Introduction

Hill and upland areas, defined as land typically above 150 m altitude, within designated agriculturally less favoured areas, and composed predominately of dwarf shrub heaths, grassland and peat bogs, make up more than one-third (5.8 M ha) of the total UK land surface (Ratcliffe & Thompson, 1988). Agriculture, in particular sheep farming, is the primary industry of such hill and upland areas, and its expansion over the last seven–eight centuries has resulted in the development of vast areas of sheep walk composed of indigenous Agrostis-Festuca, Nardus and Molinia dominant grassland. These indigenous grasslands or rough grazings presently constitute some 70% of the land within the hills and uplands (Newbould, 1985).

Traditionally, indigenous hill grasslands have been lightly grazed by pure bred sheep. Over the last few decades, however, intensities of sheep farming have increased dramatically, due largely to improvements in grassland productivity from use of fertilizer and lime. These agricultural improvements have caused considerable concern amongst conservationists, particularly for the loss of indigenous flora and fauna of the hills and uplands (Sydes & Miller, 1988; Bardgett & Marsden, 1992; Bardgett, Marsden & Howard, 1995). Recent changes in UK agricultural policy have reflected these concerns and addressed others, such as the overproduction of meat. Consequent reductions in financial subsidies based on output, and the introduction of monetary incentives for hill farmers to manage their land in such a way as to preserve or improve the environment (for example, environmentally sensitive areas) are likely to result in an overall reduction in liming and the use of fertilizer, and hence of the intensity of sheep grazing on upland grasslands.