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Helping bees using flower power
Controlling grasses on wildflower strips encourages pollinator biodiversity
8 April 2011
Farmers could help cut the decline in Britain's bumblebees by sowing wildflowers on parts of their land not used for growing crops and limiting grass growth on such patches so bees and other insect pollinators have extra pollen and nectar food resources.
Bumblebees are pollinators of key agricultural crops. © Robin Blake
Bees provide crucial 'ecosystem services' by pollinating crops from apples and strawberries to runner beans and oilseed rape. 35 per cent of global food production volumes are from crops that depend on animal pollinators (ref 1). Overall, insect pollination has been estimated to value EUR158Bn per year (ref 2) so maintaining bee and pollinator biodiversity is essential for food security.
Worldwide bee declines have led conservationists to claim the world is in the middle of a global pollination crisis. While the disappearance of the honeybee is on most people's radar, the bumblebee hasn't received quite the same attention.
In the last 20 years, two of the UK's 27 bumblebee species has gone extinct; seven are in decline, and seven are classed as stable (ref 3).
On the back of an increasing awareness of the negative effects of intensive farming on biodiversity, the UK government has funded numerous schemes to pay farmers to restore or maintain habitats that support native wildlife, such as sowing wildflower seeds to sustain pollinating insects. But previous research suggests that sowing wildflowers on such 'buffer strips' isn't enough on its own because fast-growing grasses also grow on these strips and out compete the flowers, preventing them from establishing a foot hold.
You're going to reap just what you sow
To find out if the wildflower-sowing strategy could be improved, BBSRC-funded PhD student Robin Blake and colleagues from the University of Reading and the Centre for Ecology and Hydrology, along with industry partner Syngenta, applied three different treatments to grass buffer strips on two farms in southern England.
The first grass buffer strip was left as it was to serve as a control. The second treatment was sowed with wildflower seeds. The final treatment was sowed with wildflower seeds and treated it with a grass-specific herbicide (a graminicide, fluazifop-P-butyl) to reduce the grasses and let the flowers take hold.
More strategic sowing of wildflower seeds can increase biodiversity. © Robin Blake
Significantly more wildflowers grew on the land that had been sown with wildflower seeds and treated with herbicide than in the other two treatments. Over the three years the scientists counted 279 bumblebees, the majority visiting strips that had received the final treatment; over 75 per cent of visits were to red clover and common knapweed flowers (ref 4).
"The hope is that this work could signal a new approach for agri-environmental policy, and eventually lead to increased biodiversity on UK farms," says Blake. "One of the barriers to uptake of these options is cost. Sowing wildflower seeds can be very expensive. This method utilises species that are cheap but at the same time provide valuable resources for bees and other insects."
An additional study investigated the impacts of graminicide on butterflies, and found similar results – a combination of wildflowers with graminicide gives increased more than existing buffer strips and buffer strips just sown with wildflower seeds (ref 5).
Blake says one of the impacts of modern farming practices has been the loss of species rich wildflower meadows and hedgerow habitats. "The plants in these habitats provide crucial pollen and nectar resources for bees, thus their decline has reduced the quantity of resources available. By increasing the quantity of wildflowers on farmland we can help to address these declines."
- Importance of pollinators in changing landscapes for world crops (external link).
- Economic valuation of the vulnerability of world agriculture confronted with pollinator decline (external link).
- Bumblebees: behaviour, ecology, and conservation (external link).
- Enhancing habitat to help the plight of the bumblebee (external link).
- New tools to boost butterfly habitat quality in existing grass buffer strips (external link).
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