Coral reefs are in crisis worldwide. Reefs at Risk Revisited, a World Resources Institute (WRI) project, is a groundbreaking analysis of threats to the world's coral reefs. This comprehensive assessment found that three quarters of the world's coral reefs are under threat from pollution, overfishing and climate change. Over the past ten years, the percentage of threatened reefs has increased dramatically. If current trends continue, almost all coral reefs will be under threat by 2050.

Reefs at Risk Revisited discovered that corals are under increasing stress from both human activities and climate change. Worryingly, species in the 'Coral Triangle' are particularly at risk. The Coral Triangle, a marine area stretching between the Philippines, Indonesia and the Solomon Islands, is home to an amazing 76% per cent of the world's coral species. Many of these species are found nowhere else in the world.

Climate causes chaos for corals

A major problem for coral reefs is warming seas. Rising sea temperatures cause coral bleaching, a stress response whereby corals lose their colourful symbiotic algae. Algae help corals to obtain nutrients from the ocean waters. Without algae, corals struggle to feed effectively and they become weak.

Reefs at Risk Revisited found that increasing CO₂ levels is another huge problem for corals. Increasing CO₂ levels leads to increased ocean acidity, which reduces coral growth rates. These changes in climate and ocean chemistry represent significant and growing threats to worldwide coral reefs.

Overfishing devastates coral populations

Human activities, such as overfishing, pollution and coastal development also have a huge impact of coral reefs. Overfishing is the most severe threat, affecting over half of the world's coral species. Warming seas and increased ocean acidity weakens corals and reduces their ability to withstand other threats. The combination of human activities alongside changes in climate and ocean chemistry is devastating coral reefs worldwide.

Alarmingly, protection for coral reefs is minimal and ineffective. Many countries, especially small-island nations, depend on coral reefs for tourism, protection of coastlines and to sustain livelihoods. Degradation and loss of reefs will result in significant social and economic impacts in these countries.

However Lauretta Burke, lead author of the report, says ''Despite the dire situation for many reefs, there is reason for hope...by reducing local pressures we can buy time as we find global solutions to preserve reefs for future generations.''

To read the Reefs at Risk Revisited report visit the World Resources Institute: http://www.wri.org/