Demographic Threats to the Sustainability of Brazil Nut Exploitation

Utrecht University, Utrecht, Utrecht, Netherlands
Science (Impact Factor: 33.61). 12/2003; 302(5653):2112-2114. DOI: 10.1126/science.1091698
Source: PubMed


A comparative analysis of 23 populations of the Brazil nut tree (Bertholletia excelsa) across the Brazilian, Peruvian, and Bolivian Amazon shows that the history and intensity of Brazil nut exploitation are
major determinants of population size structure. Populations subjected to persistent levels of harvest lack juvenile trees
less than 60 centimeters in diameter at breast height; only populations with a history of either light or recent exploitation
contain large numbers of juvenile trees. A harvesting model confirms that intensive exploitation levels over the past century
are such that juvenile recruitment is insufficient to maintain populations over the long term. Without management, intensively
harvested populations will succumb to a process of senescence and demographic collapse, threatening this cornerstone of the
Amazonian extractive economy.

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Available from: Rogério Gribel
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    • "The ecological sustainability of Brazil nut harvesting has been analyzed in several studies (Mori 1992; Viana et al. 1998; Peres et al. 2003; Silvertown 2004; Wadt et al. 2008; Scoles and Gribel 2011, 2012; Ribeiro et al. 2014), some of which have reached contrasting conclusions. With the exception of Peres et al. (2003) and Silvertown (2004)), these studies found no evidence that traditional extractive methods damage the regeneration of Brazil nut stands. In general, the studies show that the relative scarcity of trees of non-reproductive age (juveniles) and the low recruitment rate are not related to harvesting intensity. "
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    ABSTRACT: This study examines the population structure and regeneration of Brazil nut tree (Bertholletia excelsa) populations at sites subjected to extractive activities in the Capanã Grande Lake Extractive Reserve (Rio Madeira, Amazonas, Brazil). We analyze correlations between three regeneration levels (seedling, sapling and juvenile density) and seven possible explicatory variables related to vegetation structure and human action. The tested vegetation structure variables include adult tree density, crown area, basal area, canopy openness, and fruits opened by agoutis. We also test the time of human use and distance from residences as possible explicatory variables. The density values of the Brazil nut stands in the region are high (12.5 tree/ha), with 60 % of trees having a diameter at breast height (DBH) > 80 cm. The mean potential regeneration (24.8 seedlings/ha), pre-established regeneration (4.4 saplings/ha) and established regeneration (3.2 juveniles/ha) values are high compared to other Brazil nut tree populations and tend to be greater in the “intensively used” stands, defined as sites where human presence during the year is more frequent. The time of human use and the density of adult Brazil nut trees are the variables that best correlate with established regeneration (density of juveniles). The number of juveniles/adult Brazil nut trees is five times higher in intensively used stands than in those moderately used. These results suggest that extractive activities and disturbances in the understory caused by human presence may favor (intentionally or not) regeneration of Brazil nut trees in more-frequently used stands. The data support the concept, frequently suggested in the literature, that aggregations of Brazil nut trees could be a consequence of the activities of Amerindian populations.
    Full-text · Article · Nov 2015 · Human Ecology
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    • "For example, scatter-hoarding rodents play a pivotal role in the dispersal of largeseeded species in neotropical rain forests, especially in those once dispersed by the extinct Pleistocene megafauna (Guimar~ aes, Galetti & Jordano 2008; Jansen et al. 2012). In Amazonian forests, the overharvesting of the Brazilian nut (Bertholetia excelsa) may have important consequences not only for the recruitment of B. excelsa and agouti populations, but also for the entire scatter-hoarding dispersal service of other largeseeded tree species (Peres et al. 2003; Galetti et al. 2006). Similar examples have been reported for flying foxes, gorillas and elephants for which overhunting and habitat loss has resulted in a recruitment reduction of a significant number of large-seeded species (McConkey & Drake 2006; Beaune et al. 2013; Haurez, Petre & Doucet 2013). "
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    ABSTRACT: The effects of the present biodiversity crisis have been largely focused on the loss of species. However, a missed component of biodiversity loss that often accompanies or even precedes species disappearance is the extinction of ecological interactions. Here, we propose a novel model that (i) relates the diversity of both species and interactions along a gradient of environmental deterioration and (ii) explores how the rate of loss of ecological functions, and consequently of ecosystem services, can be accelerated or restrained depending on how the rate of species loss covaries with the rate of interactions loss. We find that the loss of species and interactions are decoupled, such that ecological interactions are often lost at a higher rate. This implies that the loss of ecological interactions may occur well before species disappearance, affecting species functionality and ecosystems services at a faster rate than species extinctions. We provide a number of empirical case studies illustrating these points. Our approach emphasizes the importance of focusing on species interactions as the major biodiversity component from which the ‘health’ of ecosystems depends.
    Full-text · Article · Nov 2014 · Functional Ecology
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    • "Due to its uncontestable economic importance, there has been concern over the sustainability of Brazil nut harvesting [17]–[20]. 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, therefore, that low levels of harvesting may play a positive role in the recruitment of this species. "
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    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.
    Full-text · Article · Jul 2014 · PLoS ONE
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