The Humedal Nacional Térraba-Sierpe is one of the best preserved mangrove forest found in Costa Rica and the largest in the Pacific coast of Central America. With about 32.000 hectares, it is one of the 12 Ramsar Sites found in the country, thus considered a unique habitat that maintains and supports several endangered resident, endemic and migratory bird species. This is the biggest wetland found in Costa Rica one of the most thriving ecosystems in the entire Osa Peninsula. Sierpe River plays an integral part of this ecosystem.

Mangrove Wildlife
This is one of the most rich ecosystems found in the entire Osa Peninsula. It is a complex of environments with tidal channels, shallows, lagoons, swamps, mangroves and forest. This reserve houses a combination of aquatic ecosystems, both natural and artificial. The expansion of rice fields and shrimp farms has had impacts on the area.

The flora and fauna here are one of the richest found all over Costa Rica with about 31 species of mammals registered, 163 species of birds, and is home of the Costa Rican endemic Mangrove Hummingbird strictly associated with the mangrove flowers. Also, the area has many more regional endemic birds such as Golden-naped Woodpecker, Yellow-billed and Turquoise Cotinga, Fiery-billed Aracari or occasionally seen, the rare Agamy Heron. There are 366 species of plants, of which 4 are endemic to the area.

The kayak tour is the most comfortable opportunity to explore one of the Osa's top wildlife and birding hotspots. The mangrove forests in Costa Rica are rich in biodiversity.