Almost 20 percent of the world’s coral reefs have disappeared. This past year has been particularly devastating for coral, with unprecedented bleaching events caused by ongoing climate change and exacerbated by an unusually strong El Nino. Bleaching occurs when waters become too warm and corals release the algae found in their tissue (known as zooxanthellae) that give them their vibrant colors and important nutrients. This causes the coral to turn completely white. While this process doesn’t directly kill corals, it does place them under stress and makes them more vulnerable to threats like disease and erosion. And the implications extend beyond the reefs—the widespread loss of corals could have severe consequences for coastal communities in more than 100 countries that depend on reefs for income, food, and revenue from tourism.

A new dataset released last week helps prioritize coral reef management in the face of climate change. The dataset was developed by the United Nations Environmental Programme (UNEP), the National Oceanic and Atmospheric Administration (NOAA), the World Wildlife Fund (WWF), and the Pacific Islands Climate Science Center (PI CSC, managed by USGS). By downscaling global climate model projections, researchers were able to identify at what point in time severe bleaching conditions can be expected to happen twice per decade, and at what point they can be expected to happen annually—at which point recovery will be very difficult.

An interesting finding of this work is the fact that there is a great deal of variation in the predicted onset of bleaching conditions, both between and even within countries in the same region. Thanks to this dataset, we now have an idea of which reefs are in the most immediate danger and should be the focus of preventative management actions. Such actions could include the establishment of marine protected areas, fisheries restrictions, or reducing pollution from land.

Two Pacific Islands Climate Science Center projects contributed information to the development of this dataset: 

1. In this most recent project, researchers developed projections of coral bleaching conditions for reefs worldwide. To do this, researchers performed what’s known as climate model ‘downscaling’, in which climate models that are meant to be used at a global scale are refined to allow them to be used to examine smaller sites. Learn more about this project here.

2. The second project provided assessments of coral reef resilience and vulnerability to climate change in the Commonwealth of the Northern Mariana Islands. Researchers developed a new approach to rank coral reefs based on their resilience, in order to identify reefs most in need of management attention. Learn more about this project here.

The coral bleaching dataset was launched on May 24, 2016 at the second United Nations Environment Assembly (UNEA-2) in Nairobi, and is available for download on the UNEP website.