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

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Because temperature has ceased to be a major constraint on human activities, it's easy to forget that it governs many aspects of plant and animal reproduction. For example, the gender of some reptile offspring is controlled by the eggs' incubation temperature. Alligator eggs incubated at 93 degrees or above produce males; temperatures below 86 degrees produce females. (In sea turtles, it's just the reverse: Warmer temperatures produce females.) "It's conceivable that we could end up with a total absence of one sex," says biologist Daniel Rubenstein of Princeton University.

University of California at Berkeley ecologist John Harte fears that an altered climate will have ripple effects that could be far more damaging than the more obvious direct impacts. For example, a melting of permafrost in Alaska's Arctic National Wildlife Refuge would destroy its tundra ecosystem. These windswept plains are the main calving grounds for 180,000 caribou and a critical staging area for snow geese and other birds. As the tundra thawed, the underlying peat would begin to decay. This would release immense quantities of carbon dioxide, leading to even more warming.

Oceans are the largest Pandora's box in the global-warming scenario. The greenhouse effect has the potential to change the upwelling patterns that sustain world fisheries as well as the rainfall patterns on which agriculture depends. If oceans warm and rise, coral reefs, which currently harbor two-thirds of the fish in tropical waters, may shrivel. Even ocean currents could switch--a nasty surprise whose impacts, says Oppenheimer, "would dwarf those of the ozone hole." If the Gulf Stream stopped carrying warm water from the Caribbean northward, for instance, temperatures in northern Europe could fall 8 to 15 degrees, ushering in a new ice age.

The implications of global warming for conservation policy could not be more profound. The warming is expected to be more rapid than any in human history; yet all preservation efforts to date have assumed a stable climate. If climatic upheaval yanks the habitat "rug" from beneath national parks, forests, rangelands, and wildlife refuges, we can expect a wholesale reshuffling of biotic communities, disruption of predator-prey relationships, and the loss of many species. The conclusion is inescapable: The specter of global warming puts everything conservationists thought they had saved at risk once again. We're back to square one.

In a world where rapid climatic change became the norm, conservationists would have to consider not merely how to preserve a species in a place, but also how to preserve it through time. UC Berkeley's Harte thinks we should hedge our bets by diversifying the number, location, and size of the parks in our portfolio, and by making conservation of biodiversity a higher priority on the 95 percent of the planet not dedicated to parklands.

"If we are concerned with maintaining biological diversity--not just to eke out another 50 years or so of species survival but to preserve some remnants of the natural world for the year 2100 and beyond--we must begin now to incorporate information about global warming, as it becomes available, in the planning process," Robert Peters says.

This would mean different things in different places. For instance, coastal preserves might be expanded inland to include terrain at a variety of elevations. "That way," says biologist Larry Harris of the University of Florida, "whatever the sea-level rise, you'll have something left."

Climatologists believe that we're already committed to one to three degrees of warming due to past greenhouse-gas emissions. Beyond that, however, additional warming is not inevitable--the planet's destiny is cradled in human hands. More than a few ecologists think this may be the spookiest thing of all. Placing the challenge in a cultural context, George Woodwell says, "Until now Western civilization has assumed that the world would take care of itself. But Earth is no longer large enough to accommodate the assaults of contemporary civilization. . . . The world is life itself, and we need to provide a new stewardship that we have not yet been willing to provide. That stewardship must bring about a revolution in the world's governments--or we face a crippling, global biotic impoverishment."

JAMES R. UDALL has covered Utah wilderness, water marketing, and the Arctic National Wildlife Refuge for Sierra. He also writes for Audubon, National Wildlife, and Outside.