In many countries, coastal areas, river basins and land generally is subject to quarrying of sand and gravel for concrete, aggregate for roads and clay for production of bricks. Many national governments and local authorities are currently licensing exploitation of these raw materials for revenue-collecting purposes. They are seldom concerned with the appropriateness of the use to which such land is put. For example, in some countries areas have been licensed for clay or stone quarrying at the expense of the agricultural and livestock sector.