To save bees, focus first on habitat, then pesticides: scientists

Hedgerows and wild grass in field margins, which previously served as semi-natural habitats, are being swallowed by agricultural production.

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While scientists have suggested pesticide use and habitat loss are detrimental to pollinators, their relative impacts were unclear.

A recent study by researchers in China, the U.K. and the Netherlands offers insight. It shows
that semi-natural habitats play a more important role than pesticide use in rice fields, a finding key to efforts to stem the decline in pollinator diversity.

Researchers studied honeybees (Apis mellifera) and mason bees (Osmia excavata) across 20 rice fields within the Yangtze River Valley in China.

“Non-crop habitats are important for pollinators in agricultural fields as these provide essential resources and nesting sites,” said Yi Zou, associate professor at Xi’an Jiaotong-Liverpool University, China, who co-led the team.

“Although the impact of pesticides cannot be ignored in efforts to reduce the decline in pollinator diversity, our results suggest it would be better to concentrate on conservation of semi-natural habitat than on reduction of pesticide use in rice fields.”

One of the resources these habitats provide is food, says XiaoYu Shi, a postdoctoral researcher at the Chinese Academy of Sciences.

“Our study shows that in regions with a lower percentage of rice fields and more semi-natural habitat, there was more food available for female mason bees to feed their larvae with,” he said.

The team believes this is the first study to include O.excavata, a native species of China, as an indicator of pesticide levels and food acquisition in an agricultural landscape. This species is used commercially in orchard pollination.

“Pollinator diversity in Chinese small-holder agricultural ecosystems is very high, likely due to the diverse and complex landscape,” said Zou. “Therefore, conserving semi-natural habitats in these agricultural systems is crucial.

“However, the impact of pesticides is still an important consideration. We found honeybees have a higher pesticide exposure risk in more intensified rice field(s).”

He said many aspects remain poorly understood.

“We need long-term monitoring of pollinator populations and their exposure to pesticides to better inform conservation efforts.”