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The two-lane road into this region of Panama is flanked sporadically with ramshackle houses and open-air classroom buildings. Chickens strut alongside the road, sometimes chased by small groups of laughing children who walk to and from school for up to four hours a day.

The simple life in Las Pavas has an air of tranquility. Indeed, city life seems far away, although the drive from the capital, Panama City, takes only about 11/2 hours on the InterAmerican Highway.But the stands of hibiscus, ripe mangos hanging from trees and acres of lush green hillsides in Las Pavas are something of an illusion wrought by the high humidity of rainy season. When the rains stop, says Dr. Gilberto Ocana, a biologist at the Smithsonian Tropical Research Institute headquartered in Panama City, these hills and valleys will turn brown, dramatically revealing the wasteland Las Pavas has become. In many respects, he says, the area resembles a desert more than a tropical forest land.

People who live in Las Pavas, and campesinos throughout Latin America, practice a centuries-old form of subsistence farming known as "slash-and-burn" agriculture. Slash-and-burn agriculture consists of cutting down a section of tropical forest, burning it and then planting small plots of corn and other vegetables.

In a year or less, these plots become fallow. Unlike soils in temperate zones, tropical soils are poor in nutrients. Most nutrients are held within the trees and other forest plants. To continue growing food, the farmers must cut down new areas of forest, leaving the past year's plots behind. Millions of acres of tropical forest have been wiped out by this endless cycle, pushed along by cattle ranching - which destroys the majority of tropical forests in Latin America. Many of the campesinos, Ocana says, will sell or rent fallow fields to cattle ranchers to squeeze a little more money from the nearly useless land.

When heat waves in North America, concerns about the Earth's ozone layer and other environmental problems dominated world news this past summer, attention turned to this grave situation in the tropics. Tropical forests are regulators of global climate, as well as home to many plant and animal species of possible benefit to humankind. Experts warn that if the forests continue to fall, the recent discomforts only foreshadow greater environmental catastrophes. As things stand now, one-fifth of the world's remaining tropical forests face destruction or permanent damage by the year 2000.

In an effort to transform Las Pavas into productive land and prevent further destruction of the area's remaining forest, Ocana, a native Panamanian, developed the "Forest Garden Project." With funding from the W. Alton Jones Foundation, he began the project in 1984 to investigate plant species that could replenish soil nutrients and to develop agricultural techniques that provide subsistence farmers with crops and marketable goods, year after year, from the same plot of land. The project will also create a buffer zone, protecting from human encroachment the mainland areas of the Barro Colorado Nature Monument, 9,386 acres of tropical forest land under the custodianship of the Smithsonian.

The project is one of several "alternatives to destruction" being developed at the Tropical Research Institute. Other researchers there are developing techniques for domesticating and rearing forest mammals, and the basic research phase of the Institute's Iguana Management Project was recently completed. That innovative project, which involved developing methods of captively rearing iguanas as a high-protein food source, will move to Costa Rica for application throughout Latin America.

One of the first steps in his project, Ocana says, was to find a tree species that would not only help replenish the soil, but halt the spread of an obnoxious weed - introduced to Panama from Southeast Asia - that quickly invades and prevents the growth of other plant species. Ocana tried several different tree species, including species of pine. None, however, did well in the acidic and poorly drained soils of Las Pavas.

From the scientific literature, Ocana knew of a family of trees - the acacias - that showed promise for reforestation in the Old World tropics of Asia and Africa. No one, however, had grown them successfully in Latin America. He shows a visitor to Las Pavas the dramatic results of his effort. Along a roadside, acacia trees tower 27 to 42 feet high. "These trees were planted less than 31/2 years ago," he says with a smile. "Everything good about acacias came true at Las Pavas."

Ocana experimented with several acacia species and had the best results with Acacia mangium. Acacias are leguminous trees, meaning they bear small bean pods. Besides their fast growth, which helps crowd out weeds and promotes the secondary growth of other forest plants, acacias, like other legumes, can generate and replenish soil nutrients. Small, peppercorn-size "nodules" on their roots contain bacteria that convert nitrogen gas from the air into a soluble compound absorbed by the tree, eliminating the need for chemical fertilizers.

The timber from acacias, a hardwood, can be used to build small structures. In Ocana's forest gardening project, the trees will be planted in rows. Some trees will be allowed to grow tall, while others would be periodically harvested.

At another site, Ocana has set up an experimental plot for "alley farming," an agriculture technique first developed in Kenya in the 1970s. In alley farming, leguminous trees - acacias in this case - are planted in rows. Between each two rows of trees - or alley - various crops are planted, such as corn and other vegetables. The trees are pruned periodically - a task Ocana describes as more of an art than a science - to prevent shading the crops and to allow fallen leaves and branches to further enrich the soil.

To prepare the site at Las Pavas, Ocana first planted a variety of kudzu, a rapidly growing ground cover that also fixes nitrogen. "Because of the kudzu," he says, "we never really had to clear out weeds." In fact, he says, the entire project is designed to be low cost and to require little maintenance and no insecticides or expensive equipment, especially tractors and other farm machinery.

Last spring, Ocana discovered, as a result of an unfortunate accident, the resilience of this forest garden. Children playing with matches nearby set fire to the land, and Ocana's experimental site was burned in the blaze. The older acacia trees, however, which are naturally fire-resistant, came back to life and the hardy kudzu rapidly re-covered the ground, preventing opportunistic weeds from taking over.

Along with subsistence crops, Ocana says, alley farming can be used to help farmers make money, an important consideration for any agricultural alternatives to cattle ranching. "The end product of any alternative agricultural project," Ocana stresses, "must have an economic value."

On the experimental plot, he has constructed an open-air, thatch-roof hut with a slat floor. Such huts, he points out, can be built with timber from the acacia trees.

While it provides welcome shade for people, Ocana says, the hut is really for goats. Goats normally cannot tolerate the full heat of the tropics, he says, but the huts will provide a spacious shelter. The slat floor will keep the enclosure clean of goat droppings, another source of fertilizer for the forest garden. Cassava, a tuber planted in the forest garden, will provide a high-protein fodder.

Various products from goats - milk, cheese and meat - Ocana explains, are gourmet food items in Panama City and other nearby markets. Few farmers in Panama raise goats, he adds, and the nearest large producer for such foods is in Costa Rica, Panama's neighbor to the north. Farmers in Las Pavas, he says, could command twice the price per pound for goat meat alone as for beef from cattle.

In addition to halting destruction of tropical forests, Ocana's project provides a realistic alternative for the rural poor in Las Pavas, one that could raise their standard of living. The development of such alternatives is crucial, not only for Central America, but worldwide.

An estimated 15 percent of the people in Central America are undernourished. "The leading factors in hunger and malnutrition are poverty and ecological problems," says Dr. Robert F. Chandler, an acclaimed agricultural researcher and the 1988 recipient of the General Foods World Food Prize. He recommends innovative agricultural research as part of the solution.

Projects such as that of Ocana are a major step in that direction.