Climate change blamed for killing 14% of the world’s coral reefs in just 10 years

Over the course of a single decade, climate change helped kill 14 percent of the world’s coral reefs, a new study has found.
David Knowles, October 5, 2021

Over the course of a single decade, climate change helped kill 14 percent of the world’s coral reefs, a new study has found.

In its first global report since 2008, the Global Coral Reef Monitoring Network (GCRMN) finds that rising ocean temperatures due to climate change led to a succession of “large-scale bleaching events” that resulted in the decline of coral reefs worldwide. Though the report lists other causes such as pollution, overfishing and construction, the bleaching caused by warmer ocean waters was by far the biggest contributor behind the die-off of coral.

“Large-scale coral bleaching events caused by elevated sea surface temperatures are the greatest disturbance to the world’s coral reefs,” the report states.

Coral reefs support over 25 percent of all marine species on earth yet cover just 0.2 percent of the ocean floor. The death of reefs would trigger the collapse of an entire ecosystem, scientists have long warned.

The GCRMN report, which drew its findings based on data compiled over 40 years in 73 countries, finds a marked spike in the amount of algae on the world’s coral reefs in just a decade.

“There was 20% more algae on the world’s coral reefs in 2019 than in 2010. Increases in the amount of algae, a globally recognized indicator of stress on coral reefs, were associated with declines in the amount of hard coral,” the report states.

Divers swim above a bed of dead corals
Divers swim above a bed of dead corals in the South China Sea. (David Loh/Reuters)

Yet it notes that following a 1998 mass bleaching event, coral reefs were able to rebound to a degree, especially in places where pollution and overfishing were kept at bay.

“While the results of the report are sobering, there are examples of the ability of coral reefs to recover in the absence of major disturbances,” Margaret Johnson, general manager of the Great Barrier Reef Marine Park Authority in Australia, said in a statement accompanying the report. “This reinforces our conviction that we need to step up and accelerate efforts at all levels to address key threats and increase global action at all levels to reduce the extent of climate change impacts.”

Despite the fact that they can rebound from individual bleaching events, coral reef systems remain at risk because oceans absorb the vast majority of heat caused by climate change. Last year, the oceans reached their warmest temperature on record, and five of the warmest years recorded have all occurred since 2015.

“Most of the excess atmospheric heat is passed back to the ocean. As a result, upper ocean heat content has increased significantly over the past few decades,” the National Oceanic and Atmospheric Administration says on its website.

Coral reefs, which require sunlight, are found in shallow waters, where the impact of temperature rise has been profound.

“We are running out of time: We can reverse losses, but we have to act now,” Inger Andersen, head of the United Nations Environment Program, said in a statement regarding the report’s findings.

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