Unraveling another Mayan mystery - food production

UNRAVELING ANOTHER MYSTERY How did the Maya feed their huge population? By savvy management of the t

In the great green stillness of a Yucatan tropical forest, two men make their way through the underbrush, seeking a stone monument to the glory of the Maya. When they find it, the monument seems unimpressive: just a grey rock wall, two or three feet high, enclosing a small area about the size of a backyard garden. Yet to Arturo Gomez-Pompa, a botanist and conservationist at the Uni- versity of California at Riverside, this centuries-old pet kot is as exciting as the architectural and artistic splendors of Chichen Itza.

The reason becomes clear when Gomez-Pompa and his helpers step over the wall and begin a careful survey of the plant life within. Instead of the trees found in the surrounding area, the pet kot -- Mayan for round wall of stone -- encloses an unusual variety of species valuable to man: the ramon, a tree whose seeds can be ground as a substitute for maize; fruit-bearing sapodilla, mamey, sapote, and citrus trees; cacao plants; mahogany trees for hardwood; and herbs and shrubs that aren't native to the region but must have been planted by ancient Mayan farmers.

This pet kot, and many more like it scattered through the tropical forests of the Yucatan peninsula, demonstrates that the Maya practiced sophisticated forest management long before the conquistadores set foot in the New World.

To archaeologists, the pet kotoob (plural of pet kot) and other evidences of Mayan ecological savvy tell as much about that vanished culture as the famous hieroglyphs at Tikal, for they help solve the riddle of how the Maya fed their huge population.

The Maya flourished on lands ranging from dry lowland scrub and swamp in the southern Yucatan to highland rain forests in southeastern Mexico, Guatemala, and British Honduras. None of these is especially hospitable to agriculture: swamps have too much water, arid areas have too little, and the rain forest soils are thin and fragile. Yet the lowland population density ranged from 300 to 400 people per square mile in A.D. 800, about the peak of Mayan culture, according to Billie Lee Turner II, director of the Graduate School of Geography at Clark University in Worcester, Mass. (For comparison, the U.S. has a population density of only 65.8 per square mile.)

The pet kotoob studies are also forcing scientists to seek new explanations for the mysterious catastrophe that overtook the Maya. Between the early 800s and 1500, before the Spanish conquest of 1524, the population plummeted to only twelve per square mile. Scientists used to blame the collapse on famine caused by ecologically unsound agriculture. Investigations by Gomez-Pompa and others suggest otherwise.

To Gomez-Pompa, however, the pet kotoob are even more important for solving the problems of today than for understanding the distant past. Tropical forests cover less than 16 per cent of the earth's land surface, yet are home to about half of its plant and animal species -- a biological treasure of incalculable value. Yet a recent World Resources Institute report says that more than 42,000 square miles of tropical forest are vanishing each year, an area the size of Tennessee. If modern Third World farmers could apply the ancient Mayan methods of agricultura management, Gomez-Pompa argues, it would slow the deforestation.

It was modern ecological concerns that drew Gomez-Pompa to ancient agriculture. He was studying the plant resources of the Mexican state of Veracruz in the early 1970s when he began worrying about the future of its rain forests. In Veracruz, as in other tropical regions, peasants often have no choice but to cut down the forest for farmland. But after a few years of cultivation, the soil gives out and the peasants move on -- usually to another forested area.

Gomez-Pompa saw no end to this spiral, and, in an article in Science in 1972, he and two co-authors warned that the forests were in danger of ''a mass extinction of most of their species.'' The scientific and practical repercussions would be stunning: herbs that could have yielded new medicines (about one-quarter of all prescriptions are for drugs derived from plants) would go undiscovered, as would pestor disease-resistant plants that could have been used to breed hardier crops.

If modern farming was so tough on rain forests, Gomez-Pompa wondered, why hadn't the same been true in antiquity? ''The Maya and many other cultures flourished in the tropics,'' he says. ''How did they conserve the biological diversity that we're destroying?''

The question was especially puzzling in the case of the Maya, because their agriculture was thought to have been quite primitive. It was long assumed that the Maya practiced slash-and-burn agriculture, in which a farmer clears a section of forest and then burns it to release nutrients into the soil. Two to four years later the soil is exhausted and the farmer abandons it for new ground. It takes another eight to ten years for natural processes to restore fertility to the land.