This paper considers participatory modelling to integrate biodiversity conservation into land use planning and to facilitate the incorporation of ecological knowledge into public decision making for spatial planning. Réunion Island has experienced rapid urban and agricultural expansion, which threaten its unique biodiversity. In this context, we designed three participatory modelling sequences, involving overall 24 multidisciplinary researchers and stakeholders. The sequences aimed 1) to map land-use and biodiversity, 2) to develop a conservation plan following systematic conservation planning principles using a spatial optimization tool (MARXAN) and 3) to simulate coupled landuse/conservation scenarios using a multi-agent system (MAS). The conservation plan confirms that priority areas for biodiversity protection are located on the coast where rapid land-use changes occur. Nevertheless, stakeholders from the urban and agricultural sector didn't participate to this sequence. Indeed, conservation planning tools are useful to locate conservation priorities but they have to be designed with stakeholders to be accepted as negotiation tool. Besides, the researchers engaged in this second sequence were perceived as conservation stakeholders rather than holders of scientific knowledge. In the third sequence, the researchers involved adopted the stance of facilitating the elicitation of each stake and gathered trust from stakeholders. Overall, we conclude that the participatory development of land-use simulation models should be promoted to explore alternative scenarios for biodiversity conservation with stakeholders. In a situation of land-use conflict, a gradual and sequential participatory modelling approach should be implemented to fit into public decisionmaking processes.

Decentralization and people's participation have been key features of government environmental policy since the 1990s. In Madagascar, the policy of Secured Local Management of Natural Resources, known as the GELOSE act, has created a framework for the transfer of rights from central government to local communities. This article analyses the practical implementation of this policy by focusing on the nature of the rights transferred and on the nature of the contracts and incentives developed. The Aghion and Tirole model for allocation of formal and real authority in an organization is used to shed light on the contractual definition process and on the trade-offs between giving responsibilities to local communities and losing control over natural resources management. It is shown that a congruence of interests between the parties is crucial for effective delegation of authority to local communities and that this congruence may emerge in relation to the transfer of exclusion rights.

This paper aims to clarify two distinct but complementary questions on economic and legal additionality in the payments for environmental services (PES) debate based on examples from the literature and direct observations made in Madagascar and Mexico. For the economic dimension of additionality, we explain two ‘regimes of justification’, efficiency on the one hand and social equity on the other, and discuss how analysts position themselves with regard to both regimes. For the legal dimension, we review and analyse specific cases in which PES are implemented in addition to existing environmental regulations. We propose a renewed framework of analysis to distinguish ‘compensation’ and ‘reward’ in PES by crossing the opportunity cost dimension and the legal constraint vis‐à‐vis the environment. We show how difficult it is to fully maintain the objective of efficiency when PES are implemented simultaneously across different combinations of opportunity costs and regulation constraints. We propose policy options to address the contradiction between incentive and coercive instruments. These options are land sparing, social targeting and chronological combinations. Copyright © 2017 John Wiley & Sons, Ltd and ERP Environment

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