Costanera Sur Ecological Reserve — Buenos Aires' 350-Hectare Urban Wetland & Wildlife Refuge

The City of Buenos Aires declared the Costanera Sur Ecological Reserve a protected natural area in 1986, on 350 hectares of land reclaimed from the Río de la Plata using construction rubble in the 1970s and then left to regenerate spontaneously into wetlands, grasslands and woodland along the riverfront.
The reserve is now the largest and most biodiverse green space in the city, documented by the City government, BirdLife International/Aves Argentinas and C40 Cities to host more than 300 bird species and more than 500 native plant species; it received Ramsar Convention wetland recognition and BirdLife's Important Bird Area designation in 2005. In 2016, the Argentine Flag butterfly (Chorinea sylphina), previously believed extinct in the area, was rediscovered within the reserve. The site draws roughly 1 million visitors a year and is managed by the City's Secretariat of Environment alongside two smaller sister reserves, Lugano Lake (36 ha) and Costanera Norte–Ciudad Universitaria (23 ha), which together bring the city's protected reserve network to 409 hectares.
Documentation focuses on species counts and formal protection status; no site-specific quantified data on carbon storage, flood attenuation or water quality was found, so those benefits are inferred rather than measured.

Read the full analysis: https://turismo.buenosaires.gob.ar/en/atractivo/costanera-sur-ecological-reserve