Geotecnologias aplicadas a degradação ambiental da subbacia do Rio Piancó no semiárido paraibano: uma análise espaço-temporal.

Abstract

The Brazilian Northeast is part of the semi-arid regions that make up the globe, called Caatinga in Brazil. It differs from other seasonally dry tropical forests in the world, as it has the greatest diversity of species. This region has been populated since the 16th century, becoming the most populated semi-arid zone. Its inhabitants are concentrated in places close to water sources, due to water scarcity in certain periods, exploiting natural resources, and promoting agriculture and livestock. One of the main Hydrographic Basins in the Northeast is the Piranha-Açu Hydrographic Basin, located in the hinterlands of Paraibano and Potiguar, which is divided into 11 Sub-Basins, among them we have the Piancó River Sub-Basin, which has one of the main sources of water resources for the residents of Sertão da Paraíba. In this context, the present research aimed to classify the environmental degradation and vegetation cover of the Piancó River Sub-Basin in the Paraíba hinterland over a period of 30 years. Using Remote Sensing and Digital Image Processing techniques. To this end, geotechnology was used to identify and monitor areas in the process of degradation. The methodology was based on a deductive and comparative approach in the analysis of uses and environmental degradation, allowing the identification of spatial, temporal and semantic patterns of vegetation and environmental degradation, generating detailed information on vegetation classes and levels of degradation of the environment. Piancó River Sub-Basin. To this end, the climatological average and descriptive statistics of precipitation for each municipality that make up the Sub-Basin were analyzed. Also, a survey of land use was carried out by IBGE's SIDRA Platform, observing the agricultural census and the harvested area. For digital image processing, the free code software QGis was used. Initially, the study site was characterized and satellite images were acquired from the USGS website. The images used are those from the TM/LANDSAT-5 satellite and the OLI/LANDSAT-8 satellite. To classify vegetation and degradation classes, the NDVI corresponding to the years 1993, 2003, 2014 and 2023 was used. In which, through multitemporal orbital images and applied digital image processing techniques, the characterization was obtained spatio temporal vegetation and degradation levels in the study area. Subsequently, field observations were made to support the classification and creation of thematic maps. The Sub-Basin presented, during the analyzed period of 30 years, greater levels of vegetation in the semi-dense and thin class. As for the degradation classes, in 1993, 42.78% of the SBRP presented moderately severe levels of degradation. In the years that follow, the SBRP remains for most of its extent with significant moderate-severe levels. However, there is an attenuation in the levels of serious degradation, which in 2003, 2014 and 2023 corresponded to 14.79, 12.07 and 7.99%, respectively. At the same time, the moderate level of degradation increases from 18.14% in 2003 to 62.76% in 2023. The results show the suppression of vegetation over time, a fact that reverberates in the levels of degradation obtained. Periods of greater degradation are intrinsically correlated with periods of greater agricultural activity, indicating a need for adequate management for the exploration of the Sub-Basin.