From 2009 to 2018, 14 percent of the world’s coral reefs died, according to the largest study ever carried out on coral stocks, which the scientific network Global Coral Reef Monitoring Network presented on Tuesday.
Heat overwhelms coral reefs
Corals in South Asia and in the Pacific, around the Arabian Peninsula, and the corals off the coast of Australia are particularly hard hit by the mass extinction. Paul Hardisty, director of the Australian Institute of Marine Sciences and one of the more than 300 scientists involved in the report, called climate change “the greatest threat to reefs in the world”.
The world’s oceans absorb more than 90 percent of the excess heat caused by greenhouse gas emissions, according to the report. This causes long-lasting heat waves that overwhelm many species of coral. In 1998, according to the study, a single coral bleaching had destroyed eight percent of the world’s coral population.
Economic value of the coral reefs
Coral reefs cover only about 0.2 percent of the sea floor, but are habitat for at least a quarter of all marine animals and plants. Corals also serve hundreds of millions of people as sources of protein and protection from storms and coastal erosion. In addition, numerous jobs in tourism depend on them. The report puts the economic value of the coral reefs at around 2.7 trillion dollars (2.3 trillion euros) per year, including 36 billion dollars in tourism.
The UN Environment Program (UNEP), which supported the preparation of the report, called for countermeasures. “Since 2009 we have lost more corals worldwide than corals live in Australia,” said UNEP Director Inger Anderson. “We can reverse the losses, but we have to act now.”
70 to 90 percent of coral reefs could disappear
The earth has warmed up by 1.1 degrees since the pre-industrial age. The Intergovernmental Panel on Climate Change (IPCC) expects in its latest report that the earth will have warmed by 1.5 degrees by the end of this decade. This means that 70 to 90 percent of the world’s corals will disappear. According to the IPCC, just one percent of the corals could survive if the global temperature rose by two degrees.
In their investigation, the report authors also found reasons for cautious optimism. “Some reefs have shown remarkable ability to recover,” said Hardisty. This gives “some hope for a future recovery of destroyed reefs”.