Drawing a green line: Costa Rica makes audacious plans to reclaim its forests.

On a sunny January afternoon, as a steady wind sweeps across Costa Rica's Pacific slope, 18-year-old conservation worker Dunia Garcia settles down to sort the insects she has collected during the past week. From the porch of her two-room, wooden biological station perched on the shoulder of an idle volcano, GarCia has an astounding view - literally from the continental divide to the Pacific Ocean. Her view also defines the choices facing Costa Rica. Will the Central American country follow the path Garcia can see to the west - where dusty pastures stretch without relief to the Pacific shore, on land that was once dry tropical forest? Or will it choose the path she sees to the north and east, in the protected forests of the three national parks within the Guanacaste Conservation Area?

Although Costa Rica is a pioneer of tropical restoration, its 35 national parks and nature reserves face ecological and social problems. Too many of them are now islands of natural habitat with a dwindling number of animal and plant species, set amidst a sea of farms and pasture.

In 1993, illegal farmers began slashing-and-burning in the rainforest of Corcovado National Park, along the southern Pacific coast. In response to these twin ecological and social challenges, Costa Rica embarked on an ambitious project to consolidate its reserves and more than double their size. The existing reserves, covering 12.2 percent of the landscape, are being merged with newly acquired land (at a cost estimated at. $1 billion) to form conservation areas on 27 percent of the national real estate.

The environmental idea is to bequeath large, functioning ecosystem to future generations. Not scraps of land, not reserves specifically for quetzals, panthers or hummingbirds, but big chunks of natural habitat where hundreds of thousands of native species can live, migrate and evolve.

Socially, the idea is to invent non-destructive uses for the preserved mountains, forests, wetlands and reefs that will make them too valuable to destroy. Unlike national parks, the conservation areas are not supposed to be idle land behind "no farming, no hunting" signs. Instead, they will be profitable centers for eco-tourism, education and research. A key goal is to prospect for new products such as drugs and biological pest controls.

Costa Rica's conservation programs are important for several reasons. Not only is the country, situated on the land bridge between the Americas, a world leader in preservation, but it has an unusual endowment of natural wealth, including 205 distinct mammals, 845 birds, 1,013 fish and roughly 10,000 higher plants.

With last year's election of President Jose Figueres, who says he wants "a constructive alliance with nature," the conservation areas are being made a top priority. Equally important, dozens of local environmental groups have sprung up in recent years. One, La Voz del Pueblo (The Voice of the People), is campaigning to preserve scraps of forest near Palo Verde National Park. A member of La Voz who worked all his life as a cowboy (and insisted on anonymity) spoke of the change he's seen in the pastures and forests. "Now there are deserts where there once were forested mountains, lands of solitude where not even grass grows," he said. "It's so obvious that the forest is the source of life for humans."

The best way to see how the conservation areas are supposed to function is to visit the area in Guanacaste Province, a pilot project for the national system. The Guanacaste Conservation Area is in the central highlands, just south of the Nicaraguan border, where cattle pastures have been slowly replacing the dry, tropical forest for four centuries. The original closed-canopy forest has been reduced to less than two percent of its former range.

The 423-square-mile Guanacaste Conservation region is dominated by large deciduous and evergreen trees, but it also includes rainforests, reefs, beaches, mangrove swamps, rivers and a couple of volcanoes. It supports about 325,000 species, mostly insects, but also including mountain lions and 550 species of birds. Guanacaste is attracting an increasing number of eco-tourists, who come to See the white-faced capuchin, howler and spider monkeys, to swim in the ocean, or watch newly hatched Pacific Ridley sea turtles struggle down a black beach into the surf.

With a staff of 87 - mostly Guanacaste natives - several new labs and dormitories, new vehicles, three satellite biological stations, and a determination to make itself a "user-friendly" bastion of tropical science, Guanacaste receives a stream of Costa Rican and foreign researchers. Some of its first royalties may come from a British company working to develop a new tree-derived natural pesticide that attacks banana-killing nematodes.

Guanacaste Director Sigifredo Marin says the conservation areas are an important improvement on traditional parks. "The park rangers' only functions were security, maintenance, prevention of fires and anti-poaching. Now we've added eco-tourism, education and research," he says.

Each of Costa Rica's other six or seven conservation areas will be built, as Guanacaste was, on existing preserves. If successful, Costa Rica's conservation areas could provide a model for other Central American nations. As national park founder Mario Boza observes, "Central America has about 10 percent of the world's biodiversity, but it's endangered by deforestation, colonialism, fire and pollution - and unless we make a major preservation effort, it will disappear within five, seven or 10 years."

One of the prime movers behind Guanacaste is Daniel Janzen, a 54-year-old University of Pennsylvania ecologist who has been working in the area for almost 30 years. Janzen, an entomologist, specializes in butterflies and moths, but doesn't mind crossing boundaries into other scientific specialties.

Janzen was the first to describe a mutually beneficial relationship between ants and acacia trees, in which neither species could survive without the other. The ants patrol the trees and use a stinging bite to protect them from intruders; in return, the ants live in hollow thorns and drink nectar the tree produces. The ants are so effective that the trees have lost their chemical defenses. Janzen found that if the ants are removed, the acacia leaves will be gobbled up like lettuce.

For this discovery, Janzen received the Crafoord Prize - sometimes called the Nobel of biology - in 1984. Janzen has a deserved reputation as a single-minded, outspoken scientist and conservationist, and he says that pure preservation must be replaced by a more businesslike approach: "Conservation areas have to be working assets for society," he says. "Nobody rips the altar out of a church."

Janzen says humanity's habit of destroying the environment is not an accident but a relic of history and evolution. The war on nature, he says, was once as natural and logical as survival itself. But the war is over, he says. "Humanity has basically won. Now, do you sweep the battlefield clean and plant your corn and alfalfa, or do you look at the corpses, the organisms left on the battlefield, and recognize that they have something to offer?"

Contact: The Costa Rica Office for Sustainable Development, 1300 North 17th Street, Suite 1330, Arlington, VA 22209/[phone].