International audience Biodiversity offsetting has been promoted as a promising political tool to combine economic development and nature conservation. It designates a planned process of creating or enhancing biodiversity to offset local losses or degradation of biodiversity. In practice, the implementation of biodiversity offsetting is a complex, experimental process and raises numerous controversies. Our interdisciplinary team of social scientists, ecologists, game and literature scholars and artists has designed a biodiversity offsetting game to communicate about the process of biodiversity offsetting to transdisciplinary audiences and manage conflicts related to it. The originality of the game is to simulate the affective dimension of biodiversity offsetting and use it as a basis for experiential learning.While the role of affects in game experience and conservation practice have been well studied, their potential as learning devices in conservation games remains to be examined. Studying biodiversity offsetting through affects is especially relevant because it has been promoted as a tool to reconcile economic development and nature conservation. Biodiversity offsetting has fuelled hopes to respond to the environmental crisis as well as fears of economising nature. Drawing on Finnish and French case studies, we have explored the contrasted practices of compensation, their modalities, the criticism they encounter, and the different regulations they are related to. This first step of the project has helped us to understand the affective dimension of biodiversity offsetting.Together with ecologists, nature managers and developers, we have then designed a prototype version of a one-hour biodiversity offsetting social card game. Played by 4-6 (desirable) to 12 players (possible), the game introduces the key mechanisms of biodiversity offsetting, as well as the power relationships between various actors. We approach games as performative communication devices, which frame understanding of scientific knowledge and exploration of policy development affectively, in terms of entertainment and trust building. The game introduces biodiversity offsetting in a fun and engaging manner and triggers the interest of various actors. The game stages a fictional natural area hosting several protected species but threatened by development projects. Players can embody different kinds of developers and nature conservationists with their respective powers and interests. In addition, a local resident, a decision maker and a biodiversity offsetting bank can be played when more than 6 players are present. The players can cooperate or oppose themselves to apply the mitigation hierarchy and change the rules of biodiversity offsetting (stronger/smaller ratios, flexible offsetting, offsetting of ordinary nature). From an affective point of view, we decided to emphasise the affects experienced by the actors: the frustration of being a traditional conservationist; the feeling of betrayal among conservationists when some start to cooperate with developers; the sense of unity and brotherhood when conservationists successfully block a project; the sense of power of developers due to their facilitated access to resources; their frustration face to the difficulty of applying the mitigation hierarchy; the sense of responsibility of some of them who get involved in sustainability projects. In overall, the game also underlines the surprise and uncertainty generated by the offsetting process.Around ten gaming sessions were, or are about to be, organised with ecologists, developers, biodiversity offsetting officers and nature conservationists in Finland, France and Germany. Game sessions are followed by debriefing sessions focusing on the experience of players and the implementation of biodiversity offsetting. Debriefing sessions constitute a privileged moment for building trust among the players and cool down the heated debates of game play. They also enable us to get feedback on the game and improve it for a final version planned for November 2019. The entire meetings were anonymously audio and video tapped to analyse the discursive and bodily expression of affects and understand how they help to learn about biodiversity offsetting. Inspired by the principles of grounded theory, the results are currently being collected and analysed at the same time. They highlight the importance of affects to communicate key messages about biodiversity offsetting. When relating their game plays, actors relied on highly affective moments (frustrating or joyful) experienced during the game to indicate their understanding of biodiversity offsetting and its potential as tool for nature conservation. In some cases, the affects experienced provided a basis for sharing hopeful and pessimistic stories about nature conservation. The affects also fostered the formation of different subjectivities among players. Developers and conservationists could exchange their roles and understand the emotional work required by the other profession. These results invite to pay attention to the affective potential of games as facilitating devices for learning about nature conservation and explore different political options.ReferencesBrunet, L. (2016). Faire l'expérience des «services écosystémiques». Émotions et transformations du rapport aux espaces naturels. Carnets de géographes, (9).Bryant, J., & Fondren, W. (2009). 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