The loss of biological riches could deny us vast, vital knowledge

SHORTLY BEFORE DAWN, TED Parker picks up his microphone and tape recorder and walks from his tent into the brambled undergrowth of the Gran Chaco, a vast, subtropical wilderness in southeastern Bolivia. Crouching, he whistles sharply in imitation of an avian distress call. "Birds are territorial," he explains softly. "They'll come in now to see who's intruding." Instantly sounds begin flooding back. Parker, an all-star ornithologist and research associate at Louisiana State University's Museum of Natural Science, can identify 4,000 birds—nearly half of the species on earth—by sound alone. He starts ticking off names: "Stripe-capped Sparrow, Aimophila strigiceps, on your right; Crowned Slaty Flycatcher, stopping here on its migration route; Pearly-vented Tody Tyrant; Lark-like Brushrunner..." On this morning, he will identify more than 70 of Bolivia's 1,400 bird species. "The importance here is that at least a third of the birds are endemic—they're found only in the Chaco," he says. "It's a good reason to protect an area. If it's destroyed, entire species will be lost."

The danger is real. According to the Food and Agriculture Organization of the United Nations, 42 million acres of tropical forests were leveled in 1990, more than an acre per second. Alarmingly these forests—most of them in Latin America—harbor the richest diversity of animal and plant life on earth, much of it unstudied. In Bolivia land titles are being given out daily to loggers, cattle ranchers and soybean farmers, and there are plans for a natural-gas pipeline in the Chaco.

It is this pressing threat that brings Parker to Santa Cruz de la Sierra, a frontier boomtown fueled by cocaine and agriculture. With him are three of the world's top field biologists: Louise Emmons, 48, a mammalogist and research associate at the Smithsonian Institution in Washington, D.C.; Alwyn Gentry, 47, a botanist and senior curator at the Missouri Botanical Garden in St. Louis; and Robin Foster, 46, a plant community ecologist with the Smithsonian Tropical Research Institute in Panama and at Chicago's Field Museum of Natural History. At the invitation of a Bolivian environmental group, Friends of Nature Foundation (FAN), they have come to take inventory of Chaco birds, plants and animals and to provide an assessment of the area's biological value. "Two years ago the government announced an 'ecological pause' to reassess the impact of hunting and development" says Hermes Justiniano, FAN's director. "There's interest in making a park or reserve in the Chaco, but we don't have the scientific expertise to decide where."

That is where Parker and company come in. A sort of ecological SWAT team, they are the cutting edge of a new conservation strategy called the Rapid Assessment Program (RAP), in which scientists fly in to take a quick census in key unexplored wilderness areas. Sponsored by Conservation International, a Washington, D.C.-based environmental organization, the foursome have already worked with the governments and conservation groups in Ecuador and Mexico. "It's the greatest team of experts ever to set foot in Latin America," says Russell Mittermeier, Conservation International's president, who funds their work with a $680,000 grant from the MacArthur Foundation. "What they can learn in two weeks might take another team of biologists years."

From Santa Cruz, the team flew south to Curuyuqui, a dirt airstrip scratched out of the wild by a would-be cattle rancher. After setting up camp, each member heads off to catalog flora or fauna—much as Charles Darwin did more than 160 years ago, also in South America, prior to formulating his theory of evolution.

As Parker, 38, sets out to record birdsong, Al Gentry marks off a 6-ft.-by-150-ft. transect in which he will collect a specimen from every plant at least chest high and more than 2.5 cm in diameter. Gentry is a quirky character, a passionate scientist who is capable of identifying 10,000 tropical plants, even without seeing their distinguishing flowers. In 20-odd years he has collected 75,000 different plants. The Chaco inventory will allow Gentry to compare the diversity of plants at this site with others he has studied in 30 countries throughout the tropics. "This is amazing," he says, holding up a spindly stem with tiny red mimosa-like flowers. He drops it into his specimen bag. "It's a leafless legume. I've never seen one before." Gentry believes there may be much of value to be discovered in the chemistry of little-known plants. "Tropical forests are like genetic libraries of evolution," he says. "So far we only know 1.5 million species out of a possible 50 million on the planet. The others may provide new foods, chemicals, life-saving drugs."

Robin Foster is the squad's aerial reconnaissance expert. Working with satellite photographs and maps 500 feet above the forest, he picks out ridges and valleys on which different and unusual plant communities are growing. "If this is going to be a future park or reserve, we need to know what maintains the plants and animals," he explains. "The Parapeti River flowing through here is critically important. If the forested slopes by the river's headwaters are cleared, the whole system could be in danger. Vegetation is a sponge that holds water and allows it to be released gradually. Without continuous water, you would lose mammals, birds and plant communities."

Shortly after dusk on the fifth day of the Rapid Assessment Program, Louise Emmons prepares for her foray into the world of the night forest. An expert in identifying night mammals by their reflected eyeshine, she has studied jaguars in Peru, squirrels in Gabon and tree shrews in Borneo. In 1990 she published the first—and still the only—field guide to neotropical rain-forest mammals. "The Chaco is almost completely unknown," she says, strapping on a headlamp. "In 1975 a wild pig called a Chacoan peccary was sighted here. Scientists thought it had disappeared in the Pleistocene epoch, nearly 2 million years ago." Amid the strange whistles and wails of the night, she walks quietly through the bush, turning her head from side to side and casting a beam into the darkness. Suddenly she stops. "Over there, to the left," she whispers. Fifty feet away, two small yellow dots shimmer in the blackness. "It's a fox," she says, scribbling the location in her book. "From tracks I can tell there's a huge biomass of mammals out here—tapir, pumas, ocelots. And the highest concentration of jaguars I've ever seen." Emmons dismisses the notion that she might become dinner for one of them. "There are much tastier things out here than me."

Not that field work is without its hazards. In northern Peru, Gentry was bitten by a fer-de-lance, a large, poisonous snake, and was saved only because local tribesmen kept antivenin for such emergencies. Emmons picked up bubonic plague on the last RAP trip to Bolivia, in June 1990. Foster's liver was severely damaged by hepatitis contracted by drinking water from Peru's Madre de Dios River. "All of us have had leishmaniasis, a treatable parasite that eats skin and cartilage," says Parker.

Other occupational hazards aren't physical. The demands of field work can test even solid relationships, and not all survive. Among the team members, Emmons and Gentry are both divorced, Parker is separated and Foster has never married. "You get out of touch, personally and culturally," says Foster, who says he missed watching the Clarence Thomas hearings. "It's hot, tough work," admits Emmons, who between field trips lives on a houseboat on the Potomac River in Maryland. "It's hard on your time and your personal life. But I wouldn't be doing anything else."

The four share a passion for nature than began in childhood. Parker, who grew up in Lancaster, Pa., kept elaborate lists of butterflies, fish and birds he saw. He began his avian education by listening to birdsong records that accompanied Roger Tory Peterson's famous field guides. By 18, Parker had broken the North American record for bird species sighted in a single year: 626. Al Gentry collected butterflies as a boy in Clay Center, Kans. "I remember seeing some so rare and beautiful I'd actually start shaking," he says. Emmons, the daughter of a diplomat, was fascinated by exotic animals she saw during her childhood in Uruguay, Spain, Australia and Malaysia. Foster's great-grandparents were friends of Sierra Club founder John Muir in California. Foster's parents encouraged him in his rock collecting, and he still remembers the girl who beat him out for a blue ribbon in a mineralogical contest. "People assume the world is fully known, but it's not," says Emmons. "New discoveries are being made every day."

Emmons's words prove prescient. On their last day in the Chaco, the team flies west, over a once lush area now transformed into desert by cattle. Their curiosity has been piqued by a local rancher's report of a group of guanacos, the largest members of the llama family. Few have ever been sighted in this part of the country. Now, with the plane carving wide arcs above the desert, the four gringos intently scan the ground below. "There they are, seven of them!" gasps Emmons, pointing at the brown animals galloping gracefully near a flowering purple jacaranda tree. "They must be the last herd in lowland Bolivia." The conversation turns to the dazzling diversity of life-forms the scientists have witnessed in the Gran Chaco—and the fragility of existence. "We have a historic opportunity to save these species and habitats," says Parker. "My nightmare is that one day they'll be gone and people will look back and say, 'How could we have ever let this happen?' "