Study Shows Coral Deaths Continue to Rise

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A newly published international report confirms global warming has damaged coral reefs throughout the world’s oceans. The Status of Coral Reefs of the World: 2020 published by the Global Coral Reef Monitoring Network (GCRMN), stated, the world has lost about 14% of its coral reefs since 2009. This report, the first of its kind, used data from more than 12,000 collection sites across 73 countries and spanned over 40 years (1978-2019). Although the GCRMN findings confirm the drastic effects of climate change on oceans and coral reefs worldwide, there was a 2% increase in coral reefs in 2009, signaling a sliver of optimism and demonstrating instances of reef resilience.

Coral reefs are integral to both the marine and global ecosystems. Over 25% of the ocean’s fish and over half a billion people currently rely on healthy coral reefs. Coral reef destruction has systematic consequences: people depend on reefs for food, income, and coastal protection. According to the National Oceanic and Atmospheric Administration (NOAA), coral reefs have an estimated economic value of 3.4 billion dollars per year and create 94 million dollars in savings from flood protection.

Coral are best described as animals that rely on a symbiotic relationship with plant-like algae. The algae use photosynthesis to provide the coral with food and oxygen. Coral have thousands of polyps, which are short tentacles used to digest food. These collections of polyps serve as shelter and food for a variety of fish. While corals are resilient, they are susceptible to dramatic rises in oceanic temperature. In cases where water temperatures spike 1-2 degrees Celsius above normal, coral reefs undergo a phenomenon called bleaching.

Coral bleaching is a process where coral expel their symbiotic algae (zooxanthella algae that provide the coral with food) when exposed to high temperatures or other environmental stressors. This expulsion leads to corals becoming a bleached white color, and while they can occasionally recover from bleaching, this process often kills the coral. Since the late 1990s, marine scientists have observed five separate mass bleaching events. Signs of mass bleaching were observed in 2020, especially in the Great Barrier Reef. These events have become increasingly prevalent with sea surface temperatures now one degree warmer than during the pre-industrial period (oceans trap and store about 90% of the world’s excess heat). If these trends continue, scientists predict that over 90% of coral could die by 2050.

While policy responses to coral degradation have had some success, more action is needed in the future to conserve coral ecosystems. In the United States, the Clean Water Act has reduced dredging and improved water quality near coral reefs by making it unlawful to discharge certain pollutants into public waters. The Magnuson-Stevens Act (MSA) has also limited the amount of fishing that can occur near coral reefs, leading to improved habitats. While overfishing and coastal development are large menaces to these ecosystems, scientists agree that rising sea surface temperatures currently pose the largest threat. For this reason, organizations like NOAA, Coral Gardeners, and Hope Reef are applying more proactive strategies, working to replant corals worldwide. While this strategy is increasingly popular and may be our best option to protect coral, replanting coral is expensive, and new research and development is necessary to identify cheaper methods of replanting. Whether this nature-based solution can keep up with the rates of coral decay is yet to be seen.

The new GCRMN report undoubtedly relays a bleak outlook for global coral reef populations. Its findings, however, will hopefully increase public interest in coral reef rehabilitation. Coral reefs are just one of many habitats facing stress from global warming, but failure to act in their defense will continue to lead to detrimental global reverberations.

  1. “The Sixth Status of Corals of the World: 2020 Report.” GCRMN, February 25, 2022. https://gcrmn.net/2020-report/ .
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