Impact of agricultural intensification of pastoral systems on bird distributions in Britain 1970–1990

Abstract

The distribution of six species of birds known to depend on extensive pastoral systems, as published in atlases of breeding birds, was mapped in Britain for two time periods: 1968–1972 and 1990–1992. The species chosen (corncrake Crex crex, golden eagle Aquila chrysaetos, hen harrier Circus cyaneus, stone curlew Burhinus oedicnemus, chough Pyrrhocorax pyrrhocorax and red-backed shrike Lanius collurio) are known to be declining or vulnerable across large parts of their European range. Summed species distribution was compared with available data on the distribution of low intensity agricultural land in Britain. In 1990, bird and land-use distribution was similar. Thus it is concluded that it may be possible to use summed species distribution to predict areas where ecologically beneficial farming systems exist elsewhere in Europe. Most coincidence in species distribution now occurs in Scotland, northern England and Wales. However, large parts of mid-west Scotland have less selected pastoral species than in 1968–1972. The most obvious changes have occurred throughout East Anglia, the south-east and south-west of England. There has been significant fragmentation of coincidence along the north Norfolk coast and along the coasts of Suffolk and Essex. The extent of summed distribution of the indicator bird species chosen declined and fragmented dramatically between 1970 and 1990. There was a significant negative relationship between livestock units per hectare (both sheep and total), and mean species coincidence (average number of species occurring in each 10km 2) for six regions in Scotland and northern England in 1990. In each of these six regions, mean species coincidence declined as sheep livestock units per hectare increased between 1970 and 1990. The need for changes to agricultural policies at the level of the European Community in order to reverse this serious conservation problem, is discussed.