Agri-environment Measures Boost Wildlife Populations in Long-term Farm Study

Agri-environment schemes can significantly increase local bird and butterfly populations without damaging food production, a long-term research project has found.

Scientists from the UK Centre for Ecology & Hydrology (UKCEH) spent a decade intensively monitoring the impacts of a large-scale Defra-funded experiment at Hillesden, a 1,000-hectare commercial arable farm in Buckinghamshire. Beginning in 2005, this involved creating several wildlife habitats, including seed-bearing plants for birds, wildflowers for pollinators and tussocky grass margins to support a range of birds, insects and small mammals.

The experiment assessed the effectiveness of these agri-environmental measures in reducing biodiversity losses caused by the intensification of UK farming practices since the Second World War, including declines in species that are essential for agricultural production such as pollinators and predators of crop pests.

In the longest-running monitoring study of its kind, researchers found numbers of the majority of species did better at Hillesden than in other comparable farmed landscapes without agri-environment measures over the same timeframes. There were increases of a third across populations of all bird species between 2006 and 2016, compared to an average of just under 13 percent at other monitored sites, and 40 percent among all butterflies 2009-2017, compared to 21 percent elsewhere.

A previous UKCEH study of six years' harvesting data published in Proceedings of the Royal Society B: Biological Sciences found overall yields at Hillesden were maintained—and enhanced for some crops—despite the loss of agricultural land for habitat creation.

Abundance of the common linnet more than doubled at Hillesden, while other seed-eating birds that fared better there compared to other sites included yellowhammer and chaffinch. Meanwhile, birds that usually feed on insects benefited from the shelter provided by hedges and grass margins, including the great tit (up 88 percent) and blue tit (up 73 percent).

Butterflies that did particularly well at Hillesden over the period studied included the gatekeeper, which feeds on grasses and the green-veined white, which feeds on wildflowers in field margins. The numbers of both species doubled over the period studied.