Ivy bees and rare carder bees in a warming world

Saturday 9th December 2023

…a guest blog written by Jamie Buxton-Gould, Conservation Officer for the West Country Buzz project, with Bumblebee Conservation Trust, as part of our COP28 impacts of climate change on invertebrates series.

Of our 270 native bee species, most prefer warm conditions, with Britain forming the natural northern edge of their European range. Many insect species have demonstrated the capacity to cross the English Channel and with a more favourable climate, have colonised our islands quickly.

The Ivy Bee (Colletes hederae) is a species that has been turning up in lots of new places in recent years, finding an ideal niche for its autumnal life cycle. Ivy Bees are known to have been present on the Channel Islands since the 1970’s, and only arrived on the British mainland in 2001 – the first record was in Dorset. Since then, they have spread rapidly across the UK and Ireland, with recent northerly records from Scotland.

As their name indicates, this bee favours ivy flowers as a key source of nectar and pollen, but will visit other late-season flowers, being on the wing from September to November. As well as spreading from continental Europe into the UK, it is also expanding into south-eastern Europe, being able to cope with a range of climatic conditions, although warm autumn weather can favour larval development and enable longer foraging times, benefitting the bees. Another reason for their success could be the current absence of a key parasite that attacks them on the continent, the meloid beetle Stenoria analis.

Even though Ivy Bees are newcomers with potentially unknown interactions with our native pollinators, it has been found that around 50% of the nectar and pollen ivy produces is available and not being collected by other insects; clearly they have found an abundant resource in the UK! As ivy flowers better with increasing warmth, there is potential for Ivy Bees to spread further north – a potential winner in a world of climate change.

Brown-banded Carder Bee (Bombus humilis) © Jamie Buxton-Gould
Brown-banded Carder Bee (Bombus humilis) © Jamie Buxton-Gould

Unfortunately, there are other warmth-loving species that are not faring so well in the UK. The Brown-banded Carder Bee (Bombus humilis) and Shrill Carder Bee (Bombus sylvarum) both like warm and dry conditions and may benefit from a slightly warmer climate. But in contrast to the expanding range of the Ivy Bee, they have undergone significant population declines over the last 100 years and are now threatened, with the Shrill Carder Bee holding the unlucky title of the UK’s most endangered bumblebee.

Shrill Carder Bees are at the northern edge of their range in Britain; they were formerly found across southern England, Wales and locations in north and central England. Now their remaining populations are  dotted across south Wales and southeast England, with localised extinction having occurred in many places. Brown-banded Carder Bee populations overlap with Shrill Carders, but they are also found along the southern coasts. Both species have the similar habitat requirements of abundant flower-rich grasslands in which to feed and tussocky grasslands to nest in. Their disappearance has been driven by our vanishing species-rich grasslands, which once covered a substantial part of the countryside. Before fertilisers (which favour vigorous grasses) and pesticides (which eliminate non-crop species), meadows and grasslands would have been numerous, diverse, colourful and accompanied by the hum of our now rare bumblebees. Modern farming practices and a ‘tidy’ mindset have left many pollinators hungry and homeless, as habitats are lost, degraded and fragmented.

Shrill Carder Bee (Bombus sylvarum) © Peter Harvey
Shrill Carder Bee (Bombus sylvarum) © Peter Harvey

Whilst a warmer climate may suit these two species, bumblebees simply can’t survive without food and somewhere to nest. The limiting factor is the lack of favourable habitat that is well-connected across the countryside, with rarer bumblebees unable to disperse further than 10km. With isolated populations on small, remaining islands of good habitat, extinction risk increases as genetic diversity is reduced. Extreme weather events can compound the threats of habitat loss and fragmentation, leaving tiny, scattered populations unable to recover. Where wetland habitats have been lost, vital damp oases of nectar-rich plants aren’t there to help pollinators during dry spells. Lack of grazing or cutting, leaving grasses to form a thatch that is too thick can change the warm, dry microclimatic conditions required for a successful bumblebee nest site.

Encouragingly, recent projects by the Bumblebee Conservation Trust, in collaboration with Buglife and a range of other partners and landowners, have begun to see glimmers of hope in the recovery of both of these species. A number of projects across England and Wales are working to conserve Shrill Carders and have seen the species appear in new locations.

The West Country Buzz project in North Devon has carried out targeted habitat creation and observed Brown-banded Carder Bees expanding and reclaiming some of their former territories. Increasing the abundance of these bumblebees with a greater distribution throughout the landscape will enhance their resilience into the future. The crucial provision of much needed connected flower-rich habitat could see these warmth-loving species recover and thrive once more.

Want to know more? Buglife’s projects in Cornwall, South Devon, South Wales and the Thames Estuary are also contributing to the recovery of Brown-banded Carder Bees and Shrill Carder Bees.

Our B-Lines initiative is improving the connectivity of wildlife habitats across the UK, restoring wildflower-rich grasslands and other habitats, and enabling bees and other wildlife to move more freely through our countryside in response to climate change and other pressures.  If you are helping pollinators on your home patch, be sure to add you dot to our B-Line map!

You can also follow the Bumblebee Conservation Trust’s West Country Buzz on Twitter (X)