Dinâmica e complexidade da paisagem do projeto de assentamento Benfica, sudeste paraense.

Abstract

Due to various human activities the recent occupation of Amazonia has resulted in relevant changes in the landscape and loss of biodiversity. One of the most critical areas of deforestation is the Southeast Pará Mesoregion which is under the pressure of the agricultural frontiers. In this context, this study aimed to examine the dynamics and complexity of the landscape of the Benfica Settling Project (PA-Benfica), which represents a critical area of deforestation caused by agriculture during the settlement process. The study approach includes a range of information about the field of Landscape Components (constituent elements as: forest, secondary forest, pasture, etc.), and Landscape Types (representing a portion of an homogeneous area and coherent with the arrangement and the frequency of its components). This methodological strategy required a geographical approach to understand the context related to definition of a landscape typology and the aspects of its dynamics and complexity. It was used in this work process some products and techniques of remote sensing and geo orbit. Satellite images from Landsat-TM were purchased for five different dates (1987, 1992, 1996, 2001 and 2005) and analyzed by SPRING system, being considered the supervised classification by regions for space analysis dynamics. The use of integrated remote sensing with Geographic Information System (GIS), a field of intense work, as well as landscape theoretical models, endorsed the identification and characterization of 10 Components of Landscape. These components represented the following vegetation cover and land use patterns: Forest Remnant (CP1); Gallery Forest (CP2); Wetlands (CP3); High Secondary Forest (CP4); Secondary Forest with Solanum (CP5); Low Secondary Forest (CP6); Pasture with Woody Plants (CP7); Field with Babaçu Palm (CP8); Pasture with Babaçu Palm (CP9); and Clean Field (CP10). The area of Forest Remnant (CP1) component presented 60% of deforestation during the period 1987-2005: For the same period, the areas of secondary forest and pasture showed an expansion of 30%, respectively. In addition to these results, it was also identified, defined and characterized five different Landscape Types: Forest (TPO), Agriculture Mosaic (TP1), Agricultural Mosaic with Pasture (TP2), Large Extents of Pasture (TP3), Large Extents of Pasture with Babaçu (TP4) and Babaçu Forest (TP5). The results showed that in the dynamic process occurred the conversion from forest to pasture, when the highlight landscapes were Large Extents of Pasture (TP3), Large Extents of Pasture with Babaçu (TP4) and Babaçu Forest (TP5). Doing the integration of both information it was possible to devise a specific scale of complexity for both Components of the Landscape, as well as for Types of Landscapes, to estimate the complexity degree of the landscape from the simplest (0) to the more complex (12), and based on three indicators of the internal structure and on the order of plant formations: Indicator of Diversity, Indicator of Stratification and Indicator of Transformation. The intensity degrees of greater complexity match to the landscape types Forest (TPO), Agriculture Mosaic (TP1) and Agricultural Mosaic with Pasture (TP2). The median level refers to the landscape type Large Extents of Pasture with Babaçu (CP4), while the lower level of intensity is associated with Large Extents of Pasture (TP3). From these results 1t was possible to assess the evolution of the complexity of all landscape types for the dates considered in this study. The set of results point out that the landscape types can be considered and evaluated regarding to a greater or lesser environmental impact which are directly related to a range of degrees of complexity of its components. Thus, they may be used as units for territorial management on the application of public policies concerning to land use planning and biodiversity conservation.