Is nature adapting to climate change? Underwater coral reefs in the Pacific that were predicted to vanish by 2050 show ‘historic increase’ in climate resistance

Coral reefs are dying out worldwide due to warming waters due to climate change. only one Pacific coral chain is experiencing a recovery.

Researchers found that underwater ecosystems along Palau Island have adapted to higher ocean temperatures — which could prevent future bleaching and the die-off that occurs when they expel algae in their tissues and turn white.

Referred to as the “rainforests of the sea,” the coral is home to somewhere close to 25 percent of the ocean’s biodiversity. Colonies of small coral polyps grow, leaving huge limestone skeletons as they expand and provide habitat for other marine species.

But that complex life chain is disappearing as the temperature of the oceans rises.

The new study suggests there is hope for many coral reefs once considered doomed. “High-frequency bleaching can be completely mitigated on some reefs under low-to-medium emissions scenarios,” the researchers report.

In other words, the coral may meet humanity halfway, but is still at risk from the current state of fossil fuel use and greenhouse gas emissions. The mass die-off of coral, they said, “can only be delayed under high-emission scenarios.”

Corals’ thermal tolerance has increased by 0.18 degrees Celsius per decade since the late 1990s, demonstrating that their once-bleached white limestone skeletons could return to bright and vibrant life.

The study comes a year after environmental scientists warned that the world’s coral reefs would likely disappear by 2050 without climate action — but those around the island tell a different story.

Coral reefs have long been considered one of the first and most important ecological casualties of global warming, which has regularly led to marine heat waves worldwide.

This has led to a massive die-off of bleach in the tropics.

Bleaching occurs when ocean temperatures are too hot, forcing corals to expel their colorful symbiotic algae that provide them with food.

Researchers announced in 2022 that with a warming of 1.5 degrees Celsius, 99 percent of the world’s reefs will experience heat waves that are too frequent to recover.

Study co-author and coral reef ecologist James Guest of Newcastle University said: ‘We know that coral reefs can increase their overall thermal tolerance over time through acclimation, genetic adaptation or shifts in community structure, but we know very little about the speed at which this happens. happens.’

The coral around Palau, known as Rock Island, is the most extensive underwater ecosystem in the Indo-Pacific, with over 164 coral species.

The coral around Palau, known as Rock Island, is the most extensive underwater ecosystem in the Indo-Pacific, with over 164 coral species

Coral reef cover exceeds 45 percent in some areas that experts have contributed to Palau’s efforts to preserve their natural marine heritage; it has a long history of marine conservation.

And unlike other regions, Palau’s coral has not undergone major bleaching.

The team from Newcastle University examined historical mass bleaching events, focusing on the Palau case study.

The study also tested different levels of global action to mitigate climate change and reduce carbon emissions, examining four emission scenarios and their impact on future coral bleaching projections.

Research has shown that from 2011 through 2018, water temperatures averaged 84F, while the average global temperature is 68F.

They believe the higher temperatures off the coast of Palau served “as a filter, selecting for thermally tolerant corals and simultaneously selecting for less thermally tolerant larvae that originated from outer reefs,” according to the study published in Nature.

And because the coral is separated from other underwater ecosystems, the larva cannot leave its place and gene flow between populations is limited.

“We saw strong genetic differentiation between the lineages and found that reefs within the Rock Islands have a different lineage composition than the outer reefs,” the researchers shared.

“The outer reef-associated DB line showed significantly higher bleaching (lower thermal tolerance) than other lines.”

The increased tolerance suggests that natural mechanisms, such as genetic adaptation or acclimation of corals or their symbiotic microalgae, could have contributed to improving coral thermal tolerance.

Co-author of the study, Prof. Peter Mumby from the University of Queensland and the Palau International Coral Reef Centre, indicates that ‘some of the challenges ahead will be unraveling the mechanisms driving these potential shifts in tolerance caused, and understanding the possibility of further increases in the future. in thermal tolerance.’