April 28, 1997 - Week 17
International Year of the Reef

Corals Can’t Stand the Heat: Global Climate Change and Coral Reefs

Just like people, corals must endure stress from many different sources in order to survive. Some of these stresses are natural, such as black band disease or grazing by other marine organisms. However, the greatest threats to coral survival are stresses which are anthropogenic, or ‘created by humans.’ The most serious anthropogenic stresses include: sedimentation caused by poor land-use practices; pollution and over-nutrification from domestic, agricultural, and industrial waste; physical alteration of coral reefs during coastal construction projects; destructive fishing practices such as poison and blast fishing; ship groundings; and coastal tourism, which brings millions of eager divers and snorkellers to coral-rich areas of the world each year. In some parts of the world, coral reefs are subjected to many or all of these stresses simultaneously. Today, 10% of the world’s coral reefs have already been destroyed, and scientists predict that we will lose an additional 30% within the next twenty years as the intensity and frequency of these anthropogenic stresses increase along with the size and density of coastal human populations.

As if coral reefs didn’t have enough to worry about, it now appears that they are also threatened by global climate change. These threats are outlined in a recent report by the World Wildlife Fund (WWF) titled Coral Reefs and Climate Change. According to an earlier report -- Reefs at Risk (a joint publication of the United Nations Environment Programme [UNEP], Intergovernmental Oceanographic Commission [IOC], World Meteorological Organization [WMO],International Union for the Conservation of Nature [IUCN], and WWF) -- global climate change is expected to lead to the following changes over the next century:

· increased air and sea-surface temperatures;
· rises in sea-level;
· changes in weather patterns;
· more frequent storms, droughts, floods and other extreme weather in some places;
· possible alteration in the pattern of ocean circulation; and
· changes in the chemistry of seawater from higher concentrations of carbon dioxide.

Coral reefs will be affected by changes in the intensity of wave action and ultra-violet radiation, and by changes in water chemistry, dissolved nutrients, and water temperature.

We may already be seeing the negative impact of increased sea-surface temperatures on the health of corals. The most visible symptom of declining coral health is coral bleaching. Because many corals live in water which is already near their upper temperature limit, a water temperature increase of only a few degrees can be deadly. As water temperatures rise, corals become increasingly stressed. When stress levels get too high, corals expel the symbiotic algae, or zooxanthellae (tiny one-celled plants) which live within the thin layer of live coral tissue. Zooxanthellae are important because they turn sunlight into food for their coral hosts. They also facilitate the formation of the coral skeleton -- the main structural component of coral reefs. Because zooxanthellae give corals their various rich colors, a coral without zooxanthellae appears bleached. Corals can not thrive without zooxanthellae. For coral reefs that are already stressed due to poor water quality, destructive fishing, or frequent interactions with irresponsible divers and snorkellers, increased water temperatures could become the proverbial straw that breaks the camel’s back.

Although the global climate does experience natural, long-term fluctuations over thousand year-long periods, the global climate change which we are currently experiencing is fairly rapid and is largely anthropogenic. The 1995 report of the Intergovernmental Panel on Climate Change (IPCC) has determined that there is a direct link between today’s global climate change and the buildup of greenhouse gases, such as carbon dioxide, in our atmosphere. Most of these greenhouse gases come from the burning of coal, oil, and gas which provides electricity and heat for our homes, and fuel for our automobiles.

Coral reefs will never be entirely free from the stresses of global climate change. However, there are some practical steps which we can all take in order to minimize that stress. If we walk to work or take public transportation instead of driving our cars, turn off unused lights, and turn our thermostats down a few degrees in the winter and up a few degrees in the summer, we can help ensure the long-term health of coral reefs . For more information about what you can do, visit the WWF website at http://www.panda.org/climate

Upcoming Event

· Watch for the U.S. release of the WWF Climate Change Campaign report Coral Reefs and Climate Change during the week of April 28th.

FOR MORE INFORMATION ON THE INTERNATIONAL YEAR OF THE REEF PLEASE CONTACT:

FOR MORE INFORMATION ON SEA SURFACE TEMPERATURES, GLOBAL CLIMATE CHANGE, AND CORAL REEFS CHECK OUT THESE WEBSITES:

http://psbsgi1.nesdis.noaa.gov:8080/PSB/EPS/SST/sst_anal_fields.html http://ghsun1.kgs.ukans.edu/welcome.html

OR CONTACT:

IUCN - The World Conservation Union and the US Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA) are working together to publicize the urgent need for conservation and sustainable use of coral reefs as part of the International Year of the Reef (IYOR). The IUCN - NOAA partnership will heighten public awareness by providing a coral reef story idea to international media outlets each week throughout the IYOR. To provide story ideas which highlight coral reef issues of local, national, regional and international importance, IUCN and NOAA are in contact with NGOs, coral reef scientists, government officials, inter-governmental organizations and others to submit story ideas for possible use in the media outreach program.