Ecosystem services are the benefits people reap from the presence of ecosystems. The forests of Nazaré Paulista, for instance, are responsible for several ecosystem services, such as absorption of CO2 from the atmosphere (mitigating the greenhouse effect), prevention of silting in water supply reservoirs, and erosion control, among others. IPÊ has launched a project to evaluate the economic and ecological importance of ecosystem services in the region of Nazaré Paulista. With the information gathered by the project, it will be possible to develop mechanisms to back public policies and decision-making concerning land use and occupation. For example, after learning how many tons of soil the forest prevents to be lost and carried to a river or a reservoir, and after learning what this represents economically, a public manager will have better conditions to seek alternatives to deforestation. Therefore, this project will provide decision-makers with technical e economic information about ecosystem services.