Future loss of local-scale thermal refugia in coral reef ecosystems

Published in PLOS Climate, February 2022

A.M. Dixon, P.M. Forster, S.F. Heron, A.M.K. Stoner, and M. Beger

Summary

A new study, published in PLOS Climate in February, led by Adele Dixon of the University of Leeds, U.K., and co-authored, among others, by Dr. Anne Stoner at Earth Knowledge Inc., predicts that rising ocean temperatures caused by climate change will result in near-total to total loss of areas where coral reefs are currently sheltered from rising ocean temperatures.

Coral reefs around the world require specific conditions, such as upwelling ocean currents, to thrive under fluctuating ocean temperatures and warming events. However, as a result of climate change, locations where these conditions exist are being threatened by continually increasing ocean temperatures. These locations are also known as thermal refugia.

Satellite observations of sea surface temperatures are available at 1km resolution and can be used to study areas where corals have historically thrived. Currently, approximately 84% of the world’s coral reefs are in thermal refugia. To be able to examine future thermal refugia conditions, global climate models from the most recent Coupled Model Intercomparison Project (CMIP6) were statistically downscaled to the same resolution of the satellite data.

Results show that with a global mean temperature increase of just 1.5°C above pre-industrial levels, only 0.2% of corals will be located in thermal refugia, and with 2°C global mean temperature increase, existing thermal refugia that support the existence of corals will completely disappear, most likely resulting in catastrophic losses of coral reefs.

Facilitating coral migration and promoting coral adaptation to higher ocean temperatures may be the only solution to secure the survival of coral reefs.

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