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July 2023 was considered the Earth’s hottest month on record, and possibly the hottest single month in roughly 120,000 years, according to a report published by the European Union’s Copernicus Climate Change Service and the World Meteorological Organization. One of the catastrophic impacts of these high temperatures has been the widespread devastation of coral reefs, especially in the Florida Keys, where water temperatures are at record-high levels.
As a teenager, those reefs mesmerized me with their colorful, teeming life and profound beauty. I knew from that young age that I would become a marine scientist. It is deeply heartbreaking to see those reefs—which have been in rapid decline for more than 50 years—estimated to be 80 to 90 percent dead. Making an already dire situation worse, the remaining corals are now bleaching in record-breaking ocean temperatures, facing a “disastrous bleaching event.” Climate change is a significant contributor to the death of coral reefs, which are being pushed beyond their thermal tolerance. This is resulting in the disturbing images we currently see in the media of bleached corals, a weakened state that often leads to their death.
Since 1970, the Caribbean has tragically lost half its coral reefs. It is estimated that the world will lose between 70 and 90 percent of its reefs by the end of the century. Coral reefs are essential to countless marine species that depend upon them—perhaps up to 9 million different species. Humans also depend greatly upon coral reefs, which help bring billions of dollars to the global economy from fishing, tourism, and coastal protection. For instance, coral reefs can absorb an astonishing 97 percent of wave energy. In the medical realm, more than half of new cancer drug research is focused on marine life, and much of that is on coral reef ecosystems.
While the media and public focus on climate change as the underlying cause of bleached coral reefs, research shows that a host of other factors are just as crucial to the health of coral reefs as the changing climate. For decades, these factors have slowly contributed to an underwater disaster, of which the public is largely unaware. Nutrient pollution, primarily from fertilizers used for agriculture and our lawns, fuels the rampant growth of algae in the ocean, which can smother and kill coral reefs. Meanwhile, herbivorous reef fish—many of which graze upon algae and keep coral reefs “clean” and safe from being smothered—end up on our dinner plates. A growing number of lethal diseases threaten coral reefs, some originating from human waste leaking from septic tanks and ships. Sedimentation from deforestation and coastal development can also be fatal to coral reefs.
As dismal and overwhelming as all of this may seem, there remains a message of hope: many of these are factors we can control, meaning that there are actions that we can take now to buy more time for corals in rapidly warming seas. Recent studies demonstrate that local factors are as important as (and perhaps even more important than) global factors (i.e., climate change) in ensuring the health of coral reefs. Despite the ravages of climate change, there are examples of remarkably healthy corals in parts of Cuba, the Bahamas, the Dominican Republic, and Brazil.
While the past 60 years have seen the worst decline in ocean health in human history, Cuba’s coral reefs in particular remain remarkably healthy. I have spent more than two decades working in Cuba and will never forget the joy and disbelief of coming face-to-face with stunning, healthy coral reefs. I bore witness to an extraordinary part of a 30-mile-long barrier reef along the southern waters of Cuba, largely comprised of elkhorn coral, one of the most important reef-building corals in the Caribbean. The stands of beautiful, mustard-colored elkhorn coral I saw were impossibly packed with grunt, snapper, goatfish, and many other spectacular reef species. In contrast, elkhorn coral is now nearly gone from the Florida Keys, and is listed as a “Threatened” species throughout its range under the U.S. Endangered Species Act. It is also listed as a “Critically Endangered” species on the IUCN Red List, just one category away from being classified as “Extinct in the Wild.”
This begs the question: “Why are Cuba’s ocean waters so healthy?” The answer is deeply entwined with the country’s extraordinary and unique history, from its dramatic political past to its world-class environmental protections influenced by an unlikely partner, Jacques Cousteau, who had a profound influence on Fidel Castro after they met in 1985. Following their meeting, Cuba implemented a set of exceptionally strong environmental laws. The collapse of the Soviet Union largely resulted in a large loss of financial and agricultural support in Cuba. Subsequently, Cuban agriculture became, and continues to be, largely organic. Without industrial fertilizers, there is little nutrient pollution to fuel the harmful growth of algae on coral reefs. Additionally, the country has not overfished its coral reefs, related to the establishment of enormous marine-protected areas that restrict fishing.
All these local actions have helped Cuba’s corals become more resilient (though not immune) to warming ocean temperatures. A recent study finds that coral reefs in Cuban waters represent 10 percent of the planet’s reefs most likely to survive by the end of the century. This, in part, has motivated strong collaboration between Cuban and U.S. scientists, considered to be one of the best examples of collaboration between the two countries despite political differences. As I observe in my new book, The Remarkable Reefs of Cuba, “… marine scientists…quietly and steadfastly built strong relationships between our countries where official diplomats and politicians had for decades fallen short.”
Examples of our collaborative activities include research expeditions, ecosystem mapping, research on sharks, sea turtles, manatees, coral reefs, environmental economics, and tourism impacts. We have also developed joint education programs and exchanges. Dozens of scientific publications have resulted from this work.
Cuba is a striking example of how, if we properly manage the local factors that impact coral reefs, we can build coral reef resilience worldwide, and along with it, hope for a brighter future for the ocean in the face of a formidable global threat.
Dr. David E. Guggenheim is founder and president of Ocean Doctor, a non-profit dedicated to ocean conservation. He is also an adjunct professor at Johns Hopkins University. He has spent more than two decades leading collaborative research programs with Cuba and is author of the new book, “The Remarkable Reefs of Cuba: Hopeful Stories from the Ocean Doctor.” He holds a Ph.D. in Environmental Science and Public Policy from George Mason University; a Master’s Degree in Aquatic/Population Biology from the University of California, Santa Barbara; and a Bachelor’s Degree in Environmental Studies from University of Pennsylvania.
