The article reviews the relevant concepts in assessing sustainability at the sector level for British agriculture and forestry. It notes that the use of reproducible capital is not sustainable in the sector as depreciation has exceeded gross fixed capital formation for some years, although that retrenchment may, however, be an appropriate response to expected lower farm prices and increased efficiency in the use of capital. It then exemplifies the problems of measuring the sustainability of use of natural capital by reference to specific problems, namely the release of global pollutants from agriculture and forestry, the economic cost of soil erosion and the economic cost associated with damage to Sites of Special Scientific Interest (SSSI). On the basis of a wider review of the context of these changes, it is concluded that the sustainability of primary land use, as currently practised, must await substantial research before positive claims can be made for its overall sustainability.