Climate change contributes to widespread declines among bumble bees across continents

Increasing temperatures and declines

One aspect of climate change is an increasing number of days with extreme heat. Soroye et al. analyzed a large dataset of bumble bee occurrences across North America and Europe and found that an increasing frequency of unusually hot days is increasing local extinction rates, reducing colonization and site occupancy, and decreasing species richness within a region, independent of land-use change or condition (see the Perspective by Bridle and van Rensburg). As average temperatures continue to rise, bumble bees may be faced with an untenable increase in frequency of extreme temperatures.

Science , this issue p. [Related article:]685 ; see also p. [Related article:]626

Abstract

An increasing frequency of hot days results in bumble bee decline.

Abstract

Climate change could increase species’ extinction risk as temperatures and precipitation begin to exceed species’ historically observed tolerances. Using long-term data for 66 bumble bee species across North America and Europe, we tested whether this mechanism altered likelihoods of bumble bee species’ extinction or colonization. Increasing frequency of hotter temperatures predicts species’ local extinction risk, chances of colonizing a new area, and changing species richness. Effects are independent of changing land uses. The method developed in this study permits spatially explicit predictions of climate change–related population extinction-colonization dynamics within species that explains observed patterns of geographical range loss and expansion across continents. Increasing frequencies of temperatures that exceed historically observed tolerances help explain widespread bumble bee species decline. This mechanism may also contribute to biodiversity loss more generally.