For several decades taxonomy has been marginalized in academic labs and universities. Today, rising concerns over biodiversity and ecosystem services are creating an unprecedented opportunity for it to be viewed as a crucially relevant field. This article aims to scrutinize how the biodiversity concerns entail new collaboration designs between taxonomists and nature managers and between taxonomists and ecologists. Our key point is that taxonomy's environmental relevance is not given: instead, taxonomic data have to be made relevant by taxonomists and their partners in specific collaborative and organizational arrangements. The article draws on an empirical study of an All Taxa Biodiversity Inventory (ATBI) in a national park in the French Alps, including an ethnographic survey combined with scientometric analysis. It was found that the collaboration initiated in the ATBI between taxonomists, ecologists and the park managers was paved with disappointments and reorientations because it partly failed to address the tension between a taxonomic and an ecological approach to the relevance of taxonomic data. The rise of biodiversity and ecosystem services concerns constitutes a “double-edged sword” for taxonomists: while there is greater opportunity for taxonomists to render their work visible through new research collaboration arrangements with ecologists, it also entails a risk that they remain mere data providers for nature managers and ecologists interested in ecosystem functioning.