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Science: For Crops, Wild Pollinators Needed

A Diadem butterfly visiting a sunflower in South Africa - -one of the many wild insects around the world that provide farmers with free pollination services. (Photo: Luisa G. Carvalheiro)

Worldwide, honeybees are declining. And that has farmers worried about the crops that bees pollinate. But, in many farming areas, wild insects have been declining too.

Now, a huge study in Science shows that these wild pollinators—including flies, beetles, and butterflies—are more important than domesticated honeybees for boosting crop yields.

"Our surprising result is that native pollinators enhance production of crops, regardless of whether farmers use managed honeybees to augment pollination," notes University of Vermont biologist Taylor Ricketts, one of the study’s co-authors.

Setting fruit

The new study, published online on Feb. 28,  synthesized more than forty experiments from 600 farm fields in twenty countries — including one conducted by Ricketts, director of UVM’s Gund Institute for Ecological Economics. The key result: in every crop system studied, wild pollinators increased the number of flowers that set fruit, while honeybees did so in only fourteen percent of the crop systems.

"This suggests that honeybees do not — as popularly thought — replace the pollination services that native pollinators provide to crops around the world," Ricketts writes. Instead, pollination work by wild insects increased "fruit set" twice as much as visits from honeybees.

Also, pollination visits by wild insects and honeybees "promoted fruit set independently," the scientists write, so honeybees can supplement, but can’t replace, pollination by wild insects. The study, with fifty authors, looked at major crops — fruits, nuts, and grains — grown on every continent.

"Conserving pollinators and their habitats is therefore an important part of ensuring an adequate crop," Ricketts notes — underlining the limitations on finding domesticated substitutes for the wild species that provide benefits to people.

Wild farms

"Our study shows that losses of wild insects from agricultural landscapes impact not only our natural heritage but also our agricultural harvests," noted the study’s lead author, Lucas A. Garibaldi, from Argentina’s Universidad Nacional de Río Negro. "Long term, productive agricultural systems should include habitat for both honeybees and diverse wild insects."

One of the practices underlying these new findings is the separation of intensive agricultural landscapes from landscapes with greater biodiversity. "Our study shows that this separation can have negative consequences for pollination services," notes Alexandra-Maria Klein, a co-author from Leuphana University of Lüneburg, Germany—a problem that is "not buffered by honeybee management."

"We urgently need more research that informs but also involves the global and wider society," she says, “to explore novel management designs for agricultural landscapes." For example, farmers may find that restoring patches of more natural and wildlife-friendly land on their farms will increase yields.