Introduction
The Mesoamerican Reef is the second largest barrier reef in the world, stretching over 1000 kilometers from Mexico’s Yucatan Peninsula to the Bay Islands in Honduras and serves a variety of functions, including protecting the land from natural disasters, providing a source of food, and creating economic growth (Helganson, 2017). In addition to an economic and social asset, the Mesoamerican Reef is a UNESCO World Heritage Site and is naturally very beautiful with mesmerizing coral, stunning turquoise water, and immense biodiversity, described by Charles Darwin as being “the most remarkable reef in the West Indies” (Root, 2018). However, the reef is greatly affected by climate change, making it especially susceptible to coral bleaching, eutrophication, and ocean acidification, all of which damage the structure of the reef and endanger aquatic organisms, placing the reef on UNESCO’s danger list in 2009 (Root, 2018). With 80% off the coast of Honduras, 59% in Belize, and large quantities of reef in Mexico and Guatemala showing signs of bleaching, the damage of climate change is already critical (Helganson, 2017).
This is especially a problem to these nations because economies of Latin America rely on the reef for tourism and resources, an example being Belize where the reef provides $559 million per year in goods and services and employs over 50% of the people (Nawaz et al, 2017). Most damage to the Mesoamerican Reef is caused by human action, and humans are most affected by this damage. Climate change and fossil fuels cause coral bleaching, which is caused by rising ocean temperatures leading to expulsion of zooxanthella that protects coral from the sun and provides it with energy (CoralWatch, 2018), and ocean acidification, which results from ocean surfaces absorbing carbon dioxide released from fossil fuels (Ocean Changes, 2011). Climate change and fossil fuels negatively affect the health of the Mesoamerican Reef in Central America by causing coral bleaching and ocean acidification, which negatively impacts the reef-based economies of Central America.
Background
The Mesoamerican reef is susceptible to damage caused by climate change. Climate change not only causes environmental damage on the reef and aquatic ecosystem, but also on the social structure and economy of Central American reef-based economies such as Belize, Mexico, and Honduras. Coral bleaching is caused by rising ocean temperatures (CoralWatch, 2018). Coral, an animal, has a mutually symbiotic relationship with zooxanthellae, a type of algae that performs photosynthesis and provides coral with energy (Davy, 2018). In return, the algae receive ammonia and phosphate so that they can complete the nitrogen cycle (CoralWatch, 2018). However, the zooxanthellae are destabilized by severe stress, such as high ocean temperatures. This impairs the zooxanthellae’s ability to perform photosynthesis because of photosystem degradation and the increase of the photosynthetic apparatus, where photosynthesis takes place, which occurs when ocean temperatures rise (Davy, 2018). The zooxanthellae release excess amounts of oxygen, forcing the coral to expel it, despite needing it for energy and oxygen. This initiates coral bleaching (Davy, 2018). Coral bleaching is indicated by the color of the coral. Healthy coral should appear brown when it has adequate amounts of algae that allow it to survive. However, when the algae are expelled because of rising ocean temperatures, the calcium carbonate skeleton of the coral is exposed, and the coral appears white (CoralWatch, 2018). The excess oxygen released by zooxanthellae causes macroalgae populations to rapidly grow and cover coral, which blocks sunlight from reaching the dwindling number of zooxanthellae that need sunlight to survive and perform photosynthesis, posing an even bigger threat to coral (Blanco & Cho-Ricketts, 2015). Coral takes years to even begin to recover from bleaching.
Additionally, the burning of fossil fuels poses large threats to the Mesoamerican Reef health. Fossil fuels emit carbon dioxide into the atmosphere. About 25% of this carbon dioxide emitted by humans is absorbed by the ocean, which causes the pH of the ocean to become more acidic (Hoegh-Guldberg et al., 2007). This carbon dioxide absorbed reacts with water to form carbonic acid that dissolves to form bicarbonate ions and protons which react with carbonate ions and reduce the availability of carbonate to organisms that need it to complete the carbon cycle (Hoegh-Guldberg et al., 2007). Since less carbonate is available, coral is weakened, and the rate of calcification is increased since coral cover consists largely of carbonate (Davy, 2018). Because of fossil fuel emissions, the pH of the ocean is expected to change by .4, in which coral could not survive (Hoegh-Guldberg et al, 2007). In the 20th century, fossil fuels and climate change caused ocean temperatures to rise .74 degrees C and 17cm, and the concentration of carbon dioxide in earth’s atmosphere to rise 80ppm, which is unsustainable for coral and aquatic ecosystems (Hoegh-Guldberg et al., 2007). Coral reefs provide homes for hundreds of aquatic organisms, food sources for fish and humans alike, and valuable resources. Fossil fuel emissions and climate change have a lasting detrimental impact on reefs and ecosystems.
Description of Environmental Impacts
Rising ocean temperatures and ocean acidity have very negative environmental impacts. A prime example is Turneffe Atoll Marine Reserve, the largest area of the Mesoamerican reef in Belize. This area of the reef is known for its abundance of fish and coral that was once one of the healthiest reefs in the world, but recent environmental changes have caused massive damage (Blanco & Cho-Ricketts, 2015). This area of the reef has seen a decrease from 28.2% to .9% in turf algae (zooxanthella) and a major increase in macroalgae (from 25% to 40%) that blocks sunlight from reaching zooxanthella (Blanco & Cho-Ricketts, 2015). The coral cover is less than 15% of the reef, which makes coral more susceptible to bleaching since coral cover functions in blocking harmful UV rays. However, the algae cover is over 50% as a result of excess nutrients and more sunlight (Blanco & Cho-Ricketts, 2015). Sea urchins, which are an indicator of reef health since they need healthy coral as a habitat to survive, had a very low abundance, placing reef health of Turneffe Atoll in the critical health level. Additionally, the reef had few commercial fish present, meaning that fish native to the reef were migrating or dying as a result of the reef condition, which was characterized as poor due to the critical levels of macroalgae cover and critical amounts of fish (Blanco & Cho-Ricketts, 2015). This reef is a prime tourist destination in Belize for recreational activities like scuba diving and snorkeling, so the condition of the reef affects more than just environmental health. Because of the high incidence of coral bleaching, fish leave the reef and algae overgrows since fewer fish control the population size, destroying the ecosystem (Root, 2018).
Over 80% of sites on the Mesoamerican reef have less than 20% coral cover because of coral bleaching, hurricane damage, and anthropogenic stressors that include tourism to the area and human action such as overfishing (Rioja-Nieto et al, 2018). Coral cover has changed drastically in the past few decades- in the 1980s, nearly 55% of sites on the Mesoamerican reef had a coral cover over 20%-but now coral cover is around 15% on average (Rioja-Nieto et al, 2018). Coral cover is the amount of live coral on the surface of the reef. It is crucial to reef health as it provides habitats for many aquatic organisms, protection from harmful UV rays, hosts algae that performs photosynthesis, releasing oxygen into the ocean and maintaining nitrogen and carbon levels, and providing food and protection for organisms (CoralWatch, 2018). Coral bleaching not only weakens the coral structure but inhibits its ability to reproduce, so the loss of coral will continue to decline if action isn’t taken (Rioja-Nieto et al., 2018). The loss of coral cover due to bleaching severely affects fish communities on the Mesoamerican Reef- the mean density of fish has decreased drastically in the past few decades and GIS shows drastically more coverage by macroalgae in the past decade (Rioja-Nieto et al, 2018) which is bad because macroalgae blocks sunlight. The image to the left shows how macroalgae has increased drastically in Cozumel, an area of the Mesoamerican Reef off the coast of Mexico. This macroalgae blocks sunlight and causes decreases in coral cover. The environmental impact of climate change and fossil fuel emissions is devastating to the Mesoamerican Reef- fish populations are dropping, sea grass and macroalgae is growing rapidly, and loss of coral cover is destroying habitats and food sources. This causes changes in the food chain, leading to many predators losing their prey and the loss of larger reef animals such as sharks that serve a vital role in the aquatic ecosystem (Rioja-Nieto et al., 2018). Ultimately, the impacts of coral bleaching and ocean acidification decrease biodiversity which limits the availability of food and resources to humans and eliminates populations that control macroalgae growth, so rapid growth and coral degradation continues and is unable to recover.
Description of Economic Impact
The economies of countries on the Mesoamerican Reef are dependent on the reef for tourism and fish. The Mesoamerican reef provides up to $559million/year to Belize and employs 50% of people (Nawaz et al, 2017), with the majority of the country’s GDP coming directly from resources provided by the reef. Scuba diving is a $5 billion industry in the Caribbean and is wholly dependent on coral reefs and coral reefs have an estimated value of $1million per hectare per year, attracting over 25million visitors per year (Agardy et al, 2018). Shark diving generates a revenue of $780 million per year but sharks are an indicator of reef health- poor reefs have few sharks. The Mesoamerican reef is seeing a large decline in shark presence, which negatively affects both the food chain and the economy (Agardy et al, 2018). Total landing of coral reef fisheries of Mesoamerican reef is 64% higher than can be sustained; an extra 156,000 km of coral reef is needed to support population growth (Hoegh-Guldberg et al, 2007). Coral reefs are necessary to create sand and protect shorelines from storms, offer recreational and tourism opportunities such as scuba diving and sailing, providing habitats for commercial fish, and grow the ecotourism industry; sustainable fisheries create jobs and food, marine ecosystems and mangroves absorb greenhouse gases, and reefs increase biodiversity. The Central American economy is primarily fueled by the reef through food and tourism and Central American economies have seen a growth of 7.7% in the last decade solely because of tourism, which has contributed $364 billion of the region’s GDP. (Agardy et al, 2018). The loss of assets from the Mesoamerican Reef would destroy the region’s economy with millions of people losing their jobs due to declines in fisheries and loss of tourism because of poor scuba diving and a degraded aquatic environment. The reef is crucial for the economic success of coastal nations, and since the globalized world economy is so linked, economic loss of the Mesoamerican reef region would not just affect Central American countries; it would affect the whole world economy. Loss of the reef and eroded beaches would cause fewer tourists to visit the region and loss of resources such as fish and medicines found in the reef would affect the whole world (CoralWatch, 2018).
Description of Social Impacts
As climate change continues to hurt the Mesoamerican Reef and rehabilitation is slow if not stagnant, socioeconomic consequences are expected to worsen. As carbon dioxide levels increase, they become unmanageable and unrepairable damage at 500ppm. Climate change alters the draw of coral reefs to tourists and Central American countries have low capacity to respond to climate change, but their economies will crash if the reefs deteriorate (Hoegh-Guldberg et al., 2017). An important role that the Mesoamerican Reef plays as a barrier reef is protecting land from natural disasters. When it is strong, the reef stops tsunamis from destroying the shore and weakens hurricanes. This is important because Central American countries are developing, so tend to have weak infrastructure, especially on the coast (Cheal et al., 2017). However, rising ocean temperatures cause natural disasters such as cyclones and hurricanes to become more intense, and the weakening reef system has little chance of defending against these natural disasters (Cheal et al, 2017). Natural disasters pose a threat to both people on land and the reef itself, posing a significant threat to biodiversity since fish abundance decreased by 52% as a result of reef threats including cyclones. Natural disasters are stronger and more dangerous because of weaker coral barriers and higher ocean temps, which poses a large threat to the communities that live and rely on the ocean for their livelihood (Cheal et al, 2017). This means that coral bleaching forces people to relocate and places them at a higher risk of natural disaster.
Reefs provide a critical role in protecting coastlines from storms, but decreasing rates of reef accretion, increasing rates of bio erosion, and rising sea levels lead to stronger storms which jeopardize costal barriers, putting people and infrastructure at risk of storm impacts, specifically cyclones and hurricanes (Hoegh-Guldberg et al, 2007). Losses of beach sand which is formed in many cases by coral reefs will occur as a result of ocean acidification and thermal stresses, which leads to erosion and less stable beaches, as well as inhibits organisms such as sea turtles that need the beach to reproduce, and hurts the economy since over 50% of tourism in Central America is to beaches (Blanco & Cho-Ricketts, 2015). So, climate change and fossil fuels destroying coral cover weakens the barrier against natural disasters, putting lives at risk and forcing people to relocate. Additionally, coral creates beaches which are a major draw for tourists, and the loss of coral cover causes erosion, which dispels tourists, thus hurting the economy. For the millions of people that rely on the reef, their lives are completely changing because of climate change.
Discussion
Action must be taken to prevent further damage of the Mesoamerican Reef and protect the economies and individuals’ livelihoods of Central American countries. The Smithsonian Healthy Reefs for Healthy People Initiative (HRI) releases a report every other year on the state of the Mesoamerican Reef as well as plans for protecting and preserving the reef (Frost, 2018). This year, the report announced that coral cover has increased by around 38% since 2006, despite increasing ocean acidification and coral bleaching events (Frost, 2018). HRI attributes this growth in coral cover to the protection of certain species that are critical for preserving reef health, such as parrotfish. Parrotfish eat algae that grows on coral cover, thus reducing the algal population that has been rapidly growing as a result of ocean acidification and rising ocean temperatures (Frost, 2018). These fish are now protected from fishing in Belize, Honduras, and Guatemala, and the results have been very positive for reef health. HRI is now studying whether restoring populations of the Caribbean King Crab and the Diadema sea urchin will decrease macroalgae and increase coral cover (Frost, 2018). Thus, reserving biodiversity is crucial for protecting the Mesoamerican Reef and the economies and social structure of Guatemala, Mexico, Honduras, and Belize.
Another necessary action is the establishment of Marine Protected Areas (MPAs) to protect reefs, limit over-fishing, and give coral time to recover from bleaching. Turneffe Atoll is a marine reserve in hopes of restoring it to its healthy, abundant state (Blanco & Cho-Ricketts, 2015). Restrictions on fishing would be effective at maintaining biodiversity as currently, coral reefs are overfished (Hoegh-Guldberg et al, 2007). There are currently 47 MPAs covering over 34,000 square km on the Mesoamerican Reef, but only 3% of this area is completely closed off from fishing (Frost, 2018). The HRI found that the majority of large fish and sharks live in these non-fishing areas and the majority of reproduction occurs here. The safety of non-fishing MPAs for reproduction caused the Nassau grouper population to recover after being almost completely overfished (Frost, 2018). By establishing more non-fishing MPAs, populations and coral can continue to recover from damage from climate change and overfishing, thus strengthening coral reef ecosystems and further protecting coastal land from storm damage and erosion.
Central American countries have taken many political actions to protect the Mesoamerican Reef. In December of 2017, Belize became the first country in the world to vote “no” to offshore oil exploration and drilling to protect the reef (Root, 2018). Belize also issued an environmental tax that goes directly to reef conservation efforts, increased no-take fishing zones from 3 to 10%, and made plans to ban single-use plastic and Styrofoam products by Earth dDy of 2019 (Root, 2018). Other nations that rely on the reef have followed in Belize’s footsteps, with Mexico banning oil drilling in the Yucatan Peninsula. Passing this legislation was a hard-fought battle, but in the end, the countries realized that the Mesoamerican Reef is not only the heart of their economy, but has immense social, political, and cultural value that must be protected (Root, 2018).
Further research on coral resilience and on what technologies can improve reef health, such as genetically-engineered coral covers and coral nurseries, could provide necessary in savaging coral cover. Ecotourism must be planned in a way that protects coastlines and reefs, such as by reminding tourists to respect marine life, focusing on sustainable development, and minimizing the carbon footprint. Mangrove forests should be planted to filter harmful runoff from entering oceans and streams, protecting against natural disasters, and providing a habitat to organisms. Overall, coral reefs are just an example of the problem of climate change as a whole; we must decrease fossil fuel usage to really decrease the threat to coral reefs.
Conclusion
Climate change and fossil fuel emissions cause ocean acidification and coral bleaching because of increased carbon dioxide in the ocean and rising ocean temperatures, which makes coral less resilient and decreases the coral cover to unsustainably low levels, which hurts overall reef health. The Mesoamerican reef is currently ranked in poor condition because of the high presence of coral bleaching, which decreases biodiversity and weakens the entire reef system, making coastal areas more susceptible to natural disasters and beaches more prone to erosion. The Central American economy relies on the reef for tourism and fishing, and many people rely on it for their livelihood. The destruction of coral reefs greatly hurts the Central American economy, which has a large potential of growth if development is sustainable but will crash if no improvements or changes to reef health are made. This puts entire communities at risk with rising ocean temperatures leading to more natural disasters and a weakened barrier reef providing less protection. Possible solutions include planning sustainable development, researching coral regeneration, establishing MPAs, and taking action to prevent climate change. Ultimately, the future of the Mesoamerican Reef, Central America, and the entire ocean comes down to human action as we are the ones destroying everything, and we are the only ones that can create change. This requires a combination of science, policy, and passionate people working to better the planet for future generations.