The Site is located on the north-eastern coast of the country, in the State of Maranhao. It presents rich biodiversity within a complex range of ecosystems, including rivers, their floodplains and estuaries, riverine forests, swamps and lagoons. This mosaic makes the Environmental Protection Area an extremely important conservation unit, since it enables large-scale ecological processes and supports a mangrove area that regulates local fish stocks. The fertile floodplains provide resting, feeding and breeding sites to more than 20 species of resident or migratory waterbirds. The Site is also important for the conservation of globally vulnerable species, such as the maned sloth (Bradypus torquatus), the West Indian manatee (Trichechus manatus) and the red-spectacled amazon (Amazona pretrei). Dolphins and several species of fish use the Baixada Maranhense in their migratory routes, while populations of reptiles and native mammals use the wetlands as a refuge. Extensive and intensive agriculture is the threat that most affects the site, as well as deforestation, erosion, and sedimentation of rivers in the surrounding areas.