Coral Threats Require Global Solutions

By Jean-Michel Cousteau

As divers, we know the value of a coral reef. It is not only a favorite place to explore, but for those of us in dive-related businesses, it is the “bread and butter” of our livelihood. And for some 90 nations that depend on coral communities, diving and other reef-related tourism are a source of prosperity and hope for the future.

Unfortunately, as we all know, corals are under siege. By now we are all acquainted with the traditional causes of coral destruction: overfishing depletes diversity and weakens coral function; agricultural and municipal effluent fertilizes algae blooms that choke reefs; deforestation leads to sediment outflow that cuts off the sunlight needed by the zooxanthellae algae on which corals rely for food; and reckless diving practices damage coral heads and increase turbidity.

But while these traditional impacts continue to damage corals, another factor, climate change, is emerging as the single greatest threat to coral species overall. In sum, a full 27 percent of all reefs have been “effectively lost” as a result of human activities, according to the Global Coral Reef Monitoring Network. Of the 27 percent lost, 16 percent were damaged in a single climatic event, the El Niño/La Niña of 1998.
During this event, reefs in the Persian Gulf were virtually annihilated, and Kenya and Tanzania saw their reefs reduced by 90 percent. Southeast Asia was hit hard, with localized losses of 60 to 90 percent.

This shocking news was just one of many enlightening details presented last fall at the Ninth International Coral Reef Symposium in Bali, Indonesia. Within the diversity of subjects, climate change was the most common refrain.

Climate change affects corals on many levels. The first is heat stress. Scientists expect sea surface temperatures to rise between 1 and 4°F over the next 20 years. Since most corals are already at their upper heat tolerance limit, further increases are likely to result in widespread bleaching and death.

Several studies presented in Bali illuminated more subtle effects. Warmer temperatures were found to suppress primary productivity and reduce a coral’s ability to withstand other types of stress.

One study demonstrated that corals that recover after a bleaching event showed a decrease in the number of reproductive polyps, a reduction in the number of eggs produced and an increase in susceptibility to future bleaching. Another study showed that free-floating coral larvae have a harder time establishing themselves in warmer conditions.

Heightened levels of CO2 in the atmosphere are a cause of global warming and thus indirectly a cause of coral stress. But they can have a more direct effect. Even small increases in CO2 can inhibit the photosynthetic abilities of zooxanthellae. One study concluded that projected levels of CO2 will have an effect comparable to a rise in temperature of up to 5.5°F.

High levels of CO2 also alter the carbonate balance and reduce pH, thus hampering calcification. This inhibits corals’ ability to build—and rebuild—reefs.

Fortunately, the Coral Reef Symposium was not all gloom and doom. Many reports highlighted progress in coral reef management. Marine Protected Areas are a success. Seaweed farming and other alternatives to damaging reef exploitation are proving financially viable. And international efforts to monitor, manage and conserve reefs are becoming more technologically sophisticated and institutionally diverse.
But these advances are not enough. Climate change is a global challenge that requires global action. And sadly, policymakers responsible for such action seem to prefer inertia.

Last November, representatives of 170 nations met at The Hague to work out the detailed mechanisms for implementing the 1997 Kyoto Protocol on climate change. But disagreements over “nuts and bolts” issues, such as emission credits and carbon sinks, overshadowed the overall purpose, and the Sixth Conference of the Parties to the Convention on Climate Change ended in disarray. It was another missed opportunity.

The parties convene again in May. We can only hope that the wealth of new information from Bali and elsewhere spawns a renewed commitment among nations to work together on a truly global solution. As divers, for whom the Year of the Ocean is every year, we have a stake in the future of corals and should make our voices heard whenever and wherever we can.