Biodiversity under threat in glacier-fed river systems

Freshwater biodiversity is under threat across the globe(1), with climate change being a significant contributor(2,3). One impact of climate change is the rapid shrinking of glaciers(4), resulting in a reduction in glacial meltwater contribution to river flow in many glacierized catchments(5,6). These changes potentially affect the biodiversity of specialized glacier-fed river communities(7). Perhaps surprisingly then, although freshwater biodiversity is a major conservation priority(3), the effects of shrinkage and disappearance of glaciers on river biodiversity have hitherto been poorly quantified. Here we focus on macroinvertebrates (mainly insect larvae) and demonstrate that local (alpha) and regional (gamma) diversity, as well as turnover among reaches (beta-diversity), will be consistently reduced by the shrinkage of glaciers. We show that 11-38% of the regional species pools, including endemics, can be expected to be lost following complete disappearance of glaciers in a catchment, and steady shrinkage is likely to reduce taxon turnover in proglacial river systems and local richness at downstream reaches where glacial cover in the catchment is less than 5-30%. Our analysis demonstrates not only the vulnerability of local biodiversity hotspots but also that extinction will probably greatly exceed the few known endemic species in glacier-fed rivers.