Besides the multiple functions attributed to mangroves (natural shelter against storms and tsunamis, stabilization of shoreline, nursery for fish and shrimp, refuge habitat for birds, water purification, firewood, etc,), these last years, a particular attention has been put on their ability to store carbone and so, attenuate the climate change. Also, mangrove reforestation incentives have spread throughout the world in the frame of REED+ (Reduction of Emission from Deforestation and Degradation). This growing interest for mangrove invites to analyse the politics of mangrove reforestation. In this contribution, we first assess the world stakes, second analyse the effects of public policies on the local dynamics, third question the scientific and societal legitimacy of reforestation actions based on the study case of the large scale programme « Plant your tree » conducted by NGO Ocenium in Casamance. The discursive approach of litteratures and the fieldwork conducted since 30 years in Casamance (Cormier-Salem, 1992; 1994 ; 1999 ; Dièye, 2007, 2011 ; 2013) and more recently in the framework of PATEO Laboratory (www.pateo.ird.fr), show : 1) mangrove is not a simple forest of mangle trees that sequestre carbone. In Lower Casamance, the local people (Diola) have converted them into rice fields and controled their communal territory sine at least the 15th century. The mangrove landscapes, beween sea and land, are the Diola heritage. 2) The Casamance mangroves areas have dramatically regressed in the 1970-90s for various reasons (drought, rural exodus, infrastructures..). However, since two decades, a reconquest is reported 3) Reforestation campaigns are remarkably successful in terms of reforested surfaces and international visibility. Nevertheless, their efficiency is more limited in terms of carbone sequestration, biodiversity and amenities for local people. Finally, we argue that reforestation politics could lead to negative synergies between services and to environmental injustice. They confort the interests of some actors (private companies, NGO) to the detriment of local people and do not serve the cause of biodiversity or climate change.