The Brazil nut tree, known scientifically as Bertholletia excelsa, flourishes throughout the Amazon's lowland forests. Large and long-lived, mature Brazil nut trees produce hundreds of extremely hard, softball-sized fruits containing 10 to 25 seeds or "nuts." Local harvesters collect the fruit on the ground, where they fall from heights of 150 feet or more, and open them with machetes.
In the sparsely populated Amazon, where barter is common and opportunities to earn cash are few, Brazil nuts are a vital industry. In the Brazilian Amazon alone, harvesters annually collect about 45,000 tons valued at about $43 million worldwide, according to the Science paper. In parts of the Amazon forest where traditional peoples still live in the forest, the nuts are their primary source of income, Kainer said.
Wild trees are the exclusive source of Brazil nuts because plantations have not been successful, Kainer said, a situation for which she said there are several possible explanations. In the wild, large bees called euglossines are important pollinators of Brazil nut trees, but these bees depend on orchids that grow almost exclusively in the rainforest and may not thrive in plantations. The nutritive content of the soil in plantations also may be a problem, she said.
Some scientists have argued that collection of the nuts doesn't affect the wild trees, which makes some intuitive sense. Even the best harvesters can't get 100 percent of the nuts.
Rabbit-sized rodents called agoutis also target the nuts, burying them like squirrels for later consumption. These agoutis don't retrieve all of their stashes, and their buried nuts are an important source of new trees. As Kainer put it, "there are just leaks in the system, and you don't need that many to rejuvenate."
The scientists examined the issue comprehensively, comparing surveys of young and adult Brazil nut trees in nearly two dozen A
Contact: Karen Kainer
University of Florida