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A third of wild bee and hoverfly species are in decline across Great Britain, raising concerns about biodiversity declines and the potential loss of pollinators.

Analysis of 700,000 naturalist records going back to 1980 has found that about 33 per cent of 353 species studied declined in the extent of their range across the island. Losses worsened in wild bees after 2007, four years after the introduction of a group of pesticides known as neonicotinoids, which have since been almost entirely banned by the EU.

The assessment found that the key group of 22 wild bees and hoverflies behind crop pollination had been doing relatively well. Overall, 11 per cent of the species studied increased their range between 1980 and 2013.

That is no reason for complacency though, says Gary Powney of the Centre for Ecology and Hydrology, who was involved in the work. “It’s a risky pollination strategy to rely on just 22 species.”

While not immediate cause for alarm in terms of food production, the shrinking of many species’ range is a concern for a loss of richness in nature.

“The widespread common species, in very broad terms, are doing okay. The rarer species are doing less well. If you only care about wildlife and biodiversity, it’s bad news. If you only care about whether your crops are being pollinated, it’s okay,” says Nick Isaac, who also worked on the research at the Centre for Ecology and Hydrology.

The once widespread red-shanked carder bee��(���dz����ܲ���ruderarius) is among the losers, down 42 per cent. By contrast, the ashy mining bee��(Andrena�������Ա����������) increased its range fivefold.

Farming, habitat loss and pesticide use have all been blamed for insect losses in recent years. Key crop pollinators could be doing well because of a sevenfold increase in land given over to oilseed rape since 1980, and more strips of wildflowers in farm fields, experts say.

“If further evidence were needed, this new study confirms that declines in insects are ongoing,” says Dave Goulson at the University of Sussex, UK.

Emily Bailes of Royal Holloway, University of London, says the research suggests that agricultural environment schemes are having a positive impact. However, she foresees new threats: “I see climate change as an increasing issue for pollinators in the future, alongside habitat loss from urban development.”