BUnderneath are fish, sea urchins, snails – and also an important coastal protection: the Great Barrier Reef off the east coast of Australia is a unique natural structure. But it has been affected for years by pollution and warming oceans. Last December, it was hotter than ever on Earth’s largest coral reef. Extreme heat stress can cause coral to bleach again, for the fourth time in just seven years.

Coral bleaching is a clear sign that corals are doing poorly: hollows, whose calcium secretions ensure that peculiar reef formations pile up, algae lose their colors due to heat stress. Coral reefs are dwindling. Cnidarians can also live without algae for a certain period of time. Although animals can also recover from bleaching, if this continues for a long time or is repeated often, corals will often die completely.

Then the corals died, and other sea creatures that mate here and give birth to their offspring now avoid them. And where there are no longer crowds of small animals, sharks and other marine predators can no longer find food.

In all, the 2,300-kilometre reef has experienced five mass bleaching events in the past few decades – in 1998, 2002, 2016, 2017, and 2020. These were all the result of rising sea temperatures, caused in large part by global warming.

Half of the corals are already dead

It didn’t show up until November study, published in “Current Biology” has found that 98 percent of individual corals have already bleached since 1998. Only one group of corals is far south of the Great Barrier Reef, in a small area that has remained consistently cold during all five mass bleaching events. remain unbleached.

In October 2020 was another study He also concluded that the number of small, medium and large corals on the Great Barrier Reef has declined by more than 50 percent since the 1990s.

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Not only is climate change to blame, but sewage from agriculture, sediment from coal ports, storms or thorny starfish have played their part. Report of the World Conservation Union (IUCN) In December 2020, he explained how dire the situation was: He downgraded the reef to “critical” for the first time.

Only clouds and rain can prevent bleaching

The current undersea heat wave, which is well above normal for this time of year, has put researchers on renewed alert. So did the US Meteorological Agency NOAA Recently he put the northern reef on alert at level two. This means the researchers believe severe coral bleaching is likely in the coming weeks. Only more clouds and rain in February could prevent a bleaching event – something that would be possible thanks to the La Niña season.

In addition to this risk, it was recently revealed that the Australian state of Queensland, off the coast where the Great Barrier Reef is located, has cleared vast areas in recent years. More than 680,000 hectares were removed in 2018/19. According to the environmental organization WWF A third of this cleared area is in the watershed where the waterways flow toward the reef.

topped the rescue package

All this does not set the right course a few weeks before the IUCN’s visit to the country. Last year, corals narrowly missed the red list after a massive marketing campaign by the Australian government UNESCO scrape by. But until then, the World Heritage Committee said it had noted the three recent mass bleaching events with “the greatest concern and regret”.

In addition, the “insufficient” progress that has been made regarding water quality and agriculture to date has been criticized. So it is uncertain how the committee will decide at its meeting this year, but the IUCN’s analysis will not go unnoticed.

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Climate change and coral reefs

In order to calm things down a bit in advance, the Australian government last week promised more money. Should the election be won, the current $2 billion rescue package would be increased by another A$1 billion – roughly €630 million. The money will flow to preserve the world heritage over the next nine years.

But the money is decorating the windows. Scientists and environmental experts welcomed the news of the planned investment. But at the same time they did not spare their criticism: coral expert Terry Hughes commented TwitterThat Australia, despite the infusion of cash, is still Coal and gas across the Great Barrier Reef are exported abroad every day.

And John ChurchA climate scientist at the University of New South Wales, in Sydney, complained that the investment was “negligible” compared to the environmental and economic damage burning of fossil fuels and climate change would inflict on coral reefs.

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And also a coral reef expert at the World Wide Fund for Nature, Richard LakeHe stressed that cash alone will not solve coral reef problems. “We need to protect forests better and work harder on water quality,” he said. In addition, Australia must adhere to a climate policy consistent with limiting warming to 1.5 degrees.

According to Leck, coral reefs have a chance of survival if Australia becomes the world’s largest source of renewable energy by 2030 while reducing both domestic and exported emissions.