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