Under shifting cultivation or walking economy (English shifting cultivation even better Wandering farmstead called ) refers to various forms of land use in which fields for a certain period intensively used and then abandoned. Closely linked with the shifting cultivation is the slash and burn, so that frequently spoken of " slash and burn economy." The slash and burn the nutrients in the plants remain in the ashes back to the future acreage and provide short-term fertility. If the deforested biomass burned but not charred, the produced wood and coal plants are then incorporated into the soil. Here they wear to be able to buffer due to their large surface water and nutrients for soil improvement. This approach seems to be in the Amazon basin of origin of terra preta.
The shifting cultivation is one of the oldest agricultural land use of the earth and delivers ideally sufficiently intensive use for subsistence agriculture with optimal ecological adaptation to the local shared peripheral in the tropics. According to estimates of the Food and Agriculture Organization ( FAO) to live and do business today, about 258 million people in this agricultural system.
The concept of shifting cultivation is in German literature today often replaced by the English term " shifting cultivation ". Shifting cultivation is now run primarily by indigenous peoples in tropical and sub-tropical forest areas where they farm lands for 3-5 years and then move the fields to re- fire clearance surfaces, so that the previous cleared area must be in the following years, replaced by secondary forest ( monoculture or grasslands ). The transitions from shifting to spatially more limited and more stationary economies with changing between cultivation and fallow are fluid. If only the economy faces and not farmsteads laid in alternate years, this is called shifting cultivation.
Transitions to other forms of economic
Even today more developed societies have a long time, at least in part driven economies, which included a long-term fallow. In this way, there is now shifting cultivation or shifting cultivation, for example, in Central America ( Milpa economy ), supplemented in part by irrigation, or even in the West African peasant peoples. In the early European Middle Ages shifting cultivation was partly operated. A remarkable transition from slash and burn economy to ongoing intensive use can be found historically in the Tupi in the Amazon: In recent years, the growing evidence that the so-called " terra preta " was produced artificially by the resulting clearance by fire short-term soil improvement ( amelioration ) by the addition of deliberately produced charcoal ( the longer the soil adheres ) was significantly prolonged.
Nutrient cycling and regeneration phase
The length of the required fallow phase has a direct impact on the population density, the longer it lasts, the less people can live in a particular area of shifting cultivation. The length of the fallow phase is dependent on the type of use and the crops, climatic conditions and soil quality. In tropical soils, which are usually deep weathered and low in nutrients, the recovery phase can last up to 25 years. Due to the tropical conditions such as humidity and temperature, and by the high age of the soils is their ability to store nutrients severely restricted (low cation exchange capacity, CEC). The nutrients are therefore in the humid tropics in a continuous cycle ( tropical nutrient cycling ). Almost all nutrients in the tropical rainforest are thus included in the plants and animals.
Ecological and socio-economic importance
In its original form of shifting cultivation was not ecologically questionable if the abandoned land were left for several decades in peace. Due to lack of space and the increase in population and the associated food shortages, the fallow periods are, however, increasingly shortened. As a rule, migrated in an intervals of 10 to 15 years, the settlements in previously untouched forest areas, where a new village was decorated with new fields. Today the settlements, however, usually remain in place, there's no more room for the relocation of the settlement by population growth and additional forms of use ( plantations, etc.). Some of the fallow periods have been reduced to to under 5 years, resulting in serious ecological problems. The shifting cultivation is not nearly as effective as, for example, crop rotation, which is fine however in the humid tropics with great technical effort feasible and usually only for self-catering. Many young people are leaving the traditional villages in the city to escape the harsh living conditions and to earn money. The only way they can (eg, clothes, radio, television, cars, etc. ) satisfy the "new" needs.
In the small-scale slash and burn small trees and shrubs on the future field just before the dry season initially cleared with a machete or an ax, larger trees are scored on a height of 3 meters and die so after a short time. At the end of the dry season the vegetation is then precipitated burned. After this slash and burn the field is littered with felled tree trunks and not precipitated, ash and charred trunks. Only through the ash, which contains valuable nutrients and is used as a fertilizer, a management is possible. The sowing of maize, vegetables and cassava is then before the rainy season; sometimes bananas are grown. After two to three years, new areas are cleared, burned and ordered because the nutrient supply of low humus layer is depleted quickly. Depending on how much acreage is required, the rich land near a village no longer sufficient to feed the residents. Then the whole village migrates to other areas, where new fields can be created. The slash and burn is always the risk of an uncontrollable forest fire. This often large parts of natural forests to be destroyed senselessly.
A few decades ago, Madagascar was still covered in large part with forest, and in the north with rain forest. Now there is in the north of Madagascar, only small remnants of the rainforest. The trees have been felled and burned. The climate of Madagascar has thus become much drier and hotter. It does not rain as often and the soil is delivered to the weather without protection. Because 90 % of the forests were cleared, it comes now to erosion. Where there is no longer worth farming, because people have the floor demanded too much, the country is left to itself. Forest, or in the rain forest can not grow because it is too dry. So thorn bushes and cacti grow now in areas that were once covered by forest. These plants do not require much water, not shade the ground, however. This dries out completely unprotected and is washed away by the rare but heavy rains.
So it is in Madagascar does not like so that no more forest is growing because it is too hot and too dry. Therefore, it is hot and dry, because the ground is not covered with forest.