What does a changing climate mean for the UK’s bumblebees?

6 December 2021

By Dr Richard Comont, Science Manager and Darryl Cox, Senior Science and Policy Officer

With the world talking climate following COP26, our science team take a look at what a changing world means for the UK bumblebees.

At a global scale, bumblebees are cool-weather creatures, most at home in the world’s cool, damp temperate regions. The climate of these areas is predicted to be changed substantially by global warming.  Research on bumblebees’ global ranges finds that, as the climate warms, the area of hospitable conditions for each species (its climate niche) is moving towards the Poles. Therefore, bumblebees in Europe will need to move northwards to stay within their niche.  This will be particularly apparent at the southern edge of species’ ranges: if species don’t manage to move northwards fast enough, they won’t survive.

Most of our UK species are towards or at the northern edge of their ranges in Britain.  These species may become more widespread across the country in the near future – for instance, the northwards movement of several species such as the Buff-tailed bumblebee (Bombus terrestris) over the past few decades is likely to be at least partially linked to the changing climate. However, we also have species which are close to their southern range edge. These species are likely to be more and more at risk as the climate changes, and the size of their habitable areas shrinks. For example, the Great Yellow bumblebee (Bombus distinguendus) is now only found on some Scottish islands and a thin strip of the mainland north coast, and the Moss carder bee (Bombus muscorum) is widespread in Scotland but undergoing a severe decline further south, in England and Wales.

Other species are at risk because they are specialised to a habitat which itself will decline as the climate warms. The Bilberry bumblebee (Bombus monticola) thrives on bilberry moorland, mostly above 300m. As climate change takes effect, the habitable zone for these species moves not just northwards but also uphill, leaving smaller areas of isolated habitat (essentially, hilltops) which eventually become too small and the species will die out there.

For bumblebees to survive in a climate change world, they must be able to move northwards, tracking their habitable zones. There is evidence that species’ southern range edges are moving northwards, and other species are moving uphill. Concerningly, however, there is little evidence of northwards range shifts, meaning species ranges are growing increasingly restricted. A recent climate risk atlas for European bumblebee species found that most species are likely to decline significantly under current warming scenarios.

So why should this be the case? Well, we know that bumblebees also experience other pressures and, in the UK and across most of Western Europe, the historical driving force behind bumblebee declines has been the loss and fragmentation of bumblebee habitat, driven by development and the intensification of agriculture. In fragmented and flower-depleted landscapes, it is more difficult for species to move through the landscape and migrate into new areas. This is particularly difficult for species which are more sensitive to habitat quality, for example those with stronger preferences for particular flowers or shorter foraging ranges, and for those species which are not strong dispersers. In both cases the nearest suitable habitat is likely to be too far away or too hard to reach. The combined effect of climate change and habitat loss & degradation is to leave small pockets of populations isolated in areas which are becoming increasingly unsuitable for them – like fish in evaporating puddles after a flood.

Of course, climate change doesn’t just mean that temperatures increase: it also increases the frequency and severity of extreme weather events like floods, storms and droughts. It is these which will present the most immediate climate-related impacts for bumblebees in Britain.  Floods can wipe out hibernating queens, and colonies nesting in the ground. Severe droughts can reduce nectar availability at critical points of the colony lifecycle, reducing the nest’s production of new queens – next year’s colonies. Increased storm frequency and severity, particularly allied to sea level rises in coastal areas, could have severe impacts for some of our rarest species. Many of these are now largely coastal, or are restricted to low-lying areas such as the Somerset or Gwent Levels at risk of seawater infiltration or flooding.  The Great Yellow bumblebee, one of our rarest species, is almost entirely restricted to the machair, dune grasslands at risk from Atlantic storms and rising sea levels.

More widely, shifts in seasonal patterns such as earlier springs could create a mis-match of timings between flower availability and bumblebee queens. Queen bumblebees emerging from their winter dormancy need to find nectar as soon as they can in order to recover from their long months of hibernation. Queens then need to find both nectar and pollen as they establish a nest on their own. Reducing the food available to them at this crucial point can have a major effect on survival.

What can be done to help bumblebees combat climate change? 

Obviously a key thing is minimising the amount of climate change that happens. Without this crucial step, other actions are treating the symptoms rather than the root cause.

Unfortunately, even in the best-case scenario there will be a considerable change to the climate and we must help bumblebees to survive the change. We know that well-fed bumblebees with high-quality places to nest and hibernate are better able to respond to the challenges they face. The priority for bumblebees therefore remains getting flowers back into the landscape and ensuring they have flowers available right through their flight season, March-October. This is something that everyone can help with, from individual gardens or window boxes, to community greenspace planting, right through to large-scale meadow creation. Our Bee the Change campaign has resources to help you achieve this.

Thankfully, meadow creation – one of the very best ways to help bumblebees and lots of other wonderful wildlife – is also a really good way of storing carbon in our landscapes. By restoring or creating the flower-rich grasslands we have lost over the last hundred years, we can help our plant life and wildlife to recover and tackle the climate crisis. Increasing the abundance and diversity of flowers in these habitats boosts biodiversity and increases the amount of carbon stored in the soil below. Take a look at our Land Management for guidance.

Beyond providing food and habitats for bumblebees, you can join in with the Bumblebee Conservation Trust’s work through attending an event, volunteering, donating, or becoming a member to help create a world in which bumblebees can thrive.