Almost all of the world’s coral reefs are at risk unless drastic action is taken to keep temperature rises below 2°C, according to new research.
The study, published in Nature Climate Change, found that unless effective emission reduction policies are implemented urgently approximately two thirds of corals could suffer by 2030.
“Our findings show that under current assumptions regarding thermal sensitivity, coral reefs might no longer be prominent coastal ecosystems if global mean temperatures actually exceed 2°C above the pre-industrial level,” said lead-author Katja Frieler.
“Without a yet uncertain process of adaptation or acclimation, however, already about 70% of corals are projected to suffer from long-term degradation by 2030 even under an ambitious mitigation scenario.”
The researchers warn that to protect at least half of global coral reefs increases in warming must be limited to 1.5°C.
Coral reefs are home to a quarter of all ocean species. They protect coastlines, attract tourists and are a source of food to over 500 million people worldwide.
Ocean warming and acidification – both driven by man-made climate change – pose major threats to coral ecosystems.
Corals get most of their energy from the algae which covers them. This relationship between coral and algae can breakdown in warmer waters, causing coral bleaching. While corals can survive this, if warming conditions persist for long periods of time they can die.
While it is possible for corals to adapt to rising temperatures, the latest study also takes into account the double effect of ocean acidification.
The study predicts the process of acidification – which threatens the calcification process which is crucial to the growth or corals – would reduce their resilience to warming temperatures.
The researchers, from the Postdam Institute for Climate Impact Research, the University of British of Columbia and the Universities of Melbourne and Queensland, warned that this latest study shows how close we are to a world without coral reefs.
“The window of opportunity to preserve the majority of coral reefs, part of the world’s natural heritage, is small,” said report co-author Malte Meinshausen. “We close this window, if we follow another decade of ballooning global greenhouse-gas emissions.”