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Scientists are warning that the export of Brazil nuts collected in the Amazon region could collapse if intensive harvesting practices continue.

Until now, harvesting the nuts — which in the Brazilian Amazon alone generates more than US$33 million a year — has been thought to be a sustainable way of preventing more environmentally destructive activities such as ranching.

But in this week’s Science, an international team of researchers, led by Carlos Peres, a tropical conservation biologist from the UK’s University of East Anglia, reports that current harvesting practices are not sustainable in the long term.

The scientists surveyed 23 natural Brazil nut tree populations in the Brazilian, Bolivian and Peruvian Amazon. They found that populations that have been extensively harvested over several decades are dominated by older trees, suggesting that younger trees are unable to establish themselves in such areas.

Computer models confirm that, as a result, populations of the trees will dwindle over the long term if current practices persist.

Brazil nuts are the only internationally traded seed crop collected from the wild. They are traditionally harvested from trees that can reach 50 metres in height and more than 16 metres in circumference. At least 45,000 tonnes of nuts are harvested each year in the Amazon region.

In order to avoid a collapse of the Brazil nut industry, the researchers recommend close monitoring and careful management of exploited populations of trees to encourage young trees to become established.

They also suggest that the annual quota of seeds that can be harvested should be managed, and that a rotation system should be implemented, alternating areas in which harvesting would not take place.

Link to Science news story: Too much crunching on rainforest nuts?

Link to research paper in Science by Carlos Peres et al

Reference: Science 302, 2049 (2003) / Science 302, 2112 (2003)