Degradação da cobertura vegetal e suas consequências ambientais no município de Barra de Santana, PB.

Abstract

Evidence of environmental degradation in the Brazilian territory date from the Lusitanian occupation initially on the northeastern coast zone, then directed into the territory (rural and backwoods). The spatialization of the developed activities in Paraíba backwoods, for instance livestock, the cotton industry, deforestation, associated with events of prolonged drought and the vulnerability of the rural population caused negative environmental impacts. In some microregions of Paraiba state, taking Eastern Cariri as an example, there are areas in advanced stage of desertification, which is not the case of the county Barra de Santana was taken for the realization of this study for being insert in the microregion previously mentioned as well as for being susceptible to the desertification process. The main objective of this research was to analyze the relationship between the natural and anthropogenic conditions in the process of degradation of the vegetation cover in the municipality of Barra de Santana between the period of 1987 to 2015 (28 years) and its consequences, justified by the scarce studies on the environmental degradation processes in the semi-arid region of Paraiba, in particular in the aforementioned municipality. This research was developed in three stages, initially with the review of literature dealing with historical, social, environmental and economic aspects related to degradation of regional and local Caatinga Biome. The second stage took place with the application of semi-structured questionnaires objectives in rural city studied. The third step was carried out through the use of Remote Sensing and Geographic Information Systems (GIS) with the use of satellite images that helped in the analysis of biophysical aspects of plant cover of the municipality studied by the dynamics of vegetation of Caatinga and the calculation of Soil Adjusted Vegetation Index (SAVI). It was verified the importance of some social programs in ameliorating the vulnerability of the rural population conditions, such as the Bolsa Família, Bolsa Estiagem, Seguro Safra, Água Para Todos and social technologies such as board tanks that have guaranteed minimum water security and food for families living in the countryside. Considering that, even being attended by some social programs, only the social vulnerability was presented as moderate (29,1%), the other ones such as economic (92,1%), technological (67,8%) e hydric (64,7%) were identified with high levels. The results obtained from the comparison between images of SAVI for the years 1987 and 2015 show a reduction of 37 % of the area occupied by dense Arboreal and Subarboreal Caatinga present in 1987, representing a deforestation rate of 2.8 Km² /year. There was an increase of 49.7% of the open Caatinga Shrub classes, sparse Subshrub, very thin Subshrub and soil exposed, an increase of 2.9 km2 /year. The mapping of Natural Susceptibility to Environmental Degradation obtained from overlapping vegetation maps, soil erodibility and slope indicate a reduction in susceptibility areas belonging to the Very Low Susceptibility classes from 25% (1987) to 11.2% (2015). In areas belonging to class with high level of susceptibility there was an increase between 1987 and 2015 from 12.8% to 16%, the susceptibility of Very High class increased from 14.8% (1987) to 23.5% (2015), this increase occurred in areas that have steep slopes and very high capacity loss ground, in this case it must be stressed the importance of preserving native vegetation to ensure the stability of the soil, which does not prevent the use of these areas for development economic activities that are sustainable.