Mitigating anthropogenic barriers to facilitate distributional shifts helps reduce vulnerability of a large herbivore to climate change

Abstract

AbstractClimate change is among the greatest threats to biodiversity conservation worldwide. Understanding which species are vulnerable to climate change and in what ways is essential for adaptation planning and mitigation. We used the NatureServe Climate Change Vulnerability Index (CCVI) to conduct a range‐wide assessment of tule elk (Cervus canadensis nannodes) – a California‐endemic ungulate with low genetic diversity, occupying highly fragmented landscapes – to climate change. Using results from the CCVI, we tested the hypothesis that increasing connectivity among populations, by mitigating anthropogenic barriers to movement and dispersal, decreases vulnerability of tule elk to climate change. We compared CCVI scores given predicted conditions within current ranges with CCVI scores as if anthropogenic barriers were mitigated, with and without allowing elk to shift distributions up to 50 km to areas predicted to experience less warming, drying, or overall exposure to climate change (indicated by an interaction between warming and drying). Vulnerability of tule elk to climate change varied among populations; from most to least vulnerable rankings in the CCVI, 1 population was ranked extremely vulnerable, 1 was highly vulnerable, 12 were moderately vulnerable, and 4 were less vulnerable. Mitigating anthropogenic barriers alone did not have a significant effect on vulnerability to climate change compared to original CCVI estimates, nor did mitigation of anthropogenic barriers and shifts in distribution to areas expected to experience the least amount of warming. Mitigation of anthropogenic barriers coupled with elk shifting distributions to areas predicted to experience less drying than current ranges or less overall exposure to climate change significantly reduced climate change vulnerability. Our findings illustrate the need to prioritize increasing landscape connectivity for tule elk across California as part of climate change mitigation measures, but also may apply to non‐migratory ungulates more generally, particularly where drying and warming are predicted to increase under climate change.