The world’s coral reef cover has halved since the 1950s, ravaged by global heating, overfishing, pollution and habitat destruction, according to an analysis of thousands of reef surveys.
From the 1,430-mile (2,300km) Great Barrier Reef in Australia to the Saya de Malha Bank in the Indian Ocean, coral reefs and the diversity of fish species they support are in steep decline, a trend that is projected to continue as the planet continues to heat in the 21st century.
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A review of 14,705 reef surveys in 87 countries found that the effort required to maintain fish catches had surged dramatically since the mid-1990s, reflecting their worsening health, with catches from reef species peaking in 2002 and declining ever since.
The study, published on Friday in the journal One Earth, found that the diversity of species on reefs has dropped by more than 60% and total reef cover had approximately halved, accompanied by a similar fall in services that the ecosystems provide for human populations.
Coral reefs are a vital source of food for millions of people around the world, especially island indigenous communities where fish is the primary source of animal protein, and researchers said the declines raised fears about future food stability.
While the review of data from 3,582 reefs covered only the period from 1957 to 2007, scientists said they were confident the global trend had continued, with bleaching, disease and disturbances driving the declines.
Tyler Eddy, a research scientist at the Memorial University of Newfoundland who led the study, said even though the decline of coral reef ecosystems had long been recorded at a national level, he was surprised by the extent of the scale of the global decline.
“Coral reefs are among the most sensitive ecosystems on the planet so they’re the first ones that are really experiencing these effects of climate change. There’s quite dramatic declines in the 60s and 70s. Then, in the 80s, there’s still a slight decline in the coverage through time but it’s not as steep,” he said.
“If you look at the country-level trends of the coral reef cover, we see some of the biggest declines occurring in Papua New Guinea, Jamaica and Belize.”
While reviewing the surveys, Eddy said researchers noticed that the composition of species on the reef was changing in some areas, with temperature-sensitive fish declining and more resilient species becoming dominant.
John Bruno, a marine ecologist at the University of North Carolina and co-author of the study, said despite regional differences, global coral reef health had continued to decline.
“Unfortunately, we’ve continued to lose coral from most of the world’s reefs since the data for this study ends. Marine heatwaves are rapidly intensifying, leading to more frequent and severe bleaching events, including on some of the world’s most isolated and pristine coral reefs,” he said.
In the Caribbean, a recent study found reefs had been declining by about 0.25% a year, with only about 10% of the seabed occupied by living corals by 2017.
“Over the last few years, Caribbean reefs have been clobbered by hurricanes and new diseases, both linked to ocean warming. Frankly, the global picture for coral reefs is pretty grim,” Bruno added.
The world’s oceans absorbed more than 90% of the heat trapped by greenhouse gases and average water temperatures have continued to rise as the planet heats.
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