The necessary coral reefs are very likely doomed to disappear due to global warming, according to a study published on Tuesday February 1, even if the objectives of the Paris agreement are respected. With an average temperature rise of 1.5°C compared to the pre-industrial era, the most ambitious goal of the Paris agreement, more than 99% of corals would be unable to recover from marine heat waves more and more frequent, estimates the study published in the journal PLOS Climate (in English).
And with a warming of +2°C, their mortality would be 100%, according to researchers who used a whole new generation of climate models analyzing the oceans at a resolution of one square kilometer. “The stark reality is that there is no threshold of safe warming for coral reefs”, comments lead author Adele Dixon, of the University of Leeds. These natural structures are home to a quarter of marine life.
In a previous report from 2018, the IPCC predicted the disappearance of 70 to 90% of corals at +1.5°C, and 99% at +2°C. Corn “Our research shows that corals around the world will be at even greater risk from climate change than we thought”, says Adele Dixon. After a bleaching episode related to the increase in water temperature, reefs generally need at least ten years to recover, if all other factors (water quality for example) are “optimal”, notes Maria Berger, another author of the study. Warming multiplies sea heat waves and makes this recovery time impossible.
The 2015 Paris Agreement aims to limit warming to well below +2°C, if possible +1.5°C. “Even 1.5°C is too much warming for ecosystems on the front line of global warming”, explains Adele Dixon to AFP. Faced with the multiplication of heat waves, storms and floods on a planet which has so far gained around 1.1°C, the threshold of +1.5°C has de facto become the main objective. But it could already be reached around 2030, according to the latest report from UN climate experts (IPCC).
Due to warming and pollution, 14% of corals disappeared between 2009 and 2018, turning underwater landscapes vibrant with color and life into cemeteries of bleached skeletons, according to recent research. Australia’s Great Barrier Reef has suffered five major bleaching events in the past 25 years. According to a study by experts from the US Oceanic and Atmospheric Administration (NOAA), not yet published but obtained by AFP, the Great Barrier Reef was the victim in November and December of a new heat wave without previous.