Desertification is the degradation of once-productive land into unproductive or poorly productive land. Since the first great urban-agricultural centers in Mesopotamia nearly 6,000 years ago
Which of the following statements is true about desertification?
A. It has a history as long as that of civilization.
B. It was just as serious in the past as it is today.
C. It is a fairly recent problem.
D. Ancient societies managed the problem well.