Climate change: 14% of global coral lost as sea temperatures rise

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Close to 14 per cent of the world’s coral reef have been lost since 2019 as rising temperatures take a toll on marine ecosystems across the planet. The new figures were released on Tuesday as part of the Status of Coral Reefs of the World: 2020 report, which analysed global coral reef health spanning 40 years in 73 countries.

More than 300 scientists worked across 12,000 coral sites to conduct two million individual observations and document the relentless stress on the ecosystem caused by climate change and other local pressures such as overfishing, unsustainable coastal development and declining water quality.

“Since 2009 we have lost more coral, worldwide, than all the living coral in Australia. We are running out of time: we can reverse losses, but we have to act now,” Inger Andersen, Executive Director of the UN Environment Program (UNEP) said.
Scientists analysed 10 coral reef-bearing regions around the world, which showed that coral bleaching events caused by elevated sea surface temperatures (SSTs) were the main driver of coral loss. They estimated that an acute event in 1998 killed eight per cent of the world’s corals, which is more than all the coral that is currently living on reefs in the Caribbean or the Red Sea and Gulf of Aden regions.

The analysis investigates changes in the cover of both live hard coral and algae. Live hard coral cover is a scientifically based indicator of coral reef health, while increases in algae are a widely accepted signal of stress to reefs. The report said that Since 1978 there has been a 9 per cent decline in the amount of hard coral worldwide, while between 2010 and 2019, the amount of algae has increased by 20 per cent.

“This study is the most detailed analysis to date on the state of the world’s coral reefs, and the news is mixed. There are clearly unsettling trends toward coral loss, and we can expect these to continue as warming persists. A clear message from the study is that climate change is the biggest threat to the world’s reefs, and we must all do our part by urgently curbing global greenhouse gas emissions,” Dr Paul Hardisty, CEO of the Australian Institute of Marine Science said in a statement.

The researchers found that large scale coral bleaching events are the greatest disturbance to the world’s coral reefs. The greatest impacts of this mass bleaching event were seen in the Indian Ocean, Japan, and the Caribbean, with smaller impacts observed in the Red Sea, The Gulf, the northern Pacific in Hawaii and the Caroline Islands.

Meanwhile, the study estimates that between 2009 and 2018, the world lost around 11,700 square kilometres of coral. The study establishes a correlation between coral loss and climate change as sharp declines in coral cover corresponded with rapid increases in sea surface temperatures. In a relief for marine biologists, coral reefs in East Asia’s Coral Triangle, which is the centre of coral reef biodiversity accounts for more than 30 per cent of the world’s reefs, have been less impacted by rising sea surface temperatures.

The UNEP in a statement said that in the upcoming climate conference in Glasgow and biodiversity conference in Kunming, decision-makers have an opportunity to show leadership and save our reefs, but only if they are willing to take bold steps.

“We must not leave future generations to inherit a world without coral,” Inger Andersen said. Although reefs cover only 0.2 per cent of the ocean floor they are home to at least a quarter of all marine species, providing critical habitat and a fundamental source of protein, as well as life-saving medicines.

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