Threading its way 600 miles (1,000 kms) through the coastal waters of Mexico, Guatemala, Belize and Honduras, the Mesoamerican Reef is a nursery and refuge to hundreds of species of fish and invertebrates, a food and income source for tens of thousands of people—and a beleaguered ecosystem fighting for its very survival. Over the last 25 years, the reef has been battered by climate change, overfishing and pollution. From the early 1990s to 2006, coral cover on the Mesoamerican Reef seabed declined from around 30% to approximately 10%. A 2014 report by the United Nations Intergovernmental Panel on Climate Change warns that the by mid-century the reef could collapse, with a die-off that would cause “major economic and environmental losses.”

Yet amidst the gloom there is now a sliver of light. A report released Jan. 10 by the Healthy Reefs for Healthy People Initiative (HRI), a consortium of governmental and non-governmental organizations, concludes that the coral cover has increased over the last 10 years from 10% to 18%, and the total biomass of the reef’s herbivorous and commercial fish has climbed as well. The only major indicator that continues to worsen is the quantity of unwanted fleshy algae known as macroalgae, or seaweed, which crowds out coral. The amount of macroalgae doubled over the last ten years, thanks in part to nutrients coming from the ocean-bound sewage flowing out of coastal towns and resorts. “Three of four major indicators have improved, and that’s really good news,” said scientist Melanie McField, the director of HRI, in an interview this month with EcoAméricas.

Experts attribute the reef’s improved health to good luck in climate and weather and to growing awareness of the importance of reef protection. In June 1997, the presidents of Mexico, Belize, Guatemala, and Honduras met in Tulúm, Mexico to sign an agreement aimed at reversing the decline of coral reefs. The accord helped fuel government marine-conservation advances as well as reef-protection initiatives by international environmental groups and development agencies. And local communities, recognizing the important role reef ecosystems play in protecting the coast from storms and in generating billions of dollars annually in tourism and fishing income, stepped up their collaboration in research and environmental enforcement.

“There has been an evolution of attitudes by sectors across the board, from government to local communities,” says Carlos Saavedra, senior director for biodiversity at the Summit Foundation, a private family foundation in Washington, D.C. dedicated in part to conservation of the Mesoamerican Reef. “There’s a realization that from climate change to pollution and overfishing, there’s an imperative to act.”

Development decisions

New attitudes have affected crucial development considerations, such as those concerning fossil fuels. Last December, the government of Belizean Prime Minister Dean Barrow yielded to pressure from green groups and signed a law adopting a permanent ban on oil exploration in his country’s territorial waters, the first ever for a developing nation. Environmentalist had worried that seismic airgun blasting underwater by exploration crews could take a toll—for instance, by killing fish eggs and larvae or damaging the hearing systems of marine animals. They also fear ed oil leaks from offshore rigs could threaten the reef and the marine life it sustains. The ban appears to have averted those risks in a nation where fishing and tourism linked to the reef account for an estimated 15% of the gross domestic product.

“This is great news for Belize,” said Nadia Bood, a reef scientist for the environmental group WWF, in a communiqué released after the decision. “Not only has the government listened to calls to protect the Belize Barrier Reef [part of the Mesoamerican Reef], which only a year ago was under threat from seismic oil exploration, it has stepped up to become a world leader in ocean protection by ending all oil activity in its waters.”

The news comes amid dire tidings for reefs around the world. Australia’s Great Barrier Reef, the only reef system larger than the Mesoamerican Reef, lost more than half of its coral cover between 1985 and 2012, according to a 2012 paper in the Proceedings of the National Academy of Sciences. Losses have continued since, including a three-year, episode of excessively warm waters during 2015-17 in which hundreds of miles of the reef have died off.

A big part of the problem, say scientists, is a global-warming-related rise in seawater temperature of around 1 degree Celsius (1.8 degrees Fahrenheit) since the mid-19th Century. Warmer waters cause corals to expel photosynthetic algae known as zooxanthellae, that live within them in a mutualistic relationship, giving corals their distinct color and, most importantly, nutrients. As the corals eject the zooxanthellae, they turn a pale white, in a process known as bleaching, and begin to starve. In the worst cases, they die. Add the problems of farm runoff, sewage discharges, plastic pollutants and overfishing, and reefs on a global scale are still very much in danger, with only the hope of reduced climate change and better human management to save them.

“Corals are like rainforests: complex, tightly interwoven systems that can be upset by very little disturbance,” says Douglas Rader, chief oceans scientist at the New York-based Environmental Defense Fund (EDF). “They’re increasingly stressed by warm waters and bleaching, and additional stressors can push them over the edge.”

Back from brink

In 1998, the Mesoamerican Reef suffered from a global bleaching event which, combined with a devastating hurricane, caused the reef to lose an estimated 50% of its coral cover in Belize and sustain significant losses in other countries as well. Since then the corals have been able to regrow. Moreover, they have caught a few breaks: the global bleaching events of the last three years triggered little mortality in Mesoamerica. While the reasons for this are not entirely clear, experts believe hurricanes churned up cold waters from the deep without directly hitting the reef—thus cooling the reef without damaging it. The 1998 bleaching event, they believe, may also have weeded out weaker member of different coral species, leaving hardier ones behind to resist the next onslaught. “We were lucky,” says McField. “There’s only so much heat above normal temperatures that a reef can withstand and we were fortunate during the last three years not to get there. Corals might have bleached, and [might have been] basically starving for a few months, not growing or reproducing. But we didn’t see widespread mortality.”

Today, a coral restoration project run by a small community-based nonprofit in Belize known as Fragments of Hope attempts to speed recovery. Over the last ten years, the group has raised over 90,000 corals from various coral species in nurseries on the seabed. The corals are then transplanted onto the reef itself, generating a 35% increase in coral cover in places where the experiment is unfolding. Scientists now are using new techniques involving gently breaking staghorn coral (Acropora cervicornis) into small fragments to encourage faster growth in nurseries. The methods are currently being tried throughout the region.

A major problem for the reef is the untreated wastewater and agricultural runoff that reach it after flowing into coastal waters, stimulating the growth of coral-smothering macroalgae. Counteracting that is the ecosystem’s own cleanup team of macroalgae-eating herbivores. These include parrotfish, which have bird-like beaks that they use to pluck macroalgae off the coral, as well as surgeonfish, Caribbean king crab and the long-spined sea urchin. Groupers and snappers also play a key reef-protection role by feeding on damselfish, which harm coral as they poke around for food.

Unfortunately, overfishing of both herbivorous and large commercial fish, as well as disease in the case of the long-spined sea urchin, have culled populations of ecologically important reef species. Declines in the number of herbivores have allowed macroalgae to flourish, while the lack of groupers and snappers have benefitted the destructive damselfish.

Taking initiative

Governments have pushed back, increasing the number of marine protected areas over the last two decades to cover roughly 57% of territorial waters and boosting the number of so-called replenishment zones, where no fishing is permitted, to about 3%. In 2009, after witnessing the population of parrotfish nosedive, the Belizean government banned harvesting of those fish. Honduras in 2010 declared a similar ban for the waters off its Bay Islands, around which much of that country’s portion of the Mesoamerican Reef is located, and Guatemala followed suit in 2015. And non-governmental groups are looking to revive populations of the herbivorous Caribbean king crab and long-spined sea urchin, with strategies ranging from aquaculture in the case of the crabs to lab rearing and reintroduction in that of urchins.

Over the last two years, a nationwide program of fishing rights also has been implemented in Belize. Under the program, fishermen are granted concessions in certain areas in exchange for commitments to respect replenishment zones, report their catch and enforce regulations, including patrolling for illegal fishing. EDF, which supports the project, reports that illegal fishing in Belize has dropped 60% as a result. In Mexico, meanwhile, work in the state of Quintana Roo, home to over a third of the Mesoamerican Reef, has resulted in new replenishment zones just as fishers are becoming increasingly involved in protecting and monitoring the health of the reef.

All these measures have contributed to the increase in herbivorous- and commercial-fish biomass, scientists say. “The total amount of big fish of all kinds, herbivores and predators, are the best predictors of overall reef health, and by that I mean coral cover, the presence of fleshy algae, and species richness,” says Rader. “You empower fishermen to be stewards. You buy them into an interactive process that results in better management so they can see the benefits, and the situation improves.”

Threats persist

Still, the environmental pressure from coastal development remains intense. Mangroves and seagrass normally strain out much of the nutrients from farming runoff and discharges of untreated wastewater before those nutrients can reach the reef. They also remove accompanying bacteria and viruses. But developers clear mangrove stands and dig up seagrass to make way for new sandy islands and resorts. Experts say that issuing statements of concern and enacting regulations don’t seem to be enough to stop the destruction.

The development simply seems to be outpacing the ability of governments to cope. In Quintana Roo, for example, resorts of the Riviera Maya have mushroomed in recent decades, and the region’s population has boomed. Many neighborhoods still remain unconnected to the sewage system. As a result untreated wastewater moves through the porous limestone and sinkholes of the local karst topography, seeping into underground watercourses and ultimately reaching the sea—and the Mesoamerican Reef.

“Most government officials are well intentioned,” says Mélina Soto, HRI’s coordinator for Mexico. “But they don’t have sufficient resources to keep pace with development and build enough wastewater treatment plants.”

How the progress and continued obstacles to reef health will balance out over the long run is anyone’s guess. Experts say the recent report by HRI is unquestionably positive. But as McField says, “improvements have been gradual and not overwhelming.” All agree that there is still a long road to travel.

“There is a consensus that reef ecosystems and the people who depend on them will be in real trouble by 2050, if not before, as waters warm and acidify, sea levels rise, storms intensify and the effects of pollution and overfishing accumulate, eliminating species and introducing all kinds of cascade effects,” says the EDF’s Rader. “The question is what we can do in the short and medium term to maximize the resilience of the coral world [and] enhance its ecological conditions.”