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Slash-and-burn is an agricultural technique that involves the cutting and burning of plants in forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology. It is typically key in shifting cultivation agriculture, and in transhumance livestock herding.〔Tony Waters, ''The Persistence of Subsistence Agriculture'', p. 3. Lexington Books (2007).〕 Old terms for ''slash-and-burn'' in English include ''assarting'', ''swidden'', and ''fire-fallow cultivation''. Today the term ''slash-and-burn'' is mainly associated with tropical rain forests. Slash-and-burn is used by 200 million to 500 million people worldwide.〔(Slash and burn ), Encyclopedia of Earth〕〔Skegg, Martin.''True Stories: Up In Smoke'' The Guardian 24 September 2011.〕 In 2004 it was estimated that, in Brazil alone, 500,000 small farmers cleared an average of one hectare of forest per year each. The technique is not sustainable in large populations, because without the trees, the soil quality becomes too poor to support crops. The farmers would have to move on to virgin forest and repeat the process. Methods such as Inga alley farming have been proposed as alternatives to this ecological destruction.〔Elkan, Daniel. ''Slash-and-burn farming has become a major threat to the world's rainforest'' The Guardian 21 April 2004〕 ==History== Historically, slash-and-burn cultivation has been practiced throughout much of the world, in grasslands as well as woodlands. During the Neolithic Revolution, which included agricultural advancements, groups of hunter-gatherers domesticated various plants and animals, permitting them to settle down and practice agriculture, which provides more nutrition per hectare than hunting and gathering. This happened in the river valleys of Egypt and Mesopotamia. Due to this decrease in food from hunting, as human populations increased, agriculture became more important. Some groups could easily plant their crops in open fields along river valleys, but others had forests blocking their farming land. In this context, humans used slash-and-burn agriculture to clear more land to make it suitable for plants and animals. Thus, since Neolithic times, slash-and-burn techniques have been widely used for converting forests into crop fields and pasture.〔Jaime Awe, ''Maya Cities and Sacred Caves'', Cu bola Books (2006)〕 Fire was used before the Neolithic as well, and by hunter-gatherers up to present times. Clearings created by fire were made for many reasons, such as to draw game animals and to promote certain kinds of edible plants such as berries. Slash-and-burn fields are typically used and owned by a family until the soil is exhausted. At this point the ownership rights are abandoned, the family clears a new field, and trees and shrubs are permitted to grow on the former field. After a few decades, another family or clan may then use the land and claim usufructuary rights. In such a system there is typically no market in farmland, so land is not bought or sold in the open market and land rights are traditional. In slash-and-burn agriculture, forests are typically cut months before a dry season. The "slash" is permitted to dry, and then burned in the following dry season. The resulting ash fertilizes the soil and the burned field is then planted at the beginning of the next rainy season with crops such as upland rice, maize, cassava, or other staples. Most of this work is typically done by hand, using such basic tools as machetes, axes, hoes, and makeshift shovels. Large families or clans wandering in the lush woodlands long continued to be the most common form of life through human history. Axes to fell trees and sickles for harvesting grain were the only tools people might bring with them. All other tools were made from materials they found at the site, such as fire stakes of birch, long rods (vanko), and harrows made of spruce tops. The extended family conquered the lush virgin forest, burned and cultivated their carefully selected swidden plots, sowed one or more crops, and then proceeded on to forests that had been noted in their wanderings. In the temperate zone the forest regenerated in the course of a lifetime. So swidden was repeated several times in the same area over the years. But in the tropics the forest floor gradually depleted. It was not only in the moors, as in Northern Europe, but also in the steppe, savannah, prairie, pampas and barren desert in tropical areas where shifting cultivation is the oldest type of farming (Clark 1952 91-107).〔Clark J.G.D. 1952, Farming: Clearance and Cultivation II Prehistoric Europe: The Economic Basis, Cambridge.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Slash-and-burn」の詳細全文を読む スポンサード リンク
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