Illustrations by Dugald Stermer
	When the icy current that had cooled their island dissipated, Galapagos penguins succumbed to the tropical heat.     Slide Show

pecies are built to last. The rich fossil record of marine life over the past half-billion years tells us that the likes of clams, corals and crabs typically endure well over five million ye ars. On land, where environmental change more readily upsets the ecological apple cart, the life expectancies of mammals are shorter (though still impressive, on the order of one million to two million years). And yet, here we are at the brink of the year 2000, asking an unnerving question: what species on earth right now will not be here when people open the Times Capsule in the year 3000?

Only in times of momentous ecological tumult would such doomsaying be justified. And such upheavals are vanishingly rare. In fact, during the past half-billion years, there have been just five global mass-extinction events (like the comet impact that mos t likely felled the dinosaurs 65 million years ago). Yet the sad fact is that we are living amid a sixth extinction event -- one that, according to the Harvard biologist E. O. Wilson, is costing the earth some 30,000 species a year. Biologists estimate th at there are at least 10 million species on earth right now. At this rate, the vast majority of the species on earth today will be gone by the next millennium.

Ever since humans domesticated plant crops and barnyard animals beginning some 10,000 years ago, our numbers have shot up from an estimated six million to six billion. We have engaged in a radical, systematic transformation of the world's ecosystems -- replacing grasslands and woodlands with arable fields, cities, suburbs, malls and roadways. We have exploited dwindling stands of timber and fisheries; we have fouled the earth, the atmosphere and even much of the oceans; and we have introduced alien spec ies around the globe. In short, we bear an uncanny resemblance to those Cretaceous comets.

Species depletion isn't merely the concern of nature lovers. Each day, humans make use of some 40,000 species for food, shelter, clothing and fuel. We rely on the natural pharmacopoeia locked up in the plant species that are still mostly unknown and in a wide assortment of marine invertebrates. We need the wild congeners of our increasingly homogeneous domestic crops to replenish their genetic diversity. But beyond such practical matters lies a moral question: how can we condone, however passively, the d estruction of our fellow species?

Niles Eldredge, a paleontologist and a curator at the American Museum of Natural History, is the author of "Life in the Balance: Humanity and the Biodiversity Crisis."

What follows is a short list -- culled from the vast array of potential candidates -- of species likely to be victims of the sixth extinction. It would be wonderful if these predictions proved inaccurate. By confronting what we are doing to the species a nd ecosystems of our planet, we can perhaps change our consumption patterns and conserve what remains of our ecosystems and species. If not, however, this field guide to the soon-to-be dead will give the inhabitants of the year 3000 some sense of what the y're missing.

OVERHARVESTING

Prairie Dogs: These little ground-dwelling rodents once lived by the millions in extensive colonies on the grasslands of North America. But by the year 2000, black-tailed prairie dogs were being shot by the thousands by "sportsmen" at ranches in the Ameri can West, who usually didn't even bother to collect the dead carcasses. As the hunting practice spread, colonies fell below critical size -- and the entire species suddenly vanished.

Pollock: With the love for sushi having gone global around the year 2000, it was easy to predict that the succulent blue-fin tuna would soon succumb to overfishing. Much less obvious was the damage being done to more mundane (and abundant) commercially ha rvested fishes. The several species of pollock -- a large, silvery fish that looked much like cod -- were then a staple of the world's marine fisheries. Known as the poor man's cod, pollock had done yeoman service as a stand-in for that fish, as well as b eing a component of the crab substitute surimi. But mechanized international fishing fleets in places like the Bering Sea became so efficient -- not only netting but also literally vacuuming the ocean floors clean (and discarding most of the other fish an d invertebrates sucked up) -- that extinction was inevitable. Pollock stocks simply had no opportunity to replenish themselves.

Mahogany: It wasn't long before the world was stripped bare of these tropical hardwood trees. Mahogany, celebrated for the rich, dark color of its wood, had been highly coveted by the makers and owners of fine furniture. Indeed, it was but one of many tro pical trees exploited for a specialized use. The dark wood of ebony trees was harvested to make fine piano keys. Indeed, the losses to the musical world through deforest-ation were manifold: granadilla, which provided the traditional wood for clarinets, v anished, as did the high-quality cane reeds that served as reeds for clarinets, oboes and saxophones. In fact, almost every single tropical hardwood species in demand in the world's markets was wiped out -- not only through direct harvesting but also as a byproduct of the relentless cutting and burning down of tropical forests from Brazil to Borneo.

Truffles: The delights of truffles -- small, fleshy fungi that had been avidly sought after for centuries -- will never be experienced firsthand again. The intense, earthy flavor of these fungi (usually found below ground near tree roots, sniffed out by h ogs or dogs) was matched by their potent mushroomy smell. Celebrated particularly by the chefs of Western Europe, truffles never had a chance, since they resisted the most determined attempts to farm them. They were gourmandized to extinction.

HABITAT DESTRUCTION

The African Black Rhinoceros: No mammals conjured up the remote past of early mammalian evolution more vividly than rhinos -- with their ponderous gait, primitive leer and not altogether undeserved reputation for stolid stupidity. Although all five specie s of rhinoceros on the planet in the year 2000 were doomed, the black rhino of the African plains was the first to go. For one thing, its numbers had already dwindled to a precious few. Relentless demand for powdered-rhino-horn aphrodisiacs eventually won out over the captive-breeding programs of zoos and African conservation parks.

The black rhino was a prime example of a type of African megafauna known in 20th-century ecotourism circles as "the big hairies." More large mammals survived to 2000 in Africa than anywhere else because Homo sapiens evolved on the same primordial savanna ; as a result, animals there developed a tactical wariness toward humankind, while species elsewhere, unaccustomed to human hunters, were defenseless. Alas, we humans eventually returned to Africa with modern hunting technology -- and an even more devasta ting capacity to convert savannas into pastures.

The African Wild Dog: In 2000, these feral canines were still clinging to life in such outposts as the Okavango Delta, in Botswana. But they soon became the permanent victims of disappearing habitats and disease. Their intricate social structures provided a role and place for each dog, no two of which looked alike. To watch wild dogs hunt, whether in packs or as dominant loners (as often happened in the Okavango); to see them kill a small impala only to have it wrested away by a pack of spotted hyenas; to see the wizened, almost mummified remains of last night's meal -- such sights are no more.

INVADING SPECIES

The Helmet Vanga of Madagascar: Islands, in their splendid isolation, are notorious "laboratories of evolution," and Madagascar's biodiversity was particularly remarkable. At one point, there were 13 species of vangid -- a melodious family of birds relate d to shrikes -- endemic to the island. But only a few of these birds (like the hook-billed vanga) were able to cope with the transitional habitats created when encroaching rice fields met forests. The helmet vanga, a more delicate creature, couldn't survi ve outside the deep rain forest. The bird was doomed by the clear-cutting of Madagascar's jungles.

The Hawaiian Coot: During World War II (1939-1945), the brown tree snake started moving around the Pacific, hitching rides in airborne cargo. Despite determined efforts to police air shipments and prevent the snake from eating the eggs of many of Hawaii's native birds, the snake won out. Its appetite accelerated the job already begun by human development in obliterating most of the island's indigenous flora and fauna. The ducklike Hawaiian coot, a slate gray bird of ponds and marshes, succumbed to this ma rauding invader despite its penchant for laying eggs on floating nests sequestered in vegetation.

GLOBAL WARMING

The Galapagos Penguin: The only penguin ever known to have lived on the Equator, this 14-inch-tall bird, with its bold black stripe crossing the upper part of its white breast, used to be seen within a mile or two of flocks of the quintessentially tropica l flamingo. It owed its presence there to the frigid Humboldt current, which cooled down an island that would otherwise have been fatally warm. For a while, the rapidly melting ice sheets of Antarctica kept the cold waters flowing northward, but finally t hings became far too warm on land, the current pattern changed -- and the Galapagos penguin was no more.

Musk Ox: Global warming eliminated most of the tundra -- the frozen stretches of grasses and lichens in the far reaches of the Northern Hemisphere. As the earth warmed, shrubs, then finally trees, invaded these primordially flat and open spaces. The gorge ous musk oxen, with their silken brown coats hanging nearly to the ground and their flattened horns plastered to their foreheads, needed the tundra's wide-open spaces, and native flora, to graze. The loss of their habitat finished them off for good.