Nature Under Glass
A gaseous greenhouse threatens nearly every park, plant, and animal that conservationists have worked to save.
by James R. Udall

LAST SUMMER'S SCORCHING DROUGHT spawned a firestorm of articles analyzing the potential impact of global warming on humankind. But few of these starve-drown-and-swelter pieces paid more than passing attention to how species and ecosystems might fare. If rapid climatic change could cause a disruption equivalent to a nuclear war for Homo sapiens--one of the world's most adaptable species and, moreover, the only one that will have been forewarned--what unfathomable decimation might it wreak on the rest of Earth's creatures?

Climatologists believe Earth will warm 3 to 9 degrees Fahrenheit by 2050 if current trends in greenhouse-gas emissions continue. Biologists are more than alarmed by these figures--they are spooked by the possibility that global warming, if and when it occurs, may cause a biological apocalypse. Their fears might be hard to understand. Spooked? Why? A warming of a few degrees--won't that just mean less snow, more Coppertone?

George Woodwell, a greenhouse expert who is director of the Woods Hole Research Center in Massachusetts, doesn't see it that way. "Rapid change is, almost by definition, the enemy of life," he says. "Great caution seems appropriate before committing the world to irreversible changes of unknown magnitude and effects."

According to ecologist Norman Myers, there's a striking correlation in the fossil record between previous mass extinctions and climatic change. Habitat destruction has already put hundreds of thousands of species at death's door, Myers says. Global warming may well open it and shove them through.

Michael Oppenheimer, an atmospheric scientist with the Environmental Defense Fund, says that by fundamentally altering the composition of the atmosphere we are venturing into uncharted, risky terrain. "Remember," Oppenheimer cautions, "nobody predicted the ozone hole. This suggests that we ought to be extremely skeptical of our predictive capabilities regarding global warming--and we ought to expect further nasty surprises."

So much for the generalities. But how will warming affect polar bears? Turtles? Redwoods? Plankton? Alligators? Oceans? The Arctic National Wildlife Refuge?

Last October, at a conference organized by the World Wildlife Fund, nearly 400 scientists and environmentalists met to compare notes on these and similar questions. Using a West African term for magic, conference organizer and conservation biologist Robert Peters summarized the grim take-home message succinctly: "Lots of bad juju."

"If the climate models turn out to be right, the new world will be biologically less rich and less stable," said Dennis Murphy of the Center for Conservation Biology at Stanford University. "As climatic zones move north and south, away from the equator, species will have to move too, in order to survive. Some will fail and become extinct."

Peters warned that when it comes time to move, many species will find themselves "man-locked," their escape routes blocked by highways, cities, and "agricultural deserts." According to Peters, types of species and communities particularly at risk include poor dispersers (snails and most trees, for example), peripheral populations (plants and animals now found at the edges of their ranges), geographically localized species (redwoods), genetically impoverished species (any currently endangered), specialized species (the Everglades kite, which is dependent on the apple snail as its single food source), annuals (which would suffer reproductive failure due to droughts and heat waves), montane and alpine communities (butterflies and wildflowers isolated on mountaintops), Arctic communities (where temperatures are predicted to increase most), and coastal ecosystems (which would be devastated by sea-level rises).

Of course, not every species would see its range shrink. Environmental disruption would usher in a heyday for plant and animal pests. Tropical insects, parasites, and diseases would migrate to more temperate regions. The range of the African tsetse fly, for example, would shift southward, bringing sleeping sickness with it. Hookworm infestations could become rampant throughout the Northern Hemisphere.

Because global warming is projected to be greatest at high latitudes, polar regions would likely show the first signs of ecological damage. The Arctic and Antarctic oceans currently harbor the world's most productive fisheries. At the base of these fertile food chains are plankton--microscopic plants and animals that thrive beneath the ice covering these waters for much of the year. Declines in the extent of sea ice, however, could cause a plankton crash that would topple a huge biomass of fish and seabirds. And if the sea ice vanishes, as some climate models predict, polar bears, seals, walruses, and other animals that depend on it will vanish, too.

Research by Margaret Davis, an ecologist at the University of Minnesota, indicates that forests throughout the United States would shrink like cheap T-shirts along their warmer and drier margins, with the Southeast's forests vanishing entirely over a period of decades. By the year 2090, climate zones in the East would have shifted 300 miles to the north--at rates ten times faster than most tree species can migrate. "Trees aren't very good at picking up and walking north," notes Deborah Jensen, an ecologist at the Pacific Institute. Acorns get carried around by birds and squirrels, so oaks may have a chance to track the changing climate. But many other tree species will be left behind."

Sea-level rises would devastate coastal wetlands. For example, a three-foot rise, possible by 2050, would drown most of Everglades National Park and the already endangered Louisiana coastal wetlands. Attempts to protect buildings and roads with sea walls would only compound the biological loss by directing the full force of storm surges onto adjacent wetlands.

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