Considering the critical state of environmental systems in the world, there is an urgent need for academic research commitment to generate knowledge in order to elucidate the various social and environmental issues involved in environmental conservation. This small study intended to contribute to this matter by studying in situ conservation on private land. The aim of the study was to identify which factors had driven owners' decisions to create Private Natural Heritage Reserve (RPPNs). It also aimed to understand what motivations permeate the dynamics of preservation decisions. Semi-structured interviews were conducted with the "RPPNnistas" who own land within São Paulo Green Belt Biosphere Reserve -RBCV-SP guided by closed question forms, Likert scale (1932), and open questions. On the answers, content analysis was applied (BARDIN, 1977) in search of greater objectivity in the collected material interpretation. Polygonal, satellite imagery, maps, legislation, owner and public agency documents, management plans and other technical documents were also analyzed. From the group of 27 respondents representing 33 RRPNs, most of them considered nature conservation as their main reason and motivation for the reserves creation (58%), with the belonging factor being considered relevant. Personal factors, incentives and property protection were considered indifferent by the majority. In corporate RPPNs, environmental marketing was indicated as relevant. The "RPPNnistas" were classified by a "typology" which considered their increasing participation and involvement in the exercise of their legal rights and duties. The results grouped the owners into four categories: 1) Legally Bound Owner, denominated Non-Voluntary Owners followed by three others named Voluntary Owners: 2) Obligatory Legal Activities Owner; 3) Owners of Non-Mandatory Legal Activities and 4) Owners of Activities Not Suggested in the Law. In the first category figures RPPNs created by some form of bargaining or compensation with the Government, passing through those who only strictly comply with the law, followed by those predisposed to execute what the legislation allows them to, and reaching those who go beyond that, and those who fulfill the previous categories presenting greater transformative power. The results showed that most RPPNs were voluntarily created (67%), with a large number of non-volunteers (33%). Changing the criterion to total occupied area (ha), the index is inverted and presents the majority of the RPPNs from RBCV-SP lands created by non-voluntary acts (58%) followed by the voluntary acts categories (42%). This demonstrates opposition to an initial idea of altruistic motivation for the creation of RPPNs in the study area.