sustainability Article The Competing Social and Environmental Functions of Private Urban Land: The Case of an Informal Land Occupation in São Paulo’s South Periphery Ana Paula Pimentel Walker * and María Arquero de Alarcón A. Alfred Taubman College of Architecture and Urban Planning, University of Michigan, Ann Arbor, MI 48109, USA; marquero@umich.edu * Correspondence: appiment@umich.edu; Tel.: +1-734-764-8292 Received: 19 September 2018; Accepted: 8 November 2018; Published: 12 November 2018   Abstract: This article examines the role of legal actors in mediating urban land conflicts involving informal settlements and the social and environmental functions of private property. This problem reveals the challenges of conciliating two constitutional rights—the right to adequate housing and the right to a healthy environment. Methods include an analysis of the urban policy and legal framework regulating environmental protection, housing provision, property rights, and land use law. The legal case analysis of Ocupação Anchieta, a young land occupation in São Paulo’s periphery, offers additional evidence through interviews with key informants, fieldwork including household surveys, participatory planning meetings, direct observation, and mapping of existing conditions. Findings demonstrate that private property rights continue to have uncontested power in the legal system, especially during the first years of an informal settlement. Furthermore, planning regulations do little to help young land occupations, vis-à-vis consolidated informal settlements, in establishing sustainable practices from the beginning. Peripheral urbanisation through informal land occupations of environmentally protected areas remains one of the most pressing problems of the Global South. Thus, legal actors and planners should develop land use laws, urban policy, and mechanisms of private property conflict mediation that distinguish between young land occupations and consolidated informal settlements. Keywords: social function of private property; environmental protection; peripheral urbanization; land use conflicts; informal settlements; young land occupations; 2001 City Statute; 2012 Forest Code; 2014 São Paulo Master Plan; ZEIS—special zones of social interest; the Courts. 1. Introduction From the 1980s on, Latin American democratic constitutions have established the rights to housing and a healthy environment, and have consolidated the social function of property as a way of limiting the dominance of private property rights [1]. Although most Latin American countries have adapted their legal interpretations of the social function of property to include ecological functions [2], the regulation and enforcement of the constitutional rights to housing, private property, and environmental protection can generate land use conflicts, with important repercussions for urban sustainability. This article analyses one concrete conflict between the rights to adequate housing, environmental protection, and private property in Brazil. This land use conflict, which resulted in a court case, represents a common sustainability problem in the Global South: the urbanisation of environmentally protected and private land via the establishment of informal settlements. The goal of this article is to examine the ways in which legal actors and municipal planners enable and/or Sustainability 2018, 10, 4160; doi:10.3390/su10114160 www.mdpi.com/journal/sustainability