Coral reef ‘safe havens’ less vulnerable to rising temperatures identified

New research shows the impact of warming seas on fragile marine ecosystems depends on nearby coastal development and coral type. 

A team of Arizona State University scientists working with the Julie Ann Wrigley Global Futures Laboratory have published findings that show coral reefs may be able to survive mass bleaching events and cope with rising temperatures better than previously thought, depending on other influencing factors. 

Based on the Hawaiian Islands, the ASU team and the Center for Global Discovery and Conservation Science took off in the Global Airborne Observatory, an aircraft equipped with advanced spectrometers capable of mapping ecosystems on land and below sea level. This data was then used to assess changes to the stability, size, and therefore health of coral reefs over time. 

The Pacific archipelago and the most distant US state from the mainland experienced a mass bleaching event in 2019, and scientists had mapped coral along eight of the islands’ coastline before the event. Readings were then taken immediately after, with potential ‘refugia’ identified where coral mortality was up to 40% lower than nearby reefs, despite the fact heat stress was at a similar level. 

The results show that reefs close to heavily developed coastlines are significantly more susceptible to die-off during heat waves compared with those more removed from developed areas on land. This is likely due to the level of pollution entering the ocean from developed locations, creating an unfavourable environment for reefs to thrive. 

‘This study supports Hawaii’s Holomua Marine 30×30 Initiative by not only identifying areas impacted by ocean heat waves, but also areas of refugia,’ said Brian Neilson, study co-author and head of Hawaii’s Division of Aquatic Resources. The Holuma Marine 30×30 project has a goal of establishing marine management areas covering 30% of Hawaii’s nearshore waters. ‘These findings can be incorporated into management plans to aid in building a resilient network of reef regions and sustaining Hawaii’s reefs and the communities that depend on them into the future.’

In related news, last month the Vibrant Oceans Initiative issued a global warning that coral reefs would largely disappear by 2050 without urgent intervention and a concerted effort to meet the targets of the Paris Agreement. 

Image credit: Peter Thomas