The effects of deforestation on natural ecosystems

Since the 14th century, people have been clearing areas of forest for inhabiting, but in comparison with today’s rates, the effects were minimal. Deforestation is defined as the destruction of forest for timber, fuel, charcoal, and the clearing for agricultural purposes, without replacing the trees that were lost (reforestation). In most areas of the world, forest is the natural climax community, though deforestation is mainly occurring in tropical areas – though all have a high diversity and complex food webs surrounding them. However, due to a growth in the human population, demands for land to farm and for grazing, deforestation has become a problem for the natural ecosystems.

Soil erosion becomes one of many problems when the land has been cleared. Although tropical forests appear to be lush, the soils beneath them are relatively poor, with most of the nutrients being held in the vegetation. This becomes a problem when the land is cleared of all plants and organisms, as the nutrients have been taken away totally. Where there are no trees to keep the land together, the soil dries out and cracks under the sun. In high temperatures, nitrogen can be lost from it, further reducing the fertility of the soil, and when rainfall comes, the remaining nutrients are washed away. This means that crops planted here later on will not have the benefits of rich, fertile soils and this may become barren land. Replanting trees will not replenish the soil, as by the time they have matured, the soil will be devoid of the necessary nutrients, rendering the land useless.

Flooding becomes another problem as a result of deforestation and soil erosion. Clearing the forests increases the surface run-off from rain, as there is no vegetation to absorb it. This can remove valuable topsoil and has been particularly a problem in areas like Bangladesh, where the land is low lying anyway.

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Trees are the basis of the majority of food webs and have thousands of species depending on them as they also provide a habitat. Entire populations of species can be eradicated or severely reduced in size due to the removal of forest environments. Birds, small mammals, insects and even down to the decomposing fungi living in the roots of the trees, are all affected. Diversity is dramatically reduced, as the producers in the food webs are being taken away. Without this, many species can be endangered or even made extinct. The environment is made to become unstable and have extreme conditions which organisms find very hard to live in. Abiotic factors become more extreme also.

Finally, the Carbon and Nitrogen cycles are greatly affected. On a basic level, the loss of plants and tress means less photosynthesis is taking place, and so Carbon Dioxide levels in the air will increase. When the trees are removed, they are burnt which also adds to the increase. Since more CO2 is being added to the air, and the methods for removing it are themselves being taken away, the greenhouse effect is being increased, which in the long term could result in a change of climate and again, unbalance in the ecosystem. In the Nitrogen cycle, nitrate ions come from the decomposition of organic remains, which is how the ions get recycled. When trees are removed and burnt, this does not happen, and the decomposing fungi that lived in the soil and roots of the trees is also being extracted. As a result, the soil becomes a poor source of minerals and not the best place to farm crops. Replanting is very difficult, because as the soil loses fertility, it can support less, and therefore leads to a lower diversity.

Although attempts are being made to encourage the sustainable use of forests, the damage has already been done. To do this, yields and profits from deforestation have to be compared with the alternative uses if the forest is kept. Not surprisingly, forests are much more profit making kept in tact, diversity is retained and the ecosystem survives. Sadly though, there are many areas that have already been destroyed, and it can only be hoped that deforestation rates will be reduced, to save the animals, the environment, and the world we live in.