Planet is experiencing massive coral bleaching – 04/15/2024 – Environment

The world’s coral reefs are experiencing a global bleaching event caused by extraordinary ocean temperatures, NOAA (National Oceanic and Atmospheric Administration) and international partners announced this Monday (15).

It is the fourth global event of its kind on record and is expected to affect more reefs than any other. Bleaching occurs when corals become so stressed that they lose the symbiotic algae they need to survive. Bleached corals can recover, but if the water around them is too hot for too long, they die.

Coral reefs are vital ecosystems: limestone cradles of marine life that nourish about a quarter of ocean species at some point in their life cycles, support fish that provide protein for millions of people, and protect coasts from storms. The economic value of the world’s coral reefs has been estimated annually at US$2.7 trillion (R$14 trillion).

Over the past year, ocean temperatures have been unusual.

“This is scary because coral reefs are so important,” said Derek Manzello, coordinator of NOAA’s Coral Reef Watch program, which monitors and predicts bleaching events.

The news is the latest example of climate scientists’ alarming predictions coming true as the planet warms. Despite decades of warnings from scientists and promises from leaders, nations are burning more fossil fuels than ever and greenhouse gas emissions continue to rise.

Substantial coral deaths have been confirmed around Florida and the Caribbean, especially among species Acropora cervicornis It is Acropora palmatabut scientists say it is still too early to estimate what the extent of global mortality will be.

To determine a global bleaching event, NOAA and its global partner group, the International Coral Reef Initiative, use a combination of sea surface temperatures and evidence from the reefs.

According to their criteria, all three oceans that are home to coral reefs — the Pacific, Indian and Atlantic — must experience bleaching within 365 days, and at least 12% of the reefs in each ocean must be subjected to temperatures that cause bleaching.

Currently, more than 54% of the world’s coral area has experienced bleaching heat stress in the last year, and that number is increasing by about 1% per week, Manzello said.

He added that within a week or two, “this event will likely be the most extensive global bleaching event in terms of area on record.”

Each of the three past global bleaching events was worse than the last. During the first, in 1998, 20% of the world’s reef areas experienced bleaching heat stress. In 2010, it was 35%. The third occurred from 2014 to 2017 and affected 56% of the reefs.

The current event is expected to be short-lived, Manzello said, because El Niño, a natural weather pattern associated with warmer oceans, is weakening and forecasters predict a cooler period of La Niña will set in by the end of the year.

Bleaching has been confirmed in 54 countries, territories and local economies, as far apart as Florida, Saudi Arabia and Fiji. The Great Barrier Reef in Australia is experiencing what appears to be its most serious bleaching event; about one-third of aerially observed reefs showed very high or extreme bleaching prevalence, and at least three-quarters showed some bleaching.

“Sometimes I get depressed, because it feels like, ‘Oh my God, this is happening,'” said Ove Hoegh-Guldberg, a professor of marine studies at the University of Queensland who published early predictions about how global warming would be catastrophic for humans. coral reefs.

“Now we’re at the point where we’re in a disaster movie,” he said.

The most recent confirmation of widespread bleaching, which prompted Monday’s announcement, came from the Western Indian Ocean, including Tanzania, Kenya, Mauritius, Seychelles and the region off the west coast of Indonesia.

Swaleh Aboud, a coral reef scientist at Cordio East Africa, a nonprofit research and conservation group based in Kenya and focused on the Indian Ocean, said coral species known to be thermally resilient are bleaching, as are reefs in a coldest area considered a climate refuge.

He recently visited a fishing community in Kenya called Kuruwitu, which has worked to revive its reef. Many of the restored coral colonies had turned ghost white. Others were pale, apparently on the way to bleaching.

“Urgent global action is needed to reduce future bleaching events, primarily driven by carbon emissions,” Aboud said.

Scientists are still learning about corals’ ability to adapt to climate change. There are efforts underway to breed corals that tolerate higher temperatures. In some places, including Australia and Japan, corals appear to be migrating toward the polar region, beginning to occupy new places.

But scientists say a variety of factors, such as the amount of light that penetrates the water and the topography of the sea floor, make such migration limited or unlikely across much of the world.

Additionally, there is the problem of ocean acidification; As seawater absorbs carbon dioxide from the atmosphere, it becomes more acidic, making it harder for corals to build and maintain reefs.

Hoegh-Guldberg, who has studied the impact of climate change on coral reefs for more than three decades, authored a 2018 report from the Intergovernmental Panel on Climate Change that found the world would lose the vast majority of its coral reefs with 1 .5°C of heating, and practically all at 2°C. Current pledges by nations put the Earth on a path to about 2.5°C of warming by 2100. Still, he hasn’t given up hope.

“I think we will solve the problem if we stand up and fight to solve it,” Hoegh-Guldberg said. “If we just keep making empty speeches and not looking for solutions, then we are fooling ourselves.”