The world lost about 14% of its coral reefs in the decade after 2009, mostly due to climate change, according to an international report on the state of the world’s corals.
The report, released Monday evening, highlights the catastrophic consequences of global warming while offering some hope that some coral reefs can be saved if humans act quickly to bring greenhouse gases under control.
“Coral reefs are the canary in the coal mine that tells us how quickly it can go wrong,” said David Obura, one of the report’s editors and chair of the Coral Specialist Group for the International Union for nature conservation.
The 14% drop, he said, was a cause for deep concern. “In finance, we worry about half percent cuts and half percent changes in employment and interest rates.”
The trajectory is particularly alarming, the report’s editors said. The first episode of global bleaching occurred in 1998, but many reefs rebounded. This no longer appears to be the case.
“Since 2009, it has been a constant decline globally,” said Serge Planes, researcher at the Insular Research Center and the Environmental Observatory of Moorea, French Polynesia, who also edited the report.
While coral reefs cover a tiny fraction of the ocean floor, they offer people inordinate benefits. Their fish provide an essential source of protein for hundreds of millions of people. Their limestone branches protect the coasts from storms. Their beauty supports billions of dollars in tourism. Collectively, they support about $ 2.7 trillion a year in goods and services, according to the report released by the International Coral Reef Initiative, a partnership of countries and organizations that work to protect the world’s coral reefs.
There are perhaps 900 species of corals, and the researchers noted that some appear to be more resistant to the heat and acidification that accompanies climate change. Unfortunately, these tend to be slower growing and not the more familiar, reef-building varieties, which support the richest biodiversity.
Terry Hughes, who heads a center for coral reef studies at James Cook University in Australia and who was not involved in the analysis, also warned that the vast underlying data, collected by more than 300 scientists in 73 countries, could skew towards healthier reefs. .
“Researchers and monitoring programs often abandon degrading sites or do not establish new studies there because no one wants to study a reef covered in silt and algae instead of corals,” said Dr Hughes. .
Yet he and the report both pointed out that corals could recover or regenerate if the world limits global warming. “Many of the world’s coral reefs remain resilient and can recover if conditions allow,” the report says.
While tackling climate change is the most important factor in saving coral reefs, scientists said, reducing pollution is also essential. Corals need to be as healthy as possible to survive warming temperatures already locked in. Harmful pollution often includes human sewage and agricultural runoff which can cause algae blooms, as well as heavy metals or other chemicals from manufacturing. Destructive fishing practices also harm reefs.
The report comes just before world leaders meet next week to discuss a new global biodiversity deal. While some are pushing to protect the most pristine reefs, Dr Obura said this approach will not be enough.
“People are so dependent on reefs all over the world that we have to focus a lot of effort on poor reefs, or all other reefs as well,” Dr Obura said. “We have to make them work so that people’s livelihoods can continue. “