The municipality contains a small part of the Baixada Maranhense Environmental Protection Area, a 1,775,035.6 hectares (4,386,208 acres) sustainable use conservation unit created in 1991 that has been a Ramsar Site since 2000.[6] The 2022 Brazilian census revealed that the municipality of Serrano do Maranhão had a total population of 10,202 inhabitants, with 58.5% identifying as Black and 55.7% declaring themselves as quilombolas. This makes it the municipality in Brazil with the highest proportion of Black residents.[7]
^"Divisão Territorial do Brasil" (in Portuguese). Divisão Territorial do Brasil e Limites Territoriais, Instituto Brasileiro de Geografia e Estatística (IBGE). July 1, 2008. Retrieved December 17, 2009.