Impacts of Agricultural Change on Farmland Biodiversity in the UK NIGEL D. BOATMAN, HAZEL R. PARRY, JULIE D. BISHOP AND ANDREW G.S. CUTHBERTSON 1 Introduction Over the past 50 years, there has been a marked decline shown by many species closely associated with lowland farmland in the UK, which is widely considered to be a key issue in British nature conservation. Increased availability of survey data has meant it is now possible to quantify changes in biodiversity for some groups. Changes have occurred in many farming practices and these have affected biodiversity in a variety of ways. Mixed agriculture in Britain has been lost and farms have become specialised; traditional crop rotations have de- clined and pastoral and arable farming have become polarised. Farming has intensified; for example, wheat yields in Scotland increased by 201% during the period 1967–1999 due to more effective tillage, application of fertilisers and pesticides and plant breeding. Field sizes have increased, reducing non-crop habitat at field margins. Other changes include more autumn sowing of crops and more efficient harvesting, more non-inversion tillage, drainage and reseed- ing of grassland, a switch from hay to silage, increased stocking rates and the use of avermectin wormers. 1 This has all impacted upon wildlife species that inhabit lowland farmland landscapes. Upland farming and livestock grazing has also intensified during this time. High grazing pressure, especially by sheep, has had a negative impact upon vegetation and wildlife in many upland regions of Britain. 2 Much of the focus on biodiversity conservation within agricultural land- scapes has been on the conservation of rare or rapidly declining species, driven in part by the UK Biodiversity Action Plan, the Government’s response to the 1992 Convention on Biological Diversity, and also by the adoption of a commitment as part of the Government’s Public Service Agreement to ‘‘care Issues in Environmental Science and Technology, No. 25 Biodiversity Under Threat Edited by RE Hester and RM Harrison r The Royal Society of Chemistry, 2007 1