Biodiversity under threat in glacier-fed river systems

Abstract

In many regions climate change is reducing the glacial meltwater contribution to river flow, but the effect of these changes on specialized glacier-fed river communities is poorly quantified. Now research demonstrates quantitatively not only the vulnerability of local biodiversity hotspots but also that the number of species lost is likely to be much higher than the few specialist species found only in glacier-fed rivers. Freshwater biodiversity is under threat across the globe1, with climate change being a significant contributor2,3. One impact of climate change is the rapid shrinking of glaciers4, resulting in a reduction in glacial meltwater contribution to river flow in many glacierized catchments5,6. These changes potentially affect the biodiversity of specialized glacier-fed river communities7. Perhaps surprisingly then, although freshwater biodiversity is a major conservation priority3, 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 (α) and regional (γ) diversity, as well as turnover among reaches (β-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.