Global biodiversity loss is occurring at a rapid pace, stemming from multiple anthropogenic drivers including overexploitation, pollution, invasive species, and climate change. Despite increasing research on the impact of climate change on wildlife, few studies have formally attributed observed biodiversity declines to climate change or quantified its contribution relative to other factors. In this new study, Belgian researchers isolated and quantified the contribution of climate change to changes in European areas ecologically suitable for bumblebee species, which constitute a group of key pollinators whose populations have declined in recent decades. To this end, the researchers used more than 800,000 georeferenced occurrence records of 47 species to train species-specific ecological niche models and projected them under two sets of climatic conditions: the historical climate observed between 1901 and 2019, and a counterfactual climate where any long-term trend correlated with global warming is removed. Quantifying the difference between these two kinds of projections allowed the researchers to evaluate the isolated impact of climate change on the habitat of European bumblebees.

Their results show that climate change has already substantially reshaped European areas ecologically suitable for bumblebee species, with a reduction in suitability attributable to climate change of 5% on average and up to 19% locally. Their analyses also highlight an overall impact increasingly pronounced from the 1980s onwards, which coincides with faster rates of warming, as well as a more pronounced impact on southern and central regions. In contrast, their results also show that, in the Alpine and Boreal regions, gains in ecologically suitability at higher altitudes partially offset losses at lower latitudes and altitudes, resulting in minimal net changes.

The researchers conclude that climate change is already altering the environmental conditions suitable for European bumblebees and that these changes are likely to intensify as warming continues. They stress that climate mitigation, alongside habitat management and conservation measures, will be essential to limit further climate-driven changes in the distribution of insect species, including pollinator species constituting vital ecosystem service providers.