Análise da contribuição da pecuária bovina nas mudanças de uso da terra: uma abordagem multiescala no estado do Pará.

Abstract

Brazilian Amazon has gone through a number of different economic cycles linked to the exploitation of natural resources, integrated with global markets, which have intensified since the 1960s, most recently through the ongoing expansion of agribusiness. During this process of territorial construction, land use changes have occurred heterogeneously in both space and time, with mechanisms operating at a number of different scales. The present study analyzes the shifts in land use and the contribution of cattle ranching to the process of territorial construction based on monitoring methods and indicators applied at varying scales, from the local to the regional, as a contribution to territorial management. In the Brazilian state of Pará, the study was based on the diachronic cartography of the pioneer fronts, which was used to represent and delimit the regional contrasts among these fronts. The relationship between these pioneer fronts and the dynamics of the deforestation process was also analyzed, by period, between 2002 and 2017, which allowed the territories to be classified as (i) consolidated, in which ranching is being intensified, (ii) expanding, in which the fronts are used as a strategy of occupation, and (iii) areas free of deforestation. In the municipality of Paragominas, located in a territory undergoing consolidation, the landscape dynamics were analyzed by superimposing the maps of land use with those of the agricultural aptitude of the land and the distance to the principal highways, with the aim of developing a model for the restoration of the landscape. The local landscape dynamics can be divided into two principal systems of land use, one that is based on the expansion of the pasture in valleys with sandy soils, and the other, based on mechanized farming, which is currently expanding on the clayey plateaus. The analysis of these two systems provided three important insights for the eventual restoration of the landscape. The first point is that the intensification of land use increases the pressure on the forests, principally in the areas most adequate for farming. The second is that the intensification of land use frees up areas that are inadequate for mechanization, and could potentially be used for the restoration of the forest. The third point is that local governance should be employed to define spatially explicit policies capable of transforming the landscape. In the areas sampled, in southeastern Pará, observations were conducted at specific points for visual description of the characteristics of the pasture, which were used to construct a typology of the process of pasture degradation. When this pasture typology is related to the vegetation indices (NDVI, EVI-2, NDII-5, NDII-7) extracted from Landsat 7 (ETM+) images, it can be noted that the well-formed pasture, which is associated with a reduction in the cover and height of the vegetation, was also related to a reduction in the vegetation indices. In degraded and degrading pasture, there was a lack of precision in the differentiation of the well-formed pasture. The degraded pastures or those undergoing biological degradation were identified better, but still imprecisely in comparison with the well-formed pasture with low vegetation cover, whereas the pasture undergoing agricultural degradation was confused with the well-formed pasture with a medium to high percentage of vegetation cover. This approach has considerable potential for the monitoring of areas of pasture, but needs to be refined. The analyses at different scales reflect the importance of understanding shifts in land use during the process of territorial construction, with the primary objective of transforming this knowledge into an easily-understood diagnostic tool that should facilitate adequate decision-making.