The greatest adverse impact of Deforestation is Greenhouse effect:
As described earlier, an approximate area of more than thirty five football grounds of rainforest are deforested all over the world in every minute. The main area attacked for deforestation is the tropical rainforest – situated in on and around equator.
A. The main reason for deforestation is the demand for fuel, wood and paper products, cattle ranching, farming, mining and road construction.
a. 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. Most of the trees cut are not replaced, causing the problems.
b. Wood and Paper Products: The use of wood and paper is a huge factor driving deforestation all over the world. Hardwoods like mahogany are sought after for furniture and are consequently very valuable. Some time, for small number of mahogany, whole forest area is often cut down for those few trees.
c. 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
d. Farming: Large areas of rainforest are cleared for farmland all over the world. In developing countries there are two main types of farming: (i) 'Slash and Burn' and (ii) 'Subsistence Farming'.
(i) 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.
(ii) 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 fertilizers before eventually being forced to move.
e. Mining and Infrastructure: 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. 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.
f. Population Increase: The world population is increasing day by day. With this explosion of population the amount of land needed for humans to live on also increases exponentially. More and more forest areas are being cleared to provide living space. This is known as ‘urbanization’.
B. The adverse effects of deforestation:
(i) 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.
(ii) 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.
(iii) If large areas of rainforest are cleared, the pattern of precipitation may change. This is because less evapotranspiration (evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and water bodies) 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.
(iv) Another very worrying effect of deforestation is global warming (please refer ‘description on global warming’ in the box below). The Earth is made habitable by a process called the greenhouse effect. Gases, mainly carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and water vapor (H2O), are found in the atmosphere. 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.
C. How to help in mitigating the global warming:
(i) We should turn off the light when we do not require, and to 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.
(ii) 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 or share with some body to save petrol. This reduces CO2 emissions.
(iii) Try to buy paper or wood products that are certified by the Forestry Commission as being from sustainable, managed woodlands. Using recycled paper and its promotion help in reduction of destruction of forest.
(iv) 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.
(v) 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.
(vi) Encourage people you know to do any or all of the things above.
Consider a glasshouse in the open air - greenhouse works because of the glass panels that line the roof and walls. The glass is transparent to the visible light from the sun, so sunlight can shine in and warm things inside the greenhouse. Now a body at about 35°C emits mostly infrared radiation. (On the other hand our sun, with a surface temperature of about 5500°C, emits mostly visible light.) The glass panels are opaque to infrared light. The result is that the glass lets the energy of the sun in, but won't let it back out. This keeps the inside of a greenhouse warm.
Replace the greenhouse with Earth and glass panels with atmosphere in the above example, and that is how the Earth's greenhouse effect works.
Now to show why the greenhouse effect is a very good thing here are examples from our solar system.
(i) Mercury: Mercury is the closest planet to the sun, so you would expect it to be hot. It is, but only on the day side. During a Mercurian day temperatures reach 464°C, but because there is no atmosphere to cause a greenhouse effect, temperatures drop to -183°C at night. That's cold enough to warrant an investment in triple-paned windows.
(ii) Earth: Our greenhouse effect keeps our night side almost as warm as our day side, allowing life to flourish and keeping the world's collective heating bill manageable.
(iii) Venus: Venus is an example of having a greenhouse that is too good at trapping in the heat.
Even though Venus is twice as far away from the Sun as Mercury, Venus is the planet with the hottest surface temperature day or night. At about 484°C, lead melts on the surface at any time of the day.
The reason why this doesn't happen to Earth is due to the fact that Venus has a much thicker atmosphere with many different kinds of gases. Earth's atmosphere is full of gases that trap infrared radiation (so-called greenhouse gases), but they only trap certain wavelengths at a certain efficiency. In other words, a lot escapes. Venus's atmosphere is more diverse as well as denser, so it traps more wavelengths of infrared radiation at a greater efficiency, making the surface hellishly hot.
That is where the greenhouse effect gets its bad reputation. We do not have a lot of carbon dioxide in our atmosphere right now, and if more is released into the atmosphere, more of the infrared radiation that it traps will be held in, making the world warmer than it is. This kind of global warming is a bad thing.