In 2021 Argentina extended the area of the Site from 3,000 hectares to 5,561.31 ha. It now includes a much greater area of grasslands, marshes, forests, rivers, streams and lagoons. The Site supports a notable wealth of species, with its 400 vertebrate species including 21 which are classified as vulnerable, including the marsh deer (Blastocerus dichotomus) and the dot-winged crake (Porzana spiloptera). The Park is also recognized as an Important Bird and Biodiversity Area (IBA); it hosts 285 bird species including 169 species of waterbird such as the black-necked swan (Cygnus melancoryphus), the Chilean flamingo (Phoenicopterus chilensis) and the black-headed duck (Heteronetta atricapilla). Ciervo de los Pantanos is also a National Park protected under national law. However, given its location near Buenos Aires, the country's largest urban, agricultural and industrial centre, the site has been impacted by urban development and pollution from sewage discharges.