Deforestation

This article is about the process of deforestation in the environment. For the program transformation in computer science, see Deforestation (computer science).

"Deforest" redirects here. For the people with the name Deforest, see DeForest.

File:Deforestationriobranco.jpg

A NASA satellite observation of illegal deforestation near Rio Branco in Brazil observed July 28 2000

Djouce Mountain, along with the island of Ireland, was systematically clear-felled during the 17th and 18th centuries, in order to obtain wood mainly for shipbuilding.

Deforestation is the conversion of forested areas to non-forest land for use such as arable land, pasture, urban use, logged area, or wasteland. Since forests support greater numbers of animals and more species than arable land, pastures or cities removal or destruction of significant areas of forest cover has resulted in a degraded environment with reduced biodiversity . In a few countries, massive deforestation is ongoing and is shaping climate and geography. Deforestation results from removal of trees without sufficient reforestation, and results in declines in habitat and biodiversity.

From about the mid-1800s, around 1852, the planet has experienced an unprecedented rate of change of destruction of forests worldwide. Forests in Europe are adversely affected by acid rain and very large areas of Siberia have been harvested since the collapse of the Soviet Union. In the last two decades , Afghanistan has lost over 70% of its forests throughout the country. However, it is in the world's great tropical rainforests where the destruction is most pronounced at the current time and where clearcutting is having an adverse effect on biodiversity and contributing to the ongoing Holocene mass extinction.

About half of the mature tropical forests, between 750 to 800 million hectares of the original 1.5 to 1.6 billion hectares that once covered the planet have been cleared. The forest loss is already acute in Southeast Asia, the second of the world's great biodiversity hot spots. Much of what remains is in the Amazon basin, where the Amazon Rainforest covered more than 600 million hectares. The forests are being destroyed at a pace tracking the rapid pace of human population growth . Unless significant measures are taken on a worldwide basis to preserve them, by 2030 there will only be ten percent remaining with another ten percent in a degraded condition. 80 percent will have been lost and with them the irreversible loss of hundreds of thousands of species.

Many tropical countries, including Indonesia, Thailand, Malaysia, Bangladesh, China, Sri Lanka, Laos, Nigeria, Liberia, Guinea, Ghana and the Cote d'lvoire have lost large areas of their rainforest. Rainforests once covered 14% of the worlds land surface, they now only cover 6%. 90% of the forests of the Philippine archipelago have been cut. In 1960 Central America still had 4/5 of its original forest; now it is left with only 2/5. Madagascar has lost 95% of its rainforests. Brazil has lost 90-95% of its Mata Atlântica forest. Half of the Brazilian state of Rondonia's 24.3 million hectares have been destroyed or severely degraded in recent years. As of 2007, less than 1% of Haiti's forests remain, causing many to call Haiti a Caribbean desert. Between 1990 and 2005, Nigeria lost a staggering 81% of its old-growth forests. Several countries, notably the Philippines, Thailand and India have declared their deforestation a national emergency.

Impact on the environment

Orbital photograph of human deforestation in progress in the Tierras Bajas project in eastern Bolivia. Photograph courtesy NASA.

Generally, the removal or destruction of significant areas of forest cover has resulted in a degraded environment with reduced biodiversity. In many countries, massive deforestation is ongoing and is shaping climate and geography.

Deforestation is a substantial contributor to global warming, The worlds rain forests are widely believed by laymen to contribute a significant amount of world's oxygen although it is now accepted by scientists that rainforests contribute little net oxygen to the atmosphere and deforestation will have no effect whatsoever on atmospheric oxygen levels.. However, the incineration and burning of forest plants in order to clear land releases tonnes of CO₂ which contributes to global warming.

Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture. Deforestation reduces soil cohesion, so that erosion, flooding and landslides often ensue. Forests support considerable biodiversity, providing valuable habitat for wildlife; moreover, forests foster medicinal conservation.Forests enhance the recharge of aquifers in some locales however forests are a major source of aquifer depletion on most locales . With forest biotopes being a major, irreplaceable source of new drugs (like taxol), deforestation can destroy genetic variations (such as crop resistance) irretrievably.

Shrinking forest cover lessens the landscape's capacity to intercept, retain and transport precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased evapotranspiration, which lessens atmospheric moisture which in some cases affects precipitation levels down wind from the deforested area, as water is not recycled to downwind forests, but is lost in runoff and returns directly to the oceans. According to one preliminary study, in deforested north and northwest China, the average annual precipitation decreased by one third between the 1950s and the 1980s .

Longterm gains can be obtained by managing forest lands sustainably to maintain both forest cover and provide a biodegradable renewable resource. Forests are also important stores of organic carbon, and forests can extract carbon dioxide and pollutants from the air, thus contributing to biosphere stability. Deforestation (mainly in tropical areas) account for up to one-third of total anthropogenic carbon dioxide emissions. Forests are also valued for their aesthetic beauty and as a cultural resource and tourist attraction.

Experts estimate that we are losing 137 plant, animal and insect species every single day due to rainforest deforestation, which equates to 50,000 species a year.

“Reducing emissions from tropical deforestation and forest degradation (REDD) in developing countries has emerged as 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”.

Economic impact

Historically utilization of forest products, including timber and fuel wood, have played a key role in human societies, comparable to the roles of water and cultivable land. Today, developed countries continue to utilize timber for building houses, and wood pulp for paper. In developing countries almost three billion people rely on wood for heating and cooking. The forest products industry is a large part of the economy in both developed and developing countries. Short-term economic gains made by conversion of forest to agriculture, or over-exploitation of wood products, typically leads to loss of long-term income and long term biological productivity (hence reduction in nature's services). West Africa, Madagascar, Southeast Asia and many other regions have experienced lower revenue because of declining timber harvests. Illegal logging causes billions of dollars of losses to national economies annually.

A new study found that the emerging market for carbon credits: "Deforestation in tropical countries is often driven by the perverse economic reality that forests are worth more dead than alive. But a new study by an international consortium of researchers has found that the emerging market for carbon credits has the potential to radically alter that equation." The new procedures to get the massive amounts of wood are causing more harm to the economy and over powers the amount of money spent by people employed in logging. According to a study, "in most areas studied, the various ventures that prompted deforestation rarely generated more than US$5 for every ton of carbon they released and frequently returned far less than US $1." The price on the European market for an offset tied to a one-ton reduction in carbon is 23 euro (about $35).

Characterization

Throughout most of history, humans have considered forest clearing as necessary for most activities besides forestry>. In most countries, only after serious shortages of wood and other forest products are policies implemented to ensure forest resources are used in a sustainable manner. Typically in developed countries, as urbanization and economic development increases, land previously used for farming is abandoned and reverted to forests. Today, in the developed world, most countries are experiencing forest restoration and most losses in forest land are primarily driven by expanding urban areas.

In developing countries, human-caused deforestation and the degradation of forest habitat is primarily due to expansion of agriculture, slash and burn practices (instead of slash-and-char), urban sprawl, illegal logging, over harvest of fuel wood, mining, and petroleum exploration.

It has been argued that deforestation trends follow the Kuznets curve however even if true this is problematic in so-called hot-spots because of the risk of irreversible loss of non-economic forest values for example valuable habitat or species loss.

The effects of human related deforestation can be mitigated through environmentally sustainable practices that reduce permanent destruction of forests or even act to preserve and rehabilitate disrupted forestland (see Reforestation and Treeplanting). These methods help the cause and provide a sustainable growth of forests and allow lumber to become a renewable resource

Definitions of deforestation

Deforestation is the conversion of forested areas to non-forest land for use such as arable land, pasture, urban use, logged area, or wasteland. Generally, the removal or destruction of significant areas of forest cover has resulted in a degraded environment with reduced biodiversity. In many countries, massive deforestation is ongoing and is shaping climate and geography. Deforestation results from removal of trees without sufficient reforestation, and results in declines in habitat and biodiversity, wood for fuel and industrial use, and quality of life. Environmental effects

Atmospheric pollution Deforestation is often cited as one of the major causes of the enhanced greenhouse effect. According to the Intergovernmental Panel on Climate Change, deforestation, mainly in tropical areas, accounts for up to one-third of total anthropogenic carbon dioxide emissions.[14] Trees and other plants remove carbon (in the form of carbon dioxide) from the atmosphere during the process of photosynthesis. Both the decay and burning of wood releases much of this stored carbon back to the atmosphere. Deforestation also causes carbon stores held in soil to be released. Forests are stores of carbon and can be either sinks or sources depending upon environmental circumstances. Mature forests can be net sinks or net sources of carbon dioxide (see Carbon dioxide sink and Carbon cycle).

The water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the region cannot hold as much water and can result in a much drier climate.

Biodiversity Some forests are rich in biological diversity. Deforestation can cause the destruction of the habitats that support this biological diversity, thus contributing to the ongoing Holocene extinction event. Numerous countries have developed Biodiversity Action Plans to limit clear cutting and slash and burn agricultural practices as deleterious to wildlife and vegetation, particularly when endangered species are present.

Landslides Tree roots bind soil together, and if the soil is sufficiently shallow they act to keep the soil in place by also binding with underlying bedrock. Tree removal on steep slopes with shallow soil thus increases the risk of landslides, which can threaten people living nearby. However most deforestation only affects the trunks of trees, allowing for the roots to stay rooted, negating the landslide. Controlling deforestation Farming New methods are being developed to farm more intensively, such as high-yield hybrid crops, greenhouse, autonomous building gardens, and hydroponics. These methods are often dependent on massive chemical inputs to maintain necessary yields. In cyclic agriculture, cattle are grazed on farm land that is resting and rejuvenating. Cyclic agriculture actually increases the fertility of the soil. Intensive farming can also decrease soil nutrients by consuming at an accelerated rate the trace minerals needed for crop growth.

Forest management Efforts to stop or slow deforestation have been attempted for many centuries because it has long been known that deforestation can cause environmental damage sufficient in some cases to cause societies to collapse. In Tonga, paramount rulers developed policies designed to prevent conflicts between short-term gains from converting forest to farmland and long-term problems forest loss would cause,[49] while during the seventeenth and eighteenth centuries in Tokugawa Japan[50] the shoguns developed a highly sophisticated system of long-term planning to stop and even reverse deforestation of the preceding centuries through substituting timber by other products and more efficient use of land that had been farmed for many centuries. In sixteenth century Germany landowners also developed silviculture to deal with the problem of deforestation. However, these policies tend to be limited to environments with good rainfall, no dry season and very young soils (through volcanism or glaciation). This is because on older and less fertile soils trees grow too slowly for silviculture to be economic, whilst in areas with a strong dry season there is always a risk of forest fires destroying a tree crop before it matures. Historical causes Further information: Timeline of environmental events {| class="wikitable"

Use of the term deforestation

It has been argued that the lack of specificity in use of the term deforestation distorts forestry issues. The term deforestation is used to refer to activities that use the forest, for example, fuel wood cutting, commercial logging, as well as activities that cause temporary removal of forest cover such as the slash and burn technique, a component of some shifting cultivation agricultural systems or clearcutting. It is also used to describe forest clearing for annual crops and forest loss from over-grazing. Some definitions of deforestation include activities such as establishment of industrial forest plantations that are considered afforestation by others. It has also been argued that the term deforestation is such an emotional term that is used "so ambiguously that it is virtually meaningless" unless it is specified what is meant. More specific terms terms include forest decline, forest fragmentation and forest degradation, loss of forest cover and land use conversion.

The term also has a traditional legal sense of the conversion of Royal forest land into purlieu or other non-forest land use.

Historical causes

Further information: Timeline of environmental events

Prehistory

Prehistory Deforestation has been practiced by humans for tens of thousands of years before the beginnings of civilization. Fire was the first tool that allowed humans to modify the landscape. The first evidence of deforestation appears in the Mesolithic period. It was probably used to convert closed forests into more open ecosystems favourable to game animals. With the advent of agriculture, fire became the prime tool to clear land for crops. In Europe there is little solid evidence before 7000 BC. Mesolithic foragers used fire to create openings for red deer and wild boar. In Great Britain shade tolerant species such as oak and ash are replaced in the pollen record by hazels, brambles, grasses and nettles. Removal of the forests led to decreased transpiration resulting in the formation of upland peat bogs. Widespread decrease in elm pollen across Europe between 8400-8300 BC and 7200-7000 BC, starting in southern Europe and gradually moving north to Great Britain, may represent land clearing by fire at the onset of Neolithic agriculture.

An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools.

The Neolithic period saw much more extensive deforestation for farming land>. Stone axes were now being made not just from flint, but from a wide variety of hard rocks from across Britain and North America as well

Easter Island has suffered from heavy soil erosion in recent centuries, perhaps aggravated by agriculture and massive deforestation. Jared Diamond gives an extensive look into the collapse of the ancient Easter Islanders in his book Collapse. The disappearance of the island's trees seems to coincide with a decline of its civilization around the 17th and 18th century.

The famous silting up of the harbor for Bruges, which moved port commerce to Antwerp, also follow a period of increased settlement growth (and apparently of deforestation) in the upper river basins. In early medieval Riez in upper Provence, alluvial silt from two small rivers raised the riverbeds and widened the floodplain, which slowly buried the Roman settlement in alluvium and gradually moved new construction to higher ground; concurrently the headwater valleys above Riez were being opened to pasturage.

A typical progress trap is that cities were often built in a forested area providing wood for some industry (e.g. construction, shipbuilding, pottery). When deforestation occurs without proper replanting, local wood supplies become difficult to obtain near enough to remain competitive, leading to the city's abandonment, as happened repeatedly in Ancient Asia Minor. The combination of mining and metallurgy often went along this self-destructive path.

Meanwhile most of the population remaining active in (or indirectly dependent on) the agricultural sector, the main pressure in most areas remained land clearing for crop and cattle farming; fortunately enough wild green was usually left standing (and partially used, e.g. to collect firewood, timber and fruits, or to graze pigs) for wildlife to remain viable, and the hunting privileges of the elite (nobility and higher clergy) often protected significant woodlands.

Major parts in the spread (and thus more durable growth) of the population were played by monastical 'pioneering' (especially by the benedictine and cistercian orders) and some feudal lords actively attracting farmers to settle (and become tax payers) by offering relatively good legal and fiscal conditions – even when they did so to launch or encourage cities, there always was an agricultural belt around and even quite some within the walls. When on the other hand demography took a real blow by such causes as the Black Death or devastating warfare (e.g. Genghis Khan's Mongol hordes in eastern and central Europe, Thirty Years' War in Germany) this could lead to settlements being abandoned, leaving land to be reclaimed by nature, even though the secondary forests usually lacked the original biodiversity.

From 1100 to 1500 AD significant deforestation took place in Western Europe as a result of the expanding human population. The large-scale building of wooden sailing ships by European (coastal) naval owners since the 15th century for exploration, colonization, slave – and other trade on the high seas and (often related) naval warfare (the failed invasion of England by the Spanish Armada in 1559 and the battle of Lepanto 1571 are early cases of huge waste of prime timber; each of Nelson's Royal navy war ships at Trafalgar had required 6000 mature oaks) and piracy meant that whole woody regions were over-harvested, as in Spain, where this contributed to the paradoxical weakening of the domestic economy since Columbus' discovery of America made the colonial activities (plundering, mining, cattle, plantations, trade ...) predominant.

In Changes in the Land (1983), William Cronon collected 17th century New England Englishmen's reports of increased seasonal flooding during the time that the forests were initially cleared, and it was widely believed that it was linked with widespread forest clearing upstream.

The massive use of charcoal on an industrial scale in Early Modern Europe was a new acceleration of the onslaught on western forests; even in Stuart England, the relatively primitive production of charcoal has already reached an impressive level. For ship timbers, Stuart England was so widely deforested that it depended on the Baltic trade and looked to the untapped forests of New England to supply the need. In France, Colbert planted oak forests to supply the French navy in the future; as it turned out, as the oak plantations matured in the mid-nineteenth century, the masts were no longer required.

Norman F. Cantor's summary of the effects of late medieval deforestation applies equally well to Early Modern Europe:

"Europeans had lived in the midst of vast forests throughout the earlier medieval centuries. After 1250 they became so skilled at deforestation that by 1500 AD they were running short of wood for heating and cooking. They were faced with a nutritional decline because of the elimination of the generous supply of wild game that had inhabited the now-disappearing forests, which throughout medieval times had provided the staple of their carnivorous high-protein diet. By 1500 Europe was on the edge of a fuel and nutritional disaster, [from] which it was saved in the sixteenth century only by the burning of soft coal and the cultivation of potatoes and maize."

Specific parallels are seen in twentieth century deforestation occurring in many developing nations.

Deforestation today

Jungle burned for agriculture in southern Mexico.

Slash-and-burn is a method sometimes used by shifting cultivators to create short term yields from marginal soils. When practiced repeatedly, or without intervening fallow periods, the nutrient poor soils may be exhausted or eroded to an unproductive state. Slash-and-burn techniques are used by native populations of over 200 million people worldwide. Short-sighted, market-driven forestry practices are often} one of the leading causes of forest degradation. The principal human-related causes of deforestation are agriculture and livestock grazing, urban sprawl, mining, and petroleum extraction. Growing worldwide demand for wood to be used for fire wood or in construction, paper and furniture - as well as clearing land for commercial and industrial development (including road construction) have combined with growing local populations and their demands for agricultural expansion and wood fuel to endanger ever larger forest areas.

Agricultural development schemes in Mexico, Brazil and Indonesia (transmigration program) moved large populations into the rainforest zone, further increasing deforestation rates. One fifth of the world's tropical rainforest was destroyed between 1960 and 1990. Estimates of deforestation of tropical forest for the 1990s range from about 55,630 to 120,000 square kilometres each year. At this rate, all tropical forests may be gone by the year 2090.

According to British environmentalist Norman Myers, 5% of deforestation is due to cattle ranching, 19% to over-heavy logging, 22% to the growing sector of palm oil plantations, and 54% due to slash-and-burn farming.

Ethiopia

Main article: Deforestation in Ethiopia

The main cause of deforestation in Ethiopia, located in East Africa, is a growing population and subsequent higher demand for agriculture, livestock production and fuel wood. Other reasons include low education and inactivity from the government, although the current government has taken some steps to tackle deforestation. Organizations such as Farm Africa are working with the federal and local governments to create a system of forest management. Ethiopia, the third largest country in Africa by population, has been hit by famine many times because of shortages of rain and a depletion of natural resources. Deforestation has lowered the chance of getting rain, which is already low, and thus causes erosion. Bercele Bayisa, an Ethiopian farmer, offers one example why deforestation occurs. He said that his district was forested and full of wildlife, but overpopulation caused people to come to that land and clear it to plant crops, cutting all trees to sell as fire wood.

Ethiopia has lost 98% of its forested regions in the last 50 years. At the beginning of the 20th century, around 420,000 km² or 35% of Ethiopia's land was covered with forests. Recent reports indicate that forests cover less than 14.2% or even only 11.9% now. Between 1990 and 2005, the country lost 14% of its forests or 21,000 km².

Madagascar

Massive deforestation with resulting desertification, water resource degradation and soil loss has affected approximately 94% of Madagascar's previously biologically productive lands. Most of this loss has occurred since independence from the French, and is the result of local people using slash-and-burn agricultural practises as they try to subsist. Largely due to deforestation, the country is currently unable to provide adequate food, fresh water and sanitation for its fast growing population.

Nigeria

Main article: Deforestation in Nigeria

According to the FAO, Nigeria has the world's highest deforestation rate of primary forests. It has lost more than half of its primary forest in the last five years. Causes cited are logging, subsistence agriculture, and the collection of fuel wood.

Brazil

Main article: Deforestation in Brazil

In Brazil the rate of deforestation is largely driven by commodity prices and world population growth. Recent development of a new variety of soybean has led to the displacement of beef ranches and farms of other crops, which, in turn, move farther into the forest. Certain areas such as the Atlantic Rainforest have been diminished to less than 10% of their original size. Although much conservation work has been done, few national parks or reserves are efficiently enforced. In 2008, Brazil's Government has announced a record rate of deforestation in the Amazon.

Indonesia

There are significantly large areas of forest in Indonesia that are being lost as native forest is cleared by large multi-national pulp companies and being replaced by plantations. In Sumatra millions of hectares of forest have been cleared often under the command of the central government in Jakarta who comply with multi national companies to remove the forest because of the need to pay off international debt obligations and to develop economically. In Kalimantan the consequences of deforestation have been profound and between 1991 and 1999 large areas of the forest were burned because of uncontrollable fire causing atmospheric pollution across South-East Asia. Every year, forest are burned by farmers (slash-and-burn techniques are used by between 200 and 500 million people worldwide) and plantation owners. A major source of deforestation is the logging industry, driven spectacularly by China and Japan.

United States

File:Oldgrowth3.jpg

Loss of old growth forest in the United States.
1620, 1850, and 1920 maps: William B. Greeley, The Relation of Geography to Timber Supply, Economic Geography, 1925, vol. 1, p. 1-11. Source of TODAY map: compiled by George Draffan from roadless area map in The Big Outside: A Descriptive Inventory of the Big Wilderness Areas of the United States, by Dave Foreman and Howie Wolke (Harmony Books, 1992). These maps represent only virgin forest lost. Some regrowth has occurred but not to the age, size or extent of 1620 due to population increases and food cultivation. See United States entry on left

Prior to the arrival of European-Americans about one half of the United States land area was forest, about 4 million square kilometers (1 billion acres) in 1600. For the next 300 years land was cleared, mostly for agriculture at a rate that matched the rate of population growth. For every person added to the population, one to two hectares of land was cultivated. This trend continued until the 1920s when the amount of crop land stabilized in spite of continued population growth. As abandoned farm land reverted to forest the amount of forest land increased from 1952 reaching a peak in 1963 of 3,080,000 km² (762 million acres). Since 1963 there has been a steady decrease of forest area with the exception of some gains from 1997. Gains in forest land have resulted from conversions from crop land and pastures at a higher rate than loss of forest to development. Because urban development is expected to continue, an estimated 93,000 km² (23 million acres) of forest land is projected be lost by 2050, a 3% reduction from 1997. Other qualitative issues have been identified such as the continued loss of old-growth forest, the increased fragmentation of forest lands, and the increased urbanization of forest land.

Species extinctions in the Eastern Forest

According to a report by Stuart L. Pimm the extent of forest cover in the Eastern United States reached its lowest point in roughly 1872 with about 48 percent compared to the amount of forest cover in 1620. Of the 28 forest bird species with habitat exclusively in that forest, Pimm claims 4 become extinct either wholly or mostly because of habitat loss, the passenger pigeon, Carolina parakeet, ivory-billed woodpecker, and Bachman's Warbler.

Australia

Victoria and NSW's remnant red gum forests including the Murray River's Barmah-Millewa, are increasingly being clear-felled using mechanical harvesters, destroying already rare habitat. Macnally estimates that approximately 82% of fallen timber has been removed from the southern Murray Darling basin, and the Mid-Murray Forest Management Area (including the Barmah and Gunbower forests) provides about 90% of Victoria's red gum timber.

Environmental effects

Atmospheric pollution

Deforestation is often cited as one of the major causes of the enhanced greenhouse effect. According to the Intergovernmental Panel on Climate Change deforestation, mainly in tropical areas, account for up to one-third of total anthropogenic carbon dioxide emissions. Trees and other plants remove carbon (in the form of carbon dioxide) from the atmosphere during the process of photosynthesis. Both the decay and burning of wood releases much of this stored carbon back to the atmosphere. Deforestation also causes carbon stores held in soil to be released. Forests are stores of carbon and can be either sinks or sources depending upon environmental circumstances. Mature forests can be net sinks of carbon dioxide (see Carbon dioxide sink and Carbon cycle).

The water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the region cannot hold as much water and can result in a much drier climate.

Biodiversity

Some forests are rich in biological diversity. Deforestation can cause the destruction of the habitats that support this biological diversity, thus contributing to the ongoing Holocene extinction event. Numerous countries have developed Biodiversity Action Plans to limit clear cutting and slash and burn agricultural practices as deleterious to wildlife and vegetation, particularly when endangered species are present.

Water cycle and water resources

Trees, and plants in general, affect the water cycle significantly:

• their canopies intercept a proportion of precipitation, which is then evaporated back to the atmosphere (canopy interception);
• their litter, stems and trunks slow down surface runoff;
• their roots create macropores - large conduits - in the soil that increase infiltration of water;
• they contribute to terrestrial evaporation and reduce soil moisture via transpiration;
• their litter and other organic residue change soil properties that affect the capacity of soil to store water.

As a result, the presence or absence of trees can change the quantity of water on the surface, in the soil or groundwater, or in the atmosphere. This in turn changes erosion rates and the availability of water for either ecosystem functions or human services.

The forest may have little impact on flooding in the case of large rainfall events, which overwhelm the storage capacity of forest soil if the soils are at or close to saturation.

Tropical rainforests produce about 30% of our planets fresh water.

Soil erosion

Undisturbed forest has very low rates of soil loss, approximately 2 metric tons per square kilometre (6 short tons per square mile). Deforestation generally increases rates of soil erosion, by increasing the amount of runoff and reducing the protection of the soil from tree litter. This can be an advantage in excessively leached tropical rain forest soils. Forestry operations themselves also increase erosion through the development of roads and the use of mechanized equipment.

China's Loess Plateau was cleared of forest millennia ago. Since then it has been eroding, creating dramatic incised valleys, and providing the sediment that gives the Yellow River its yellow color and that causes the flooding of the river in the lower reaches (hence the river's nickname 'China's sorrow').

Removal of trees does not always increase erosion rates. In certain regions of southwest US, shrubs and trees have been encroaching on grassland. The trees themselves enhance the loss of grass between tree canopies. The bare intercanopy areas become highly erodible. The US Forest Service, in Bandelier National Monument for example, is studying how to restore the former ecosystem, and reduce erosion, by removing the trees.

Landslides

Tree roots bind soil together, and if the soil is sufficiently shallow they act to keep the soil in place by also binding with underlying bedrock. Tree removal on steep slopes with shallow soil thus increases the risk of landslides, which can threaten people living nearby. However most deforestation only affects the trunks of trees, allowing for the roots to stay rooted, negating the landslide.

Controlling deforestation

Farming

New methods are being developed to farm more intensively, such as high-yield hybrid crops, greenhouse, autonomous building gardens, and hydroponics. These methods are often dependent on massive chemical inputs to maintain necessary yields. In cyclic agriculture, cattle are grazed on farm land that is resting and rejuvenating. Cyclic agriculture actually increases the fertility of the soil. Intensive farming can also decrease soil nutrients by consuming at an accelerated rate the trace minerals needed for crop growth.

Forest management

Efforts to stop or slow deforestation have been attempted for many centuries because it has long been known that deforestation can cause environmental damage sufficient in some cases to cause societies to collapse. In Tonga, paramount rulers developed policies designed to prevent conflicts between short-term gains from converting forest to farmland and long-term problems forest loss would cause, while during the seventeenth and eighteenth centuries in Tokugawa Japan the shoguns developed a highly sophisticated system of long-term planning to stop and even reverse deforestation of the preceding centuries through substituting timber by other products and more efficient use of land that had been farmed for many centuries. In sixteenth century Germany landowners also developed silviculture to deal with the problem of deforestation. However, these policies tend to be limited to environments with good rainfall, no dry season and very young soils (through volcanism or glaciation). This is because on older and less fertile soils trees grow too slowly for silviculture to be economic, whilst in areas with a strong dry season there is always a risk of forest fires destroying a tree crop before it matures.

In the areas where "slash-and-burn” is practiced, switching to “slash-and-char” would prevent the rapid deforestation and subsequent degradation of soils. The biochar thus created, given back to the soil, is not only a durable carbon sequestration method, but it also is an extremely beneficial amendment to the soil. Mixed with biomass it brings the creation of terra preta, one of the richest soils on the planet and the only one known to regenerate itself.

Reforestation

In the People's Republic of China, where large scale destruction of forests has occurred, the government has in the past required that every able-bodied citizen between the ages of 11 and 60 plant three to five trees per year or do the equivalent amount of work in other forest services. The government claims that at least 1 billion trees have been planted in China every year since 1982. This is no longer required today, but March 12 of every year in China is the Planting Holiday. Also, it has introduced the Green Wall of China-project which aims to halt the expansion of the Gobi-desert through the planting of trees. However, due to the large percentage of trees dying off after planting (up to 75%), the project is not very successful and regular carbon ofsetting through the Flexible Mechanisms might have been a better option. In western countries, increasing consumer demand for wood products that have been produced and harvested in a sustainable manner are causing forest landowners and forest industries to become increasingly accountable for their forest management and timber harvesting practices. The Arbor Day Foundation's Rain Forest Rescue program is a charity that helps to prevent deforestation. The charity uses donated money to buy up and preserve rainforest land before the lumber companies can buy it. The Arbor Day Foundation then protects the land from deforestation. This also locks in the way of life of the primitive tribes living on the forest land. Organizations such as Community Forestry International, The Nature Conservancy, World Wide Fund for Nature, Conservation International, African Conservation Foundation and Greenpeace also focus on preserving forest habitats. Greenpeace in particular has also mapped out the forests that are still intact and published this information unto the internet. . HowStuffWorks in turn, made a more simple thematic map showing the amount of forests present just before the age of man (8000 years ago) and the current (reduced) levels of forest. This Greenpeace map thus created, as well as this thematic map from howstuffworks marks the amount of afforestation thus again required to repair the damage caused by man.

Forest plantations

To meet the worlds demand for wood it has been suggested by forestry writers Botkins and Sedjo that high-yielding forest plantations are suitable. It has been calculated that plantations yielding 10 cubic meters per hectare annually could supply all the timber required for international trade on 5 percent of the world's existing forestland. By contrast natural forests produce about 1-2 cubic meters per hectare, therefore 5 to 10 times more forest land would be required to meet demand. Forester Chad Oliver has suggested a forest mosaic with high-yield forest lands interpersed with conservation land.

According to an international team of scientists, led by Pekka Kauppi, professor of environmental science and policy at Helsinki University, the deforestation already done could still be reverted by tree plantings (eg CDM & JI afforestation/reforestation projects) in 30 years. The conclusion was made, through analysis of data acquired from FAO.

Reforestation through tree planting (trough eg the noted CDM & JI A/R-projects), might take advantage of the changing precipitation due to climate change. This may be done through studying where the precipitation is perceived to be increased (see the globalis thematic map of the 2050 precipitation) and setting up reforestation projects in these locations. Especially areas such as Niger, Sierra Leone and Liberia are important candidates; in huge part because they also suffer from an expanding desert (the Sahara) and decreasing biodiversity (while being an important biodiversity hotspot).

Military context

American Sherman tanks knocked out by Japanese artillery on Okinawa.

While the preponderance of deforestation is due to demands for agricultural and urban use for the human population, there are some examples of military causes. One example of deliberate deforestation is that which took place in the U.S. zone of occupation in Germany after World War II. Before the onset of the Cold War defeated Germany was still considered a potential future threat rather than potential future ally. To address this threat, attempts were made to lower German industrial potential, of which forests were deemed an element. Sources in the U.S. government admitted that the purpose of this was the "ultimate destruction of the war potential of German forests." As a consequence of the practice of clear-felling, deforestation resulted which could "be replaced only by long forestry development over perhaps a century."

War can also be a cause of deforestation, either deliberately such as through the use of Agent Orange during the Vietnam War where, together with bombs and bulldozers, it contributed to the destruction of 44 percent of the forest cover, or inadvertently such as in the 1945 Battle of Okinawa where bombardment and other combat operations reduced the lush tropical landscape into "a vast field of mud, lead, decay and maggots".

References

General references

• BBC 2005 TV series on the history of geological factors shaping human history (name?)
• A Natural History of Europe - 2005 co-production including BBC and ZDF
• Whitney, Gordon G. (1996). From Coastal Wilderness to Fruited Plain : A History of Environmental Change in Temperate North America from 1500 to the Present. Cambridge University Press. ISBN 0-521-57658-X
• Williams, Michael. (2003). Deforesting the Earth. University of Chicago Press, Chicago. ISBN 0-226-89926-8
• Wunder, Sven. (2000). The Economics of Deforestation: The Example of Ecuador. Macmillan Press, London. ISBN 0-333-73146-8
• FAO&CIFOR report: Forests and Floods: Drowning in Fiction or Thriving on Facts?
• Fenical, William (1983). "Marine Plants: A Unique and Unexplored Resource". Plants: the potentials for extracting protein, medicines, and other useful chemicals (workshop proceedings). DIANE Publishing. p. 147. ISBN 1428923977. {{cite book}}: Unknown parameter |month= ignored (help)

Ethiopia deforestation references

• Parry, J. (2003). Tree choppers become tree planters. Appropriate Technology, 30(4), 38-39. Retrieved November 22, 2006, from ABI/INFORM Global database. (Document ID: 538367341).
• Hillstrom, K & Hillstrom, C. (2003). Africa and the Middle east. A continental Overview of Environmental Issues. Santabarbara, CA: ABC CLIO.
• Williams, M. (2006). Deforesting the earth: From prehistory to global crisis: An Abridgment. Chicago: The university of Chicago Press.
• Mccann. J.C. (1990). A Great Agrarian cycle? Productivity in Highland Ethiopia, 1900 To 1987. Journal of Interdisciplinary History, xx: 3,389-416. Retrieved November 18, 2006, from JSTOR database.

See also

• Assarting
• Biochar
• CDM & JI A/R projects
• Deforestation during the Roman period
• Deforestation in Oregon
• Desertification
• Ecoforestry
• Forestry
• Illegal logging
• Land use, land-use change and forestry
• Moisture recycling
• Mountaintop removal
• Neolithic
• Overpopulation
• Rainforest
• Richard St. Barbe Baker
• Slash-and-burn
• Slash-and-char
• Terra preta
• Wilderness

External links

• Prevent Deforestation
• Encyclopedia of Earth: Deforestation in Amazonia
• Global Forest Resources Assessment 2005 by the FAO Comprehensive assessment of forests and forestry. Includes 350 page report and 15 page summary
• United Nations EarthWatch
• EU Forestry.
• United Nations Forum on Forests
• CFAN - CIDA Forestry Advisory Network DEFORESTATION: Tropical Forests in Decline
• Amazon Deforestation (Google maps)
• Our disappearing forests - Greenpeace China

In the media

• March 14, 2007, Independent Online: Destruction of forests in developing world 'out of control'