Schematic diagram showing how the risk or incidence of malaria first increases and then decreases as deforestation proceeds. Before deforestation (bottom left) the forest is largely pristine, with a low population density and activities that do not cause deforestation. Malaria can be epidemic (1) and mostly driven by environmental/climatic conditions. As deforestation proceeds (bottom middle), humans start to colonize the area, roads (shown in grey) are built, and agricultural (yellow) and urban areas (white) follow. Malaria risk is enhanced (2) at this modified boundary between human settlements and the forest. Once deforestation is widespread, and after some time that depends on the region and alteration of the landscape (bottom right), the area can sustain only low but endemic malaria transmission (3); however, the risk of infection increases for other diseases transmitted by mosquitoes that thrive in this domesticated environment, such as dengue and Zika.