Pesticides and fertilisers are making bumblebees increasingly opt for the more abundant flowers on road-facing hedgerows, while leaving the poor pickings on the crop-facing side alone, ecologists at Plymouth University say.
Farming methods are affecting the most common species of bumblebees, the researchers wrote in the Journal of Insect Conservation (citation below).
Dr. Mick Hanley, Lecturer in Terrestrial Ecology and undergraduate Joshua Wilkins say fertiliser and pesticide usage are undermining the bees’ potential habitats.
Bumblebees are spending more time on the road-side of hedgerows because of pesticide and fertiliser usage. (Image: Bumblebee Conservation Trust)
Solution: widen the barrier
There could be a simple solution to the problem, the authors say. Farmers should be encouraged to leave a wider barrier between their crops and hedgerows, which would reduce the effects of chemicals and encourage wildflowers to flourish.
“There have been hedgerows and field boundaries in these locations for centuries, and even if you go back 50 or 60 years, you would not have seen this phenomenon.”
“Both sides of hedgerows would have been flourishing, and bees and other insects would have been numerous on both sides, but that was before an increase in the use of fertilisers.”
Today, chemicals are having a considerable effect on one side, with hedgerows acting as a filter, protecting the road-facing edge. The end result is a diminishing source of food for bumblebees, which in turn is reducing their numbers.
Widening the barrier between crops and hedgerows is one solution.
Insect pollinator population falling
Several studies have pointed to a decline in several insect pollinators globally. Scientists have concluded that this has been mainly due to fragmentation and habitat loss, plus the direct and indirect impacts of pesticide usage.
Examples of insect pollinators in the UK include honeybees, beetles, butterflies, bumblebees, solitary bees, hoverflies, and moths.
The authors say that organic farming might offer some advantages for the conservation of pollinators, since it lessens field margin exposure to pesticides and fertilisers. Organic farming refers to farming the natural way, i.e. without artificial pesticides, fertilisers, etc.
However, conventional farming is expected to dominate, so modifications to current practices, including the use of wildflower strips, should be encouraged, the researchers say.
Dr Hanley adds:
“The pesticides and fertilisers in use today tend to mean plants such as nettles flourish, whereas honeysuckle and other bee-friendly species do not. But we would argue that if farmers were a bit more sympathetic, any work they do to encourage bees and other insects could have reciprocal benefits for them and their crops.”
“Bees and pollinators fulfil a vital role in the ecosystem services of this country, and there is legislation in places which would allow farmers to do more to support them.”
Flowers abandoning the British landscape
According to the Bumblebee Conservation Trust, bumblebee populations in the UK have been declining because of changes in farming practices that have largely removed flowers from the landscape, leaving the insects with little to feed upon.
Most UK species have declined considerably in recent years, while two have become extinct in Britain since 1940.
Of the approximately 250 species of bumblebees that exist worldwide, 24 are found in the UK.
Bumblebees vs. Honeybees: Bumblebees are fat and furry in appearance, while honeybees are smaller, slim and more wasp-like. All bumblebees live in the wild. The majority of honeybees (not all) are looked after by beekeepers. Bumblebees can sting more than once. Honeybees die after stinging. A honeybee’s sting is barbed and sticks in the skin. Bumblebees only sting if aggravated.
Citation: “On the verge? Preferential use of road-facing hedgerow margins by bumblebees in agro-ecosystems,” Mick E. Hanley and Joshua P. Wilkins. Journal of Insect Conservation. DOI: 10.1007/s10841-014-9744-3.
BBC Video – Clever Queen Bumblebee
In an episode of Life in the Undergrowth, Sir David Attenborough uses a thermal imaging camera to how a queen bumblebee heats up in the cold morning air.
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