Terrestrial isopods (Crustacea) are macro decomposers of organic matter and bio-accumulators of metals. Soil management and farming practices have changed the population dynamics of isopods, jeopardizing the balance of agro ecosystems. We investigated the potential of preserved forest areas as a refuge for isopod populations in agro-ecosystems. The investigation was carried out in areas with different cover types: beans, corn, soybeans, rye grass and adjacent preserved native forest areas. We sampled three points at random using squares of 40 cm x 40 cm, in which we collected the litter of the forest area and a 0-10 cm layer of soil. We also estimated the organic matter, pH and soil moisture. The isopods were removed from the samples, counted and preserved. Forty-three specimens were 677 Reservas legais: um importante refúgio para os isópodas terrestres … Rev. Ambient. Água vol. 10 n. 3 Taubaté -Jul. / Sep. 2015 found in the forest samples and none in the samples from cultivated areas. Only two distinct species were identified. The results showed the impact of agricultural areas on populations of terrestrial isopods, and the importance of preserved forest areas as a refuge for isopods.