Fragmentation of native vegetation in a watershed

Abstract

This study aimed to evaluate patterns of the fragmentation of native vegetation of the Upper São Bartolomeu River Watershed (USBRW) in the Federal District, Brazil, with an extension of 21,178.77 ha. The landscape metrics for the USBRW were drawn up after extracting the fragments of native vegetation, in shapefile format, from the vector map of land use and occupation, obtained in matrix format by unsupervised classification in the ArcMap 10.5 program. Images were acquired from the LANDSAT-1 and LANDSAT-8 satellites with pass dates of June 26, 1975, and September 3, 2020, referring to orbit/point 237/071 and 221/071, respectively. The USBRW native vegetation fragments were grouped for the years 1975 and 2020 using vector maps in area size classes. The landscape metrics were area (total core area, average fragment area, core area index and edge density), shape (mean perimeter-area ratio and mean shape indicator), and proximity (distance from nearest neighbor fragment given in meters and proximity index). According to the landscape metrics of the USBRW, it was found that continuous human activities for land use and occupation have led to the fragmentation of land into increasingly smaller portions. As a result, there has been a reduction in the size of fragments of native vegetation, making them less protected and more susceptible to the edge effect, with a lower degree of connectivity between them since they are further apart.