Shifting cultivation
When shifting , Wanderhackbau or traveling economy ( English often cultivation shifting as an umbrella term for shifting cultivation and land rotation , so aptly: wandering farmstead ) is an area extensive , traditional form of agriculture called, are used in the fields intensively for only a few years and then a transfer of the acreage and the settlements take place, i.e. in a form of semi-sedentariness .
The time to move is reached when the decreasing soil fertility no longer allows sufficient yields. Shifting cultivation is one of the oldest forms of agricultural use in the world and ideally provides sufficient food for a self-sufficient subsistence economy with optimal ecological adaptation to the local environmental conditions. Today it is mainly the ever-humid tropical rainforests and the alternately humid savannas that are affected by this type of economy. Bulbous plants such as cassava , taro or yams in particular are grown in this way. Around 250 million people are currently dependent on this small-scale, extensive form of agriculture . The term shifting cultivation is in the current German often literature by English shifting cultivation replaced.
Shifting cultivation is also known as slash-and-burn farming, as this type of cultivation is usually associated with prior slash and burn of "forest islands". With fire clearing (better waste , because the roots are not removed as with real clearing), the substances contained in the plants remain as ash on the planned cultivation area and briefly ensure a higher pH value in the very acidic tropical forest soils. This improves the growing conditions for the food plants. The additional release of plant nutrients from the ash is of much less importance than was previously assumed. If the wasted biomass is only charred instead of burned, the resulting wood and plant charcoal is then worked into the soil; it contributes significantly to soil improvement because its particularly large inner surface enables it to buffer water and nutrients (→ activated carbon ). This approach seems to be the origin of the “black earth” found in the South American Amazon basin ( terra preta ) .
Moving field farming is now mainly practiced by indigenous and traditional ethnic groups , where they cultivate lands for 2 to 4 years and then relocate the fields to new slash and burn areas, so that (with classically low usage intensity) a secondary forest with fewer species will grow back on the previous cultivated area in the following years . Former fire field areas need 15 to 30 years to be used again economically and ecologically.
The transitions from shifting cultivation to spatially more limited and more stationary forms of farming with the change between cultivation and fallow land are fluid. If only the agricultural areas and the farms are not moved or only moved after several cycles in alternating cycles, one speaks of land change management .
Transitions to other forms of economy
Shifting cultivation represents - with population densities of less than 6 inhabitants per km² - an efficient and adapted agricultural strategy on barren and sensitive soils, as is common in the tropics. In the past, shifting cultivation was also practiced in the temperate regions. In the past, if yields fell due to climatic factors or increasing population pressure , people were forced to migrate or to develop new technologies that allowed agriculture to be intensified. The associated overexploitation usually leads to such a strong degradation of the soil that the reduced soil fertility does not allow further cultivation of the area. This is how the field economy was introduced in Europe or the land change economy in the tropics. For example in Central America ( Milpa agriculture of the Maya ) - partly supplemented by irrigation measures - or with the West African farmers.
The modern “ population explosion ” and the destruction of ever larger forest areas also call for solutions in order to be able to continue to feed the forest dwellers sustainably. A promising approach to sustainable intensive use is to supplement the short-term soil improvement of slash and burn ( melioration ) through the conscious addition of additional charcoal, human faeces, dung, compost and the like. This finding is not even new, because many Indian peoples of the Amazon region (example Tupí ) have produced and used this anthropogenically modified soil, which is now called terra preta , for centuries.
Nutrient cycle and regeneration phase
The length of the fallow phase required has a direct impact on population density: the longer it lasts, the fewer people can live from shifting cultivation in a certain area. The length of the fallow phase depends on the type of use and crops, climatic conditions and soil quality. In tropical soils, which are mostly deeply weathered and poor in nutrients, the regeneration phase can take up to 30 years. Due to the tropical conditions such as humidity and temperature and the old age of the soils, their minerals can only store a few nutrients (low cation exchange capacity , KAK ). The nutrients are therefore almost exclusively contained in the biomass (mainly plants, but also animals and microorganisms) and in the humus , i.e. in the organic fraction of the soil. Many are in a short-circuited cycle (tropical nutrient cycle).
The slash and burn increases the solar radiation and thus the soil temperature, which causes an increased mineralization , whereby the humus content is reduced so much that only a few nutrients can be stored there. After the slash and burn, the majority of the nutrients are initially in the ashes, from which a large proportion of them are then lost through precipitation: either they are either washed away by heavy rain directly on the surface, or the downward flow of water in the ground carries the nutrients into it so great depths that plant roots can no longer reach them. The nutrient content of the topsoil is reduced and further cultivation is no longer worthwhile. However, if sufficiently long fallow periods are observed, the vegetation can regenerate and a degraded forest can form. This also leads to the rebuilding of the humus in the soil.
Ecological and socio-economic importance
In its original form, shifting cultivation was not ecologically questionable if the abandoned areas were left alone for a few decades. However, due to the lack of space and the increase in population and the associated food shortage , fallow periods are increasingly being shortened. As a rule, the settlements also migrated - in a somewhat longer cycle of 10 to 15 years - to previously untouched forest areas, where a new village with new fields was established. Today, however, the settlements usually stay in place, as there is no longer any space for the settlement to be relocated due to population growth and additional forms of use (plantations, etc.). In some cases, the fallow phases have been reduced to less than 5 years, which results in serious ecological problems. The secondary vegetation can no longer develop sufficiently. The next time the ash is cleared and burned, fewer nutrients will be found in the ashes.
Shifting cultivation is by far not as effective as, for example, crop rotation , which in the humid tropics can only be implemented with great technical effort and is usually only suitable for self-sufficiency. Many young people leave the traditional villages for the city in order to escape the difficult living conditions and to earn money. Only in this way can they meet the “new” needs (for example modern clothing, radio, television, cars).
execution
In small-scale slash and burn, smaller trees and bushes are first removed from the future field shortly before the dry season with a machete or a hatchet, larger trees are notched at a height of three meters and thus die after a short time. At the end of the dry season, the felled vegetation is burned down. After this slash and burn, the field is littered with felled and not felled tree stumps, ashes and charred trunks. Management is only possible through the ashes. At the beginning of the rainy season, the seeds are sown in hollows or pre-grown seedlings are planted with the plant. Depending on how much cultivation area is required, after a few years the areas near a village are no longer sufficient to feed the residents. Then the entire village moves to other areas where new fields can be created.
When clearing by fire, there is always the risk of an uncontrollable forest fire , so that large parts of the natural forest can easily be destroyed in this way.
Example Madagascar
Until around the year 1000, the island of Madagascar was still largely covered with forest: in the west with dry forests and in the north and east with rainforests . Now there are only small remnants of the rainforest in northern Madagascar. The most common explanation for this is the increased slash and burn due to the rapidly growing population. In this way, 60 percent of the rainforests are said to have been lost. (However, this has not yet been proven. Likewise, natural climate changes in the past may have led to the decline of the rainforest, which is on the edge of its range anyway.) Without a doubt, human activity has played a large part in the destruction of forests, so that the climate in Madagascar got even drier and hotter. It no longer rains as often and the ground is exposed to the weather without any protection. Another 30% of the forests were destroyed in the 20th century: now erosion occurs . In places where agriculture is no longer worthwhile because people have demanded too much from the soil, the land is left to its own devices. Forests - especially rainforests - can no longer grow back because they are far too dry. Thorn bushes and cacti are now growing in what were once forest areas. Such succulents do not need a lot of water, but they do not shade the soil. It dries up and is washed away by the rare but heavy rains.
See also
literature
- Stijn Arnoldussen: Dutch Bronze Age Residential Mobility. A Commentary on the "Wandering Farmstead" model. In: Alexandra Krenn-Leeb (Ed.): Varia neolithica, part 5: Mobility, migration and communication in Europe during the Neolithic and the Bronze Age. (= Contributions to the prehistory and early history of Central Europe. Volume 55). Beier & Beran, Langenweißbach 2009, ISBN 978-3-941171-27-5 , pp. 147–159 ( PDF file; 7 MB; 16 pages on archeologischeonderzoek.nl; contribution from the meetings of the Neolithic and Bronze Age working groups during the annual meeting of the West and South German Association for Ancient Research e.V. in Xanten in June 2006).
Individual evidence
- ↑ a b c d Jürgen Schultz: The ecological zones of the earth. 4th, completely revised edition. Ulmer UTB, Stuttgart 2008, ISBN 978-3-8252-1514-9 , pp. 342-344.
- ^ J. Dixon, A. Gulliver, D. Gibbon: Farming systems and poverty. Improving farm-ers' livelihoods in a changing world. FAO, Rome 2001. Quoted in: Cheryl Ann Palm, Stephen A. Vosti, Pedro A. Sanchez, Polly J. Ericksen (Eds.): Slash-and-Burn Agriculture - the search for alternatives. Columbia University Press, New York 2005, ISBN 0-231-13450-9 , p. 8. PDF version , accessed December 4, 2015.
- ↑ The ecosystem of the always humid tropics. In: TERRA method. Klett, pp. 46–55 ( PDF file; 2.1 MB; 5 pages ).
- ↑ Christoph Steiner: Slash and Char as Alternative to Slash and Burn. Dissertation . Cuvillier Verlag, Göttingen 2007, ISBN 978-3-86727-444-9 , pp. 13-17.
- ^ W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the world. 2nd Edition. Springer Spectrum, Heidelberg 2014, ISBN 978-3-642-36574-4 .
- ^ Alfred Bittner: Madagascar: Man and Nature in Conflict. Birkhäuser, Basel 1992, ISBN 3-7643-2680-8 , p. 40.
- ↑ Wolf Dieter Sick: Madagascar: Tropical developing country between the continents. Knowledge Buchges., 1979, ISBN 3-534-05822-4 , p. 65.