Of the renewable resources of The Biosphere, agricultural land, including its water resources, is very high among the most important, because it is elemental for human and domestic-animal life. The stability and sustained fertility of the soil largely depend on both prevailing soil–climate conditions and on anthropogenic influences.

There are strict limits to the human interference which soil substrates, ground, soil, and surface water, flora, fauna, and microorganisms, can tolerate under moderate, let alone subtropical and tropical, soil–climate conditions. Economic, social, and aesthetic, yield of agricultural resources is limited even where economically and technically optimal use is made of capital and labour. A ‘maximum sustainable yield’ varies as a function of the soil–climate location, the established land-use system, and the technology applied, but only as long as this yield is not exceeded is the enduring availability of the resource ensured.

With the demand for land and energy to produce food and agricultural raw materials rising throughout the world, per caput food production continuing to fall (especially in Africa), and the cultivated area per caput declining worldwide, the urgent question for the long term is how to preserve the natural resources of water, soil, and vegetation cover, and how to arrest desertification, deforestation, salinization, soil degradation, and soil erosion.

These reflections centre on the call for farming systems which are suited to given locations and do no harm to the environment, and also for sustainability of agricultural production—two aspects which have been badly neglected in the past. The necessary simultaneous tasks of developing farming systems and preserving resources, can be tackled only in relation to specific locations and in a conducive development ‘climate’, where appropriate general conditions prevail. As a rule, the microeconomic development options for coping with these tasks can be improved only at a supra-farm and community level, and require new, environmentally oriented national agricultural and rural development policies.