Economy and agriculture has had to cope with population increases and growing demand for food, and thus has intensified production systems. Already, the consequences of modern farming methods include a loss of biodiversity, exploitation of natural resources and contamination of soil, water and air. Today, there is little land left to turn into farming, except for remaining forests that for several reasons need to be protected. Expansion of cultivated land has reached an ecological – and politically acceptable – limit. The concept of sustainable agriculture aims at preserving biodiversity and maintaining soil fertility and water purity. It also contributes to the conservation and improvement of the soil. Conserving Nature. About one third of the world’s surface is land, and about one-tenth of this is used for permanent crops. Although new land may be put into production in parts of Latin America and Sub-Saharan Africa, there are several limitations to new acreage that can be used for agriculture. Such constraints on the use of these potential agricultural land resources for cultivation are partly agronomical, partly political. In some cases, potential areas simply do not have the desired soil quality or a reliable rainfall pattern to make cultivation feasible. A lack of infrastructure may restrict development. In other cases, where soil and water are adequate, environmental concerns argue against cultivation. The threshold for clearing forest for cultivation has been raised along with acquired knowledge about global warming and concern over climate change. Bad experiences from deforestation, especially the reduction of tropical rain forests, further limits the expansion of farmland.