Nuts, but not for much longer
brazil nuts might not be for much longer if intensive harvesting
practices continue in 'persistently exploited' areas.
Writing in this week's issue of the journal Science, the main author of the report, Dr Carlos Peres of the university of East Anglia in the UK said:"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 metres in height and 16.5 metres 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. They report that 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 (€26 million).
In order to avert an eventual collapse of the Brazil nut industry, the researchers recommend close monitoring and careful management of exploited populations to avoid future regeneration failure and encourage establishment of younger trees.
Other suggestions include managing the annual quota of seeds that can be harvested and implementing a rotation system with alternating areas where harvesting would not take place.
Planting of viable seeds or nursery-grown seedlings could also increase the supply of young trees within natural populations, and control of seed eaters and large herbivores could help maximise the chance of seeds germinating and seedlings surviving to become established juveniles.
Although continued intensive harvesting is a concern, the scientists conclude that the trade itself is not a threat and that there are other, more immediate worries for the Brazil nut extractive industry including deforestation and forest degradation.
"Both sound proactive management of natural Brazil nut tree populations and protection of the larger primary forest areas where the trees are found are required to avert the decline of Brazil nut populations and the erosion of this cornerstone of the Amazonian economy," they conclude.
The paper, 'Demographic Threats to the Sustainability of Brazil Nut Exploitation,' by Dr Carlos Peres et al is published in the 19 December issue of Science.