Rising sea temperatures around the world have caused a bleaching phenomenon that is expected to be the largest ever recorded.
On Monday, the National Oceanic and Atmospheric Administration (NOAA) and its international partners announced that coral reefs around the world are suffering from a global bleaching phenomenon caused by extraordinary ocean temperatures.
This is the fourth recorded global phenomenon of its kind 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 warm for too long, they die.
Coral reefs are vital ecosystems: calcareous cradles of marine life that nourish a quarter of ocean species at some point in their life cycles, support fish that provide protein for millions of people, and protect coastlines from storms.
In the last year, ocean temperatures have skyrocketed.
“This is scary, because coral reefs are so important,” said Derek Manzello, coordinator of NOAA’s Coral Reef Monitoring program, which monitors and predicts bleaching events.
The news is the latest example that climate scientists’ alarming predictions are coming true as the planet warms. Despite decades of warnings from scientists and promises from authorities, countries burn more fossil fuels than ever and greenhouse gas emissions continue to rise.
Substantial coral die-offs have been confirmed around Florida and the Caribbean, particularly among the elkhorn and staghorn species, but scientists say it is too early to estimate the extent of global mortality.
To determine a global bleaching event, NOAA and global partner group the International Coral Reef Initiative use a combination of sea surface temperatures and evidence from reefs. According to their criteria, the three ocean basins that host coral reefs – the Pacific, the Indian and the Atlantic – must experience bleaching within 365 days, and at least 12 percent of the reefs in each basin They must be subjected to temperatures that cause whitening.
Currently, more than 54 percent of the global coral surface has suffered bleaching-level thermal stress in the last year, and that number is increasing about 1 percent per week, according to Manzello.
He added that within a week or two, “this event is likely to be the most spatially extensive global bleaching on record.”
Each of the three previous global whitewashes has been worse than the last. During the first, in 1998, 20 percent of the world’s reef areas suffered bleaching-level thermal stress. In 2010, it was 35 percent. The third extended from 2014 to 2017 and affected 56 percent of the reefs.
According to Manzello, the current phenomenon is expected to last less time as El Niño, a natural weather pattern associated with warmer oceans, is weakening and meteorologists predict that a colder La Niña period will take hold later in the year.
The economic value of the world’s coral reefs has been estimated at US$2.7 trillion annually.
Bleaching has been confirmed in 54 countries, territories and local economies, as far apart as Florida, Saudi Arabia and Fiji. Australia’s Great Barrier Reef is suffering what appears to be its most serious bleaching episode; About one-third of reefs surveyed by air showed very high or extreme bleaching prevalence, and at least three-quarters showed some bleaching.
“Sometimes I get depressed, because my feeling is, ‘Oh my God, this is happening,’” said Ove Hoegh-Guldberg, a professor of marine studies at the University of Queensland who published the first predictions about how catastrophic global warming would be for us. coral reefs.
“We are now at a point where we are in the disaster movie,” he said.
The most recent confirmation of widespread bleaching, which prompted Monday’s announcement, comes from the western Indian Ocean, which includes Tanzania, Kenya, Mauritius, the Seychelles and the western coast of Indonesia.
Swaleh Aboud, a coral reef scientist at CORDIO East Africa, a Kenya-based nonprofit research and conservation group focused on the Indian Ocean, said coral species known for their thermal resistance are bleaching, as well as the reefs of a colder area considered a climatic refuge.
He recently visited a Kenyan fishing community called Kuruwitu that has been working to restore its reef. Many of the restored coral colonies had turned a ghostly white. Others were pale, apparently in the process of disappearing.
“Urgent global action is needed to reduce future bleaching events, driven primarily by carbon emissions,” Aboud said.
Scientists continue to learn about corals’ ability to adapt to climate change. Efforts are underway to breed corals that tolerate higher temperatures. In some places, such as Australia and Japan, corals appear to be migrating poleward, beginning to occupy new locations. But scientists say several factors, such as the amount of light penetrating the water and the topography of the seafloor, make such migration limited or unlikely in much of the world. Additionally, there is the problem of ocean acidification: as sea water absorbs carbon dioxide from the atmosphere, it becomes more acidic, making it difficult for coral reefs to form and maintain.
Hoegh-Guldberg, who has studied the impact of climate change on coral reefs for more than three decades, authored a 2018 report by the Intergovernmental Panel on Climate Change that concluded the world would lose the vast majority of its coral reefs with a warming of 1.5 degrees Celsius, and practically all with 2 degrees. Current commitments by nations put the Earth on a path to 2.5 degrees by 2100. Still, hope is not lost.
“I think we will solve the problem if we stand up and fight to solve it,” Hoegh-Guldberg said. “If we continue paying lip service, but don’t start looking for solutions, we will be fooling ourselves.”
#worlds #largest #coral #crisis #occur #weeks #experts #warn