Dinâmica espaço-temporal dos recursos hídricos e da cobertura vegetal da região Nordeste do Brasil

Abstract

The applicability of geotechnologies and sets of remote sensing techniques and satellite images allows to detection of changes in land cover and use at the local, regional and global levels. The spatial-temporal diagnosis of climate variability and patterns of environmental changes in arid and semiarid regions, especially the degradation of native vegetation, water bodies, and the soil, it’s a key piece element in minimizing to pressures and impacts to the natural ecosystems. This study aimed to diagnose and analyze the spatial-temporal dynamics of the water resources and vegetation cover of the Brazilian Northeast, with use of the geoprocessing and remote sensing, estimating physical-hydric parameters to the surface, during 20 years (2000-2019). For the development of the research, geospatial data from different satellites/sensors (Landsat, MODIS, TRMM) were implemented along with the applicability of software and digital processing scripts of satellite images, responsible for performing estimates of vegetation index (NDVI, EVI, SAVI, and LAI) and water (NDWI and MNDWI), albedo and surface temperature, rainfall and actual evapotranspiration. The patterns of distribution and spatial-temporal variability of the geophysical indices highlighted from thematic maps of land cover were statistically evaluated by analysis of the trend of land use, descriptive, multivariate, correlation, and regression statistics. The results of the trend analysis detected losses in the forest areas, while in the areas of agriculture and livestock and non-vegetated areas there was a significant increase, i.e., indicative of environmental degradation. The water bodies highlighted a spatial-temporal variability linked to the rainfall fluctuations in the Northeast region. The vegetation indices showed a similar pattern of behavior and highlighted among themselves the vulnerability of the vegetation cover in the Northeast Region and Northeastern Semiarid, due the intensification and severity of drought events, which are reflections of high rainfall variability, conditions that reflected in the water availability pattern of the Northeastern Semiarid, highlighted in the water indexes, so that the water condition showed the potential of the effects of drought, highlighting the reduction of the water bodies and increase of the non-vegetated areas in the Northeastern Semiarid. This pattern of change in coverage and land use highlighted high values of albedo and temperature, with the remarkable formation of heat islands over the Brazilian Northeast. The distribution pattern of actual evapotranspiration was shown to be conditioned to fluctuations of the rain and to presence and/or absence of vegetation cover, highlighting the lowest values about the regions of the Northeastern Semiarid. It is worth mentioning, among all the physical-hydric parameters, the remarkable period from 2012 to 2019, which presents a condition of high-water deficit. It is concluded that the rainfall variability directly impacted the dynamics and resilience of vegetation and of the water bodies, which in turn affected the energy exchange processes and the evapotranspiration of the vegetation cover. Statistical analysis and principal component highlighted strong correlations of the physical-hydric parameters in the spatial-temporal analysis. Remote sensing effectively identified the quantitative and spatial-temporal variability of the physical-hydric parameters, that presented as sensitive indicators of the water deficit conditions, environmental, soil, and water degradation.