A global synthesis of biodiversity responses to glacier retreat | Une synthèse globale de la biodiversité face au recul des glaciers

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples

International audience

English. At the interface between the cryosphere, hydrosphere, pedosphere, glacier-influenced ecosystems are particularly sensitive to the impacts of climate change. Global warming has hastened both the rate and extent of glacial melting, which foreshadows global-scale modification in biodiversity patterns and functions and make these ecosystems critically endangered. Usually, these glacier-fed systems are referred as hostile environments characterized by low diversity and productivity. However, glacial influence also creates specific habitats sheltering unique ecosystems. Although our understanding of the ecological consequences of glacier retreat has improved significantly in the past decade, we still lack a comprehensive framework that can predict biodiversity responses to glacier retreat globally. To address these gaps, we conduct a meta-analysis of biodiversity change across glacial influence using 2100 observations from more than 200 published studies in the three major glacier-influenced systems: tidewater glacier-fed fjords, glacier-fed freshwaters, and terrestrial glacier forefields. We show that on average glacial influence has a negative effect on taxa abundance and richness, thereby forecasting a general increase in local diversity as glaciers retreat (winners). However, we also observe a significant heterogeneity among community and population responses to glacial influence, with 6-11% of studied populations threatened by the glacier retreat (losers). Most losers are specialised taxa, adapted to glacial conditions while winners are generalist taxa colonizing from downstream. Our analysis further identifies key geographical variables (glacier cover, isolation and melting rates but not latitude nor altitude) and species traits (body size and trophic position) that would modulate taxa sensitivity to glacial