Writing in this week's edition of the international journal Science (19 December 2003) the main author of the report, Dr Carlos Peres of the University of East Anglia, says: "The clear message is that current Brazil nut harvesting practices at many Amazonian forest sites are not sustainable in the long term."
Brazil nuts, the only internationally traded seed crop collected from the wild, are traditionally harvested from trees that can reach 50 meters in height and 16.5 meters in circumference at breast height. The scientists surveyed 23 natural Brazil nut tree populations in the Brazilian, Bolivian and Peruvian Amazon, and found that populations that have been extensively harvested over several to many decades are dominated by older trees, with very few younger trees present, suggesting that the normal regeneration cycle has been disrupted.
Having established the facts about Brazil nut tree populations at these sites, the scientists then ran computer models to predict population trends for the next 200 years. The patterns observed in the simulations were highly consistent with those observed in real data.
Dr Peres says that both the data collected and the computer models point to a dwindling number of increasingly older trees in persistently overexploited areas, which have not been adequately replaced by young trees in recent decades.
Brazil nuts contribute significantly to the Amazonian economy with more than 45,000 tonnes collected annually from the Brazilian Amazon alone, worth more than US$33 million. The reason that Brazil nuts are so easy to collect is that the seeds fall to the ground encased in large woody fruits (about the size of a large grapefruit), each of which may contain 10-25 seeds.