Adelaaa

 Desert formation  沙漠的形成(4)

 Firewood is the chief fuel used for cooking and heating in many countries. The increased pressures of expanding populations have led to the removal of woody plants so that many cities and towns are surrounded by large areas completely lacking in trees and shrubs. The increasing use of dried animal waste as a substitute fuel has also hurt the soil because this valuable soil conditioner and source of plant nutrients is no longer being returned to the land.

  The extreme seriousness of desertification results from the vast areas of land the tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process. Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form. In areas where considerable soil still remains, though, a rigorously enforced program of land protection and cover-crop planting may make it possible to reverse the present 

(* Highlight 的單字是有解說的單字，非問題。)

單字解說：

1) chief  (N. / Adj.)  首要的；最重要的；最主要的； 領導人

2) woody (Adj.)   像木頭的 ； （植物）木本的

3)  surround  (N. /V.)  圍繞 ； 周圍地帶

4) shrub  (N.) 灌木

5)  substitute  (N. /V.)  用…代替； 代替物

6) conditioner  (N. )   護髮素 ； （衣物）柔順劑

7)  source   (N. /V.)  出處；發源地；起源； 從（某地）獲取

8) nutrients  (N. )   養分；營養物，滋養物

9)  extreme (N. / Adj.)  極大(的)；極度的；極端(的) 極嚴厲的；嚴重的；極差的  

10) vast  (Adj.)   巨大的；廣大的

11) tremendous  (Adj.)  巨大的；極好的