(b) Major causes of desertification include:
(i) Shifting of climatic zones e.g natural shifting or encroachment of the Sahara Desert towards the North estimated to be 50km per year
(ii) Climatic variations - very low rainfall
(iii) Human activities such as deforestation and overgrazing
(c) Two possible ways of combating desert encroachment include:
(i) Large scale irrigation system - This will enable water to be available in the soil and consequently promote the growth of vegetation in the area.
(ii) Afforestation - This involves the planting of trees which act as barriers to the speed of winds carrying sand from the desert