deforestation; cause and effect By: romelyn van kleeck

Originally, almost half of the United States, three-quarters of Canada, almost all of Europe, the plains of the Levant, and much of the rest of the world were forested. The forests have been mostly removed for fuel, building materials and to clear land for farming. The clearing of the forests has been one of the most historic and prodigious feats of humanity. About one half of the forests that covered the Earth are gone. Each year, another 16 million hectares disappear. The World Resources Institute estimates that only about 22% of the world’s (old growth) original forest cover remains “intact” - most of this is in three large areas: the Canadian and Alaskan boreal forest, the boreal forest of Russia, and the tropical forest of the northwestern Amazon Basin and the Guyana Shield (Guyana, Suriname, Venezuela, Columbia, etc.)Today, forests cover more than one quarter of the world’s total land area, excluding polar regions. Slightly more than 50% of the forests are found in the tropics and the rest are temperate and boreal (coniferous northern forest) zones. Seven countries (Russia, Brazil, Canada, the United States, China, Indonesia, and the Democratic Republic of Congo (formerly Zaire) account for more than 60% of the total.   For millennia, humankind has influenced the forests, although much of the impact has been relatively minor. Today, the impact is enormous. Deforestation is expanding and accelerating into the remaining areas of undisturbed forest, and the quality of the remaining forests is declining.  Forests influence climate.  The within-year fluctuations in atmospheric CO2 in the temperate zone include a spring-through-autumn decline due to plant photosynthesis during the growing season, and an autumn-through-spring rise in CO2 as respiration and decomposition exceed photosynthetic uptake.  At a more regional scale, forests influence local climate and weather.  Rain forests transport great quantities of water to the atmosphere via plant transpiration. (Water is taken up by plant roots, bringing dissolved minerals into plant tissues.  Plants exchange gases with the atmosphere through openings in their leaves, and lose water in the same way.  That water loss provides the plant with a means to transport materials upwards, and so is beneficial, so long as water loss is not excessive).  Much of that transpired water replenishes the clouds and rain that maintain the rain forest.  If the forest is cut, much more of that rain will become river water, flow to distant seas, and the region will become permanently drier.  No rain forest can regenerate if this occurs.  Forests maintain local climate and strongly influence global fluxes of oxygen and carbon dioxide.  Before green plants appeared, it is believed that there was very little oxygen in the atmosphere.
 Forests protect the top soil and husband important nutrients.  A famous study of Hubbard Brook, New Hampshire found that, after forest harvest, summer streamflows greatly increased (because the forest was no longer transpiring water) and nutrient outflow also increased greatly.  The annual flood crest of the Amazon River has increased over recent years without any concomitant increase in rainfall, presumably due to deforestation.  Damaging floods are one frequent consequence of deforestation.
 Forests harbor tremendous biological diversity, and have the potential to provide us with new crop varieties and medicines. A good example of medicinal use of tropical rain forest plants is the success of the drugs vincristine and vinblastine, developed over the past 20 years from a wild periwinkle found in the forests of Madagasgar. These drugs dramatically improved the effectiveness of treatments for leukemia and other forms of cancer, Since fewer than 1% of tropical plants have been screened for possible use to medical science, ongoing deforestation results in the permanent loss to science of other species before their value can be recognized.  The winged bean is a new food crop whose value has only recently has been recognized. Deforestation has many causes.  Population pressures, profits, and internal social and political forces can all push up the rate of forest loss.  Access to markets, requiring roads and capital, is an additional powerful force, recently expanded due to the suite of changes referred to as globalization.  Poor countries with expanding populations, inequitable distribution of wealth and power, and possibly corrupt governments are especially vulnerable. In Indonesia, powerful families allied with government rulers control large and highly valuable timber concessions.  These forests are being rapidly liquidated, at enormous profit.
 In Brazil, many of the rural poor are moving to cities for work, and not finding it.  Productive farmland is controlled by a wealthy elite with a long history of land ownership, and so many of the rural poor are landless.  By opening its frontier – the Amazon forest - to its landless poor, Brazil seeks to provide a safety valve for what otherwise might be an explosive political situation.
 In many areas, poor people have few options to make income, and forests have few protectors, and so land is cleared for agriculture and valuable timber is sold for profit.

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