Bioclimate overrules microtopography to inform on plant species’ sensitivity to climate change in proglacial ecosystems

Abstract Mountain proglacial landscapes are characterized by pronounced topographic heterogeneity that generates sharp environmental gradients and microreliefs over short distances, shaping the distribution of plant diversity. In such ecosystems, it was hypothesized that these high microtopographic variations might modulate the effects of climate warming, potentially amplifying or reducing species vulnerability. Here, we assess if microtopography may complement bioclimate in predicting species distributions and prioritize their sensitivity to climate change across 418 plant species in 408 glacier foreland ecosystems in Switzerland. The most important explanatory variables for species prioritization were mean annual temperature and isothermality. Topographic heterogeneity interacted with bioclimatic variables to modulate species–environment interactions. Microtopographic variations, including for slope and topographic position, contributed to explaining variation in alpine plant species distributions only when considered together with bioclimate. Our findings suggest that the influence of microtopography is subordinated to the one of climate, and is thus subtle, which cast doubts on its potential role in buffering climate change impacts on plant species in Swiss glacier forelands. Our reproducible framework for ranking species vulnerability constitutes a simple tool to identify potentially sensitive species to environmental change, ultimately informing conservation measures to maintain the unique Alpine plant biodiversity.