Temporal evaluation of soil use conflicts in the Formoso river basin, state of Tocantins, Brazil

Abstract

The importance of permanent preservation areas (PPA) is mainly associated to their environmental role to maintain, preserve, and conserve water resources and ecosystems within a basin. The objective of this study was to delimitate and quantify the areas of PPA along watercourses as well as anthropized areas within PPAs boundaries, in the Formoso river basin, state of Tocantins, Brazil. PPAs area was delimited considering boundaries according to the Brazilian Forest Law. We sampled areas within the watercourses classified up to hierarchical Level 4. Watercourses handling draw, automatic delimitation of PPA, and visual classification of the soil use conflicts based on LANDSAT 5 TM of 1985, 1998 and 2011 were carried out on Geographical Information System ArcGIS. PPA of the watercourses sampled in this study represent 1.14% (24,491.35 ha) of the drainage area of the Formoso river basin. For 1985, an area of about 3,616.48 ha was quantified, which is characterized by conflicts related to soil use. However, these conflict areas were reduced to 3,341.25 ha and 3,345.37 ha, respectively, for 1998 and 2011. Due to the intense agricultural land expansion observed in the basin in the last decades, the mentioned reductions in soil use conflicts between 1985 and 1998 and subsequent maintenance can be linked to changes on Brazilian environmental legislation.