Feb 24

More than three-quarters of the world’s coral reefs are seriously threatened by overfishing, pollution and climate change, according to a comprehensive new report.

The report, entitled ‘Reefs at Risk Revisited’, was compiled by the World Resources Institute (WRI) and 25 other research organisations. It builds on a 1998 analysis of coral reefs, and enables scientists to compare the changing threats to coral reefs around the world.

Photo of damselfish over an Acropora colony

Damselfish feeding above a healthy Acropora colony. Acropora corals are particularly sensitive to the effects of climate change.

Changing threats

The most immediate threat to reefs is overfishing. Since the 1998 report, there has been an 80% increase in the threat from overfishing and destructive fishing, particularly in the Indian and Pacific Oceans.

The pressure on coral reefs appears to be highest in Southeast Asia, where nearly 95% of reefs are threatened.

Photo of dead Acropora colony after cyanide fishing

A dead Acropora colony, several years after the use of destructive fishing methods.

However, by 2030 it is expected that the primary threat to coral reefs will be the effects of climate change. Mass coral bleaching, a stress response to warming waters in which corals expel their symbiotic algae and turn white, is becoming more frequent as ocean temperatures rise. Extreme bleaching events kill corals outright, while less extreme events can weaken corals, affect coral reproduction, reduce growth and calcification (vital for the development of the coral skeleton), and leave them vulnerable to disease.

Photo of boulder brain coral showing bleaching

A partly bleached boulder brain coral colony.

The report suggests that during the 2030s, roughly half of reefs will experience thermal stress sufficient to induce severe bleaching, rising to more than 95% of reefs being affected by the 2050s.

Still hope

Although the ‘Reefs at Risk’ report offers a troubling picture of the world’s coral reefs, it also offers a glimmer of hope. Reefs around the world have shown a capacity to rebound from even extreme damage, while active management is protecting reefs and aiding recovery in some areas.

There are reasons for hope,” said Lauretta Burke, senior associate at WRI and a lead author of the report. “Reefs are resilient; and by reducing the local pressures, we can help buy time to find solutions to global threats that can preserve reefs for future generations.”

Photo of blue rice coral in shallow reef

Blue rice coral is found in many parts of the United States Marine Protected Areas network.

Marine Protected Areas (MPAs) can reduce threats to reefs, often by focusing on managing overfishing and destructive fishing practices, and by reducing pollution from land.

More than a quarter of the world’s reefs are within MPAs. However, only 6% of coral reefs found in MPAs worldwide are currently rated as effectively managed, pointing to the need to designate more protected areas and improve the effectiveness of existing MPAs to protect reefs.

By tackling local threats such as overfishing and pollution head-on and by creating healthy reef systems, we may be able to “ buy time” for coral reefs in the face of climate change, the report concludes.

The report is full of solutions – real world examples where people have succeeded to turn things around,” says Dr Mark Spalding, senior marine scientist at The Nature Conservancy.

Visit the World Resources Institute website.

Read a summary of Reefs at Risk Revisited (PDF 3.9 MB) or view the full Reefs at Risk Revisited report (PDF 6.1 MB).

Learn more about corals on ARKive.

Helen Roddis, ARKive Species Text Author