This article attempts to describe the ways in which an environmental conflict in the Parana Delta region has been presented. The consolidation of the category 'wetland' has played a major role in the emergence of narratives advocating their conservation and sustainable use. An institutional language based on wetlands has evolved in these terms, which has been part of the intense political disputes over how to regulate them. In this paper I reconstruct some of these processes using ethnography to incorporate reflections on the techniques and experiences of the people who live and have daily contact with this region. I am particularly interested in contrasting the category of wetland and the local notion of the island to problematize the way in which the issue is defined in socio-environmental terms in the political sphere. The article draws on contemporary anthropological and philosophical contributions to ask what thinking about the island as a cosmopolitical proposal implies.