.S. coral reefs were alive and thriving centuries ago. Some reefs are even older than our old-growth redwood forests. They are an integral part of many cultures and our natural heritage.

Today, these important habitats are threatened by a range of human activities. Many of the world’s reefs have already been destroyed or severely damaged by pollution, unsustainable fishing practices, disease, global climate change, ship groundings and other impacts. However, we can still protect and preserve our remaining reefs for future generations if we act now.

Healthy coral reefs are among Earth’s most biologically diverse and economically valuable ecosystems and are vital around the world.

Healthy coral reefs and their habitats are important to life in the ocean and on land. Fish, corals, lobsters, clams, seahorses, sponges and sea turtles are only a few of the thousands of creatures that rely on reefs for their survival, but so do humans.

Approximately 500 million people worldwide depend upon reefs for food and their livelihoods, and 30 million are almost totally dependent upon reefs. Coral ecosystems are a source of food for millions; protect coastlines from storms and erosion; provide habitat, spawning and nursery grounds for economically important fish species; provide jobs and income to local economies from fishing, recreation, and tourism; are a source of new medicines; have cultural significance; and are hotspots of marine biodiversity.

Coral reefs contribute billions of dollars to world economies each year. The continued decline and loss of coral reef ecosystems will have significant social, cultural, economic and ecological impacts on people and communities in the U.S. and around the world.

NOAA is working to understand and address key threats to coral reef ecosystems: the impacts from global climate change, unsustainable fishing practices and pollution.

The top threats to coral reefs  — global climate change, unsustainable fishing and land-based pollution — are all due to human activities. These threats, combined with others such as tropical storms, disease outbreaks, vessel damage, marine debris and invasive species, exacerbate each other.

Climate change affects coral reef ecosystems by increasing sea surface temperatures and leads to coral bleaching , disease, sea level rise and storm activity. Additionally, increased  carbon dioxide in the atmosphere changes ocean chemistry and harms reef-building corals.

Unsustainable fishing practices in coral reef areas can lead to the loss of ecologically and economically important fish species. Such losses often have a ripple effect not just on the coral reef ecosystems themselves, but also on the local economies that depend on them.

The effects of land-based sources of pollution , such as coastal development and agricultural runoff, can impede coral growth and reproduction, disturb ecological function and cause disease. Although some of the biggest threats facing coral reefs are global in nature and require action on a similar scale, addressing local stressors — like reducing runoff and promoting sustainable fishing — is equally important.

NOAA’s research is critical to increasing what we as a nation know about the causes of reef decline and how to address these challenges.

Through the activities of the  Coral Reef Conservation Program , NOAA is doing what it can to  address key threats  that affect coral reefs. Our work takes into account the inextricable connections coral reefs have to the lands they surround and the communities and economies they support.

From coral mapping, monitoring and modeling to on-the-ground and in-water restoration activities, NOAA is leading ridge-to-reef efforts to support the management and conservation of these valuable ecosystems.

The Coral Reef Conservation Program coordinates NOAA’s role as the co-chair of the U.S. Coral Reef Task Force , a body that provides a forum for partnership on U.S. government work to protect coral reefs. The program also leads U.S. efforts abroad to enhance coral reef ecosystem management. Although NOAA research is critical to increasing what we know about the causes of reef decline, effective coral reef conservation can’t happen without you. Even if you live far from a coral reef, you can contribute to their conservation. Simple actions , such as using less water and recycling or disposing of trash responsibly, can have big and far-reaching effects.    

You can learn more about NOAA's coral reef program at our Coral Reef Conservation Program website .

Project News · 16 February 2022

Unlocking sustainable tourism

A challenge for our times.

The past couple of years have delivered a blow to the global travel and tourism industries unlike any in recent memory, impacting communities and livelihoods around the world. As some of our key coral reef sites experience a dramatic decline in visitor numbers, both challenges and opportunities are emerging. 

In November 2021, the Great Barrier Reef Foundation brought together our partners, leading experts and our teams from the Resilient Reefs pilot sites (Palau, New Caledonia, Belize and Ningaloo) to hold a Solution Exchange on Sustainable Tourism. Together, the participants explored how World Heritage Marine sites can make their local tourism industry more sustainable for both people and the environment and build resilience to events such as the COVID-19 pandemic and reduce pressure on natural resources in the face of climate change. 

The challenge

In COVID-free times, the travel and tourism sectors usually contribute around 10.4% to the global economy each year. Global coral reef tourism (pre-COVID) is a heavy hitting contributor to this, with an annual worth of $36 million. The industry can bring great economic benefits to the people who call World Heritage Marines sites home, but it can also prove unsustainable and put significant stress on local communities and the environment.  

The scale of the global coral reef tourism industry itself also presents challenges for the coral reef ecosystems and people that depend on them, with some communities being ill-equipped to cope with tourist volumes. The extent of the impact this has on local communities and the environment is influenced by factors such as the infrastructure and processes in place to support tourist numbers, the behaviour of the tourists themselves and the governance communities have in place to manage all of this. 

Tourists flock to coastal communities in COVID-free times. Credit: Michaela Hampi. (Top) Belize's tourism industry has suffered a downturn during COVID-19. Credit: Meritt Thomas

The current tourism hiatus provides us with an opportunity to look at ways to create more sustainable tourism practices to support the ongoing health and longevity of our reefs and the communities that depend on them.  

So how do we support local coral reef communities to survive and thrive when many of their livelihoods have been decimated? And how do we foster alternative income streams while also ensuring their resilience in the face of unknown future challenges?  

To begin to understand the path to sustainable tourism, the Solution Exchange focused on exploring tourism carrying capacity at sites, how to shift tourist behaviour to support local resilience goals and opportunities to diversity local livelihoods. 

Tourists take part in scuba training in the Turks and Caicos Islands. Credit: The Ocean Agency, XL Catlin Seaview Survey

We need to better identify and manage tourism carrying capacity at sites

One way we can aid sustainable tourism is to understand and monitor the carrying capacity of tourist destinations; the maximum number of tourists that can visit a location at the same time without destroying the ecological, social and economic environment.  

Impacts caused by exceeding carrying capacities at tourist destinations include: 

Ecological - damage to corals, coastal vegetation and dune systems by tourists; disturbance of wildlife

Social - reduced amenity and perceptions of overcrowding for locals or visitors; potential loss of core community values; loss of cultural values 

Economic - impacts (over the long term) on economic activity and tourism revenue from environmental degradation or overcrowding; over-utilisation of critical infrastructure and utilities  

What we learned in the Solution Exchange, is that “carrying capacities” are rarely defined and managed by local partners – they often come as an informal response to hotel or transport capacities being stretched to the limit. Coming together with key partners to identify carrying capacity proactively instead of reactively, seeking alignment on key values and gaining shared understanding of risks, are all essential steps to support sustainable tourism at coral reef sites.  

Two volunteers clean the beach in Indonesia. Credit: Ocean Cleanup Group

We need to shift tourist behaviour to better meet local resilience goals

The behaviour of tourists can have a negative impact on both coral reefs and communities. Impacts include physical damage to reefs and coral from boats, trampling and snorkelling, pollution from rubbish and human waste, wildlife disturbance where tourists aren’t maintaining a respectful distance and increased pressure from recreational fishing. 

During the Solution Exchange, we explored ways to persuade, motivate or enable tourists to change their behaviour and minimise negative impacts on reefs and local communities. Key approaches to changing behaviour include: 

Developing simple messaging that focuses on outcomes instead of complex science, such as Hawaii’s “Take what you need, not what you can” campaign 

Using local champions to get communities on board, such as a well-known person from the country or a local church leader

Using pledges to make the message mainstream, gain broad support and inspire action

Eco-volunteers in Komodo National Park, Indonesia. Credit: Martin Colognoli, Ocean Image Bank.

We need to support opportunities for diversifying local livelihoods

The Solution Exchange explored ways to both improve access to tourism jobs for First Nations Peoples and communities, as well as opportunities to diversify local livelihoods so they are not solely reliant on reef assets. 

Key to diversifying livelihoods is creating opportunities that remove pressure on natural resources and instead develop new, sustainable income streams independent from reef ecosystems. An unexpected, positive outcome of COVID-19 for some tourist destinations was how it ignited local entrepreneurship. Although COVID-19 had a devastating impact on the tourism industry in Belize, the pause in tourism created a surge in local entrepreneurship, especially among local women who are now making Belize-based products and selling them online. 

While it is not always possible to completely move away from reef-based livelihoods, there are still opportunities to reduce pressure on reefs by developing low-impact, high-value tourist activities. Tourists could pay to take part in cultural experiences such as joining local community members for a home-cooked meal, for example. 

Where to from here?

At the core of the Resilient Reefs Initiative is a drive to design innovative responses to common resilience challenges and to share and scale what works with reef managers globally. Our Solution Exchanges are intended to do just that: help catalyse action on the ground across our network and facilitate knowledge exchange well beyond.  

This Solution Exchange raised the need to provide assistance to World Heritage Marine sites to develop integrated carrying capacity studies, as well as the potential to create sustainable tourism frameworks for reef sites – something that does not currently exist. Ningaloo has already begun scoping a local carrying capacity study and has connected with a range of global experts. 

The Exchange once again highlighted how common the challenges were across the sites and the opportunity we have for collective action, problem solving and messaging. Key findings from the Exchange are available to be shared with reef managers worldwide on the Reef Resilience Network website .  

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Perspectives

How Tourism Can Be Good for Coral Reefs

Data highlights opportunities for the tourism industry to support better conservation outcomes

April 25, 2017

View The Study

Coral reefs could be considered the poster child of nature-based tourism. People come specifically to visit the reefs themselves, to swim over shimmering gardens of coral amongst hordes of fish. But even if you aren’t snorkeling or diving on a reef, your tropical beach vacation was likely made possible by a coral reef.

The world’s coral reefs perform many essential roles. They are home to the fish that provide the food - and often livelihoods - for nearly 100 million people. They also act as barriers against the worst impacts of storms, protecting the beaches and the millions of people who live around and rely upon them. By modelling the economic contributions of coral reefs to global and local economies, this work can be used to persuade governments of the importance of investing in their protection.

Quote : Source: Mapping Ocean Wealth

The global economic value of coral reefs for tourism is $36 billion/year

Source: Mapping Ocean Wealth

In a  study published in the Journal of Marine Policy , The Nature Conservancy’s Mapping Ocean Wealth (MOW) initiative and partners, used an innovative combination of data-driven academic research and crowd-sourced and social media-related data to reveal that 70 million trips are supported by the world’s coral reefs each year, making these reefs a powerful engine for tourism.

In total, coral reefs represent an astonishing $36 billion a year in economic value to the world. Of that $36 billion, $19 billion represents actual “on-reef” tourism like diving, snorkeling, glass-bottom boating and wildlife watching on reefs themselves. The other $16 billion comes from “reef-adjacent” tourism, which encompasses everything from enjoying beautiful views and beaches, to local seafood, paddleboarding and other activities that are afforded by the sheltering effect of adjacent reefs.

There are more than 70 countries across the world that generate more than 1 million dollars per square mile.

In fact, there are more than 70 countries and territories across the world that have million dollar reefs—reefs that generate more than one million dollars per square kilometer. These reefs support businesses and people in the Florida Keys, Bahamas, Mexico, Indonesia, Australia, and Mauritius, to name a few. Demonstrating this value creates a powerful incentive for local businesses and governments to preserve these essential ecosystems.

The Conservancy’s  Atlas of Ocean Wealth , and the accompanying  interactive mapping tool , serves as a valuable resource for managers and decision makers to drill down to determine not just the location of coral reefs or other important natural assets, but how much they’re worth, in terms of their economic value as well as fish production, carbon storage and coastal protection values. By revealing where benefits are produced and at what level, the MOW maps and tools can help businesses fully understand and make new investments in protecting the natural systems that underpin their businesses.

The Methodology

Along with traditional data-driven academic research, and research from the emerging fields of crowd-sourced and social media-related data, a combination of tourism datasets that included hotel rooms, general photographs, underwater photographs, dive centers and dive site were used to render and improve crude national statistics, and also to cross-validate with independent datasets – for example, using hotel locations alongside number of photos taken in a location to independently show tourism spread at national levels, and using dive-sites and locations of underwater photographs to distinguish between tourism activities that take place directly on the reef (e.g., snorkeling, diving) versus tourism activities that indirectly benefit from the presence of coral reefs (e.g., enjoying pristine beaches, calm waters, and fresh seafood).

The data is available in the  mapping application , which allows users to view and compare economic and visitation values of coral reef tourism around the world. Users can also focus on specific geographies, such as Florida, the Bahamas, the Eastern Caribbean, and Micronesia, to view a more fine-scale distribution of values in these regions.

Armed with concrete information about the value of these important natural assets, the tourism industry can start to make more informed decisions about the management and conservation of the reefs they depend on—and thus become powerful allies in the conservation movement.

The concept of valuing nature isn’t a new one, but the detailed, targeted knowledge of the MOW initiative presents an opportunity for the travel and tourism industry to lead both in the private sector, institutionalizing the value of nature into business practices and corporate sustainability investments, and in the sustainability movement more broadly by capturing the business opportunities that exist when we realize that we need nature.

Quote : Dr. Robert Brumbaugh

It’s clear that the tourism industry depends on coral reefs. But now, more than ever, coral reefs are depending on the tourism industry."

Dr. Robert Brumbaugh

For those interested in learning more, or if you have questions or feedback, contact us at  [email protected] .

Atlas of Ocean Wealth

This Atlas represents the largest collection to date of the economic, social and cultural values of coastal and marine habitats globally. View Atlas

Mapping Ocean Wealth

Understanding in quantitative terms all that the ocean does for us today, so that we make smarter investments and decisions for the ocean of tomorrow. Visit Site

Recreation and Tourism Data Portal

Dig in to visualize and simplify global, regional and local ecosystem benefits for use in natural resource planning and policy decisions. Explore the Data

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New study reveals tourists love Hawaiian coral reefs just a little too much

Researchers combine social media with aerial mapping of sea floor to find tourism negatively impacts coral reefs.

Hawaiian coral reefs are popular tourist sites. This is cause for concern, as highly visited coral reefs are negatively impacted by elevated pollution, infrastructure and development, as well as on-reef visitation and the physical damages accrued through recreating tourists. Photo by Greg Asner

Coral reefs are vibrant ecosystems for marine life and provide vital environmental benefits for humanity, such as storm wave mitigation, bountiful fish stocks and ocean-based livelihoods. They are also a global attraction for tourists, drawing millions of visitors every year and billions of dollars in tourism revenue.

However, reef ecosystems are also as fragile as they are beautiful. Coral reefs are swiftly and steadily declining due to the combined effects of global warming and local human stressors. A new study by Arizona State University and Princeton University provides insights into the local impacts of tourist visitation on live coral cover, as well as the draw reefs can have for coastal visitation.

The study , published Jan. 9 in the journal Nature Sustainability, provides novel evidence that live coral reef cover is both an attraction for and victim of tourists at a large scale, raising complex trade-offs between environment and the economy.

Even though tourism revenue is a boon to the economy and can benefit reef preservation efforts, when unmanaged, increased tourism also negatively impacts the health of coral reefs directly, both through tourism-related development and pollution, as well as on-reef activities such as swimming, scuba diving and snorkeling.

“We took the world's first live coral maps and combined them with the power of social media and data analytics to derive wholly new information on the interaction between people and reefs,” said Greg Asner , co-author on the study and director of the ASU Center for Global Discovery and Conservation Science in the Julie Ann Wrigley Global Futures Laboratory .

“The results were astonishing to see at such a large geographic scale and yet also corroborative at the local scales in which some communities have voiced significant concern about coral reef tourism,” Asner said.

“ Coastal tourism is a multibillion-dollar industry and will increasingly feature in the future use of marine resources,” said Bing Lin, a doctoral student at Princeton University’s School of Public and International Affairs and lead author of the study. “It is only through an adequate understanding of tourism’s large-scale impacts on reef ecosystems that we can appropriately pinpoint pathways to make it more sustainable."

The research team created unique, high-resolution datasets collected at the archipelago scale across the state of Hawaii, a prime coastal tourism hotspot. To determine coastal visitation rates, Lin web-scraped hundreds of thousands of Instagram posts to quantify both on-reef and overall coastal visitation. To quantify live coral cover, the authors used a high-resolution airborne mapping and a machine learning procedure to map the seafloor, a method developed by Asner and colleagues. Lin then obtained additional information from the Ocean Tipping Points project and the Hawaii Statewide GIS Program on various metrics of site accessibility, human activity and water conditions to determine the relationship between tourist visitation and live coral cover across hundreds of coastal sites in Hawaii.

ASU researchers used high-resolution airborne mapping and a machine learning procedure to map the Hawaiian sea floor. This image shows the ASU Global Airborne Observatory in action. Photo by ASU

They found that high-quality coral reefs are popular tourist sites for both overall and on-reef specific visitation. At the most highly visited sites, coral reefs were also doubly at risk from tourism. They are indirectly impacted by the elevated pollution and infrastructure development it brings and directly impacted by on-reef visitation and the physical damages accrued through recreating tourists.

These findings provide new insights into the role of local human activities in impacting coral reef health, a finding only possible through the high-resolution, meter-scale mapping methods used in this study.

“Whether it's through our airborne program in regions like Hawaii or via our global reef monitoring program, we are constantly reminded that negative local-scale impacts are outpacing climate change-related impacts on coral reefs,” Asner said. 

“Local stressors to the world’s reefs are often overshadowed by the large, looming threat of global climate change and subsequent coral bleaching. However, our research underscores the importance of localized stressors in also contributing to coral decline,” Lin said.

This study also highlights the importance of both strong reef-protecting policies and coral restoration measures, especially at popular tourist sites across Hawaii and beyond. Higher rates of on-reef visitation occur when there is better reef quality, site accessibility and water quality. This suggests that potential synergies also exist in promoting stronger coastal management practices that can simultaneously improve both reef quality and revenues generated from tourism.

This study was supported through funding from the High Meadows Foundation and the Lenfest Ocean Program of The Pew Charitable Trusts.

Keely Swan with Princeton University contributed to this article.

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Reefs at Risk in the Caribbean

Improving coastal resource management and coral reef protection by providing comprehensive information on threats to coral reefs, the value of goods and services provided by these ecosystems, and economic losses that will result from their degradation.

Key Findings

• Nearly two-thirds of coral reefs in the Caribbean are threatened by human activities. Integrating threat levels from all sources considered in this analysis (coastal development, watershed-based sediment and pollution, marine based threats, and overfishing), the Reefs at Risk Threat Index identified about one-tenth of Caribbean coral reefs at very high levels of threat, one-third at high threat, one fifth at medium threat, and one-third at low threat.
• An estimated one-third of Caribbean coral reefs are threatened by coastal development. This includes sewage discharge, urban runoff, construction, and tourist development.
• Sediment and pollution from inland sources threaten about one-third of Caribbean coral reefs. Analysis of more than 3,000 watersheds across the region identified 20 percent of coral reefs at high threat and about 15 percent at medium threat from damage caused by increased sediment and pollution from agricultural lands and other land modification.
• Marine-based threats to coral reefs are widespread across the Caribbean. Our indicator of marine-based damage and pollution identified about 15 percent of Caribbean reefs as threatened by discharge of wastewater from cruise ships, tankers and yachts, leaks or spills from oil infrastructure, and damage from ship groundings and anchors.
• Overfishing threatens over 60 percent of Caribbean coral reefs. Fishing above sustainable levels affects coral reefs by altering the ecological balance of the reef. The removal of herbivorous fish, which consume algae, facilitates algal overgrowth of corals. Declines in coral cover and increases in algal cover have been observed across the region. This analysis identified about one-third of Caribbean reefs at high threat from overfishing pressure and about 30 percent at medium threat.
• Diseases and rising sea temperatures threaten to damage coral reefs across the Caribbean region. Diseases have caused profound changes in Caribbean coral reefs in the past 30 years, with very few areas unscathed by disease, even reefs far removed from human influence. In addition, coral bleaching episodes-the most direct evidence of stress from global climate change on Caribbean marine biodiversity-are on the rise.
• Ineffective management of protected areas further threatens Caribbean coral reefs. With the growth of tourism, fisheries, and other development in coral reef areas, marine protected areas (MPAs) are an important tool for safeguarding coral reefs. At present, over 285 MPAs have been declared across the Caribbean, but the level of protection afforded by MPAs varies considerably. The Reefs at Risk Project found only 6 percent of MPAs to be rated as effectively managed and 13 percent as having partially effective management.
• The coastal communities and national economies of the Caribbean region are poised to sustain substantial economic losses if current trends in coral reef degradation continue. Coral reefs provide valuable goods and services to support local and national economies, and degradation of coral reefs can lead to significant economic losses, particularly in the coastal areas of developing countries, through loss of fishing livelihoods, malnutrition due to lack of protein, loss of tourism revenues, and increased coastal erosion. Analyses carried out by the Reefs at Risk project indicate that Caribbean coral reefs provide goods and services with an annual net economic value in 2000 estimated at between US$3.1 billion and US$4.6 billion from fisheries, dive tourism, and shoreline protection services.

Executive Summary

Many people in coastal communities throughout Latin America and the Caribbean depend on the natural resources provided by reefs for their livelihoods. Ensuring proper management of the reefs is vital for the economic and environmental health of the region, but there is a lack of quality information about the relationship between human activities and coral reef condition across the region. The Reefs at Risk in the Caribbean project was a response to this information need. The primary goal of the project was to raise awareness and improve management of coral reefs across the region through improving the knowledge base on the status of and threats to coral reefs. In collaboration with partner institutions across the region, we implemented an analysis to link human activities with reef condition. A major component of the project involved modeling (estimating) threat to coral reefs from human activities.

Reefs at Risk Caribbean on CD

The CD version of this report includes:

• Over 30 spatial data sets reflecting physical, environmental and socioeconomic variables for the Wider Caribbean;
• user-friendly map viewing software (ESRI ArcReader);
• Detailed country profiles for 35 Caribbean countries and territories
• Full technical notes on the threat modeling method;
• Technical notes on data sources and methods for the economic valuation;
• Complete set of maps in high and low resolution JPEG format.

To order a copy of the CD, contact [email protected].

Downloadable GIS Data Sets

Both download options provide estimates of threat to coral reefs for the four individual threats (coastal development, marine-based threats, overfishing, and sediment and pollution from upland sources), in addition to integrated threat -- the Reefs at Risk threat index.

Vector Data Sets (ZIP archive, 20.7 Mb) including data on coral reef locations, estimated threat to coral reefs from human activities, watersheds boundaries, and marine protected areas, all in ESRI ArcView shapefile format in Geographic projection.

This option five polygon data sets reflecting estimated threats from human activities; five point data sets reflecting coral reef locations by these estimated threats; a polygon data set of watershed boundaries (with associated erosion estimates); a point data set reflecting river mouths and estimated relative sediment delivery; a polygon data set reflecting country boundaries; a line data set reflecting the coastline; and a point data set reflecting cruise ship ports of call. The zip file also includes an ArcView project file (rrcar_vec.apr) which requires ESRI's ArcView software.

GRID Data Sets (ZIP archive, 32.7 Mb) including data on coral reef locations, estimated threat to coral reefs from human activities, relative erosion rates across the landscape, and bathymetry, all in ESRI ArcView GRID format in Lambert Equal-Area Azimuthal projection.

This option five GRID data sets reflecting estimated threat to coral reefs from human activities; five GRID data sets reflecting coral reef locations classified by estimated threat; a GRID data set reflecting estimated relative erosion rates across the landscape; and a GRID reflecting Bathymetry. All GRIDs are in Lambert Equal-Area Azimuthal projection.

In addition, the zip file includes several vector shapefiles in Geographic projection – polygon watershed boundaries (with associated erosion estimates), polygon country boundaries, and a point data set reflecting river mouths and estimated relative sediment delivery. The zip file also includes an ArcView project file (rrcar_gr.apr) which requires ESRI's ArcView software and Spatial Analyst 2.0 extension.

Technical Documentation

• Technical Notes
• Economic Valuation Methodology

Workshop Summary

Reefs at Risk in the Caribbean Threat Assessment Workshop Summary

Connected to this report

Fields of fuel, belize coastal threat atlas, reefs at risk revisited, integrated threat: the reefs at risk threat index, the caribbean region.

Reefs at Risk

Raising awareness of threats to coral reefs and providing information and tools to manage coastal habitats more effectively.

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Coral Reef Alliance

Saving the World’s Coral Reefs

Coral Reefs 101 › Why Care About Reefs?

People from around the world travel to coral reef destinations each year, attracted by the beautiful white sand beaches and warm, turquoise waters. The economic contribution of tourism to coral reefs is estimated at $36 billion to the global economy each year—this revenue supports millions of jobs in restaurants, hotels, tour operations, transportation companies, and more.

Critical species that depend on coral reefs, like parrotfish, play an important role in bringing this much-needed revenue to coastal communities. Parrotfish feed on corals, and break them down to excrete the popular white sand that tourists flock to. A single large parrotfish can produce 840 pounds of sand each year.

Help save the world’s coral reefs

This is how tourists are destroying coral reefs in Hawaii

The less people at a certain site, the more coral there are, the research found.

The millions of tourists who flock to the shores of Hawaii every year are wreaking havoc on its natural environment -- especially the coral reefs, which are at risk all over the world, a new study said.

The most popular coral reefs on the Hawaiian islands are likely being degraded by the very visitors they attract, according to a study published Monday in Nature Sustainability .

MORE: World Oceans Day 2022: How climate change and warming waters are affecting the health of the oceans

Researchers from Princeton University combed through more than 250,000 geotagged Instagram posts from 2018 to 2021 by tourists visiting Hawaiian reefs and compared them with flyover maps of live coral cover. They then used artificial intelligence to analyze reef map images at about a 2-meter resolution, or about 6.5 feet, and 16-meter, or 52.5-feet, depth, according to the study.

Bing Lin, a PhD candidate in science, technology and environmental policy at Princeton University's School of Public and International Affairs and the lead author of the study, got the idea to use social media for the research after doing fieldwork in Hawaii in 2021 and realizing that one of the first things people do when they visit a site is to take a photo and post it to Instagram, he told ABC News.

"They take pictures of the beaches, and they post on social media," he said. "Instagram is by far the main platform through which social media presence is documented, and so I came up with the idea of using Instagram to get a sense of a large-scale representation of where people are distributed in Hawaii."

MORE: More coral bleaching at Great Barrier Reef, Australia confirms

The scientists found that the accessible sites with more live coral cover were visited more often, but that at the popular sites, coral covers were more degraded compared to those at less popular sites, the paper states.

"We were able to find that coral reefs not only played a really significant role in attracting tourism, but also that the tourism subsequently seemed to suppress live coral coverage at the sites in which tourism was most concentrated," Lin said.

While tourism is mostly concentrated on the shoreline, with lots of activity on the beach, many tourists end up on excursions in which they venture further into the ocean for snorkeling or scuba diving, Lin said.

Using keywords included in captions and hashtags, such as "#scubadiving," Lin was also able to determine a certain degree of interaction with the reefs. Corals tended to thrive farther out into the water, where there are less people, Lin said.

MORE: Discovery of 'pristine' coral reef near Tahiti could help save dying coral reefs around the world, scientist says

The degradation can happen in the form of diver contact, when divers intentionally or accidentally come in contact with the reefs, as well as elevated pollution in areas that tourists frequent, Lin said.

Places in Oahu in Honolulu County, such as Waikiki Beach, Waimea Bay, Lanikai Beach and Shark's Cove, were among the biggest spots for degraded reefs, Lin said. Areas on the Big Island were also among the sites with the most degraded coral, he added.

Coral reefs are vulnerable all over the world due to ocean water warming and pollution. A study published in the Proceedings of the National Academy of Sciences in 2021 found that coral reefs could stop growing in 10 years unless greenhouse gases are significantly reduced.

Coral bleaching, a process that occurs when water is too warm and the algae the corals expel from their tissues cause them to turn completely white, is inundating reefs all over the world, including the Great Barrier Reef in Australia.

MORE: Coral reefs could stop growing in 10 years unless greenhouse gases are significantly reduced, new study says

In addition to their biodiversity and beauty, coral reefs serve as vital ecosystems, nurture fisheries and protect coasts.

Included in the reef tourism industry should be a method to incentivize conservation by generating funds and supporting local livelihoods focused on protecting the reefs. The United Nations' 2030 Agenda for Sustainable Development has set goals to promote sustainable use of marine and coastal resources, but tourists can harm live corals directly or indirectly, such as by polluting the surrounding sea.

"The impacts of tourism is detectable across hundreds of sites," Lin said.

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The end of coral reefs as we know them

Years ago, scientists made a devastating prediction about the ocean. Now it’s unfolding.

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More than five years ago, the world’s top climate scientists made a frightening prediction: If the planet warms by 1.5 degrees Celsius, relative to preindustrial times, 70 to 90 percent of coral reefs globally would die off. At 2°C, that number jumps to more than 99 percent.

These researchers were essentially describing the global collapse of an entire ecosystem driven by climate change . Warm ocean water causes corals — large colonies of tiny animals — to “bleach,” meaning they lose a kind of beneficial algae that lives within their bodies. That algae gives coral its color and much of its food, so bleached corals are white and starving. Starved coral is more likely to die.

In not so great news, the planet is now approaching that 1.5°C mark. In 2023, the hottest year ever measured, the average global temperature was 1.52°C above the preindustrial average, as my colleague Umair Irfan reported . That doesn’t mean Earth has officially blown past this important threshold — typically, scientists measure these sorts of averages over decades, not years — but it’s a sign that we’re getting close.

So, it’s no surprise that coral reefs are, indeed, collapsing. Earlier this month, the National Oceanic and Atmospheric Administration (NOAA) announced that the planet is experiencing its fourth global “bleaching” event on record. Since early 2023, an enormous amount of coral in the Pacific, Atlantic, and Indian oceans has turned ghostly white, including in places like the Great Barrier Reef and the Florida Keys. In some regions, a lot of the coral has already died.

“What we are seeing now is essentially what scientists have been predicting was going to happen for more than 25 years,” Derek Manzello, a marine scientist at NOAA who leads the agency’s coral bleaching project , told Vox. The recent extreme ocean warming can’t solely be attributed to climate change, Manzello added; El Niño and even a volcanic eruption have supercharged temperatures.

But coral reefs were collapsing well before the current bleaching crisis. A study published in 2021 estimated that coral “has declined by half” since the mid-20th century. In some places, like the Florida Keys, nearly 90 percent of the live corals have been lost. Past bleaching events are one source of destruction, as are other threats linked to climate change, including ocean acidification.

The past and current state of corals raises an important but challenging question: If the planet continues to warm, is there a future for these iconic ecosystems?

What’s become increasingly clear is that climate change doesn’t just deal a temporary blow to these animals — it will bring about the end of reefs as we know them.

Will there be coral reefs 100 years from now?

In the next few decades, a lot of coral will die — that’s pretty much a given . And to be clear, this reality is absolutely devastating. Regardless of whether snorkeling is your thing, reefs are essential to human well-being: Coral reefs dampen waves that hit the shore, support commercial fisheries , and drive coastal tourism around the world. They’re also home to an incredible diversity of life that inspires wonder.

“I’m pretty sure that we will not see the large surface area of current reefs surviving into the future,” said Hans-Otto Pörtner, who was involved in the landmark 2018 report , led by the Intergovernmental Panel on Climate Change (IPCC), that predicted the downfall of tropical reefs at 1.5°C warming. “Every year is going to be worse.”

But even as many corals die, reefs won’t exactly disappear. The 3D formation of a typical reef is made of hard corals that produce a skeleton-like structure. When the polyps die, they leave their skeletons behind. Animals that eat live coral, such as butterfly fish and certain marine snails, will likely vanish; plenty of other fish and crabs will stick around because they can hide among those skeletons. Algae will dominate on ailing reefs, as will “weedy” kinds of coral, like sea fans, that don’t typically build the reef’s structure.

Simply put, dead reefs aren’t so much lifeless as they are home to a new community of less sensitive (and often more common) species.

“Reefs in the future will look very different,” said Jean-Pierre Gattuso , a leading marine scientist who’s also involved with the IPCC. “Restoring coral reefs to what they were prior to mass bleaching events is impossible. That is a fact.”

On the timescale of decades, even much of the reef rubble will fade away, as there will be no (or few) live corals to build new skeletons and plenty of forces to erode the ones that remain. Remarkably, about 30 percent of the carbon dioxide that we pump into the atmosphere is absorbed by the oceans. When all that CO2 reacts with water, it makes the ocean more acidic, hastening the erosion of coral skeletons and other biological structures made of calcium carbonate.

Buying time

For decades now, hard-working and passionate scientists have been trying to reverse this downward trend — in large part, by “planting” pieces of coral on damaged reefs. This practice is similar to planting saplings in a logged forest. In reef restoration, many scientists and environmental advocates see hope and a future for coral reefs.

But these efforts come with one major limitation: If the oceans continue to grow hotter, many of those planted corals will die too. Last fall, I dived a handful of reefs in the Florida Keys where thousands of pieces of elkhorn and staghorn — iconic, reef-building corals — had been planted. Nearly all of them were bleached, dead, or dying.

“When are [we] going to stop pretending that coral reefs can be restored when sea temperatures continue to rise and spike at lethal levels?” Terry Hughes, one of the world’s leading coral reef ecologists, wrote on X .

Ultimately, the only real solution is reducing carbon emissions. Period. Pretty much every marine scientist I’ve talked to agrees. “Without international cooperation to break our dependence on fossil fuels, coral bleaching events are only going to continue to increase in severity and frequency,” Manzello said. Echoing his concern, Pörtner said: “We really have no choice but to stop climate change.”

But in the meantime, other stuff can help .

Planting pieces of coral can work if those corals are more tolerant to threats like extreme heat or disease. To that end, researchers are trying to breed more heat-resistant individuals or identify those that are naturally more tolerant to stress — not only heat, but disease. Even after extreme bleaching events, many corals survive, according to Jason Spadaro, a restoration expert at Florida’s Mote Marine Laboratory. (“Massive” corals, which look a bit like boulders, had high rates of survival following recent bleaching in Florida, Spadaro said.)

Scientists also see an urgent need to curb other, non-climate related threats, like water pollution and intensive fishing. “To give corals the best possible chance, we need to reduce every other stressor impacting reefs that we can control,” Manzello told Vox.

These efforts alone will not save reefs, but they’ll buy time, experts say, helping corals hold on until emissions fall. If those interventions work — and if countries step up their climate commitments — future generations will still get to experience at least some version of these majestic, life-sustaining ecosystems.

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• Threats to Coral Reefs

Coral reefs are in decline in the U.S. and around the world. Many scientists now believe the very existence of coral reefs may be in jeopardy unless we intensify our efforts to protect them (Frieler et al. 2013). Threats to coral reefs come from both  local  and global  sources.  The impacts of these threats disproportionally affect underserved groups including minority, low-income, and indigenous populations that rely on coral reefs for nutrition from small-scale fisheries (food security) and for coastal protection (natural infrastructure) against increasingly intense storms (Reguero et al., 2015; Neumann et al., 2015; Kumar and Taylor, 2015).

Local Threats to Coral Reefs

Most coral reefs occur in shallow water near shore. As a result, they are particularly vulnerable to the effects of human activities, both through direct exploitation of reef resources, and through indirect impacts from adjacent human activities on land and in the coastal zone. Many of the human activities that degrade coral reefs are inextricably woven into the social, cultural, and economic fabric of regional coastal communities.

Coral reefs face many threats from local sources, including:

• Physical damage or destruction from coastal development, dredging, quarrying, destructive fishing practices and gear, boat anchors and groundings, and recreational misuse (touching or removing corals).
• Sedimentation from coastal development, urban stormwater runoff, forestry, and agriculture Sedimentation has been identified as a primary stressor for the existence and recovery of coral species and their habitats. Sediment deposited onto reefs can smother corals and interfere with their ability to feed, grow, and reproduce.
• Nutrients (nitrogen and phosphorous) from agricultural and residential fertilizer use, sewage discharges (including wastewater treatment plants and septic systems), and animal waste Nutrients are generally recognized as beneficial for marine ecosystems; however, coral reefs are adapted to low nutrient levels; so an excess of nutrients can lead to the growth of algae that blocks sunlight and consumes oxygen corals need for respiration. This often results in an imbalance affecting the entire ecosystem. Excess nutrients can also support growth of microorganisms, like bacteria and fungi, that can be pathogenic to corals.
• Pathogens from inadequately treated sewage, stormwater, and runoff from livestock pens Although rare, bacteria and parasites from fecal contamination can cause disease in corals, especially if they are stressed by other environmental conditions. Coral disease occurs in healthy ecosystems, but the input of pathogen-containing pollution can exacerbate the frequency and intensity of disease outbreaks.
• Toxic substances , including metals, organic chemicals and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, mining activities, and runoff from landfills Pesticides can affect coral reproduction, growth, and other physiological processes. Herbicides, in particular, can affect the symbiotic algae (plants). This can damage their partnership with coral and result in bleaching. Metals, such as mercury and lead, and organic chemicals, such as polychlorobiphenyls (PCBs), oxybenzone and dioxin, are suspected of affecting coral reproduction, growth rate, feeding, and defensive responses.
• Trash and micro-plastics from improper disposal and stormwater runoff Trash such as plastic bags, bottles, and discarded fishing gear (also called marine debris) that makes its way into the sea can snag on corals and block the sunlight needed for photosynthesis, or entangle and kill reef organisms and break or damage corals. Degraded plastics and microplastics (e.g., beads in soap) can be consumed by coral, fish, sea turtles, and other reef animals, blocking their digestive tracts and potentially introducing toxics.
• Overfishing can alter food-web structure and cause cascading effects, such as reducing the numbers of grazing fish that keep corals clean of algal overgrowth. Blast fishing (i.e., using explosives to kill fish) can cause physical damage to corals as well.
• Coral harvesting for the aquarium trade, jewelry, and curios can lead to over-harvesting of specific species, destruction of reef habitat, and reduced biodiversity.

The aggregate effects of these stressors can decrease resilience of the reef overall and increase susceptibility to disease and invasive species. Invasive species can create an imbalance in the biological checks and balances of a reef ecosystem.

Global Threats to Coral Reefs

Increased ocean temperatures and changing ocean chemistry are the greatest global threats to coral reef ecosystems. These threats are caused by warmer atmospheric temperatures and increasing levels of carbon dioxide dissolved in seawater.

As atmospheric temperatures rise, so do seawater temperatures. This warming places stress on corals and can cause them to expel the microscopic algae that produce food that they need. Without this algae coral also lose their coloration—a condition known as coral bleaching — because the loss of algae reveals the white color of the calcium carbonate structure underlying the polyps. Severe or prolonged bleaching can kill coral colonies or leave them more vulnerable to other threats such as infectious disease.

Other climate impacts, such as sea level rise, increased frequency and intensity of storms, and altered ocean circulation patterns, can also affect coral reefs.

Ocean acidification refers to a change in ocean chemistry in response to the uptake of carbon dioxide from the atmosphere. The amount of carbon dioxide in the atmosphere is in equilibrium with that in seawater, so when atmospheric concentrations increase so do oceanic concentrations. Carbon dioxide entering seawater reacts to form carbonic acid, causing an increase in acidity.

Each year, the ocean absorbs about one-quarter of the carbon dioxide emitted from the burning of fossil fuels (oil, coal, and natural gas). Since the Industrial Revolution, ocean acidity has increased by about 30%, a rate that is more than 10 times what has previously occurred for millions of years. Further, ocean acidity levels are expected to increase by an additional 40% above present levels by the end of this century.

Increases in ocean acidity (measured by lower pH values) reduce the availability of dissolved salts and ions needed by corals to form the calcium carbonate structure. Consequently, coral growth and reef growth can be slowed, with some species affected more than others. If acidification becomes severe, coral skeletons may dissolve. Locally, nutrient enrichment due to run-off from human activities on land can also cause increased acidity in coastal waters, exacerbating the effects of ocean acidification.

 Stony coral tissue loss disease (SCTLD)

First identified in the Florida Keys in 2014, stony coral tissue loss disease (SCTLD)  has spread rapidly through the Caribbean region. It is one of the most lethal coral diseases ever recorded. Learn more at Florida Sea Grant .  

Find out what is being done to understand and prevent the spread of this deadly disease.

Learn more about EPA's work with the U.S. Coast Guard and Smithsonian Environmental Research Center on SCTLD

• Coral Reefs Home
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• Additional Resources
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• What You Can Do
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• WHERE I WORK
• 02 October 2023

How damaged are coral reefs? I dive to investigate climate change

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Long Ying is a marine biologist at Prince of Songkla University in Hat Yai, Thailand. Credit: Giacomo d’Orlando for Nature

Corals are, in many ways, the trees of the seas. They generate oxygen, provide habitats for animals and protect their environments from extreme weather. They also bring many benefits to humans, including creating livelihoods such as tourism.

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doi: https://doi.org/10.1038/d41586-023-03065-8

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Can Eco-Tourism Save Coral Reefs?

Eco-tourism can be a boon—or an ecosystem destroyer.

Welcome to JSTOR Daily’s  Planet-Conscious Weekly Summer Travel Series ! From   sustainable seafood to ag ritourism , we will investigate better and greener ways to travel, eat, and interact with the world.

Birdwatching, seal-spotting, and snorkeling in picturesque coral reefs are some of travelers’ favorite activities. But how do these actions affect the ecosystems and communities that have historically grown around the bounty of natural resources? Can the planet support our growing desire to explore the wilderness?

Fueled by the increasing affluence of the developed countries, tourism has been one of the world’s fastest-growing industries in the past several decades. The industry’s growth started in the mid-twentieth century and has continued with no signs of stopping. In 1950, there were 25 million international tourists. Twenty years later, that number jumped to 183 million, and then more than doubled within eighteen years, representing 25% of international trade in services. In 2017, there were a whopping 1.3 billion international tourists, generating 1.6 trillion dollars. The World Tourism Organization expects this trend not only to continue but accelerate. The organization forecasts the number of international arrivals will skyrocket to 1.8 billion by 2030 .

Eco-tourism , a specialized form of tourism based on natural and sometimes cultural history of pristine environmental places, has been part of that rapid growth since the 1980s. In the past few decades, tourists from the wealthy countries have increasingly sought unspoiled and pristine destinations, many of which are located in the developing world. It is a paradox of industrialized development —mass-production demands an increasing use of land and natural resources, while growing numbers of affluent travelers wish to trek in tropical rainforests and take pictures of roaming wildlife.

On quite a few occasions, eco-tourism hasn’t been favorable to the ecosystems it brought people to. In Patagonia, Argentina, where marine life watching became a popular activity, dolphins were so disturbed by the approaching boats that they would flee their established feeding waters—a trend that scientists warned may exert energetic costs on their survival and reproductive capacities. When resorts build their properties near coral reefs, human activities damage the sensitive underwater ecosystems in various ways—from harmful chemicals in sunscreen to toxins in sewage effluent.

But there are also unobtrusive ways to watch wildlife, and more sustainable ecosystem management methods. In Australia, where seal viewing is a multi-million-dollar industry, scientists recently recommended that boats keep their distance at 300 feet away from the animals’ colonies , especially during breeding seasons, when adults nurture their pups and often mistake vessels for predators. In St. Augustine, Florida, an eco-conscious tour operator is lobbying the local government to reduce boat speed limits on the water to avoid striking dolphins and baby manatees.

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Moreover, when ecosystems and their inhabitants are managed with care, eco-tourism can bring significant conservation benefits, studies find. On the Maldives, where reefs around some resort spots were designated as marine protected areas, corals grew larger and had fewer diseases compared to the nearby islands where the locals fished and processed fish. In Vietnam, owners of Whale Island Resort established a no-fishing reserve zone when they noticed a decline in local fish and coral populations likely caused by overfishing and destructive fishing techniques like blasting and spraying cyanide in the water. As a result of the no-fishing zone, the biodiversity of the area increased. Other studies also find that when resorts have the finances and motivation to manage their ecologically fragile areas, they can preserve and restore ecosystems.

So while eco-tourism is a double-edged sword, research shows a balance is possible. And the 1.3 billion tourists can tip that balance towards the environmentally responsible development, when they favor resorts and destinations that follow sustainable practices over those that don’t.

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Watery, Peaceful, Wild: The Call of the Mangroves

On Curaçao, visitors can explore the trees’ habitat, where colorful birds roost on tangled branches and trunks, and small paths through the greenery beckon.

The Curaçao Rif Mangrove Park offers guided tours, elevated boardwalks, programs for local schoolchildren and a tiered entrance-fee system for residents and overseas visitors. Credit... Frank Meyer for The New York Times

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By Elisabeth Goodridge

Elisabeth Goodridge is the deputy editor for travel at The New York Times.

• May 8, 2024

It was a sunny afternoon in February at the height of the high season on the Caribbean island of Curaçao, but my partner, Aaren, and I were far from lounging on a white-sand beach, snorkeling over a coral reef or strolling among the Easter-egg-colored buildings of Willemstad, Curaçao’s capital and a UNESCO World Heritage site — typical activities for travelers to this former Dutch colony.

Instead, on a kayak tour with Serlon St Jago, a guide from the Curaçao Rif Mangrove Park , we were learning about the country’s mangrove restoration, and the vital role mangrove habitats play in coastal resilience, protection for marine and bird species, and fighting the effects of climate change.

No poisonous snakes, alligators or large predators live on Curaçao, Mr. St Jago said, reassuring information as we paddled toward a forbidding wall of mangroves lining Piscadera Bay. Up close, the trees were magnificent and cheerful. Colorful birds roosted on tangled branches and trunks, and small paths under the green and occasionally yellow leaves beckoned us to explore. With our kayaks beached, Mr. St Jago pointed out fiddler crabs and mussels, and described differences of the local mangrove species — the red, white and black — and how they adapted to live and propagate where water meets land.

“There’s so much life here,” he said with infectious enthusiasm.

We were the only tourists on the water, but getting more visitors like us interested in mangroves, perhaps even persuading them to replant some of the vital trees themselves, has been a priority of scientists, activists, park rangers and tourism operators on Curaçao in recent years.

The island isn’t alone in its efforts: Similar mangrove-focused work has started around the world, in places like Indonesia , Australia , Belize and Florida , as fragile destinations balance tourism’s growth with the conservation — and restoration — of the natural resources that captivate visitors.

“Coral reefs get all the attention. But mangroves are probably a lot more important,” said Gabby Ahmadia , a vice president with the oceans program at the World Wildlife Fund who oversees the organization’s mangrove science and restoration programs. “My favorite analogy about mangroves is that they are Swiss Army knives, because they do provide so many different benefits and they can do so many different things.”

Though these forests are one degree of separation from the sights and the activities that traditionally draw visitors to the ocean, changing perceptions might be hard. To protect the environment, mangrove kayak tours can be — as are most snorkel, fishing and bird-watching tours offered in other destinations — limited by number, and visitors must be interested in the first place. With their summer reads and beach toys, family traditions and limited vacation days, most tourists might simply agree with the old saying “Life is better at the beach.”

A foundation of life

The twisty branches, trunks and distinctive aboveground roots of mangroves are a stark, complex repudiation of how a child’s drawing portrays a common tree. The roots can arch up, pop up spikelike from the water or form stilts above and under the surface. Adapted to oxygen-poor soil, high salinity and the ebb and flow of an intertidal zone, coastal mangroves thrive where other trees and shrubs would perish. Unless they are yellow, the leaves are green, and some, if you lick them, taste salty.

Mangrove forests can appear impenetrable, muddy, smelly and swampy. For centuries, they have been cleared for firewood, farmland, urban development, aquaculture and, yes, tourism. On Curaçao, mangroves are now found on only 0.012 percent of the island. Globally, more than half of the mangrove forests have been cut down or otherwise destroyed in the past 50 years. Deforestation has slowed — but not stopped — in recent years, and rising sea levels and increased storm activity have done further damage.

But coastal mangroves — there are some 60 species worldwide — are the foundation of life above and below the water. With intricate root systems, they act as nurseries for juvenile fish and other marine life. Mangrove branches and trunks make safe feeding and nesting sites for yellow warblers , tricolored herons and other bird species, reptiles like iguanas, and insects aplenty.

Those strongly anchored roots also protect from flooding, erosion and tidal surges by slowing down seawater and trapping dirt and debris. More crucially, mangrove forests are extraordinary for decreasing the effects of global warming, by absorbing and storing carbon annually at a rate 10 times as great as tropical rainforests. Mangroves, along with other coastal wetlands, “sequester enough carbon each year to offset the burning of over one billion barrels of oil,” according to the Nature Conservancy .

Surreptitious beginnings

Ryan de Jongh, a 53-year-old Curaçao native, activist and tour guide, is the living embodiment of regenerative tourism. He’s an important reason we encountered a lush, thriving ecosystem in Piscadera Bay, and demonstrates how one person can make a difference.

Mr. de Jongh grew up swimming in the bay and watched the area’s mangroves being cleared for fuel and construction. In 2006, he surreptitiously planted the first mangrove tree — a single seedling can mature in around 15 years and lead to an entire thicket — and now, he said, more than 100,000 trees are growing. He made similarly stealthy plantings at other inlets and bays, making himself a local hero in the process.

Mr. de Jongh, who gives kayak tours himself , now works on widespread government-sanctioned restoration projects.

His aim is to eventually plant 1.3 million trees on the island. “I have to transform literally a desert back to green,” he said.

The interior of Curaçao certainly looks like a desert, with a dry, dusty landscape of cactus and other succulents. Along with its closest island neighbors, Aruba and Bonaire, Curaçao is outside the Caribbean’s hurricane belt and receives minimal rainfall. People on the island drink desalinated seawater.

The trade winds bring cooler temperatures. In the 16th century, they also brought Europeans who enslaved and deported the Indigenous population and turned Curaçao into a slaving port. The colonists also planted oranges, sugar cane and other nonnative species, with varying degrees of success, and developed giant salt pans for export, but it was the construction of an oil refinery in 1918 and growing tourism that finally brought widespread jobs. The refinery shut down in 2019 — nine years after Curaçao voted to become a semiautonomous nation from the Netherlands — an event that only emphasized tourism’s importance for Curaçao’s economy. Last year, the island, only 40 miles long, welcomed 1.3 million visitors .

Aaren and I gladly did our part to support the economy: In Willemstad, that meant eating at Plasa Bieu , the Old Market, where individual vendors cook and sell local cuisine. We fought with each other over the fried wahoo and an arepa di pampuna — pumpkin pancake — but we were warned off the cactus soup. “I live here,” said another diner, “and I don’t even eat that.” We also snapped photos, like so many other visitors, while crossing the floating Queen Emma Bridge , and watched it open and close for marine traffic.

We waited in an hourlong, locals-heavy line at De Visserij Piscadera Seafood restaurant (“slaying and filleting” since 2017), where diners choose and purchase their fish fillets before sitting down; we drank oregano punch for the first time (think mint ice tea, but oregano and oh so refreshingly delicious); and we inhaled grilled shrimp and raw fresh tuna.

Further north, we ate “williburgers” — goat burgers — at Marfa’s GoodHangout in Sint Willibrordus, which overlooks an old salt pan that, sadly, the resident flamingoes absented that day, and delighted upon coming across a coral nursery while scuba diving right off the jam-packed Kokomo Beach.

Coral reefs are crucial to Curaçao’s tourism and fishing industries and valued at more than $445 million annually, according to a 2016 economic assessment published by the nonprofit Waitt Institute. And coral reefs, which support roughly 25 percent of all marine life, are enduring cataclysmic bleaching and disease brought on or compounded by climate change.

In the last 10 years, scientists have better understood the symbiosis between coral reefs and mangroves: They don’t need each other to exist, but proximity brings benefits to both ecosystems.

“Working in this field of conservation, you might come in from one entry point and then you realize everything is connected,” said Dr. Ahmadia of the W.W.F. “We can work on coral reefs, but we should be thinking about sea grass beds and mangroves, because they are all really connected. And then of course, they are connected to the human environment.”

One morning, Aaren and I walked through the 30-acre Curaçao Rif Mangrove Park , a short stroll from the center of Willemstad and a shorter one from the island’s cruise ship terminal. Open since 2022, the park offers guided and audio tours, elevated boardwalks, programs for local schoolchildren and a tiered entrance-fee system (guilders and U.S. dollars accepted) for residents and overseas visitors. Some 17,766 people came in 2023, an increase of 14,687 from 2022.

Manfred van Veghel is the new director of the Caribbean Research and Management of Biodiversity Foundation, which oversees the mangrove park and five other national parks. Working with the government of Curaçao, local travel operators and activists like Mr. de Jongh, Dr. van Veghel aims to expand park access, construct an elevated bridge and add a visitor center, among other goals. The efforts are part of his desire to transform Curaçao into more of a nature-based tourist destination.

“We had a record last year and they are pushing to get more,” Dr. van Veghel said of Curaçao’s number of annual visitors. Yet, he said, the beaches are getting full. “So we need to get activities other than going to the beach — and the mangrove park is an excellent activity.”

Mark Spalding is a senior marine scientist with the Nature Conservancy and lead scientist of the Mapping Ocean Wealth initiative , an online tool that applies economic value to coastal ecosystems.

Dr. Spalding said a draw of mangrove activities, like boating and hiking, is that “without having to trek through the Amazon for hours and hours, you can get that sense of wilderness and experience, and also the peace and tranquillity very quickly and very easily.”

“It might only be two hours of your entire holiday,” he said, “but it’s the thing you take home with you — the story you tell.”

Follow New York Times Travel on Instagram and sign up for our weekly Travel Dispatch newsletter to get expert tips on traveling smarter and inspiration for your next vacation. Dreaming up a future getaway or just armchair traveling? Check out our 52 Places to Go in 2024 .

An earlier version of this story misidentified an nongovernmental organization. It is the World Wildlife Fund, not World Wildlife Federation.

How we handle corrections

Elisabeth is the deputy editor for the Travel Desk at The New York Times. More about Elisabeth Goodridge

Open Up Your World

Considering a trip, or just some armchair traveling here are some ideas..

52 Places:  Why do we travel? For food, culture, adventure, natural beauty? Our 2024 list has all those elements, and more .

Mumbai:  Spend 36 hours in this fast-changing Indian city  by exploring ancient caves, catching a concert in a former textile mill and feasting on mangoes.

Kyoto:  The Japanese city’s dry gardens offer spots for quiet contemplation  in an increasingly overtouristed destination.

Iceland:  The country markets itself as a destination to see the northern lights. But they can be elusive, as one writer recently found .

Texas:  Canoeing the Rio Grande near Big Bend National Park can be magical. But as the river dries, it’s getting harder to find where a boat will actually float .

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How does climate change affect coral reefs?

The varied effects of climate change are changing the ocean ; these changes dramatically affect coral reef ecosystems ..

Climate change poses a major threat to coral reefs. Download this infographic | Infographic Text

Climate change is the greatest global threat to coral reef ecosystems. Scientific evidence now clearly indicates that the Earth's atmosphere and ocean are warming, and that these changes are primarily due to greenhouse gases derived from human activities.

As temperatures rise, mass coral  bleaching  events and infectious disease  outbreaks are becoming more frequent. Additionally, carbon dioxide absorbed into the ocean from the atmosphere has already begun to reduce calcification rates in reef-building and reef-associated organisms by altering seawater chemistry through decreases in pH. This process is called  ocean acidification .

Climate change will affect coral reef ecosystems, through sea level rise, changes to the frequency and intensity of tropical storms, and altered ocean circulation patterns. When combined, all of these impacts dramatically alter ecosystem function, as well as the goods and services coral reef ecosystems provide to people around the globe.

Infographic Text

Threats to coral reefs: climate change.

Increased greenhouse gases from human activities result in climate change and ocean acidification. Climate change = ocean change. The world's ocean is a massive sink that absorbs carbon dioxide (CO 2 ). Although this has slowed global warming, it is also changing ocean chemistry.

Climate change dramatically affects coral reef ecosystems

Contributing factors that increase greenhouse gases in the atmosphere include burning fossil fuels for heat and energy, producing some industrial products, raising livestock, fertilizing crops, and deforestation. Climate change leads to:

• A warming ocean: causes thermal stress that contributes to coral bleaching and infectious disease.
• Sea level rise: may lead to increases in sedimentation for reefs located near land-based sources of sediment. Sedimentation runoff can lead to the smothering of coral.
• Changes in storm patterns: leads to stronger and more frequent storms that can cause the destruction of coral reefs.
• Changes in precipitation: increased runoff of freshwater, sediment, and land-based pollutants contribute to algal blooms and cause murky water conditions that reduce light.
• Altered ocean currents: leads to changes in connectivity and temperature regimes that contribute to lack of food for corals and hampers dispersal of coral larvae.
• Ocean acidification (a result of increased CO 2 ): causes a reduction in pH levels which decreases coral growth and structural integrity.

How you can help

Shrink your carbon footprint to reduce greenhouse gases.

• Drive less.
• Reduce, reuse, or recycle.
• Purchase energy-efficient appliances and lightbulbs.
• Print less. Download more. Use less water.

Do your part to help improve overall coral reef condition.

• Reduce the use of lawn and garden chemicals.
• DO NOT dump household chemicals in storm drains.
• Choose sustainable seafood. Visit FishWatch.gov .
• Learn about good reef etiquette and practice it when in the water.
• Volunteer for beach and waterway clean ups.

CORAL REEF THREATS Land-based Pollution

Many serious coral reef ecosystem stressors originate from land-based sources, most notably toxicants, sediments, and nutrients.

CORAL REEF THREATS Overfishing

Many coastal and island communities depend on coral reef fisheries, but overfishing can deplete key reef species and damage coral habitat.

Search Our Facts

More information.

• Download Infographic
• Coral Reef Conservation Program

Last updated: 01/20/23 Author: NOAA How to cite this article

Ocean Heroes: Coral Restoration and Hope for Our Reefs

Corals worldwide are turning white in response to the higher-than-average ocean temperatures this year. So much so that the US National Oceanic and Atmospheric Administration (NOAA) has confirmed there is mass coral stress in the Atlantic, Pacific, and Indian Oceans. But all hope is not lost. As coral reefs face unprecedented threats, coral restoration efforts offer a beacon of hope for their survival. Read on to find out more.

Rising Ocean Temperatures

In August 2023, the global average ocean temperature was at a record high and has been above average almost every day since. This surge in temperature is largely due to the effects of climate change, as the oceans absorb heat-trapping gases emitted from human activities such as burning fossil fuels. Adding to this, the natural climate pattern known as El Niño has also played a role in elevating ocean temperatures since last June

Coral Bleaching Events in 2024

In 2024, coral bleaching events have once again emerged as a pressing concern, affecting some of the world’s most iconic coral reef ecosystems, including the  Great Barrier Reef and the  Caribbean . The severeness of the past events led NOAA to confirm the  fourth worldwide mass bleaching event and the second one within this decade.

These events are becoming more and more frequent, driven by a combination of rising ocean temperatures and environmental stressors, posing significant threats to marine biodiversity and the health of our oceans. 

GET INSPIRED:  Earth Day 2024: 12 Ways to Protect the Planet’s Oceans

Causes of coral bleaching
.

Coral bleaching occurs when corals expel the symbiotic algae (Zooxanthellae) living within their tissues. The Zooxanthellae are responsible for the coral’s color and photosynthesis. The expelling of the algae is causing them to turn white. This phenomenon is primarily triggered by prolonged exposure to elevated sea temperatures, which disrupt the delicate symbiotic relationship between corals and algae. Other stressors, such as  ocean pollution ,  overfishing , and ocean acidification, can exacerbate the bleaching process, further compromising the resilience of coral reef ecosystems.
 

Impact on Coral Reefs

The consequences of coral bleaching can be devastating, with affected corals becoming more susceptible to disease, mortality, and ecosystem degradation. Stressed coral will die in most cases if it experiences temperatures 1 °C above its thermal limit for two months. If water temperatures are 2 °C higher, it can survive for around one month. 

Coral reefs can recover from heat stress but they need time, ideally several years

Bleaching events not only threaten the survival of coral species but also jeopardize the marine organisms that depend on coral reefs for food, shelter, and habitat. Furthermore, coral reefs play a crucial role in coastal protection, shoreline stabilization, and economic livelihoods, making their decline a matter of global concern. 

The Potential of Coral Restoration

Coral restoration plays a vital role in the preservation and restoration of our marine ecosystems. As coral reefs face unprecedented threats, restoration efforts offer a beacon of hope for their survival. 

By rebuilding degraded reefs, coral restoration not only enhances biodiversity but also provides critical habitat for countless marine species

Furthermore, healthy coral reefs contribute to shoreline protection, support fisheries, and drive tourism economies, highlighting their immense ecological, economic, and cultural significance. Ultimately, investing in coral restoration is essential for safeguarding the health and resilience of our oceans for future generations.


LEARN MORE:  Hard Coral vs Soft Coral: What’s the Difference?

One approach to coral restoration can involve the following steps: 

1.First, experts identify degraded reef areas that need restoration. These areas may have been damaged by coral bleaching, pollution, or physical destruction. 

2. The coral fragments or "corals of opportunity" are collected from healthy donor reefs. These fragments are carefully transported to the restoration site.

3. At the restoration site, coral fragments are strategically placed and secured to artificial structures or the existing reef substrate to promote their growth and survival.

4. Over time, these fragments grow, forming new coral colonies that contribute to the overall health and diversity of the reef ecosystem. 

In addition to coral transplantation, coral restoration efforts often involve habitat enhancement, such as the installation of artificial reef structures or the creation of underwater nurseries to propagate coral fragments.
 
 

The Livingseas Foundation

Amidst this ecological crisis, initiatives like Livingseas Asia’s coral restoration project in Padangbai, Bali, emerge as beacons of hope. With over 4,000 reef structures installed and 2,500 square meters of degraded reef restored, this project serves as a testament to the efficacy of restoration endeavors. 

The outcomes have been remarkable, witnessing the resurgence of marine life, from vibrant coral formations to the return of baby sharks

The  Livingseas Foundation employs a multifaceted approach to coral restoration, combining scientific research, community engagement, and innovative technology to maximize the impact of their efforts. By empowering local communities and collaborating with stakeholders, they aim to create sustainable solutions that address the root causes of coral reef degradation.

Love corals?  Become a certified SSI Coral Identification Diver! Insights from the Field

Leon Boey from Livingseas sheds light on the significance of their work: 

"The reefs here in Bali benefit from being situated adjacent to very deep water, rich in nutrients. However, this does not exempt Bali corals from bleaching. We have observed bleaching in shallow, warmer waters on the North coast of Bali, with incidences on the rise.

Through reef restoration, we aim to mitigate the impact of warming waters by constructing reefs slightly deeper into colder water. While corals grow slower due to reduced sunlight, they are shielded from bleaching in cooler waters."  

Continuing the Journey

While the strides made in coral restoration are noteworthy, the journey is far from over. As the project progresses toward its goal of restoring 5 hectares of coral reef, continued support and community engagement are imperative. 

So how can you get involved? Whether through volunteerism, educational initiatives, or fundraising endeavors, you can play a vital part in advancing coral restoration efforts and safeguarding the future of our oceans wherever you live.


 RELATED:  SSI x Edges of Earth: How Sri Lanka’s Divers are Fighting for Their Ocean’s Future

Raising awareness for coral reefs.

By raising awareness, fostering community engagement, and advocating for sustainable marine practices, we can collectively address the root causes of coral bleaching and ensure the long-term viability of coral reefs worldwide. Together, we can make a meaningful difference in the preservation and protection of our oceans’ fragile ecosystems. 

Join the Movement and Make a Difference

You can help ensure a brighter future for coral reefs worldwide. To learn more about coral restoration and how you can get involved, visit the  Livingseas website and follow SSI’s  Blue Oceans Program for updates on upcoming initiatives. 
 

The time to act is now. Join us in preserving and protecting our coral reefs for generations to come. Together, we can turn the tide for our reefs! JOIN THE BLUE OCEANS COMMUNITY TODAY.

Coral reefs are vital to the Maldives. This is how travelers can help restore them.

The coral fragment from the seafloor off the coast of the resort Siyam World Maldives in the Noonu Atoll had a stark contrast. One inch of the coral’s light brown tips was bumpy with living polyps, while the rest was dull white, resembling a dead tree branch.

This coral species, known as acropora hemprichii, grows in the shallow reefs of the Maldives in tapered branches which eventually look like a bush or dome as they grow. 

That piece of coral I spotted broke off from its home likely due to a powerful wave or a careless snorkeler. Once it fell into the sand, it began to die off. To the untrained eye, it seemed like there was no hope for that little coral fragment. 

However, that fragment was far from dead, and the solution to reviving it was simple. 

Coral planting is a simple act of fastening a coral fragment to a metal frame and placing it in a safe, shallow area of the ocean. In mere months, the coral has the potential to flourish once again. As the corals regenerate, the reef becomes more habitable for fish, that swim through and make the frames part of their home. Over 25% of the world’s fish inhabit and get their food from coral reefs. 

As climate change and human activity continue to threaten coral reefs, tropical destinations such as the Maldives are turning to coral restoration initiatives, such as coral planting, to save the ocean, which they heavily rely on for tourism and the local way of life.

Resort guests are encouraged to get involved and protect the very ocean that drew them to the Maldives in the first place – and the call is being answered. According to Booking.com’s Sustainable Travel Report 2023, two-thirds of its 33,000 survey respondents said they “want to leave the places they visit better than when they arrived.” 

“Ninety-nine percent of people come to the Maldives for the ocean because they want to snorkel,” said Mariyam “Thuhu” Thuhufa, a marine biologist at Siyam World Maldives, which offers marine conservation activities for guests including coral planting and lagoon cleanups. “A lot of them do get very curious, a lot of them are keen to understand what they can see and how they can help.”

No one went to the Maldive 50 years ago: Now it's one of the hottest destinations.

How important are coral reefs to the Maldives?

The Maldives is an archipelago of over 1,000 islands sitting mere feet above sea level, which means the country is 99% ocean. And that’s where most of the natural diversity exists, from manta rays in the north to hammerhead sharks in the south.

“Without the ocean, the Maldives just can’t exist,” said Thuhufa. 

All Maldivians depend on the ocean in some way, 71% rely on it for their primary source of income . Maldivians get food from line fishing at coral reefs, such as snapper or emperor fish. Fishing for big game fish like tuna is also the second largest industry , following tourism. 

Without healthy coral reefs, the islands wouldn’t even exist. “If you go to a local island, you’ll see a lot of the houses are built very close to the ocean, right next to the beach,” said Thuhufa. During monsoon season, from May to November, big swells wash away the beaches, but a healthy reef can break the wave energy before it reaches the island, she said.

The fate of coral reefs are in resorts’ hands

To Thuhufa, coral bleaching is one of the most pressing issues for the islands and “something the whole world is experiencing.” The last mass bleaching event , which occurred between 2014 and 2017, saw 15% of the world’s reefs die off. The National Oceanic and Atmospheric Administration predicts a fourth, even worse mass bleaching this year. 

"It's looking like the entirety of the Southern Hemisphere is probably going to bleach this year," said ecologist Derek Manzello, the coordinator of NOAA's Coral Reef Watch which serves as the global monitoring authority on coral bleaching risk.

“We are literally sitting on the cusp of the worst bleaching event in the history of the planet,” he said. Up to 90% of the world’s corals could be lost. 

Story continues below.

Thuhufa recalled an uninhabited island she visited for volunteer research work in high school. “The reef was so beautiful with so many vibrant colors,” she said. After the 2016 bleaching, she returned to the island to see how it was affected. “It was the most devastating thing I’ve seen,” she said. “Everything was bleached, everything was covered in algae.” 

With tourism as the country’s biggest industry, resorts play a vital role in the protection of coral reefs. 

Although construction and increased human activity can damage the fragile ecosystems of reefs, many resorts in the Maldives are working to protect their house reefs by hiring in-house marine biologists and creating nurseries for coral planting. New resorts in the Maldives need to undergo an impact assessment before they can break ground (or sand in their case). 

A 2018 study analyzing the direct impact of seven luxury Maldivian resorts on coral reef health found that the amount of live coral and the size of colonies increased over time if the resort had conservation initiatives in place. 

“Your reef is protected in the sense that there’s no fishing, and guests are told not to touch corals,” Thuhufa said. “A lot more is put into the reefs to keep them healthy.”

However, the study also revealed that resorts with poor management practices and more sedimentation and runoff can harm the reefs. 

What is it like to plant coral?

I tried coral planting for the first time during my stay at Siyam World Maldives, and it was surprisingly easy and engaging. 

Guests can book the experience via the resort app, which they download during check-in, or their resort ambassador can arrange it. 

Coral planting is an emerging type of coral restoration , and since it’s only been done on a small scale, it doesn’t tackle the root of the problem of coral bleaching or warming temperatures. It can, however, help make a specific reef a bit more habitable and spread awareness of the condition of coral reefs. 

The marine biology team met me on the beach with a hexagon-shaped metal frame and two containers filled with coral fragments they found. One by one, we attached the coral pieces to the frame using zip ties, ensuring they were flush with the metal. This way, the coral will merge and regrow over the frame. 

We splashed water on the corals every half hour to ensure they didn’t dry out. When the frame was finished, we placed it in a shallow snorkeling area to join over 100 other coral frames. The marine biology team checked on the frames and removed any algae so the coral could breathe. The frames come in shapes like hearts or rays but remain open for fish to swim through. 

Although coral is sensitive, it’s also a resilient animal – yes, corals are technically considered tiny animals since, unlike plants, they don’t make their own food. Sometimes as small as a pencil tip, polyps make up the coral structure we see and attach to rocks, the seabed or in this case, a metal frame. 

Depending on the species of coral – and there are hundreds – the coral can take around five months to attach to the frame and then a few more months to regrow, according to Thuhufa. 

As I dove underwater to explore the coral nursery, I noticed batfish, triggerfish and other colorful reef fish seamlessly swimming between anemones and among the coral frames. 

Kathleen Wong is a travel reporter for USA TODAY based in Hawaii. You can reach her at [email protected] .

Contributing: Reuters

Coral Reefs 101: Everything You Need to Know

Quick key facts.

• Roughly 20 to 25 percent of fish, molluscs and crustaceans in developing countries come from coral reefs.
• Corals grow an estimated 0.39 inches per year - one of the slowest growth rates of any animal on Earth.
• A few square kilometers of coral reef takes roughly a million years to grow.
• At nearly 135,136 square miles, Australia's Great Barrier Reef is the largest structure in the world made by living organisms, and can be seen from outer space.
• The Great Barrier Reef is actually made up of nearly 3,000 separate reefs.
• Corals like strong currents because they circulate seawater quickly, keeping the temperature - especially at the surface - cooler and more stable.

Scientists have predicted that by 2055, 90 percent of coral reefs worldwide will experience severe annual bleaching.

What Are ‘Coral Reefs'?

Coral reefs consist of hundreds of thousands of coral polyps - marine animal invertebrates with hard calcium carbonate exoskeletons. Different species grow to form a variety of measurements and shapes - from the size of a pinhead to as large as a foot in diameter.

Coral colonies are habitats and breeding grounds for many marine species, including sharks, manatees, dugongs, fish, sea urchins, molluscs and sea sponges.

Types of Coral Reefs

There are three main types of coral reefs : fringing, barrier and atoll , the most common of which is the fringing reef. A fringing reef extends from the shore out into the ocean , forming a border along the coastline and nearby islands.

Fringing reefs grow more successfully on rising or stable shorelines. They consist of the reef flat, also known as the "back reef," and the reef slope, or "fore reef." The fore reef is the part closest to the sea, while the back reef makes up the widest portion of the reef. Corals in a fringing reef grow upward toward the ocean's surface or outward in the direction of the sea.

The planet's largest fringing reef is the Ningaloo Reef, which extends 155 miles along Australia's western coast . It is home to 300 coral species, 500 fish species, 600 species of mollusks and a host of other sea life and marine invertebrates.

The largest type of coral reef, barrier reefs border the continental shelf like fringing reefs, but grow further out in a linear fashion, separated by a frequently deep lagoon of water. Shallow parts of the reef sometimes touch the surface, forming a "barrier" that can impede boat traffic.

Barrier reefs can be hundreds of miles long and several miles wide, but are not nearly as common as the two other main types of reefs.

Probably the best known barrier reef in the world, the Great Barrier Reef is located off the coast of Australia in the Coral Sea. The Great Barrier Reef is Earth's largest coral reef system - rather than one reef, it is actually made up of nearly 3,000 separate reefs. It extends 1,429 miles over an area of nearly 135,136 square miles. The Great Barrier Reef is so extensive, it can be spotted from space.

Small islands on the Three Brothers group on the western Great Chagos Bank. Brian W. Bowen

An atoll is actually a fringing reef that once surrounded a volcano, but as the volcano sank below sea-level, the corals continued to grow, becoming the only thing visible from the surface.

Atolls are typically circular, oval or shaped like a horseshoe and have a sandy, shallow lagoon in the middle. The coral rim of an atoll may or may not entirely surround the lagoon, but if it does, little or no sea water will move in and out.

The 4,881 square-mile Great Chagos Bank, located in the Indian Ocean, is the largest atoll on the planet. It consists of the protected Eagle Islands, Danger Island, Nelson Island and the Three Brothers islands.

Why Are Coral Reefs Important? Why Do They Matter?

Support one-quarter of all marine species.

It is estimated that a quarter of marine species are supported by coral reef ecosystems , though reefs do not even comprise one percent of the seafloor.

These cradles of biodiversity act as habitat, feeding, reproduction and nursery grounds for more than a million marine species.

According to the International Union for Conservation of Nature (IUCN), many of the species living within the coral reef ecosystem have been listed under the IUCN Red List of Threatened Species , including one-third of reef-building coral species , whale sharks, the giant clam and the hawksbill sea turtle .

Protect Coastlines From Storms, Flooding and Erosion

Coral reefs act as natural barriers that protect coastlines from erosion. Corals grow laterally across the seabed and up between the seafloor and the water's surface. This stabilizes the seabed and absorbs wave energy and elements from the open ocean. Some coral reefs are capable of absorbing more than 95 percent of wave energy.

The buffer of a reef also reduces storm damage from cyclones, as well as some of the energy of tsunamis.

Reefs not only protect the shoreline and its human developments, but the ecosystems - like lagoons containing seagrass meadows - that lie between the coast and the reefs themselves.

Clean the Water

A great number of corals and sponges consume nutrients from particulate matter through the process of filter feeding . This helps prevent harmful particles from settling on the ocean floor and keeps waters clear.

Act as Cultural Heritage Sites

Corals have cultural importance for many of the world's coastal communities, such as the Torres Strait Islanders with the Great Barrier Reef, and Hawaiians, for whom the coral polyp holds significance in traditional stories.

Even for those who don't live close to the sea, coral reefs are associated with the vast and colorful scope of marine biodiversity on our planet. Visits to coral reefs result in millions of trips each year and billions in tourism dollars for local communities.

Provide Food, Income and Recreation for Humans

Roughly six million fishers count on coral reefs for the economic goods and services they provide. In the U.S., their annual commercial value is estimated to be more than $100 million, while the estimated economic value globally is $375 billion.

Hundreds of millions of people rely on coral reefs for their resources, protection and tourism. Many of the people who depend on the reefs are from island nations and developing countries and take food directly from the reef's waters.

Roughly 20 to 25 percent of fish, molluscs and crustaceans in developing countries come from coral reefs, 70 to 90 percent in Southeast Asian nations and 10 percent worldwide.

Snorkelers and divers flock to coral reefs to admire the stunning array of colorful species, with more than 100 countries reaping the benefits of reef tourism.

For many small island nations , coral reefs are responsible for most of their new economic development.

Responsibly managed reefs that limit pollution and harm from tourists can help provide sources of income for developing coastal countries.

A Source of Medicine

Corals spend their lives fixed to one spot. In order to protect themselves, they have evolved chemicals to defend against other organisms threatening their space. Some of the chemicals have been studied by scientists for their medicinal benefits related to cell aging and certain types of cancer. The skeleton of a coral is similar to human bones, and has been used for bone grafts for decades.

Only a small number of reef organisms have been tested and analyzed, so there may be undiscovered pharmaceutical remedies hiding in coral reef waters.

Challenges Facing Coral Reefs

Ocean warming & acidification.

The greatest threats to coral reefs worldwide are increasing ocean temperatures due to climate change and the resulting changes in ocean chemistry. Warmer temperatures are causing oceans to heat up, while atmospheric carbon gas dissolves into the water, causing acidification .

Atmospheric and oceanic carbon dioxide are in equilibrium with each other, so when carbon concentrations in the atmosphere increase, so do those in seawater. When carbon enters the ocean, it forms carbonic acid - a compound of carbon, hydrogen and oxygen - increasing the water's acidity.

Roughly a quarter of the carbon emitted from humans burning fossil fuels is absorbed by the ocean. The acidity of the ocean has increased about 30 percent since the Industrial Revolution - the fastest rate in millions of years. By the end of the century, ocean acidity levels are predicted to be 40 percent higher than they are now.

When ocean acidity increases, the amount of ions and salts corals need to form calcium carbonate are reduced, leading to slower coral growth. The decrease in coral growth affects species to differing degrees, but severe acidification can cause some coral skeletons to dissolve.

Runoff can lead to nutrient enrichment, increasing the acidity of coastal waters in local areas and worsening ocean acidification.

Microscopic algae grow on corals in a symbiotic relationship, providing the corals with food. The algae are expelled by their coral hosts when they become stressed due to increased ocean temperatures. This puts further strain on the corals and exposes their white calcium carbonate structure - a process called coral bleaching .

Prolonged or severe bleaching can leave coral colonies vulnerable to additional threats like infectious diseases.

Research has shown that when corals are exposed to high carbon dioxide levels, their bleaching risk increases by as much as 50 percent.

Human Activities

Since most coral reefs are near the shoreline in shallow water, they face numerous threats and are especially vulnerable to human activities. Many human actions that degrade corals are indirect - like pollutants, nutrients and microplastics - while others such as overfishing and coral harvesting are more direct.

Overfishing

Nature is about balance, so anything that involves the adding or subtracting of too many nutrients or resources disrupts its equilibrium - not just in the present, but it can lead to cascading effects and change the structure of the ecosystem.

Overfishing depletes populations of grazing fish who help keep corals from becoming overgrown with algae. An overabundance of algae is food for microbes and encourages their growth. The microbes then deplete corals' oxygen and introduce diseases into their environment. Less corals mean more algae, which further endanger the remaining corals.

The use of explosives to kill fish - blast fishing - is an especially destructive practice that can physically damage not only fish, but corals too.

Stormwater and sewage that has not been treated properly, as well as livestock runoff, can result in pathogens ending up in the ocean. Parasites and bacteria from fecal contamination - though rare - can infect corals, particularly if they are already experiencing environmental stressors.

Healthy ecosystems do sometimes experience outbreaks of coral disease, but the addition of pollution containing pathogens can make the intensity and frequency worse.

Excessive amounts of nutrients - such as phosphorus and nitrogen from sewage discharge, animal waste and residential and agricultural fertilizer and pesticides - can cause algal growth that takes away from corals' oxygen supply, occludes sunlight and can lead to bleaching. This can cause an imbalance in the ecosystem as well as the growth of fungi and bacteria that can be unhealthy for corals.

Toxic Substances

Toxic substances like chemicals and metals - such as lead, mercury, oxybenzone, dioxin and polychlorobiphenyls (PCBs) - that come from sunscreens , industrial discharge and mining can affect the growth rate, feeding, reproduction and defense responses of corals.

Trash and Microplastics

Microplastics can end up in waterways and the ocean from many sources, including old fishing gear , plastic bags , plastic bottles and the microbeads used in personal care products and cosmetics .

This marine debris can get caught on corals and damage or break them, block sunlight and kill or entangle reef organisms. Microplastics and beads can be eaten by corals, sea turtles, fish and other marine life, poisoning them with toxins and blocking their digestive tracts.

Habitat Destruction

Coastal development, ship groundings and anchors, quarrying, dredging, harmful fishing practices and the touching or removing of corals during recreation or harvesting can all lead to physical damage and destruction of coral habitat.

Sedimentation

Agriculture, coastal development, forestry and urban stormwater runoff can cause the deposit of sediments onto reefs. This sedimentation can smother corals, as well as disrupt their ability to grow, feed and reproduce.

Coral Harvesting

Collecting live corals to be used to make jewelry and curios and for use in aquariums can result in the overharvesting of certain species, as well as the destruction of coral reef habitat.

What Can We Do to Support Coral Reefs?

As a society.

The most important thing society can do to help corals and reef ecosystems is to reduce the use of fossil fuels, as they are the cause of global heating and ocean warming , which leads to ocean acidification and coral bleaching.

The U.S. Environmental Protection Agency is in charge of implementing Clean Water Act programs to reduce the pollution that degrades coastal waters and coral habitat. The natural resilience of sensitive reef systems will be enhanced by people reducing stressors to reefs in their local communities.

Another societal practice that is essential to coral reefs is to strictly manage coastal development, as it can erode the shoreline, lead to sediment deposits and encourage the overvisitation of coral reefs. It is also important that mining and agricultural runoff be limited or prohibited, as metals and chemicals from their processes can make their way into waterways and the ocean, causing damage to corals.

Overfishing must cease and sustainable fisheries be supported to ensure marine life and the balance of the coral reef ecosystem are not disrupted. Managing tourism is necessary to limit overexposure and damage to reefs. At the same time, laws prohibiting sunscreens that are toxic to corals and reef animals need to be passed and enforced.

In Our Own Lives?

There are many things individuals can do to support the health of coral reefs. When visiting reefs, be sure not to touch corals or any marine life and don't take anything away from the reef system when diving or snorkeling in the area. Reduce your use of sunscreen by wearing a rash guard or long-sleeved shirt to prevent sunburn - if you do use sunscreen, always make sure it's reef safe.

In your everyday life, save as much energy as possible by turning off lights and using energy-efficient appliances; eat sustainable seafood; use environmentally-friendly forms of transportation; reduce stormwater runoff and use green alternatives to pesticides and toxic fertilizers, since they can be washed into the sewer system and end up in rivers and the ocean; reduce your use of plastic - microplastics have become ubiquitous in every environment on Earth and can damage corals and other reef life; when buying fish for an aquarium, be sure they have been collected sustainably and don't purchase living coral; and recycle as much as possible and dispose of trash properly so it does not make its way into waterways and the ocean.

Coral reefs are some of the most beautiful ecosystems on Earth. Their vast array of marine life of all colors, shapes and sizes is an incredible testament to our planet's biodiversity. Global heating has led to ocean warming, which affects sensitive corals and has increased detrimental bleaching. Coastal development, sedimentation and toxic chemicals are all threats to reef ecosystems and must be limited or prohibited to protect them.

Everyone has a part to play in the protection of coral reefs - the decisions we make in how we travel , eat, buy, garden and conduct ourselves when visiting reef habitats all affect these unique ecosystems. Working together to protect coral reefs is the best chance they have of surviving the global climate crisis .

This article originally appeared on EcoWatch and was syndicated by MediaFeed.

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Why some corals are better off dead

As scientists rush to save ailing corals elsewhere, in Venezuela locals are trying to kill off this stinky variety.

VALLE SECO, Venezuela — Estrella Villamizar grabbed the soft red and white coral by its stem and hacked it off with a blow of her wooden knife before tossing it in a bucket with other pieces she’d already ripped out of the Caribbean waters lapping against this deserted beach.

On the sea bed, stretching for a distance as far as the eye could see, a blanket of the dark coral swayed in the warm current.

As ocean temperatures reach record highs, scientists elsewhere have been rushing to save reefs , moving coral to land nurseries to preserve it and dreaming up novel ways to cool it off at sea. But here in Venezuela, reefs face a different kind of lethal threat: Unomia stolonifera , an invasive coral species that is smothering native varieties.

Hailing from Indonesia, the slimy cauliflower-looking coral has expanded across the shores of four states in Venezuela, covering at least some 1,000 square miles.

“At this point, it is almost certain that it will invade the entirety of the Caribbean,” says Villamizar, a tropical ecology professor at the Central University of Venezuela.

She is part of a team of biologists, chemists, villagers, and entrepreneurs fighting to keep Unomia at bay. It’s a battle they’re waging with limited tools. Years of economic duress have hollowed out the Latin American country’s research centers. Government budgets to do this kind of work, meanwhile, are nonexistent. So they have come up with out-of-the-box approaches, from creating underwater hacking machines to finding ways to turn the slimy coral into a usable product, making its harvesting a profitable business.

If left unchecked, Unomia could decimate local reefs and the animals and plants that depend on it.

Already, it’s devastating local villages. Fishers report that last year was one of their worst. Israel Sosa, a longtime fisherman in these waters, says his haul has dropped from about 33,000 pounds of Albacore fish in a 48-hour shift just a few years ago to closer to 220 pounds.

“If it kills the native coral, it would completely end the coast’s life,” says 55-year-old César Jove, who spends his afternoons cleaning the beach for tourists about 310 miles away, where Unomia made its first appearance more than a decade ago.

Ground zero

Marine biologist Juan Pedro Ruiz-Allais was the first to spot Unomia in 2007 inside Mochima National Park in northeastern Venezuela, where he spent most of his childhood. As soon as he spotted the tentacle-looking stems, he realized it was not a native species.

According to local fishermen, an aquarist allegedly introduced the coral to the area, hoping to harvest it and sell it as fish tank decoration. In its native Indonesia, Unomia has natural predators such as sea slugs that keep it in check. But without a natural predator outside of the Indo-Pacific, it’s spiraled out of control in Venezuela, Ruiz-Allais said.

Surveys he conducted along with other researchers showed Unomia taking over other species of coral and seagrass beds that serve as food sources and nurseries for fish and other animals. Some of these areas were already battered by overfishing and pollution.

Ruiz-Allais also found the invasive coral has proved to be more resilient than its native counterparts, thriving in a much broader range of temperatures and light.

The researcher said he alerted the government of the invasive species years ago but didn’t get a response.

The Ministry of Ecosocialism did not respond to a request for comment. Several people familiar with the matter said the government has barred researchers who depend on it for funding from talking about Unomia.

So Ruiz-Allais created a nonprofit, the Unomia Project, that has focused on educating citizens on how to identify the invasive coral and prevent it from spreading. They advise fishers to clean their nets and beach goers to wash bathing suits and diving gear that came into contact with Unomia.

Their budget, made up mostly of donations, hasn’t stretched far enough to cover a full-fledged census of the invaders, never mind eradicating them.

Based on the group’s observations, Ruiz-Allais calculates that more than 100 kilometers — or more than 60 miles — of shore, and about 8 million square meters — three square miles — of seabed are covered by Unomia in Mochima National Park alone.

Now, Ruiz-Allais fears that Venezuelan oil vessels are transporting the invasive coral to Cuba, where it started showing up last year , according to Cuban marine biologist José Espinosa Sáez.

In Valle Seco, some locals who depend on fishing and tourism have taken to ripping it out by hand using makeshift wooden knives.

Aside from looking like a slobbery dark carpet, Unomia has a strong rotten fish smell. “It’s disgusting, sometimes even the fish smell like it and you have to wash them with lemon and vinegar to get rid of the stench,” Jove said, adding that the coral also puts off tourists.

But locals’ efforts could backfire. The small pieces of Unomia left behind can grow into a new colony, said Mariano Oñoro, a coordinator with the Unomia Project.

A coral gun

To avoid that problem, Jorge García, an industrial designer and boat captain, has been working on developing machines to help save native corals.

On a recent afternoon, García aimed his contraption, an ultrasound gun, at a cluster of Unomia growing on a native coral. After he pulled the trigger, an ultrasound wave unmoored a cluster of the invasive species before García sucked it up with another machine, releasing a strong fishy smell.

García became involved in the quest to fight Unomia after learning about its devastating effects from Ruiz-Allais and his team. Given his background as an industrial designer specializing in machine building, he decided to come up with better ways to remove Unomia.

García, who owns a vessel rebuilding company, Grenyachts, also had the funds to do it, overcoming another major obstacle in fighting Unomia. So far, he has spent almost $1 million out of pocket, which he expects to make back by renting out the machinery to international organizations and governments that may want to remove Unomia in the future. That includes Venezuelan officials, who already granted him permission to carry out some of his research.

With his current setup, he can clean one square meter, or around 10 square feet, of Unomia-covered native coral in one minute, compared to the hour or more it would take a professional diver to do it.

“This is a fight for decades, generations,” he said.

An invasive business

Meanwhile, Project Coralien, a group of marine biologists and chemists that has received some government funding to research Unomia, is looking at another way of overcoming the lack of funds. The group is trying to find a commercial use for the coral, so harvesting it becomes a business.

One idea is to make it into a waterproofing material or a fluorescent material similar to rhodamine, a dye used in biotechnology. So far, these ideas seem promising, but to test them out, the team needs a molecular magnetic resonance imaging machine to separate Unomia’s chemical compounds and determine their specific uses.

Rubén Machado, who heads the atomic energy department at the Venezuelan Institute for Scientific Research, remembers a time when the country had seven such machines. Now they have none. Once the government defunded research institutions, the equipment was not maintained and became obsolete. Looters vandalized and damaged one of the machines.

Replacing the equipment is expensive — and complicated. Foreign companies are subject to sanctions when doing business in Venezuela, so its makers are reluctant to sell it to the researchers. Álvaro Álvarez, Project Coralien’s chief chemist, wrote a letter to the United Nations authorities who oversee sanctions, asking for an exception. So far, he has received no answer.

Machado says his group will keep trying because he believes making Unomia profitable is the only way to eradicate it.

“The possibility is there,” he said. “But we need to be able to prove it.”

This story was produced in partnership with the Pulitzer Center.