Anthropogenic landscape in southeastern Amazonia: contemporary impacts of low-intensity harvesting and dispersal of Brazil nuts by the Kayapó Indigenous people.

John P Hart,Maria Beatriz N Ribeiro,Adriano Jerozolimski,Pascale De Robert,Nilson V Salles,Biribiri Kayapó,William E Magnusson,Tania P Pimentel

doi:10.1371/journal.pone.0102187

Abstract

Brazil nut, the Bertholletia excelsa seed, is one of the most important non-timber forest products in the Amazon Forest and the livelihoods of thousands of traditional Amazonian families depend on its commercialization. B. excelsa has been frequently cited as an indicator of anthropogenic forests and there is strong evidence that past human management has significantly contributed to its present distribution across the Amazon, suggesting that low levels of harvesting may play a positive role in B. excelsa recruitment. Here, we evaluate the effects of Brazil nut harvesting by the Kayapó Indigenous people of southeastern Amazonia on seedling recruitment in 20 B. excelsa groves subjected to different harvesting intensities, and investigated if management by harvesters influences patterns of B. excelsa distribution. The number of years of low-intensity Brazil nut harvesting by the Kayapó over the past two decades was positively related to B. excelsa seedling density in groves. One of the mechanisms behind the higher seedling density in harvested sites seems to be seed dispersal by harvesters along trails. The Kayapó also intentionally plant B. excelsa seeds and seedlings across their territories. Our results show not only that low-intensity Brazil nut harvesting by the Kayapó people does not reduce recruitment of seedlings, but that harvesting and/or associated activities conducted by traditional harvesters may benefit B. excelsa beyond grove borders. Our study supports the hypothesis that B. excelsa dispersal throughout the Amazon was, at least in part, influenced by indigenous groups, and strongly suggests that current human management contributes to the maintenance and formation of B. excelsa groves. We suggest that changes in Brazil nut management practices by traditional people to prevent harvesting impacts may be unnecessary and even counterproductive in many areas, and should be carefully evaluated before implementation.

Highlights

There is a growing body of evidence supporting the hypothesis that the Amazon is a mosaic of anthropogenic landscapes, managed and domesticated by indigenous pre-Columbian people in various degrees, rather than a pristine and untouched forest [1,2,3,4,5]
The occurrence of B. excelsa groves in many parts of the Amazon is associated with patches of Amazonian anthropogenic dark earths [1,8] and recruitment of B. excelsa trees is favored in agricultural fallows and disturbed sites [9,10]
We cannot predict the effect of a future possible intensive seed collection on B. excelsa recruitment in the study site, the current low-intensity harvesting conducted by the Kayapodid not reduce seedling recruitment in B. excelsa groves

Summary

Introduction

There is a growing body of evidence supporting the hypothesis that the Amazon is a mosaic of anthropogenic landscapes, managed and domesticated by indigenous pre-Columbian people in various degrees, rather than a pristine and untouched forest [1,2,3,4,5]. B. excelsa seeds, Brazil nuts, have been used for subsistence by indigenous people in the Amazon forest for thousands of years [6,7] and there is increasing evidence that those human populations have significantly influenced the current distribution of this species across the Amazon [6]. While some studies have shown that medium and even high levels of harvesting may be sustainable over the long term, a meta-analysis conducted by Peres et al [18], which was later criticized by Scoles & Gribel [20], concluded that long-term intensive Brazil nut harvesting has reduced B. excelsa recruitment throughout the Amazon. Despite the possible demographic impacts of high-intensity Brazil nut harvesting, the historical evidence [6,8,14] suggest that past human activities favored B. excelsa and, that low levels of harvesting may play a positive role in the recruitment of this species

Methods

Results

Conclusion