Forest fragmentation and deforestation are subjects of great concern in tropical regions, namely in South America and Africa, contributing to a rapid loss of tropical forest area and with serious implications for ecosystem functioning and biodiversity conservation. Despite the decrease in deforestation rates in recent years, the Brazilian Amazon, with the largest continuous region of tropical forest in the world, has suffered the greatest recorded losses, which have been contributing to continuous habitat fragmentation and a reduction in the territory occupied by Amerindian populations. In an attempt to preserve the remaining habitats and forests, Brazil has been adopting land conservation policies, including the implementation of protected areas. Protected areas (PAs) possess the potential to significantly reduce habitat fragmentation by conserving large, contiguous areas of land. In order to examine how effective PAs are at conserving forest area in the Brazilian Legal Amazon, patterns of deforestation are analyzed and compared, inside and outside the PAs, through landscape metrics calculated using the Patch Analyst and V-LATE extensions of a Geographic Information System. Two different sources (the Hansen Global Forest Change Dataset and the Brazilian National Institute for Space Research's (INPE) PRODES project) of annual forest cover-loss data derived from satellite imagery at medium-to-high spatial and temporal resolutions are compared at two-yearly intervals across 2002-2016. Additionally, fragmentation levels associated with deforestation patterns are assessed through an index modeled using a set of uncorrelated landscape metrics, and the associated change factors and trend are discussed. Results show that there is greater fragmentation in some PAs located in Mato Grosso and Pará States, especially those near the "arc of deforestation", and that Yanomami Indigenous Lands (YIL) are tending towards more fragmentation. Although some PAs are in a critical condition, findings show they all actively contribute to improved conservation of the native ecosystem and, in conjunction with sustainable management policies, will continue to help reduce or avoid forest fragmentation and degradation processes.
Resumo: Na atualidade, as sociedades tradicionais da Amazônia experimentam fortes mudanças com efeitos diretos sobre os sistemas agrícolas tradicionais, como a tendência à homogeneização de espécies e técnicas juntamente com uma dependência maior do mercado. Porém, as agriculturas amazônicas continuam diversificadas e valorizando a diversidade. O artigo descreve particularidades da agricultura Mebêngôkre-Kayapó a partir de uma metodologia elaborada com ferramentas da antropologia, da geografia e da etnobotânica em aldeias indígenas do sul do Pará. O manejo atual da agrobiodiversidade é analisado por meio da organização das roças no espaço e no tempo, e a partir de levantamentos realizados com foco na diversidade em nível de espécies e variedades de cultivos. Os resultados mostram que um grande número de plantas continua sendo cultivado e confirmam a vitalidade dos conhecimentos indígenas associados à agrobiodiversidade, mesmo em tempos de forte mudança. Os princípios de repartição, conservação, reprodução e fabricação da biodiversidade Mebêngôkre estão associados ao conceito de 'beleza' (mex), que valoriza, muito além de paisagens e técnicas agrícolas, o bom estado das redes sociais de trocas dentro e fora da aldeia, assim como valores essenciais dos Mebêngôkre.Palavras-chave: Agricultura. Biodiversidade. Mebêngôkre. Kayapó. Amazônia.Abstract: Nowadays, traditional societies of the Amazon experience strong changes that cause direct effects on traditional agricultural systems such as the trend toward homogenization of species and techniques along with a greater reliance on market. However, Amazonian agricultures still are diversified and valuing diversity. The article describes the particularities of Mebêngôkre-Kayapó agriculture from a methodology developed with tools from anthropology, geography and ethnobotany in Indian villages of southern Pará. The current management of agrobiodiversity is analyzed through the organization of the fields in space and time and from surveys conducted with a focus on diversity in the level of species and varieties of crops. The results show that a large number of plants is still cultivated and confirm the vitality of indigenous knowledge on agrobiodiversity, even in change time. The principles of partition, conservation, reproduction, and making of Mebêngôkre biodiversity are associated with the concept of 'beauty' (mex), that values, far beyond landscapes and agricultural techniques, the good condition of social networks within and outside the village, as well as essential Mebêngôkre values.
Résumé La télédétection permet de suivre dans le temps et de quantifier l’ampleur des défrichements en Amazonie brésilienne. La diversité des capteurs permet aussi une approche multiscalaire des paysages du Mato Grosso tout en précisant le rôle respectif des acteurs du défrichement : grands propriétaires éleveurs, petits colons, ou cultivateurs intégrés à l’agrobusiness du soja, du coton ou de la canne à sucre. Les paysages, très différents à l’origine, convergent vers un type unique où la forêt n’occupe plus qu’un maigre espace (réserves légales, forêts-galeries) au milieu des pâturages ou des champs cultivés.
Ce document a été généré automatiquement le 19 avril 2019. Développement Durable et Territoires est mis à disposition selon les termes de la licence Creative Commons Attribution-Pas d'Utilisation Commerciale 4.0 International. Mobiliser le paysage pour observer les territoires : quelles démarches, pour ...
Many trophic indices have been constructed for temperate aquatic environments, but few have proved reliable for tropical environments. Indices constructed on the basis of nutrients may not be effective for describing the trophic state because the fractions of nitrogen and phosphorus differ in their potential to predict the nutrient limitation in tropical aquatic environments. We developed an index based on the phytoplankton Reynolds functional groups for an Amazonian floodplain lake from samples collected during 2 contrasting hydrological periods (rising and flushing) and compared it with the index initially proposed by Carlson in 1977 and further adapted to tropical environments by Toledo in 1990. The functional group and Carlson indices matched only 37% and 56% of the sample units collected during the rising and flushing periods, respectively. Our study confirms the difficulty of assessing trophic states using only phosphorus and chlorophyll a in tropical floodplain lakes. In this environment (1) nitrogen may significantly limit phytoplankton growth and (2) complex phytoplankton-nutrient relationships occur during the hydrological cycle that cannot be accounted for through a simple phosphorus and chlorophyll a formula.
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