Climate Change Putting A Squeeze On Our Bees

by Lillian Stanton · 12th November 2016

(republished due to article loss from site)

Climate change is having a negative effect on Bumblebee (Bombus) habitat range. A new study has observed that Bumblebees do not readjust their range in response to losing Southern areas to climbing temperatures.

Bumblebees have lost considerable amounts of their southern range in both North America and Europe, with around 300km being lost from historically observed limits, but have not readjusted accordingly to use a newly ‘warmed’ northern range.

Buff-tailed Bumblebee (Photo Credit: Jonac Myrenas)

The effect of climate change on species distribution is one of the subjects that has recently acquired considerable attention. Viable habitat areas for numerous species, mostly invertebrates, are being reduced, and pushed Northwards due to increased temperatures and varying weather patterns.

Loss of habitat in the Southern limits of population territory due to climate change (factors being independent to use of machinery, physical habitat destruction and other disturbances) entails that the area no longer provides the optimum temperatures and associated environment for the species. When this occurs, it has been observed that there is a general shift of species range: On one hand, and accountable the majority of climate-change species migration, a movement to the North where the temperature could once again be within the adequate range due to prospective climate change. On the other hand, a movement to a habitat of higher altitude to counter the rise in temperature. Many species, for example tropical butterflies, have been observed to be quite adaptable to range changes related to climate change. However this is not the case with Bumblebees.

A new study published 10th July 2015 in Science focused on the effect of Climate change on natural ranges for the North American (Bombus pensylvanicus) and European Bumblebees (Bombus hypnorum).

Bumblebee conservation is becoming increasingly important Image (c) Bumble Bee Conservation Trust

Geo referenced observations acquired over 110 years (lateral and longitudinal range as well as altitude related thermal limits) of over 60 different species of both North American and European Bumblebee were compared to a base period. Despite significant loss of range in the south, there was no observed change in the Northern range of both the American and the European Bumblebees in spite of positive changes in temperature being observed in these areas (Human use of the land, including pesticide and herbicide uses were discounted as an effecting factor). To add to this, little movement to higher (and thus cooler) altitudes was observed in the Southern ranges affected by climate change.

It was concluded that both the North American and European bumblebees showed a limited capacity for re-adjusting their current ranges following climate change. Thus pre-established habitats are being reduced in surface area at the South through Climate change (increased temperatures) but not extended in the North through colony movement or adaptation on an individual level over the generations. To add to this the Northern extents of the habitat may not become more viable, with temperatures remaining too low to accommodate new species. Both North American and European Bumblebees are finding themselves confined to smaller ranges over time.

This lack of range adaptability for the Bumblebee can be highly detrimental to the colonization of new viable areas as well as the survival of populations forced into areas out of historical range. Bumblebees appear to adjust slower and less efficiently than other families faced with the same circumstances.

Bumble Bee Brood (c) Dragonfli.co.uk

Climate change plays a substantial role in Bumblebee range compression and in combination with other contributing factors, could prove highly detrimental to existing Bumblebee populations. It is essential to better understand climate change effects on population ranges as well as Bumblebee adaptation possibilities to best protect and preserve colonies.

Reference: Kerr et al. (2015) ‘Climate change impacts on bumblebees converge across continents’ Science. 349 (6244): 177-180

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