Abstract
Climate change has shaped bee distributions over the past century. Here, we conducted the first species-specific assessment of future climate change impacts on North American bumblebee distributions, using the most recent global change scenarios developed in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). We assessed potential shifts in bumblebee species distributions with models generated using Maxent. We tested different assumptions about bumblebee species’ dispersal capacities, drawing on observed patterns of range shifts to date, dispersal rates observed for bumblebee queens, and, lastly, assuming unlimited dispersal. Models show significant contractions of current ranges even under scenarios in which dispersal rates were high. Results suggest that dispersal rates may not suffice for bumblebees to track climate change as rapidly as required under any IPCC scenario for future climate change. Areas where species losses are projected overlap for many species and climate scenarios, and are concentrated in eastern parts of the continent. Models also show overlap for range expansions across many species, suggesting the presence of “hotspots” where management activities could benefit many species, across all climate scenarios. Broad-scale strategies are likely to be necessary to improve bumblebee conservation prospects under climate change.
Highlights
Bumblebees (Bombus spp.) are important pollinators of many native plant species and agricultural crops, in temperate and high-elevation regions, and are associated with vegetation abundance and diversity[1,2]
Between 0–13% of species expanded in range, varying with Representative Concentration Pathways (RCPs) scenarios, when dispersal input was closer to realistic abilities (10 km/year) by 2050
This proportion increased to 0–30% by 2070, but most expansions were only found in a single climate scenario (RCP2.6) (Fig. 2b)
Summary
Bumblebees (Bombus spp.) are important pollinators of many native plant species and agricultural crops, in temperate and high-elevation regions, and are associated with vegetation abundance and diversity[1,2]. The majority of bumblebee species have failed to disperse beyond their northern range limits, while suffering losses at their southern range limits[7]. Bumblebee decline observed at their historical southern limit, and their failure to track climate change at their northern limit, indicate the potential for increased risks of local extinction under climate change[17,18]. Low rates of species dispersal can amplify mismatches between species’ range limits and niche limits by constraining range expansions at the leading range edge[23,25]. Net extinction rates decrease if range limits track niche limits where the climate is increasingly suitable[26]. Many species’ survival depends on their capacity to disperse and track suitable conditions under climate change[27,28,29]
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