Banana split.

In the 1880s, when a young railroad baron from Brooklyn planted banana trees along the Atlantic coast o Costa Rica, he could hardly have known that he was sowing the destinies of entire economics.

Over the next century the banana trade boomed as the Old World transplant became the world's most widely consumed fruit. The business that Minor Cooper Keith started became the United Fruit Company - still the world's largest fruit producer - now known as Chiquita Brands. And, thanks too to the gunboat diplomacy that helped keep power in the hands of rulers friendly to the multinational fruit companies, Central American nations earned the epithet "Banana Republics."

What's good for bananas, though, isn't necessarily good for banana workers or the land. In Costa Rica and other banana-exporting countries, the sweet fruit has left behind a bitter legacy of environmental decline and pesticide-related health problems. But for the last year and a half, growers, government officials, workers, and environmentalists have come together in unprecedented - if sometimes uneasy - cooperation to devise ways of growing a more environmentally "friendly" banana.

Costa Rican environmentalists have long decried banana plantations for their abuse of the country's natural systems, from heavy pesticide doses to sloppily handled waste, rain forest toppling, and soil runoff. The rest of the world began to take notice in 1985, when a lawsuit was filed on behalf of some of the 2,000 banana workers allegedly sterilized by the pesticide dibromochloropropane (DBCP) in the 1970s. DBCP was used despite studies in the 1950s linking it to sterility in male lab animals. (Some of the afectados, as the workers call themselves, recently agreed to settle out of court.)

Costa Rica's plantation-grown banana crop is one of the most pesticide-intensive in the world. Unsafe methods of handling these chemicals cause hundreds of reported worker poisonings a year, as well as respiratory, skin, and eye problems among nearby residents. In fact, leading environmentalists point to pesticides as Costa Rica's top environmental problem.

The widespread criticism soon crescendoed into talk of an international boycott against Costa Rican bananas. In late 1991, the Costa Rican government and the multinational banana growers began to discuss the problems and to act on them. Bananas, after all, are the country's number one source of foreign exchange, earning $441 million in 1991 and employing 32,000 people.

The national growers' cooperative, Corbana, which includes the likes of Chiquita, Del Monte, and Dole, has directed its new environmental division to investigate pest-resistant banana strains and ways to reduce routine applications of pesticides. Checking banana trees carefully for pest problems can lead to spraying as needed, rather than on a set schedule. Such monitoring has already cut the number of aerial fumigations for black sigatoka, a common fungal disease, by more than a third. But airplanes still fog the plantations with chemicals-about once every two weeks - down from about once a week.

Why so many chemicals in the first place? Growing in a monoculture - fields of a single variety - in a steamy tropical climate, banana plants are a prime, tasty target for all sorts of pests. The bulk of the chemicals are aimed at the leaves and roots savored by most pests, but the banana "fingers" are extraordinarily sensitive. The peels are easily scarred by insects, fungi, and touching - even by dust. So in addition to spraying, banana workers wrap each cluster of bananas in a bag of blue plastic doused with pesticides.

Only minuscule residues, if any, tend to linger on the edible part of the banana. But the bags, which are not reused, contribute to a massive waste disposal problem. In fact, each banana harvested leaves behind more than twice its weight in waste: the bags, cords, and plastic pesticide buckets, and organic waste, including rejected bananas and banana cluster stems.

Pieces of blue plastic litter the countryside and wash down irrigation ditches and rivers toward the coast; some rivers are said to "run blue" after a flood. Blue shreds, caught in branches when the water rises, hang from trees lining jungle canals. Strips of the plastic jam coral reefs. And pieces choke leatherback sea turtles that mistake the plastic for jellyfish.

Until recently, growers also let other garbage wash away into streams or burned it in the open air. As a result, growers and environmental groups have been looking into waste reduction and recycling techniques. Now some growers are composting the organic materials and simply picking up and storing the plastic bags while the industry decides what to do with them. Although there is talk of incinerating the bags, Corbana and other groups are also experimenting with recycling, which might turn bags into flower pots, building bricks, and prop-up poles for the banana plants.

Some growers, too, are beginning to reforest riverbanks to stem the high rates of erosion that afflict most banana fields. Costa Rican law mandates that at least 33 feet of forest be left bordering waterways. The law has been flouted for decades, however, and bananas often grow clear down to the water's edge. The resulting erosion of land and silting of water has killed fish populations and contributed to the decline of the country's Atlantic coast coral reefs.

In addition to Corbana's work is the ambitious Banana Amigo Project, sponsored by the U.S.-based Rainforest Alliance in partnership with the Costa Rican groups Fundacion Ambio and Tsuli Tsuli/Audubon. Banana Amigo is helping all sides negotiate a code of conduct that covers waste disposal, use of water and agrochemicals, reforestation, and worker safety.

The Banana Amigo staff also hopes to promote environmental practices with a "reverse boycott." It plans to award a "Smart Banana" seal of approval to bananas grown in an ecologically improved manner and to persuade consumers to choose "Smart Bananas" even if they are blemished or smaller than other bananas. The first seals may appear in grocery stores at the beginning of 1993.

Even industry spokesmen admit that some of the changes in banana cultivation are long overdue. But the ecological improvements fail to address what is perhaps the most contentious issue of all: the amount of land - including rain forests - razed to make room for banana farms.

Hopeful of a larger European market, growers in recent years have been expanding their plantations. The area under production, currently 129 square miles in a country half the size of Tennessee, is expected to reach 193 square miles shortly. Some of this expansion has required leveling more rain forest, contributing to Costa Rica's dubious distinction of having the highest deforestation rate in Latin America over the last 30 years.

Critics also condemn the expansion of banana plantations because it disrupts Indian tribes and forces out small farmers growing food for local consumption.

While the banana industry's environmental plans do not include limiting its own growth, international politics and economics may apply the brakes instead. The European Community (EC) is now debating the possible use of tariffs to protect banana production in its countries, territories, and former colonies. Such a trade barrier could cut Costa Rica's banana exports to the EC by as much as 40 percent.

And an upstart industry - eco-tourism - is already second to bananas as a foreign exchange earner and may take the top spot in the next few years, according to the Ministry of Tourism. Eco-tourists, of course, value rain forest and a pristine environment more than plantations. Despite the alarming deforestation that has occurred over the years, Costa Rica is still home to an estimated 5 percent of the planet's biodiversity, most of that in its rain forests. If tourism manages to provide as many jobs as banana plantations have, it may prove the strongest incentive yet to clean up and limit banana production.

It is too early to tell how eagerly growers will carry out voluntary ecological guidelines. But, aided by sustained interest and gentle pressure from consumer nations, environmentalists and growers may manage, to minimize the dark stains on the yellow fruit's reputation.