Nationally designated as a Forest Reserve in 1977 and named after the Térraba and Sierpe rivers, the Humedales National Térraba‐Siepre was established on March 17, 1994 and became one of the 17 protected wildlife areas of Área de Conservación Osa.  

The lands are entirely state‐owned and are managed by the Ministry for the Environment and Energy. 

This area is located on the Pacific Coast of Costa Rica, north of Drake Bay, and approximately 10 miles south of Palmar Sur. It encompasses 66,850 acres and includes the mouths of the Térraba and Sierpe Rivers and adjacent lagoons of Sierpe and Porvenir. 

Few people live in the region and the main human settlements are in the surrounding communities of Sierpe, Palmar and Cortes. 

The Térraba River is the main source of freshwater into the estuarine system, the main tributaries are the General River and the Sierpe River, draining a basin of approximately 500 square kilometers.. ThisSierpe river is unusual in that it is tidal almost up to its source, the Sierpe Lagoon. 

The area is periodically flooded by tides with an average total tidal fluctuation of approximately 6 feet. The Rio Sierpe is roughly divisible into two wetland areas: the flooded forests of the upper Rio Sierpe basin, and the extensive mangrove swamps of its delta. 

The upper Rio Sierpe wetland is virtually uninhabited, unspoiled and contains large areas of raffia palm swamp, flooded forest and lagoons. Fingers of high ground, thickly clad in rain forest, permeate this area. 

The lower protects the extensive river mouth delta systems, estuaries and wetlands between the Terraba River And the Sierpe River, and contains the largest and most important mangrove reserve in Central America. 

The eight species of mangrove include Red, Black, Grey and Teal Mangroves. These mangroves provide an invaluable coastal ecosystem to an abundance of avian, mammalian, reptilian and aquatic species.

Biodiversity and Habitat of Térraba‐Sierpe / ACOSA is extremely rich in species diversity of plants, animals, fungi and microorganisms with at least 2659 vascular plant species. 

The wetland reserve is habitat of many species of birds, fish (55 species), shellfish (10 commercially exploited species), mammals including Agouti paca and Lutra annectens. Reptiles include Caiman crocodilus, Crocodylus acutus and Tree Boas 

Resident and migratory bird species found in Térraba Sierpe include Herons, Egrets, Cotingas and Pandion haliaetus.This area has two endemic hummingbird species: the mangrove hummingbird and the yellow-billed cotinga. 

Within the Térraba‐ Sierpe mangroves, many products are extracted for sale or recreation. The main income generating activity in the area comes from the harvesting of the clam Anadara tuberculosa, commonly referred to as“piangua”. Limited line fishing is permitted in the estuary. 

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