NATIVE BROWN hares may be benefitting from the exotic, non-native crops now growing across Britain’s farmland to fuel biodigesters.

A study conducted by researchers from the universities of Cambridge, Hull and the Open University, and published this week in the European Journal of Wildlife Research, concludes that how crops are planted is just as important as to which crops are grown in determining their impact on farmland wildlife.

Aware that changes in agricultural practices over the past century have contributed to declines in various species of farmland wildlife, the research team, led by Dr Silviu Petrovan, set out to investigate what effect biomass energy crops might have on one such threatened species, the brown hare.

Several new biomass energy crops are now being planted across the UK and Europe, and differ from most crops because they are typically planted for long-term harvests of 15 to 25 years, and are cut annually from the same sites, but otherwise require very little management.

One of the most common of these crops is a giant Asian grass called ‘elephant grass’. By tracking hares in farmland planted with different sized fields of elephant grass, Dr Petrovan’s team showed that the crop planted in small blocks provides an excellent habitat for brown hares, but if planted as a monoculture across large areas, was found to discourage them.

The team analysed the diet from hare droppings, which showed that hares avoid elephant grass as a food source, preferring more typical cereal crops, wild grasses and herbs, but they do use it to rest and shelter in. The team’s radio-tracking devices also showed that hares associated with small-scale planting had home ranges five times smaller than those living in or around large-scale planting.

Dr Petrovan said: “What is remarkable about this study is that we have recorded some of the smallest hare annual home ranges ever, at an average of just 10 hectares. It suggests that, as part of a mixed agricultural landscape and planted at the right scale, elephant grass provides many of a hare’s habitat requirements in a very small area.

"If ranges are small it indicates that the numbers of hares an area can support is high. We think that hares use elephant grass for cover and then forage around its edges. They also take advantage of the fact that it isn’t sprayed with herbicides, so in places it has quite a rich ground cover of other plants which they feed on, not unlike a small area of young woodland.

"The caveat is that hares do need other components of their habitat, so where the crop is dense and planted over a wide area, hare ranges were much bigger than normal, causing them to expend a lot more energy as they need to travel further to find natural foraging areas," he noted.

Dr Phil Wheeler from the Open University added: “In some respects, although these biomass crops are alien to the UK, they mimic unfarmed or unintensively cultivated bits of farmland, many of which have been lost as farming has intensified.

"Our research suggests that for hares, diversifying farmland by planting biomass crops in small chunks might replace something of what has been lost. The same may be true for other wildlife, but at present evidence is limited. Whether planting at small scales is economically and logistically viable for farmers is another question. If biomass crops are only viable when planted over wide areas, they may end up as another challenge to farmland wildlife.”