In addition to its main function for agricultural and forestry production, land is needed for many other purposes, including regulation of the atmospheric and water cycles, mineral supply, nature conservation, settlement, and waste disposal. There is often conflict between competing uses. Some major issues in policy and planning centre upon land use: the supply of arable land, loss of forest cover, and land needed to meet the urban expansion which is a marked feature of the developing world. Land use, the functions which it performs, is distinct from land cover, by plants or built structures. There is a need for common classifications of land use and cover, as a reference base for conversion between national systems. Means are available to survey land use, but in many less developed countries scarcely any reliable surveys have been carried out. As a result, data on land use are among the least reliable of all kinds of international statistics. Until information on land use is improved, development planning will remain without an adequate basis on many major issues. International conventions, such as the World Soil Charter, are of value mainly as a guide to policies at national level. All countries need a national land use policy, under the guidance of a committee at ministerial level, to co-ordinate and reconcile the many sectoral interests.