0
 
slash & burn 3 — Fotopedia
no description yet
Wikipedia Article
See encyclopedia photos — 
Slash-and-burn

Slash-and-burn is an agricultural technique that involves the cutting and burning of trees and plants in forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology or other tools. It is typically part of shifting cultivation agriculture, and of transhumance livestock herding.

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 techniques are used by between 200 and 500 million people worldwide. In 2004 it was estimated that, in Brazil alone, 500,000 small farmers each cleared an average of one hectare of forest per year. The technique is not sustainable beyond a certain population density because, without the trees, the soil quality soon becomes too poor to support crops. The farmers have to move on to a virgin forest and repeat the process. Methods such as Inga alley farming have been proposed as an alternative to this ecological destruction.


See encyclopedia photos — 
Deforestation

Deforestation, clearance or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use.

The term deforestation is often misused to describe any activity where all trees in an area are removed. However in temperate climates, the removal of all trees in an area—in conformance with sustainable forestry practices—is correctly described as regeneration harvest. In temperate mesic climates, natural regeneration of forest stands often will not occur in the absence of disturbance, whether natural or anthropogenic. Furthermore, biodiversity after regeneration harvest often mimics that found after natural disturbance, including biodiversity loss after naturally occurring rainforest destruction.

Deforestation occurs for many reasons: trees are cut down to be used or sold as fuel (sometimes in the form of charcoal) or timber, while cleared land is used as pasture for livestock, plantations of commodities and settlements. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. It has adverse impacts on biosequestration of atmospheric carbon dioxide. Deforestation has also been used in war to deprive the enemy of cover for its forces and also vital resources. Modern examples of this were the use of Agent Orange by the British military in Malaya during the Malayan Emergency and the United States military in Vietnam during the Vietnam War. Among countries with a per capita GDP of at least US$4,600, net deforestation rates have ceased to increase. Deforested regions typically incur significant adverse soil erosion and frequently degrade into wasteland.


See encyclopedia photos — 
Global warming

Global warming refers to an unequivocal and continuing rise in the average temperature of Earth's climate system. Since 1971, 90% of the warming has occurred in the oceans. Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface. Since the early 20th century, the global air and sea surface temperature has increased about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980. Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850.

Scientific understanding of the cause of global warming has been increasing. In its fourth assessment (AR4 2007) of the relevant scientific literature, the International Panel on Climate Change (IPCC) reported that scientists were more than 90% certain that most of global warming was being caused by increasing concentrations of greenhouse gases produced by human activities. In 2010 that finding was recognized by the national science academies of all major industrialized nations. Affirming these findings in 2013, the IPCC stated that the largest driver of global warming is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production, and land use changes such as deforestation. Its 2013 report states