The Sahara Desert is growing by 10kms each year. The whole earth gets 600km² of desert area more every year. This process is called "desertification". This term started being (1)_____ in the 1950s.
The idea of desertification was first known in the 1930s. Much of the Great Plains grew very dry (2)______ a result of drought and poor farming techniques. It was called the Dust Bowl. Millions were forced to leave their farms and their ways of life. Since then, (3)_____ have been great improvements in farming practices in the Great Plains. These have prevented the Dust Bowl disaster (4)______ again.
Grazing is one worry. Cows do two things to the soil. First, they eat grasses and plants that hold the soil in place. Second, their hooves break down the top layer of soil. The result is that the good soil can be blown away by the wind. The dirt (5)______ behind is not good for growing.