Landscape-fragmentation change due to recent agricultural expansion in the Brazilian Savanna, Western Bahia, Brazil

Abstract

The aim in this study was detect changes in landscape-fragmentation patterns resulting from the expansion of agriculture in the Cerrado region (Brazilian Savanna) during the period 1988–2011. The study area covers 7,559,783.69 ha and is restricted to the limits of the Urucuia Group (Upper Cretaceous), a geological unit formed by sedimentary rocks of continental deposits where there has been intense agricultural expansion due to favorable conditions for the use of mechanized farming. The temporal analysis considered land-use/land-cover data from Landsat TM image classification for the years 1988, 1992, 1996, 2000, 2004, 2008 and 2011. Fragmentation quantification was performed from the morphological spatial pattern analysis (MSPA) and traditional landscape metrics analysis. The calculation of MSPA attributes considered 10 edge widths, between 30 and 300 m. Traditional landscape metrics were obtained from Path Analyst and V-Late software. Change detection in MSPA classes was obtained through cross-tabulation. Cerrado deforestation in the study area increased from 795,502.61 ha in 1988 to 2804,679.75 ha in 2011. The spatial pattern of Cerrado deforestation and fragmentation has a spatial concentration in the western region of the study area that gradually progresses toward the east. Our results emphasize the fragmentation process with a reduction in the following fragmentation indicators over the past two decades: area, number of patches, core, and edge. In addition, the indicators increased in: complexity, size variation, and coreless fragments. Change detection enabled the description of spatial evolution of fragmentation indicators. The results can help define strategies for landscape planning and decision making for conservation priorities.