Sustainability

Desertification

According to the figures reported by the United Nations Environment Programme (UNEP), 25% of the earth's land is threatened by desertification. The lives of over one billion people in over 100 countries are at risk since farming and cattle breeding become less productive.
Desertification does not mean the deserts are still expanding or taking over the neighbouring lands. As defined by the UN Conference on "Environment and Development" held in Rio de Janeiro in 1992, desertification is a process of "deterioration of the arable land into dry, medium dry and sub-humid dry areas as a consequence of many factors, including climatic changes and human activities".  A common element shared by the areas threatened by desertification is the relentless reduction of the surface layer of the soil and its productive capacity. This is a serious phenomenon since it determines other ecological disasters, such as the loss of biodiversity and the increase of the temperature all over the world. 
Areas of degraded land may be found hundred of kilometres from the closest desert. But they can expand and join each other into something that may resemble a desert. The most serious reasons underlying this phenomenon are drought and human activities: intensive farming exhausts the soil; cattle breeding removes the vegetation, which would otherwise