Brazil’s Abrolhos corals, the South Atlantic’s most diverse, decline as climate warms

Coral cover of Brazil’s Abrolhos reefs, ​the most biodiverse coral ecosystem in the South ​Atlantic, has fallen by around 15% over ‌18 ​years due to climate change and human activity, researchers in Rio de Janeiro told Reuters. Marine heatwaves linked to climate change have intensified so-called bleaching events where corals expel ‌the algae that call them home, which permanently undermines coral health, said Rodrigo Leao de Moura, a marine biologist at the Federal University of Rio de Janeiro.

Coral cover of Brazil’s Abrolhos reefs, ​the most biodiverse coral ecosystem in the South ​Atlantic, has fallen by around 15% over ‌18 ​years due to climate change and human activity, researchers in Rio de Janeiro told Reuters.

Marine heatwaves linked to climate change have intensified so-called bleaching events where corals expel ‌the algae that call them home, which permanently undermines coral health, said Rodrigo Leao de Moura, a marine biologist at the Federal University of Rio de Janeiro. “With the increasing frequency of heatwaves, corals may regain their color, but they develop necrosis ‌and diseases and continue to die because their health has been compromised,” Moura said.

Coral reefs around the world sustain ‌about a quarter of marine life but are now in an almost irreversible die-off that scientists have described as the first “tipping point” in climate-driven ecosystem collapse. For reefs to recover, scientists say the world would need to drastically ramp up climate action to bring temperatures down to just 1 ⁠degree ​Celsius above the preindustrial average.

But ⁠average global temperatures have already warmed by 1.3 to 1.4 degrees Celsius (2.3 to 2.5 degrees Fahrenheit) above the preindustrial average, according to data ⁠from U.N. and EU science agencies. Researchers in Brazil studied the Abrolhos reefs from 2006 until 2023. The results, published in The Royal ​Society’s Proceedings B journal, show “insidious shifts in coral assemblages, including the collapse of branching corals.”

Larger branching corals support ⁠reef structure but are being replaced by faster-growing species that provide fewer ecological benefits, the study found. Human activity worsens the damage, with sediment stirred ⁠up by ​dredging of the shipping channel at the nearby Port of Caravelas damaging water quality and smothering corals, Moura said.

Local marine protected areas have not halted the corals’ decline, indicating that while fundamental for protecting biodiversity, they are not ⁠enough in the face of a global climate crisis, the report said. The reefs support fishing, tourism, jobs, and coastal livelihoods, ⁠said Ricardo Gomes, a biologist ⁠from the Instituto Mar Urbano, adding that the risks of collapse extend far beyond marine life.

“Putting Abrolhos at risk means putting the entire biodiversity of the Brazilian coast at ‌risk,” Gomes said.