Exploração ilegal de madeira no arquipélago de Anavilhanas (Amazônia central): variáveis humanas que determinam a distribuição espacial da exploração e efeitos estruturais sobre os táxons mais explorados

The Anavilhanas’ National Park is an Amazonian protected area facing nowadays the challenge of controlling illegal logging. To aid this task, this study aimed to determine (1) the densities of the exploited species in this area; (2) the spatial distribution of logging; (3) the effect of logging on population structure; (4) the growth rate of each species and (5) analyze the effects of human communities’ distance and wood value in the logging intensity. All trees with DBH >10 cm of the five most exploited species and the logging vestiges were registered on 84 transects uniformly distributed over the Anavilhanas Archipelago. Growth rates were measured by dendrocronology. Medium and large sized trees (10-30 and > 60cm DBH) of Virola surinamensis and Lauraceae spp (10-30 cm DBH) decreased in abundance as harvesting intensity increased. However, since growth rates of Ocotea cymbarum (Lauraceae) were high, it may recover fast if harvesting pressure stops. There was no evidence of negative effects of harvesting on the population structure of Calophyllum brasiliense, but its low growth rate and grouped distribution suggest that continued exploitation may endanger the population. There were no negative effects of logging for Macrolobium acaciifolium and Hevea spp., and their high growth rates and high abundances indicate that these species have a potential for management. Harvesting is concentrated in the southern region of the archipelago, next to the human concentrations, for most species, except for Lauraceae spp., whose timber is more valuable. The model tested indicated no relationship between the intensity of harvesting activities and the geographic distances to human communities, but a trend to choose harvesting places with greater concentration of more valuable resources. Thus, a strategy to control the illegal logging in the Anavilhanas Archipelago would be to encourage a sustainable logging plan on the buffer zone of the Park and to stimulate tourism on the South of the archipelago, where tourist presence could inhibit illegal activities.O Parque Nacional de Anavilhanas é uma unidade de conservação amazônica que enfrenta atualmente o desafio de controlar a exploração ilegal de madeira. Por isso é imprescindível a obtenção de informações a respeito da geografia e dos efeitos da exploração sobre as populações alvo dos extratores. Assim, o presente trabalho teve como finalidade determinar (1) as densidades dos táxons explorados e sua distribuição espacial; (2) a distribuição e intensidade da exploração; (3) o efeito da exploração sobre a estrutura das populações desses táxons; (4) as taxas de crescimento das árvores e (5) testou a hipótese de que a distribuição espacial da exploração está relacionada com a distribuição espacial das comunidades humanas residentes na zona de amortecimento do parque e com o valor da madeira. Para isso, foram registrados todos os indivíduos arbóreos com DAP > 10 cm dos 5 táxons mais explorados e os vestígios de exploração, em 84 transectos distribuídos uniformemente pelo arquipélago de Anavilhanas. As taxas de crescimento foram obtidas por análises dendrocronológicas. V. surinamensis e Lauraceae spp. apresentaram modificações na estrutura da população com o aumento de exploração. Como a taxa de crescimento de Ocotea cymbarum (Lauraceae) foi alta, esta espécie pode se recuperar rapidamente caso a pressão de exploração cesse. Para C. brasiliensis não houve evidência de efeito da exploração sobre a estrutura populacional, mas a sua baixa taxa de crescimento e distribuição agrupada sugerem que poderá ser afetada caso a exploração se mantenha. Em M. acaciifolium e Hevea sp. o aumento da exploração não promoveu efeitos negativos em suas populações e, além disso, suas altas taxas de crescimento e grandes densidades indicam que poderiam ser manejadas. A exploração concentra-se na região sul do arquipélago, próximo às concentrações humanas, para a maior parte das espécies, mas não para Lauraceae spp., cuja madeira tem maior valor econômico. Os modelos testados não indicaram relação entre a intensidade de exploração e as distâncias geográficas até as comunidades, mas sim uma tendência de maior intensidade de exploração onde há maior concentração de recursos mais valiosos. Assim, uma estratégia para controle da exploração ilegal no arquipélago de Anavilhanas seria apoiar o manejo florestal nas unidades de conservação que ficam na zona de amortecimento do parque e estimular a concentração do turismo na região sul do arquipélago, já que a presença de turistas pode inibir as atividades ilegais

The spatial distribution of illegal logging in the Anavilhanas archipelago (Central Amazonia) and logging impacts on species

Amazonia is one of the world's leading suppliers of timber and the Amazonian timber industry is an important source of regional income, however the economic benefits of this market are associated with environmental damage, mainly when the wood is removed illegally. The Anavilhanas National Park, located in the Brazilian state of Amazonas, has been subjected to illegal logging and elaboration of control programmes requires knowledge of the distribution of timber species and the intensity of logging. This study examines the density and growth rate of the five most harvested tree species in the Park, the spatial distribution of illegal logging operations and their effects on population structure. In total, 2332 trees with diameter at breast height greater than 10 cm, as well as stumps of cut trees, were sampled, and dendrochronology was used to estimate growth rates. Some size classes of Virola surinamensis trees and species within the family Lauraceae decreased in abundance as harvesting intensity increased. Growth rates of the most abundant species of Lauraceae, Ocotea cymbarum, were high, indicating stands may recover quickly when harvesting stops. The population structure of Calophyllum brasiliense showed no negative effects due to logging, but its low growth rate and stand distribution suggest that continued exploitation may endanger these populations. Logging had no detectable negative effects on the size structure of populations of Macrolobium acaciifolium or Hevea spp., and their high growth rates suggest that they will not be threatened by current logging rates. Overall growth rates in the Anavilhanas archipelago are higher than those recorded in other black-water floodplain forest (igapó). Logging of most species (except Lauraceae spp., which have the highest market value) is concentrated in the southern region of the Park, which has more human settlements close by. There was no general relationship between harvesting intensity and geographic distance to human settlements, but there was a tendency for harvesting to be higher in sites with concentrations of trees of high market value. Potential strategies to control illegal logging activities in the Anavilhanas archipelago include encouragement of sustainable logging in Park buffer zones and stimulation of ecotourism initiatives in the southern region of the Park. Ecotourism development can provide an economic alternative to illegal logging for local communities and inhibit logging by increasing vigilance. © 2011 Foundation for Environmental Conservation

Growth models based on tree-ring data for the Neotropical tree species Calophyllum brasiliense across different Brazilian wetlands: implications for conservation and management

Key message: Site-specific growth modeling based on tree-ring data is demonstrated to be an efficient tool for conservation and sustainable forest management of an economically important tropical tree species,Calophyllum brasiliense. Abstract: One of the main challenges in the sustained management of natural tropical forests is obtaining reliable data on tree growth, which is prerequisite information for determining harvesting volumes and felling cycles. In this study, we apply growth models based on tree-ring data and allometric equations to estimate site-specific management options for timber resources of the commercial species Calophyllum brasiliense (Calophyllaceae) comparing 16 wetland sites across different Brazilian ecoregions, the Amazon, Cerrado (savannah), Pantanal and Mata Atlântica (Coastal Atlantic Rainforest). By modeling diameter, height, and volume growth parameters, we estimate site-specific minimum logging diameters (MLD) and felling cycles analyzing a total of 341 trees. Between ecoregions, the mean diameter increments varied slightly between 4.3 ± 1.6 mm year−1 in the Amazon region (average of six sites), 4.0 ± 0.8 mm year−1 in the Cerrado and Pantanal (average of seven sites), and 4.5 ± 1.2 mm year−1 in the Mata Atlântica (average of three sites). However, between sites, we observed significant differences in diameter and volume increment rates, resulting in felling cycles varying from 14 to 63 years and MLDs in the range of 35–81 cm. This clearly indicates that forest management practices in Brazil, which generally applies a feeling cycle of 25 years and a diameter-cutting limit of 50 cm cannot guarantee a sustainable timber harvest. Timber resource management of this species requires site-specific criteria and should be restricted at sites with a low wood productivity. Moreover, long-term monitoring of the population structure and dynamics is necessary for a better understanding of the relationship between environmental factors and population dynamics, especially concerning the regeneration processes. © 2016, Springer-Verlag Berlin Heidelberg