SCIENTISTS learn more about how to use tropical plants and animals every year. The most sophisticated researchers have managed to extract a single gene from a tropical plant - for example, one that determines resistance to a certain pest - and breed it into established domesticated plants used in the United States.
Central America is particularly rich in genes used in modern food. Corn, squash, avocado, tomatoes, beans, cacao, and cassava, among others, originated in the region.
Genes from wild varieties, which have managed to survive without the help of man, are especially valuable in producing new hybrids having improved yields and pest resistance.
``We need to think about the diversity of genes we don't know anything about,'' says Karel R. Schubert, a Washington University biologist whose genetic research concentrates on a tropical palm found in Central America. ``That's why we are concerned about the conservation of genetic resources.''
The processes of identifying tropical plants and animals and tapping their genetic potential is just beginning. Scientists may have collected only 30 percent of the wild species of corn, 5 percent of yams and cassava, and 1 percent of sweet potatoes, according to Donald Plucknett, a science adviser at the World Bank.
Traditional healers use about 10 percent of known flowering plant species, according to pharmacologist Dorothy Bray. ``Only 2 percent have been chemically examined.''
Recent discoveries of new species may result in naturally caffeine-free coffee, perennial corn, or cures for AIDS. But breeding takes time. It was nearly 20 years before genes from a wild species of South American tomato successfully produced a new large tomato that, some estimate, is worth $8 million a year to US commercial farmers.
Meanwhile, concerns continue to mount that deforestation and other pressure on ecosystems will wipe out irreplaceable genetic material. Experts talk of tropical forests and woodlands disappearing every year at a rate of 42,000 square miles, an area more than twice the size of Costa Rica.
Estimates of species loss range from one an hour (about 175,000 over a 20-year period) to a 1980 National Research Council calculation of 1million by the end of the century.