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Deforestation and the Greenhouse Effect

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Every minute of every hour of every day, an area of rainforest the size of approximately thirty-seven football pitches is cut down all over the world. Why are these trees being cut down? What do we use them for?

The main habitat in which deforestation is currently taking place is tropical rainforests, situated on and around the Equator. Areas of forest in developed countries are now usually managed forests. This is because many of them were cleared during the Bronze Age, however developing countries are now destroying their forests at an alarming rate.

The Causes of Deforestation

The main reason for deforestation is the demand for fuel, wood and paper products, cattle ranching, farming, mining and road construction.

Fuel: Half of all the trees cut down in the world are used for fuel. Burning wood is common in developing countries where there are often no readily-available alternatives. This in itself is not a huge problem; only, most of these trees are not replaced, which is a problem.

Wood and Paper Products:The use of wood and paper, mainly in developed countries, is a huge factor driving deforestation all over the world. Hardwoods like mahogany are sought after for furniture and are consequently very valuable. In every square kilometre of rainforest, there are probably only half a dozen mahogany trees, yet the whole area is often cut down for those few trees, with other trees left to rot, even if they are useful for something.

Cattle-ranching: Areas of rainforest, generally in developing countries, are cleared by cutting down all the vegetation and then burning it. Pastures of grass are then grown and used for grazing cattle. As soon as the cattle are a certain age, they are slaughtered. Although some of the meat goes to the locals, a lot goes to the cheap meat industries in countries such as the UK and USA, giving products such as corned beef and burgers. Huge areas of rainforest have to be cleared to support several hundred cattle. After a few years, all the nutrients have been removed from the already poor soil and the land is useless, so another area of rainforest has to be cleared. Rejuvenation of the soil is possible, but takes a lot of time and energy.

Farming: Large areas of rainforest are cleared for farmland all over the world. In developing countries there are two main types of farming: 'Slash and Burn' and 'Subsistence Farming'.

Slash and Burn: Areas of forest are cleared to grow crops for a couple of years, then left for a few years for the rainforest to recover, then the process starts again. Slash and burn is the most sustainable of the farming methods, but only if the population in the area is low, because as soon as you get more people in an area, there is less land available for each person and areas of land don't have enough time to recover, so the soil is quickly exhausted. Slash and burn also increases air pollution.

Subsistence Farming: Small areas of land that have been cleared are farmed. The produce is used to feed the family and provide a small surplus to buy other goods. The problem with this method is that the soil is quickly exhausted of its few nutrients and they are not replaced. This means that the farmers have to rely increasingly on fertilisers before eventually being forced to move.

Mining and Infrastructure: Rare minerals such as gold, bauxite (aluminium ore) and iron ore are often discovered in areas of rainforest. To mine them huge portions of rainforest are cleared, not just the area where the mine is, but also routes for roads and areas for storage of equipment and housing for men. Examples include gold-mining in the Amazon Basin and tin-mining in Indonesia. In places where there are large rivers running through rainforest, deforestation often takes place in order to build hydroelectric power stations. The resulting dams cause enormous amounts of flooding behind the walls and large areas of drought downriver.

Population Increase: The world population is increasing. With this increase the amount of land needed for humans to live on also increases. More and more areas are being cleared to provide living space. This is known as urbanisation. In developing countries people are moving into previously undisturbed areas of rainforest to log, mine or farm. For example, on the Indonesian island of Java, the population has grown so rapidly that people are encouraged to move to other less densely populated islands where they cut down the rainforest for farming and homes.

The Effects

Immediate effects of deforestation include the washing away of soil in the monsoon season. This is because trees are no longer anchoring and binding the soil and so mud slides take place. The earth is leached of minerals by the large amounts of water. The lack of vegetation also means that there will be very few animals in the area. The lack of decomposing vegetation and animals means that the nutrients are not replaced and the area quickly becomes infertile.

Rivers often silt up as soil is moved downriver and deposition takes place. Fish and plants relying on clear water die as the river becomes more and more clogged. This has a knock-on effect through the entire food chain.

If large areas of rainforest are cleared, the pattern of precipitation1 may change. This is because less evapotranspiration2 takes place due to the lack of trees. Water is also not delayed before making its way through the ground because of the lack of trees, shrubs, and leaf litter.

Another very worrying effect of deforestation is global warming. The Earth is made habitable by a process called the greenhouse effect. Gases, mainly carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and water vapour (H2O), are found in the atmosphere. When light rays from the sun come into the Earth's atmosphere, they are absorbed by the Earth, and then emitted as infra-red rays; the greenhouse gases trap some of them in the atmosphere, warming the earth. The greenhouse effect is essential for life to be able to live on earth because without it, it would be too cold.

Current scientific theory suggests that when the level of greenhouse gases in the atmosphere increases, more of the heat rays are trapped in the atmosphere, gradually warming the Earth. This increase in temperature might seem quite nice, but it isn't good. The effects of global warming are already showing themselves; the polar ice caps are melting and if this continues we are set for a significant rise in sea level, flooding many places. Places which are now full of life could become deserts if rainfall patterns change with the temperature increases.

Deforestation may account for part of the rise of greenhouse gases because trees have a large store of carbon in them, they take in CO2 from the atmosphere through photosynthesis, and although a lot of what they absorb comes out through respiration, some of it stays in the tree in the form of carbon. When trees are cut down, and especially when they are burned, this carbon reacts with oxygen in the atmosphere and becomes CO2.

Less trees mean more carbon dioxide in the atmosphere and an increased greenhouse effect, which in turn means more global warming.

Carbon dioxide levels in the atmosphere are also rising because of the increasing burning of fossil fuels (coal, oil and natural gas). Fossil fuels are made from dead organisms, which have gradually been compressed over millions of years, so they contain a lot of carbon. This means that when they are burned carbon dioxide is released into the atmosphere. This increased use of fossil fuels contributing to global warming led 160 nations to come together in 1997 in Kyoto, Japan, to try to reduce emissions. In 2001, the newly elected president of the USA, George W Bush, declared that the USA would not sign the Kyoto Protocol because it would be economically damaging for the USA. Without the USA's backing, the Kyoto Protocol is not going to have anywhere near as much effect on global warming, because the USA has the highest emission levels in the world. However much all the other nations try, the protocol needs the USA's backing to have any real chance of reducing global warming, which, if not reduced, will have disastrous effects for all.

The Forestry Commission

The Forestry Commission is a governmental department that was set up to protect and increase the size of UK woodlands. The equivalent in the USA is the National Forest Service, which works with the National Park Service to manage federal park lands. Many other countries have a forestry management service as well.

Sustainable forestry is the act of managing a forest so that it continues to grow and the ecosystem is undisturbed. For every tree cut down, two more young ones are planted. Sustainable forestry is a good idea because even though trees are being cut down, if they are replaced, the amount of CO2 that can be absorbed and stored in the trees will stay roughly the same, thereby not contributing to the greenhouse effect.

Land is set aside for trees with agreement from the owner and the local community that the region of land should be a woodland area. Grants are given to help with costs of planting etc. Pine trees are often planted as opposed to oak and other deciduous trees because they are fast-growing and there is a high demand for pine furniture and products.

How You Can Help

  • Turn off the light when you are not in a room, and use more energy-efficient bulbs. While energy-efficient bulbs are expensive, they do last longer. Not only will this save money, but it reduces the amount of electricity that needs to be generated and so less fossil fuels have to be burned.

  • Use public transport, walk, or cycle if possible. It is said that the bicycle is the most efficient form of transport known to man. Only travel in a car when necessary and if you know people who are going to the same place: try to car share so less petrol is used. This reduces CO2 emissions.

  • Try to buy paper or wood products that are certified by the Forestry Commission as being from sustainable, managed woodlands.

  • Avoid excess printing of documents from the computer. Print non-presentation documents on the draft ink setting. If possible print on both sides of sheets of paper, thus saving both paper and money.

  • Recycle as much as possible. This is not just limited to paper, but can include glass, plastic, metal, and a number of other things. Many councils run recycling collection services.

  • Encourage people you know to do any or all of the things above.

Even if you only turn off the light when you leave a room, the amount of energy that you save builds up over a period of time. If, bit by bit, more and more people start to do that, think of how much energy will be saved, thereby reducing the amount of fossil fuels that need to be burned, and reducing the amount of CO2 that enters the atmosphere, reducing global warming.

If you print on both sides of the paper, think how much paper you will save over time. Quite a lot. If all the people on your street do that, how many trees would you save?

Small actions really do matter, even if at first they appear fairly insignificant. Most of the time, they involve little effort from you and a lot of them save you money in the long run; and while doing them, you are helping to save the world from ecological disaster. Some people would argue it is already too late to do so - but if we don't try now then it certainly will be at some point in the not-too-distant future.

1Water falling to the Earth's surface.2Water evaporating from leaves.

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