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Research Spotlight: Sea temperatures and reef restoration survival

Shawna A. Foo & Gregory P. Asner (2020). Sea surface temperature in coral reef restoration outcomes. Environmental Research Letters.



The Upshot

The majority of coral reefs are surviving at their upper thermal limit and an increase in just one degree Celsius lasting longer than a few weeks can lead to coral bleaching and death. With projections of ocean warming expected to continue to rise by as much as 1.5 degrees Celsius in this century, scientists are in a race against time to find new solutions to sustain reefs. One promising solution is coral outplanting. While effective, the technique is both time-consuming and expensive—and success isn’t always guaranteed. With temperature being one of the most fundamental factors determining coral health and survival, understanding its role in outplanting survival is crucial to restoration success. 

The Discovery

Researchers found coral outplant survival is likely to drop below 50% if sea surface temperatures exceed 30.5 degrees Celsius and that survival rates can also be predicted by considering temperature conditions in the year prior to outplanting. The study was based on an analysis of hundreds of coral outplanting projects worldwide between 1987 and 2018. The team assessed data on coral survival rates, outplant locations and dates, along with sea surface temperature data extracted from satellites to determine the effects of temperature on outplant survival. They also considered whether temperatures from the year prior to coral outplanting showed similar patterns. The results of their analysis help to determine if a restoration site is appropriate or not. 

The Impact

“Coral reefs experience a global, annual maximum sea surface temperature of about 29.4 degrees Celsius. Our study reveals that increasing the maximum temperature a site experiences by one degree higher reduces the chance of coral outplant survival to below 50%. We highlight the importance of considering temperatures a site has previously experienced to optimize outplant outcomes,” said Shawna Foo, lead author.

The Researchers

Greg Asner is the director of the Arizona State University Center for Global Discovery and Conservation Science (GDCS). Shawna Foo is a postdoctoral scholar at GDCS.