What proportion of a farm must be devoted to specific habitats, like sown field margins, to create significant wildlife changes without compromising optimal but responsible crop management?
Despite the arrival of the government’s agri-environmental schemes and plenty of small experiments highlighting their value, it remains an unanswered question.
So TAG director Jim Orson and the team behind a new 1m Sustainable Arable LINK project need help from farmers willing to offer study sites in return for payment*.
“We do expect to see more land left uncropped in future,” says Mr Orson.
“We want to find out how much you need to manage to get the level of biodiversity the public wants to see, whatever that is.”
DEFRA clearly recognises the knowledge gap by providing half the funds for the four-year project, he says.
“We know which habitats birds prefer,” says the British Trust for Ornithology’s Dan Chamberlain.
“But we don’t know how much more we need to make a difference to population trends.
For example, we don’t know what effect ELS may have.”
By establishing farm-scale studies on conventional winter cropping units in two key arable regions the team hopes to find the answers.
The first year will be used to assess the wildlife present as a baseline for comparison and to pin down 14 farms in each region for further studies.
Some farms will then be left as they are, and some will have their uncropped land managed more specifically for biodiversity, using either less than 10% of the study area or more than 20%.
To determine the best layout for the managed areas they will be located either in one or two large blocks or spread around the fields as strips next to the boundaries, and will include natural regeneration and sowings to provide over-winter bird cover as well as mixtures to encourage insects in summer.
“Hopefully, a small proportion of managed uncropped land will provide the desired level of biodiversity,” says the Game Conservancy Trust’s John Holland.
The uncropped area should not just include set-aside.
“There are restrictions on how you can manage set-aside,” says Rothamsted researcher Peter Lutman.
The team will include studies on an organic farm for comparison.
“That’s because people perceive organic farming to be good for biodiversity,” says Mr Orson.
“We are trying to challenge the perception that you can only get good biodiversity by farming organically,” adds Rothamsted’s Wilf Powell.
“We will build on previous experiments that have shown the potential value of uncropped habitats.”
CAP reform has provided the political climate for such large-scale work, notes Prof Powell.
“But we will still be taking an experimental approach,” stresses Dr Chamberlain.
“It’s not just a survey.”
Indicator species, such as skylarks and yellowhammers, will be used to assess the effects of modified management, he says.
“We expect them to respond more to changes than, say, blackbirds.”
The work will try to quantify the links between the distribution and amounts of particular types of vegetation and other wildlife, such as bees, butterflies and insects beneficial as bird food or pest predators.
“Insects are good indicators of biodiversity,” says Dr Holland.
Farmers volunteering land for the LINK work will be rewarded, says Mr Orson.
“They will be paid to take part, and for where extra management is required.
We’ll provide seed, an allowance for cultivations and any cutting or other operations required.”
* Farmers interested in taking part should contact Suzanne Arnold on 01953 713 200 or via email firstname.lastname@example.org