IT'S rainy season in Costa Rica, and a visitor has arrived in a downpour. Good practice, since the next stop, 60 miles from the capital of San Jose, is Rara Avis, a rain forest of dense virgin jungle millions of years old - annual rainfall 160 to 200 inches. Primeval Costa Rica was 99 percent rain forest; as late as 1940 it was 85 percent; today it's 16 percent, according to the World Resources Insitute. Two thirds of the remaining jungle is protected park land; one-third is unprotected. An awesome diversity of life dwells in these wilds: The Costa Rica tourism office reports that there are 8,700 species of plants, 205 species of mammals, 130 varieties of freshwater fish, 350 species of reptiles and amphibians, 850 species of birds, and 1,239 species of butterflies.
The jungles of Costa Rica are also part of a global engine. The world's rain forests extract carbon dioxide from the air, reducing the greenhouse effect; they transpire oxygen and moisture back into the air, affecting world weather. Scientists warn that much of the Amazon would become desert if its rain forests were eliminated. Yet every minute of every day all over the world, 72 acres of these forests are destroyed, the World Resources Institute says.
Unusual among its Central American neighbors, Costa Rica - a democracy with no army and high standards of health and education - has begun fostering ways to protect its jungle habit. Perhaps the most innovative is Rara Avis (``rare bird'' in Latin), a privately owned biological reserve of 800 acres of lowland tropical rain forest bordered on two sides by 2,000 protected acres of park land. Dedicated to developing rain forest products for profit, the project was founded in 1983 by 39-year-old biologist and native New Yorker, Amos Bien. It has won international praise as a unique economic as well as ecological model, attracting hundreds of scientists, officials, and ``ecotourists'' to Costa Rica.
Accompanied by Mr. Bien, the journey's first leg is a wet 90-minute jeep ride northwest out of San Jose across the hilly Monteverde cloud forest, rainy more than 300 days a year. In low country beyond the jungle, the village of Las Horquetas de Sarapiqui comes into view. There at the home of Roberto Villelobos, who oversees Rara Avis, the jeep is exchanged for an open metal trailer hitched to a tractor.
Passengers aboard, the tractor rambles along a rough muddy road into the countryside. Unfazed, Bien says, ``Look around.'' Vast swatches of treeless pasture stretch for miles. This was once virgin jungle. Now cows graze. Huge felled trees, decades old, are scattered about. A few lone groves stand forlornly. ``Costa Rica has one of the highest rates of deforestation. All this rain forest is being cut so people can make a pittance,'' he says. The cows, one of the country's major agricultural products, are the reason the forests have disappeared so quickly. According to Bien, five acres of cut forest are needed to yield one cow - a per-acre-per-year return to the small-scale Costa Rican cattle rancher of $7.
BIEN explains that with three elements in place - soil, trees, and animals, which act as seed carriers - a rain forest will regenerate. It takes 30 years to regrow, 100 years to become mature, and 200 years to be considered a fully mature jungle.
The landscape changes, more wooded now, the air thick with humidity. Fat black turkey vultures fidget on the branch of a tall tree wrapped in a strangler fig; the vine grows from the top down from seeds left in bird droppings. Bien explains that in 20 years the vine will kill the tree. He points out a solitary slender palm. ``The Chilacha Indians who once inhabited these forests used palm leaves for thatching roofs; oil came from the nuts; tortillas and bread from the flour [made from shoots]; food from the heart; floorboards, bows, arrows, blowguns, and darts from the hard outer wood; and house posts, water pipes, and gutters from the trunks. The Indians planted as they took.''
Transport to Rara Avis so far seems an endless slog over rocks and ruts. The tractor gets stuck in mud on a steep grade, and all pile out until Mr. Villelobos frees it. Still to come (though a newcomer hasn't been told yet) are three hours and seven miles more fording two rivers, over six wood bridges, and across a corduroy road of hand-hewn logs deep into the jungle. Bien and local workers built the road, hoisting the tractor and bulldozer up on a winch, cutting as it moved downhill and laying planks as they went.
Three-quarters of the way up the slope is ``El Plastico,'' a former penal colony where the prisoners slept under plastic tarps. The open-air wood structure is now a residence and field lab for Rara Avis students and researchers. Five distant volcanoes bestride the horizon like sentinels, one of which, Irazu, is active.
Sudden thunder and drizzling rain mark the entrance into virgin jungle. At the roadside are fresh jaguar tracks. Only 50 of these great cats remain in all of Costa Rica. Now unscarred green walls rise on either side of the trail. Giant trees 150-to- 200 feet high reach for the sun above the canopy. There are more species of trees in this patch of forest than in all of North America. Within is an abundant storehouse of biological knowledge and potential pharmaceuticals.
Environmental concerns tend to be lost on people who need food and homes for their families. Rara Avis, which is 90 percent virgin jungle, has shown that conservation and development need not be in conflict.
By harvesting rain forest products such as wicker, tree seedlings, ornamental plants, and hothouse moths, the project turned profitable in 1990. Its employment of local people provides a better living for them than leveling the rain forest for cattle and lumber, according to Bien. All of Las Horquetas benefits. And the value of husbanding a precious natural resource is taught.
On the side of a mountain at a cool and comfortable 2,000 feet (an average 72 degrees F. year-round) is the journey's end - the lodge, two stories high and made of native manu wood. Each room has its own porch and hammock, comfortable beds, kerosene lamps, as well as hot showers fed by a jungle stream.
A tantalizing aroma comes from a separate building, where the chef prepares a Costa Rican arroz con pollo (chicken and rice dish) on a charcoal stove. Rara Avis employs a full-time staff of six, including several trained naturalist guides, as well as part-time workers. The surroundings include an extensive series of jungle trails, ranging from easy to very difficult.
After lunch, Bien hands out rubber boots, then leads a trek along a trail with ankle-high mud and emerald green all around. Hummingbirds dart among vines of orchids, bromeliads, and philodendrons. Visitors spot toucans, great green macaws, and other rare species. Though scarce, poisonous snakes such as the bushmaster also inhabit the area.
A steady dull roar fills the air; the trail drops steeply, edging 180-foot Pilango waterfall, a magnificent cascade over three levels of terraced pools and moss-covered rocks. At the base, Bien instigates a skinny dip, swimming across a pool and climbing onto a rock ledge behind the thundering falls. This is drinking water, cool and mountain clear.
DEEPER into the jungle is Rara Avis's most amazing achievement: the unique ``Automated Web for Canopy Exploration,'' a metal cage hung from a cable that uses a pully-and-winch system to explore the rain forest canopy at a height of 150 feet. Half of all life forms live in the canopy, few of them documented. The web is acclaimed for having provided scientists their first Tarzan-level peek into this rich and many-faceted ecosystem.
A visitor volunteers for a turn, swinging out 200 feet over a tropical gorge in a cage dangling from a wire that was strung originally tree-to-tree with a crossbow. Amid the opaque green canopy festooned with rich blooms, a monkey blurs past, then a swirl of electric blue morpho butterflies.
Later back at the lodge, twilight ushers in a purple sky. Night falls windless yet virtually mosquito-free because of the altitude. Instantly, as though a switch were thrown, a serenade starts: craoking frogs; the machine-steady chirp of crickets and katydids; barking howler monkeys.
Bien suggests a night walk in the rain forest. No dangers, he promises. Armed with flashlights, the curious follow him along a narrow path; only then does he offhandedly remark that snakes do hunt at night. Bien shines a light on a tarantula nest in a hanging liana vine - nobody home. Foxfire fungus on a decomposing leaf glows ghostly blue. A bat flutters, fireflies wink.
So the forest reveals itself: fragile, complex, connective. Walk off-trail and the unseen life veins of a philodendron are severed by heavy feet. Cut a thick liana for a drink of fresh water and high up in the canopy a 25-year-old plant withers and dies. Cut enough trees and everything from ants to jaguars vanishes.
Rara Avis is an affirmation. Elsewhere, as Amos Bien is wont to repeat, birds and insects, useful and useless plants, pretty and plain animals - they're going. And once they're gone, they're gone.
For more information, contact: Rara Avis, POB 8105-1000, San Jose, Costa Rica. Telephone (506) 53-08-44. FAX (506) 21-23-14.