Study: Climate Change Causing Widespread Global Coral Reef Degradation

Global degradation of coral reefs is primarily caused by climate change instead of localized impacts associated with human population in coastal areas, as many scientists had assumed. That is the conclusion of groundbreaking new research published today in the Nature journal Scientific Reports. The study suggests that to restore and conserve healthy coral reefs globally, addressing local problems such as overfishing and pollution won't be effective unless we also tackle global warming by substantially reducing carbon dioxide emissions.

Photo by Abel Valdivia, Center for Biological Diversity. Photos are available for media use.

"We were surprised to discover that even those reefs most isolated from local impacts like pollution and fishing were no better off in terms of coral and seaweed cover," said John Bruno, a professor of marine ecology at the University of North Carolina at Chapel Hill and lead author of the study. "This finding totally overturns a major paradigm in reef ecology and conservation: the assumption that isolated reefs are near-pristine and more resilient to global warming."

The study used a database of more than 1,700 coral reef surveys across the world, previously developed by Bruno. The objective was to determine whether reefs isolated from local human impacts such as pollution and overfishing are faring better by having more living coral and less seaweed, a sign of healthy reefs. Surprisingly, they are not. Isolated coral reefs many miles away from any human residents are in no better shape than reefs adjacent to large urban centers.

"Widespread arguments that coral reef degradation is mostly caused by local factors are unsupported. We found the problem is better explained by global impacts such as climate change," said Abel Valdivia, a marine ecologist with the Center for Biological Diversity and an author of the paper. "To save coral reefs, we need to reduce our overreliance on fossil fuels and lead global efforts to swiftly and drastically cut carbon emissions in the coming decades. Local management alone won't cut it."

Most isolated and presumably pristine coral reefs of the world, located in the Great Barrier Reef and the middle of the Pacific, are currently suffering from mass bleaching and unprecedented mortality due to warming waters. Corals, the building blocks of reefs that support the entire ecosystem -- much like trees in a forest -- have been dying at an alarming rate over the past three decades. This study largely settles a debate within the scientific community about the relative importance of local versus global causes of declining coral reefs.