This refuge protects one of the most important wetland regions in Costa Rica's territory and is considered of international importance because it protects a wide range of migratory species and endangered species, as well as species which are commercially important. Cano Negro Lake-ashallow, seasonal, freshwater lake extending over 800 hectares-is a spill-off site for the adjacent Frio River and its tributary, the Monica River. The area formed by the lake and its surroundings constitutes one of the most biologically diverse regions, and is of vital importance in maintaining optimum environmental conditions in the northern part of the country. The region is also inhabited by a wide range of flora and fauna and natural communities, many of them unique and endangered. This makes the area important worldwide, since, combined with the wetland regions south of Nicaragua Lake, it is one of the most outstanding examples of wetlands in the America Continent.