6.1.1 Decrease in natural and agricultural land
Change from non-urban to urban land use causes the loss of many different types of vegetated land cover. This may be grassland used for grazing animals, cultivated fields that produce food and other crops, uncultivated areas of river banks and hillsides, and wooded areas covered with trees. Deforestation was discussed in Study Session 1 as one of the negative impacts of human use of resources.
What are the main negative effects of deforestation?
Deforestation can reduce the infiltration of water into the soil and groundwater, which can lower the water table and increase the volume and speed of surface run-off; if this happens it can increase soil erosion because the land surface is exposed. Deforestation also results in a loss of wildlife habitat and a reduction in biodiversity; and the loss of ecological services provided by trees (such as converting atmospheric carbon dioxide to oxygen by photosynthesis). You may also have mentioned the loss of the aesthetic value of trees, which are attractive elements in our biophysical environment.
The reduction in agricultural land also shifts the balance in the land area available for food production. The most productive land for agriculture tends to be near to towns. When towns expand this land gets covered with buildings and so it is no longer available for food production. This means there is less productive land available to meet the increasing demands for food from a growing urban population. The additional demands for food production in the areas around towns and cities can encourage the increased use of pesticides and fertilisers to improve productivity, which can have negative environmental impacts. It also encourages the cultivation of previously unused land such as sloping hillsides which, when ploughed, are extremely vulnerable to soil erosion when it rains.