阅读理解

第二篇 Deforestation and Desertification(沙漠化)

TheSahel zone lies between the Saharadesert and the fertilesavannahs(热带大草原)ofnorthern Nigeria and South Sudan. The word sahel comes fromArabic and means marginal or transitional ,andthis is a good description ofthesesemi-arid(半干旱)lands,whichoccupy much of the Western African countries ofMail,Mauritania,Niger,and Chad.

Unfortunately, over the last century theSahara desert has steadily creptsouthwards eating into once productive Sahellands. United Nations surveys showthat over 70 percent of the dry land inagriculture use in Africa hasdeterioratedover the last 30 years. Droughts have become more severe, the mostrecentlasting over twenty years in parts of the Sahel region. The same processofdesertification is taking place across southern Africa as the Kalaharidesertadvances into Botswana and parts of South Africa.

One ofthe major causes of this desert advance ispoor agricultural land use,driven by the pressures of increasing population.Overgrazing一 keeping too manyfarm animals on the land一means that grasses and other plants cannot recover, andscarce water suppliesare exhausted. Overcultivation一 tryingto grow too manycrops on poor land一 resultsin the soil becoming even less fertile and drier, andbeginning to break up. Soilerosion (侵蚀) follows, and the land turns intodesert.

Another cause of desertification is loss of tree cover. Trees are cutdown foruse as fuel and to clear land for agricultural use. Tree roots help tobind thesoil together, to conserve moisture, and to provide a habitat forother plantsand animals. When trees are cut down, the soil begins to dry andloosen, wind andrain erosion increase, other plant species die, and eventuallythe fertile topsoil may be almost entirely lost, leaving only bare rock anddust.

The effects of loss of topsoil and increased drought are irreversible.Theyare,however, preventable. Careful conservation of tree cover andsustainableagricultural land use have been shown to halt deterioration of soilsand lessenthe effects of shortage of rainfall. One project in Kita in south-westMalifunded by UNDP has involved local communities in sustainable managementofforest,while at the same time providing a viable(有活力的)agriculturaleconomy.This may be a model for similar projects in otherWest African countries.

35 order to prevent desertification,the author proposes ___.

A. making good use of international aids

B. developing a sustainableagricultural economy

C. gaining international support

D. converting agricultural land intoforest

答案：b

36.The Sahel zone is an area which ___.

A. is covered with sad and grass

B. has a long history

C. occupies much of South Nigeria

D. belongs to Sudan

答案：a

37. What is the situation about thedesertification in Africa?

A. The deserts are replaced withgrasslands

B. The deserts are expanding

C. the deserts are moving northwards

D. the deserts are being deserted

答案：b

38. The word “deteriorated ” in paragraph2 means ___.

A. deepened

B. suffered

C. slipped

D. worsened

答案：d

39. What is the root causeof desertification?

A. poor farming

B. overpopulation

C. radical climate change

D. disappearance of rare plant species

答案：a

40. In order to prevent desertification,the author proposes ___.

A. making good use of international aids

B. developing a sustainableagricultural economy

C. gaining international support

D. converting agricultural land intoforest

答案：b