The effects of deforestation through land fires used by farmers (specially, smallholders) are twofold. From the individual point of view, they prepare the land improving its fertility. On the other side, the aggregate decision has a negative impact on air and water quality, degrading the environment, and this is reverted as a negative impact of the productivity of the land. In this work we present an aggregative game framework which includes those effects and allows us to analyze the impact of cost fires variations and number of farmers. Finally, using data from Brazilian research institutes, we test the sign and the size of the impacts of those determinants on the aggregate deforestation in Brazil for the period 2009 to 2018.