The genus Isoëtes includes iconic plants, characteristic of a wide range of ecosystems including nutrient-poor aquatic waterbodies. They are wetland obligates which have suffered severe losses globally over time mainly due to alterations and loss in colonized habitats. This is due to their sensitivity to habitat alteration and eutrophication of water and sediment. Despite this, a global review of the ecological knowledge about aquatic species belonging to this genus is missing, and overall, we know very little at the global scale. An assessment of aquatic Isoëtes ecology is therefore important, particularly for a better understanding of what the main threats to their conservation are. Through a global, collaborative initiative a first global ecological assessment focusing on aquatic Isoëtes was carried out. It includes a literature review, an extensive new database on Isoëtes distribution and growth conditions, and ecological niche analyses. We first compiled a global aquatic Isoëtes database including all known environmental data collected between 1935 to 2023 (for a total of 1880 georeferenced records). We then used ordinations to quantify ecological niches and environmental drivers for a subset of species. Both well-established findings and unexpected results emerged, opening new perspectives for the conservation of aquatic Isoëtes.Read less <