Based on extensive ethnographic research on Mayotte (Indian Ocean), this article presents a case study on how environmentalism manifests in one of the world's richest biodiversity sites. It illustrates how Mayotte, the last and poorest French overseas department, is shaped by ‘hyper-environmentalism’ – where residents are forced to be ‘hyper-aware’, ‘hyper-educated’, and ‘hyper-committed’ to environmental issues. The paper discusses how Mayotte is constructed by the Wazungu ("white people") as a tropical ‘otherness’ and describes the process of ‘eco-infantilisation’, where the Maorais people are paternalistically portrayed as ‘children’ who need to be taught to ‘see’, ‘read’, and protect their environment. Finally, it shows how this effort to ‘change mindsets’ fails because it doesn't integrate new scientific knowledge with local expertises, which are often not recognised. The aim of this paper is to provide insights into the diverse manifestations of environmentalism in a post-colonial, tropical, insular, and ‘southern’ territory like Mayotte.