A definition of land use only based on agriculture is incomplete, because at least five other main types of land use interact competitively with agriculture in space and time. Therefore, land use is defined as the temporarily and spatially simultaneous use of six main functions of land. Within this concept, biomass production and especially the production of food is one important function of land. Due to severe competition between the six types of use, sustainable land use is defined as spatial and/or temporal harmonization of all main uses of land, minimizing irreversible ones. From this, the conclusion is drawn that sustainable agricultural land use depends on all the other types of land use and can only be sustainable if all others are sustainable as well. This is also true for food production as one specific target of land use. Based on this approach, some specific constraints for food production in the tropics and subtropics are discussed on a strategic, tactical and operational level, aiming at the definition of principles for sustainable use of natural resources in these regions.
