page_title: Deforestation
section_title: Atmospheric
hierarchical_section_title: Deforestation / Environmental effects / Atmospheric
caption_attribution_description: Fires on Borneo and Sumatra Smoke from agricultural and forest fires burning on Sumatra (left) and Borneo (right) in late September and early October 2006 blanketed a wide region with smoke that interrupted air and highway travel and pushed air quality to unhealthy levels. This image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on October 1, 2006, shows places where MODIS detected actively burning fires marked in red. Smoke spreads in a gray-white pall to the north. Despite a governmental ban on open burning, seasonal fires continue to occur on the Indonesian islands each year, peaking in the dry season of late summer and early fall. Slash-and-burn deforestation to clear land for farming or other agriculture still takes place, and fires escape from already cleared land into adjacent forest. The swampy forests of the low-lying parts of these islands sit on thick layers of peat (un-decayed vegetation), which is extremely flammable when it dries out. The peat is exceptionally smoky when it burns.
context_page_description: Deforestation, clearance, clearcutting or clearing is the removal of a forest or stand of trees from land which is then converted to a non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated deforestation occurs in tropical rainforests. About 31% of Earth's land surface is covered by forests.
  The Food and Agriculture Organization of the United Nations defines deforestation as the conversion of forest to other land uses. “Deforestation” and “forest area net change” are not the same: the latter is the sum of all forest losses and all forest gains in a given period. Net change, therefore, can be positive or negative, depending on whether gains exceed losses, or vice versa.
  The primary driver of deforestation is the expansion of agriculture. Trees are cut down for use as building material, timber or sold as fuel, while cleared land is used as pasture for livestock and agricultural crops. The vast majority of agricultural activity resulting in deforestation is subsidized by government tax revenue.
context_section_description: Deforestation is ongoing and is shaping climate and geography.
  Deforestation is a contributor to global warming, and is often cited as one of the major causes of the enhanced greenhouse effect. Tropical deforestation is responsible for approximately 20% of world greenhouse gas emissions. According to the Intergovernmental Panel on Climate Change deforestation, mainly in tropical areas, could account for up to one-third of total anthropogenic carbon dioxide emissions. But recent calculations suggest that carbon dioxide emissions from deforestation and forest degradation (excluding peatland emissions) contribute about 12% of total anthropogenic carbon dioxide emissions with a range from 6% to 17%. Deforestation causes carbon dioxide to linger in the atmosphere. As carbon dioxide accrues, it produces a layer in the atmosphere that traps radiation from the sun. The radiation converts to heat which causes global warming, which is better known as the greenhouse effect. Plants remove carbon in the form of carbon dioxide from the atmosphere during the process of photosynthesis, but release some carbon dioxide back into the atmosphere during normal respiration. Only when actively growing can a tree or forest remove carbon, by storing it in plant tissues. Both the decay and the burning of wood release much of this stored carbon back into the atmosphere. Although an accumulation of wood is generally necessary for carbon sequestration, in some forests the network of symbiotic fungi that surround the trees' roots can store a significant amount of carbon, storing it underground even if the tree which supplied it dies and decays, or is harvested and burned. Another way carbon can be sequestered by forests is for the wood to be harvested and turned into long-lived products, with new young trees replacing them. Deforestation may also cause carbon stores held in soil to be released. Forests can be either sinks or sources depending upon environmental circumstances. Mature forests alternate between being net sinks and net sources of carbon dioxide (see carbon dioxide sink and carbon cycle).
  In deforested areas, the land heats up faster and reaches a higher temperature, leading to localized upward motions that enhance the formation of clouds and ultimately produce more rainfall. However, according to the Geophysical Fluid Dynamics Laboratory, the models used to investigate remote responses to tropical deforestation showed a broad but mild temperature increase all through the tropical atmosphere. The model predicted <0.2 °C warming for upper air at 700 mb and 500 mb. However, the model shows no significant changes in other areas besides the Tropics. Though the model showed no significant changes to the climate in areas other than the Tropics, this may not be the case since the model has possible errors and the results are never absolutely definite. Deforestation affects wind flows,
  water vapour flows and absorption of solar energy thus clearly influencing local and global climate. 
  Reducing emissions from deforestation and forest degradation (REDD) in developing countries has emerged as a new potential to complement ongoing climate policies. The idea consists in providing financial compensations for the reduction of greenhouse gas (GHG) emissions from deforestation and forest degradation". REDD can be seen as an alternative to the emissions trading system as in the latter, polluters must pay for permits for the right to emit certain pollutants (i.e. CO2).
  Rainforests are widely believed by laymen to contribute a significant amount of the world's oxygen, although it is now accepted by scientists that rainforests contribute little net oxygen to the atmosphere and deforestation has only a minor effect on atmospheric oxygen levels. However, the incineration and burning of forest plants to clear land releases large amounts of CO₂, which contributes to global warming. Scientists also state that tropical deforestation releases 1.5 billion tons of carbon each year into the atmosphere.
caption: Fires on Borneo and Sumatra, 2006. People use slash-and-burn deforestation to clear land for agriculture.
exif: {"Thumbnail JPEGInterchangeFormat": "44", "Thumbnail JPEGInterchangeFormatLength": "6207"}