A level of output which can be continued indefinitely, without impairing the future productivity of any natural resources used. This is contrasted with overcropping or resource mining, which reduces or destroys the productive capacity of the resources involved. Examples are found in agriculture, where good practice can improve the soil whereas overcropping or overgrazing damage it; in forestry where a regular cycle of felling and replanting can be sustainable; or in fisheries, where a limited harvest can continue indefinitely whereas overfishing destroys breeding stocks. See also depletable resources; renewable resources.