Scientists studied 2,500 coral reefs to figure out how to save them

Local, global efforts required, according to study

By Ashley Strickland, CNN
Arc Centre of Excellence/Coral Reef Studies via CNN

LONDON - An international group of scientists has surveyed more than 2,500 coral reef systems across 44 countries to determine how to save them in the face of damage caused by climate change and humans, according to a new study.

A hundred scientists were involved in the survey that looked at coral abundance in the Indian and Pacific oceans. Many of the reef systems were found to be full of complex species that created distinctive structures and were functioning in spite of deadly marine heat waves in recent years.

The study was published Monday in the journal Nature Ecology and Evolution.

"The good news is that functioning coral reefs still exist, and our study shows that it is not too late to save them," said Emily Darling, the lead author of the study and a Wildlife Conservation Society scientist leading the global coral reef monitoring program. "Safeguarding coral reefs into the future means protecting the world's last functioning reefs and recovering reefs impacted by climate change. But realistically -- on severely degraded reefs -- coastal societies will need to find new livelihoods for the future."

Heat stress affected many coral reefs during the El Niño event between 2014 and 2017. But 450 reefs in 22 countries survived in protective cool spots. The scientists believe those areas should be the focus of urgent protection and management efforts.

Previously, the Indo-Pacific reefs were also hit by mass coral bleaching and heat stress in 1983, 1998, 2005 and 2010, before the world's most intense, longest and largest bleaching event between 2014 and 2017.

Coral bleaching occurs when ocean temperatures rise and corals release the algae that lives in their tissues, causing them to turn white, according to the National Oceanic and Atmospheric Administration.

Carbon emissions, pollution, development and overfishing have also impacted reefs.

"Saving reefs will require combining local and global efforts, such as reducing local dependence on reef fish to maintain a reef's important functions while also reducing carbon emissions to keep warming below 1.5 degrees Celsius," said Tim McClanahan, co-author of the study and Wildlife Conservation Society senior conservation zoologist.

The scientists determined that the corals responsible for the backbone of reefs, known as framework corals, thrived in areas with less climatic shock and longer windows of recovery. And more instances of abundant coral were found far away from populated coastal areas.

The study includes three strategies that will help reefs be protected, recover and transform. Protecting focuses attention on the 17% of reefs that survived in the cool spots during the long marine heat wave. Another strategy is to focus recovery efforts on reefs impacted by the heat wave and coral bleaching event -- 54% of which were analyzed in the study.

Transforming suggests coastal communities will need to rely on other things rather than depending on non-functioning reefs, which comprised 28% of the analyzed reefs.

"While coral reef sustainability depends largely on reducing carbon emissions, identifying reefs that are likely to respond -- or importantly, not respond -- to local management is critical to targeting development and management strategies to build the well-being of the millions of people dependent on coral reefs across the globe," said Georgina Gurney, study co-author at from the ARC Centre of Excellence for Coral Reef Studies at James Cook University:

"More than ever, we must consider how to manage local threats to coral reefs while keeping an eye to future climate impacts," said Gabby Ahmadia, director of marine conservation science at World Wildlife Fund and co-author of the study. "This study will help policymakers and conservationists make informed management decisions for coral reefs and the communities that rely on them."

In 2018, a study about how global warming is killing the Great Barrier Reef highlighted the importance of reef systems for people around the world.

"Almost a billion people around the world rely on coral reefs as their main source of food protein," said Mark Eakin, 2018 study author and coordinator for the US National Oceanic and Atmospheric Administration's Coral Reef Watch. "Coral reefs provide tens of billions of dollars to economies and protect shorelines and infrastructures around the world."

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