They thus help improve the well-being of urban dwellers and build urban constituencies for nature conservation. Their establishment and operation entail specific complexities, however. Protecting urban areas involves several often conflicting interests, the areas are often potential sites for residential, commercial, industrial and government buildings and urban infrastructure such as roads and landfills. Only a few urban protected areas are under federal jurisdiction, but they are among the largest (e.g. Tijuca National Park and Brasilia National Park).