Summary Agriculture represents the dominant land use throughout much of western Europe, and a significant part of European biodiversity is associated with this habitat. We attempted to quantify the changes in agriculture and biodiversity in Britain since the 1940s. There have been widespread declines in the populations of many groups of organisms associated with farmland in Britain and north‐west Europe. The declines have been particularly marked amongst habitat specialists; many of the taxa still common on farmland are habitat generalists. Farming practices have become increasingly intensive in the post‐war period, with a dramatic reduction in landscape diversity. Since 1945, there has been a 65% decline in the number of farms, a 77% decline in farm labour and an almost fourfold increase in yield. Farms have become more specialized; the greatly increased use of machinery has made operations quicker and more efficient, but has resulted in the removal of 50% of the hedgerow stock. Autumn sowing of crops has become predominant, with winter stubbles now far less prevalent. The number and extent of chemical applications has increased greatly, but the net amount applied, and their persistence, has decreased in recent years. Intensification has had a wide range of impacts on biodiversity, but data for many taxa are too scarce to permit a detailed assessment of the factors involved. Reduction in habitat diversity was important in the 1950s and 1960s; reduction in habitat quality is probably more important now. As a case study, the declines in populations of seed‐eating birds populations were assessed in relation to changing agricultural management. Generally, the declines were likely to be caused by a reduced food supply in the non‐breeding season, although other factors may be important for particular species. Agriculture will face a number of challenges in the medium term. While research into the mechanisms underlying species and habitat associations, and their interaction with scale, will be critical in under‐pinning management, consideration of farmer attitudes and socio‐economic factors is likely to be as important. Biodiversity may benefit from integrated farming techniques but these need to incorporate environmental objectives explicitly, rather than as a fringe benefit.
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