These factors contribute to desertification. 1)cactus growth 2)farming 3)landfills 4)overgrazing 5)urbanization 6)water table depletion

The main factor that causes desertification is overgrazing. There are other factors that can contribute to desertification such as farming (for example, tillage practices in agriculture that make the soil more vulnerable to wind), urbanization and the depletion of the water table.

a.   it resulted in widespread unemployment.