Contemporary society presents a very worrying environmental reality, the negative effects caused by anthropic action on the environment, has been causing an imbalance in ecosystems. Given this scenario, there is a need for public policies in the country, aiming to minimize environmental impacts. The Ecological ICMS is an economic instrument to encourage the adoption of environmental actions at Municipal level and has been used as an innovative tool in public policies to support biodiversity conservation. This instrument conditions part of the ICMS revenues passed to the Municipalities to environmental criteria, rewarding environmentally desirable performances and encouraging the implementation of actions with this objective. In the State of Rio de Janeiro, the Ecological ICMS was created by law in 2007, and its objective is to transfer a portion of the ICMS to the Municipalities that promote and prove the improvement of environmental quality in their territories, having defined a series of criteria for the transfer of the sum, being the existence of Conservation Units in Municipal territory the main one of them.