Profound changes occurred in the Brazilian Forest Code in 2012. Political solutions exceeded scientific criteria, causing considerable losses to the environment. This study aimed to evaluate the impact of the criteria adopted by Law 12651 on the delimitation of permanent preservation areas (APPs) for the upper third of hills of a river basin in the state of Rio de Janeiro. APPs were delimited in the watershed of Cacaria River in the municipality of Pirai, considering the criteria established by CONAMA Resolution 303, Law 12651. Alternatively, a change in Law 12651 was proposed - altering the criteria related to the average slope > 25º proposed. This procedure was carried out at Arcgis 10 program using a digital elevation model (DEM). We conclude that, according to Law 12651 (average slope > 25º), only 1.5% of APPs on the hill tops delimited using Resolution 303 would be left, and if the same criteria were adopted considering the line of maximum gradient instead of the average slope, this reduction in APPs would be of only 22%.
forest legislation; hill top; geomatics