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Most trees diseases are caused by fungus infections. Diseases attack trees chiefly by clogging the flowof sap, killing the leaves, or rotting the roots or wood. Some of the most destructive diseases includebeech bark disease, chestnut blight, Dutch elm disease, oak wilt, and stem blister rusts that affect pinetrees.

Floods and soil erosion

The roots of a tree make gaps in the soil so that when it rains the water can sink in before beingabsorbed by the soil. These spaces also allow air and water to reach the roots of the plants.When trees removed using heavy machinery, the soil is pushed down and the gaps fill in.Because all plants and trees need that water and air to reach roots, the conditions becomeunfriendly for new growth.

Because the soil no longer can absorb the water, when it rains the water remains on the top ofthe soil and this can result in floods. The moving water also can completely wash away the toplayer of the soil. This is called soil erosion. Without the top layer of soil, which is full nutrition,plants are not fed and find it hard to grow.

What we lose: About 24 billion tons of agricultural topsoil (the top layer of soil) wash or blowaway each year.

Drought

Forests help produce rainfall. The more trees, the more water gets absorbed into clouds andthe more rain falls. If the forests disappear, there will be less rain resulting in dryer conditionsthat eventually lead to drought. Once this happens, the damage is extensive making it difficult

to plant more trees or plants later because the soil is so hard and dry.

Greenhouse gases and acid rain

The earth's atmosphere contains a number of greenhouse gases. Greenhouse gases trap theheat from the sun inside the atmosphere. Some greenhouse gases are carbon dioxide (CO2),methane and water vapour. We need these gases in small amounts, but they can be harmful athigh levels.

Forests help remove large amounts of CO2 from the air. They absorb the gasduring photosynthesis. However, more CO2 is produced than all the trees can absorb when

fossil fuels are burned, for example and when forests are cut down, even less CO2 is beingabsorbed leaving it trapped in the atmosphere.

As greenhouse gases build up, more of the suns heat gets trapped and that can lead to climatechange (the disruption of the delicate balance of the earth's ecosystems). The added pollutionin the atmosphere can also lead to acid rain when the gases mix with water in clouds. Whenthis is deposited on forests it can damage the trees and the ecosystem as a whole.

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Species extinction

Another harmful result of deforestation is the extinction of animal and plant species. Theydisappear because their environment and life cycles have been disturbed and they are unableto adapt to the changes. When species disappear, it is called extinction. Essential habitat is lostwhen forests are cut down; wildlife species lose their homes, their food sources and their placein the web of life. Even though extinction is part of life, it is happening far too quickly now.

It is estimated that as many as 150-200 species around the world go extinct every day!

Causes and Motives for/behind Deforestation

According to The World Rainforest Movement , Among the direct causes of deforestation,some of the main ones are: the substitution of forests by other activities (agriculture, cattle-

raising, tree plantations, shrimp farming, etc.), logging, mining, oil exploitation, and constructionof large hydro electric dams (which result in the flooding of extensive areas of forest).

F orests are cleared for agri cul tur e. The deforestation rate in Amazon rainforest, the worldslargest jungle, jumped 40 percent in the 12 months to the middle of 2002. The Amazon is an areaof continuous tropical forest just under half the size of the continental United States, and has

been described as the lungs of the world because of its vast capacity to produce oxygen. It isalso home to up to 30 percent of the planets animal and plant species.

The pri mary dri ving f orce behi nd the destruction of th e rai nf orests is li vestock grazin g. Beefexporting from Brazil has increased more than fivefold in the last six years. WorldWatch magazine, in the article, Eating Beef says that From now on, the question of whetherwe get our protein from animals or plants has direct implications for how much more of theworlds remaining forest we have to raze.

F orests are destroyed by in equi table land policies. International finance institutions requirecountries to increase exports in order to keep up with their loan payments, and clear-cutting theforests for crops is often their only option. The agricultural land of peasants is taken over toincrease exports, forcing them to migrate into the forests where they cut and burn the forest inorder to survive. In many cases, governments promote migration to expand the agriculturalfrontier and allow for more farm exports.

Global warming th reatens forests worldwide . Deforestation contributes to global warming, but,in turn, global warming will increase the loss of forests. M any of the world's forests are in poorcondition, fragmented, and depredated, and so they are less able to adapt or adjust to climatechange. As the global climate warms up, patterns of rainfall will change; and 'normal'temperature patterns will be disrupted. The expected rate of global warming and sea-level risewill be too fast to allow most forests to be able to adapt quickly enough to survive.

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The organization, American Forests, reports that the U.S. could offset 20 to 40 percent of itscarbon dioxide emissions by increasing carbon storage by 300-600 million tons per year. Thiswould require a comprehensive plan to plant trees, improved forest management practices, andalternatives to wood and biomass fuels

Each year , for est f ir es, bur n between 6 and 14 mil li on h ectares of for est . A major cause of theloss and degradation of forested land comes from fire. The area lost to fire is roughly equal tothat caused by destructive logging and conversion to agriculture combined. Severe forest fires,such as those in Indonesia in 1997/1998 and in Australia in 2001/2002, bring enormous and insome cases life-threatening levels of pollutants. Governments rarely address the underlyingcauses of forest fires. Instead of prevention efforts, they just work to put the fires out. Workingon prevention will become essential because global warming will increase the number of forestfires.

F orests are har med by the trade in il legal extracted timber . Legal supplies of wood fiber fallshort of demand by up to 40 million cubic meters per year. Illegal logging fills the gap--

accounting for almost 70 percent of wood supply, meaning that illegal logging exceeds thevolume of legal logging. All told, illegal logging alone has destroyed 10 million hectares ofIndonesia's rich forests, an area the size of Virginia.

It is important to use only wood certified by the Forest Stewardship Council (FSC)--the onlylabel recognized as providing "ecologically-sound" timber. Worldwide, FSC-accrediting bodieshave certified about 24 million hectares of forests in 45 countries. When consumers demandcertified wood, non-certified sellers will have difficulty competing, and illegal logging becomesmore difficult. This certification stamp means the wood is from well-managed andenvironmentally sensitive logging operations. It also assures that the wood is not the result ofmonoculture plantations, clear-cutting, violations of indigenous land claims, or other

environmental hazards. Due to these other considerations, relying on wood labeled "second-growth" is not enough. The FSC label is the only guarantee that the wood purchased isenvironmentally sound. Currently only a small portion of the U.S. lumber market, FSC wood isgrowing in popularity in other areas, especially in Europe.

Bu il ding l arge hydroelectric dams destroys for ests . Forests are lost when farmers, displaced bydams being built, are forced to move and clear forests in other areas in order to grow their crops.Dams also require road building, allowing access to previously remote areas by loggers and"developers," causing even more deforestation.

F orests are cleared for fuel or export . Crucial to slowing the loss of the world's natural forests isfinding alternative sources of energy for low-income countries so that wood is not burned forenergy.

Consequences of Deforestation

Removing forests (and their natural functions) causes many serious problems.

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L oss of tr ees makes global warmin g worse. Through photosynthesis, trees remove carbondioxide from the air, produce oxygen, and store carbon as wood. One ton of carbon in wood orforest biomass represents 3.67 tons of atmospheric carbon dioxide recycled. We are creatingwarming, not only by putting more CO2 into the air, but also by getting rid of trees that absorband remove carbon from the air.

I mpact on Ecosystems. Forests preserve water, soils, plants and wildlife. Their destructionaggravates droughts, soil erosion, and pollution of watercourses, and causes extensive flooding,and increased pest populations due to the ecological imbalance.

L oss of Species . Tropical forests contain at least half the Earth's species, so their loss causes adramatic loss of biodiversity. Clearing and destructive logging of forests is the single greatestcause of species extinction worldwide.

H arm to Water. Forests are natural dams that catch rainwater in their canopies and in leaves andlitter on the forest floor, retaining and purifying rainwater. Forest logging allows rapid run-off

and destroys the ability of the soil to absorb water.

Policies Needed to Halt Deforestation

Despite the creation of new organizations to promote sustainable forestry, and continuing effortsof major international conservation organizations, the rate of forest loss accelerated through the1990s. In "Requiem for Nature," John Terborgh, says

Deforestation is driven by a wide range of social and economic forces, but underlying them all isthe relentless march of human population growth and the exponentially rising demand for landand forest products such growth generates. These demands are not going to slacken in the

decades ahead; indeed, they will only expand. Slowing down tropical deforestation, much lesshalting it will therefore entail bucking powerful and inexorably growing forces. It is in this starklight that the prospects for conserving tropical forests must be considered.

If we do not soon change public policy regarding tropical forests, the primary forest will probably be gone sometime before 2045

Effect on global climate

A natural rainforest emits and absorbs vast quantities of carbon dioxide. On a global scale, long-term fluxes are approximately in balance, so that an undisturbed rainforest would have a smallnet impact on atmospheric carbon dioxide levels, though they may have other climatic effects(on cloud formation, for example, by recycling water vapor). No rainforest today can beconsidered to be undisturbed. Human induced deforestation plays a significant role in causingrainforests to release carbon dioxide, as do other factors, whether human-induced or natural,which result in tree death, such as burning and drought. Some climate models operating withinteractive vegetation predict a large loss of Amazonian rainforest around 2050 due to drought,forest dieback and the subsequent release more carbon dioxide. Five million years from now, theAmazon rainforest may long since have dried and transformed itself into savannah, killing itself

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in the progress (changes such as this may happen even if all human deforestation activity ceasesovernight). The descendants of our known animals may adapt to the dry savannah of the formerAmazonian rainforest and thrive in the new, warmer temperatures.