Easy pickings. Extensive harvesting of Brazil nuts has led to a dearth of young trees, threatening the future of this rainforest crop.

Too Much Crunching on Rainforest Nuts?

As a child in Belém, Brazil, Carlos Peres would watch boats heaped with Brazil nuts plying the Amazon River. Many were headed for warehouses of his father, who at one time held a virtual monopoly on the nut trade. Even then, Peres suspected that such intense harvesting of nuts from the rainforest couldn't be sustainable. In this week's issue of Science, a team led by Peres, now a wildlife biologist, has shown it for the first time. The finding is important because Brazil nut harvesting is a major part of the Amazon economy and has been thought to be a sustainable way to prevent more-destructive activities such as ranching.

Brazil nut trees (Bertholletia excelsa) are a wonder. They're the stoutest trees of the Amazon, with girths of up to 16.5 meters. They're remarkably fertile, too, dropping vast quantities of nuts, packaged inside hard pods the size of grapefruit, for 3 months a year. At least 45,000 tons of nuts are harvested each year from the Amazon.

About 10 years ago, Peres started to investigate the impact. He first surveyed relatively untouched stands of Brazil nut trees in the remotest parts of the Amazon. Then he and 16 collaborators measured trunk diameters--a proxy for tree age--and assessed the history and intensity of harvesting through public records and interviews with local collectors. The researchers also compiled data on other relevant factors, such as amounts of rainfall and soil nutrients. The best predictor of population health, according to several statistical analyses, was the exploitation of nuts. In sum: The more harvesting, the fewer younger trees in the forest.

The good news is that the solutions may be simple, and most of the mature trees still have at least a few decades of productivity left. Peres, who's at the University of East Anglia in Norwich, U.K., says that harvest quotas, or temporary no-take areas, could help establish a next generation.

"You can't just go into the forest, pick up all the nuts, and assume that the forest will magically regenerate," concludes Charles Peters of the New York Botanical Garden in New York City. That's what Peres believed all along--and it was a source of arguments with his father. "He never believed me," recalls Peres. "It took me 25 years to prove him wrong."

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