Effects of land-cover change on soil loss in the São Gabriel do Oeste area (Pantanal, Mato Grosso do Sul, Brazil)

In the Sao Gabriel do Oeste area (Pantanal, Brazil), since the '60s, zootechnics and farming activities have developed and arable lands and pastures replaced shrubs and forests. The 1966 to 1996 land-cover change was investigated through Remote Sensing and GIS methodologies. The effect on soil loss was evaluated through the Universal Soil Loss Equation (USLE). By integrating supervised classification and visual interpretation techniques, geo-coded land-cover data bases were built from aerial photographs and Landsat TM images (years 1966, 1985, 1996). Multi-temporal land-cover data bases were produced through 'post-classification comparison.' The application of the USLE in the ARC/INFO$CPY Grid environment enabled to perform the multi-temporal analysis of the potential soil loss. The R, K, C and P factors of such equation were assumed from the literature. The flowdirection and flowaccumulation Grid functions and the DEM allowed calculating the L and S factors. The results show that from 1966 to 1985 large extent of forest and shrubs were deforested. After 1985, deforestation rate decreased and part of burnt areas and pastures changed to secondary forest. The land-cover transformations induced a meaningful growth of the computed average soil loss per unit area (A) from 1966 to 1985 ((Delta)A approximately equals 3.7 t ha-1 y-1). On the contrary, the reduction of A from 1985 to 1996 ((Delta)A approximately equals 0.8 t ha-1 y-1) suggests that more recently the human impact became steady.