By Stephen Leahy
BROOKLIN, Canada, Aug 22 2002 (IPS)

Coastal and marine ecosystems, already stressed by human development, pollution and over-fishing, are going to face significant pressure from climate change, says a new report from the Pew Centre on Global Climate Change.

A sea level increase of up to one metre over the next 100 years will have enormous ecological and economic impacts. Barrier islands and wetlands that buffer coastal areas from storms will be underwater, adding to the destructiveness of future weather systems, says Robert Twilley, director for ecology and environmental technology at the University of Louisiana.

Some impacts are already clearly visible in low-lying Pacific states such as Micronesia and Tuvalu, where mangroves marshes are dying as the ocean rises, says Twilley, co-author of the report, ‘Coastal and Marine Ecosystems and Global Climate Change’.

The loss of the trees, which act as “nurseries” for many marine species, leads to declines in local fisheries. And coastlines are increasingly damaged by storms without marshes to absorb some of the weather.

Pacific island nations are extremely worried and have chided the United States, Australia and other countries for not signing the Kyoto Protocol, a global treaty that commits countries to reducing emissions of climate-changing gases.

Last spring, Tuvalu, a country with its highest point just five metres above sea level, said it might sue the United States and Australia for failing to sign the protocol.

Other impacts of climate change remain unknown, says Twilley. “We’re in the middle of an enormous experiment,” he adds.

Sea temperature increases of just one degree Centigrade could have important and sudden impacts on fish, with cold-water species retreating north and heat-lovers claiming their territory. Entire fisheries may disappear as a result, says University of Maryland marine ecologist Victor Kennedy.

Such a temperature change is very likely in U.S. coastal waters and elsewhere before the end of the century, he adds. “We don’t know what this means for the coastal zone’s many microbial organisms. It is likely that disease-causing organisms will increase,” says Kennedy.

Paradoxically, without greenhouse gases like carbon dioxide and methane that naturally trap the heat of the sun, the earth would be little more than an ice ball. Over millennia, heat was trapped in the atmosphere, the temperature slowly rose and the earth greened. Until recently, this natural process continued to very slowly warm the planet.

But in the past 100 years, human activities have increased carbon dioxide levels by 30 percent, methane by 145 percent and nitrous oxide by 15 percent, pushing the natural warming process into fast-forward. It will go even faster as greenhouse gas emissions rise rapidly.

Climatologists say carbon dioxide levels will double any time between 2020 and 2050.

Already, ocean temperature has increase about one-half of one degree Centigrade and seas have risen 10-20 centimetres, almost certainly results of climate change, says the report from the U.S.-based centre.

The already difficult job of fisheries management is going to be much more complex as the oceans change, say its authors.

Warmer seas have already killed 25 percent of the world’s coral reefs, according to Joan Klepas, a marine ecologist with the U.S. National Centre for Atmospheric Research and another author of the report. This coral bleaching is actually the loss of a particular, temperature-sensitive alga that the coral feed on.

Some coral could recover in a few decades if enough survive and temperatures drop. But corals also appear to be much more vulnerable to disease in higher temperatures, says Klepas. Only 10 percent of the Elkhorn coral is now alive in the Caribbean because of a bacterial disease that may have been helped along by warmer waters.

Corals are also adversely affected by the changing chemistry of seawater. As the oceans absorb more carbon dioxide, the concentration of carbonate ions – an essential for corals – falls. The animals may grow more slowly and become thinner as a result, Klepas says.

The Pew report also notes that coastal precipitation and wind patterns are predicted to change, which could have a wide range of impacts on marine ecology and human populations.

Winds affect ocean currents and near-shore circulation patterns, altering the lifecycles of marine organisms. More frequent and intense storms are likely to accelerate coastal erosion, increase the risk of severe floods that can deliver nutrients and contaminants into coastal waters, and damage mangrove forests and coral reefs.

The report’s authors conclude that it is vitally important to preserve coastal wetlands and marshes, control development and reduce emissions. But despite these measures, climate change will significantly alter the oceans; more research is needed to understand exactly how.

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