Climate-driven marine heatwaves are hampering the recovery of coral reefs from global bleaching events, according to a new analysis.
A report published by the Global Coral Reef Monitoring Network (GCRMN) warns global hard coral cover has declined by approximately 9.5%, primarily driven by climate-induced heat stress.
The report claims global bleaching events, where corals expel the microscopic algae that live in their tissues are becoming more frequent
Without these algae, corals’ tissues become transparent, exposing their white skeleton.
The study also notes the time between each bleaching event is getting shorter, which means coral reefs have shorter windows to recover from them.
It says every major global bleaching event since 1998 has driven a sharp decline in global hard coral cover, creating a “staircase of decline”, according to the research.
However, following the third global coral bleaching event, global hard coral cover saw a relative increase of approximately 6% between 2017 and 2019, which the report says demonstrates recovery is possible if the reefs are sufficient recovery time.
Coral reefs cover less than 0.2% of the ocean floor, yet support at least 25% of all marine species and underpin food security, livelihoods, coastal protection, tourism and cultural heritage of close to one billion people worldwide.
Global average sea surface temperature reached a new record of 21.1 degrees Celsius earlier this month, surpassing the previous high.
This milestone follows a succession of monthly records and is attributed to the long-term warming of the global ocean due to human-driven climate change.
The report’s lead author, Dr. Manuel González Rivero, said while the global trend is towards coral reef decline, there are some regional variations, in an interview.
Dr. González Rivero added the coral reef in South-East Asia remains diverse and has been less impacted by temperature increases, compared to other regions, like Australia.
He told me climate change remains the main driver of coral mortality, and strong reductions in greenhouse gas emissions are necessary to widen the recovery windows between marine heatwave events.
He said there are also more local actions, which could be taken to protect coral reefs, including addressing overfishing and tackling poor water quality.
“There are about a billion people that that depend on these coral reef systems around the world and between 60% and 80% of the protein intake for the Pacific Islands comes from coral reef,” said Dr. González Rivero.
“Losing could actually have devastating consequences for us as society.
“Coral reef does not need us to survive. We need it to survive, and it’s important to realise we still have the capacity to act, but that action should not be delayed.”
In June, the Wildlife Conservation Society (WCS) and Macquarie University, published a report which highlights the coral reefs across 71 countries and 100 territories with the strongest potential to survive the climate crisis.
The analysis found that more than half (61%) of identified climate-resilient reefs are concentrated in five countries – Australia, the Bahamas, Cuba, Indonesia and the Philippines.
The research also identified substantial new areas of climate-resilient reefs across the Caribbean, including in Belize, Panama and the Turks and Caicos Islands.
Dr. Emily Darling, director of coral reefs at the Wildlife Conservation Society, the new report by the GCRMN shows that climate change is closing the recovery window for coral reefs, in a statement.
Dr. Darling added alongside urgent action on climate emissions, reducing local pressures from overfishing, pollution, and coastal development can give reefs their best shot to recover and survive the next heatwave.
“Using this information, governments must urgently do a lot more to protect climate-resilient coral reefs, for example by implementing national policies and plans and working with local communities and partners to reduce local pressures on coral reefs,” she said.
And Dr. Gabby Ahmadia, vice president of seascapes and science at WWF US said the report should serve as a “wake-up call”.
Dr. Ahmadia added countries need to cut the emissions driving ocean warming and put climate-resilient reefs at the heart of their adaptation plans.
“That means protecting reefs with stronger prospects for resilience and supporting the communities whose food, livelihoods and coastlines depend on them,” she added.