But ocean critters are not the only ones affected by climate change. Somero points to studies showing that a wide variety of plants, insects, birds and other organisms are expanding their ranges northward or moving to higher elevations - a likely result of global warming.

If the trend continues, warn scientists, it could have serious consequences for human health. A 1998 survey concluded that malaria, dengue fever and other mosquito-borne diseases are now occurring in the highlands of Asia, Central Africa and Latin America - an indication that mosquitoes are moving into habitats once considered too cold for their survival.

The World Wide Fund for Nature recently forecast that 20 percent of all organisms now living in colder climates could be wiped out by the end of the century. The WWF report predicts that, as global warming accelerates, plants and animals will invade cooler habitats, but many will be unable to move fast enough to avoid extinction.

Whether this catastrophic scenario actually occurs is a matter of debate, but according to Somero, the ability of an organism to quickly adapt to temperature changes may be the key to its survival.

For example, the snail species T. funebralis might be able to handle the predicted 6 F (3.3 C) rise in ocean temperature, but its cousin T. brunnea may have to undergo a biochemical change that would give its cells the ability to manufacture proteins in warmer conditions.

``Attempts to increase the thermal limits of protein production by holding snails at warm temperatures in the laboratory led to no upward shift in the temperatures at which proteins could be made,`` Somero observes.

Therefore, he points out, adapting to rising temperatures may require changes in a species` genes over many generations - an evolutionary process that may be too slow to keep pace with global warming.

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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
14-Nov-2000