Fires are major disturbances for ecosystems in Amazonia. They affect vegetation succession, alter nutrients and carbon cycling, and modify the composition of the atmosphere. Fires in this region are strongly related to land-use, land-cover and climate conditions. Because these factors are all expected to change in the future, it is reasonable to expect that fire activity will also change. Models are needed to quantitatively estimate the magnitude of these potential changes. Here we present a new fire model developed by relating satellite information on fires to corresponding statistics on climate, land-use and land-cover. The model is first shown to reproduce the main contemporary large-scale features of fire patterns in Amazonia. To estimate potential changes in fire activity in the future, we then applied the model to two alternative scenarios of development of the region. We find that in both scenarios, substantial changes in the frequency and spatial patterns of fires are expected unless steps are taken to mitigate fire activity.