第二篇 Deforestation and Desertification(沙漠化)
The Sahel zone lies between the Sahara desert and the fertilesavannahs(热带大草原)of northern Nigeria and South Sudan. The word sahel comes from Arabic and means marginal or transitional ,andthis is a good description of these semi-arid (半干旱)lands, whichoccupy much of the Western African countries of Mail, Mauritania, Niger, andChad.
Unfortunately, over the last century the Sahara desert has steadilycrept southwards eating into once productive Sahel lands. United Nationssurveys show that over 70 percent of the dry land in agriculture use in Africahas deteriorated over the last 30 years. Droughts have become more severe, themost recent lasting over twenty years in parts of the Sahel region. The sameprocess of desertification is taking place across southern Africa as theKalahari desert advances into Botswana and parts of South Africa
One of the major causes of this desert advance is poor agriculturalland use, driven by the pressures of increasing population. Overgrazing 一 keeping toomany farm animals on the land一 means that grasses and other plants cannot recover, and scarcewater supplies are exhausted. Overcultivation 一 trying to grow toomany crops on poor land 一 results in the soil becoming even less fertile and drier, andbeginning to break up. Soil erosion (侵蚀) follows, and theland turns into desert.
Another cause of desertification is loss of tree cover. Trees arecut down for use as fuel and to clear land for agricultural use. Tree rootshelp to bind the soil together, to conserve moisture, and to provide a habitatfor other plants and animals. When trees are cut down, the soil begins to dryand loosen, wind and rain erosion increase, other plant species die, andeventually the fertile topsoil may be almost entirely lost, leaving only barerock and dust.
The effects of loss of topsoil and increased drought are irreversible.They are, however, preventable. Careful conservation of tree cover andsustainable agricultural land use have been shown to halt deterioration ofsoils and lessen the effects of shortage of rainfall. One project in Kita insouth-west Mali funded by UNDP has involved local communities in sustainablemanagement of forest, while at the same time providing a viable(有活力的)agriculturaleconomy. This may be a model for similar projects in other West Africancountries.
36.The Sahel zone is anarea which ___.
A.is covered with sad and grass
B. has a long history
C. occupies much of South Nigeria
D. belongs to Sudan
37. What is the situation about thedesertification in Africa?
A. The deserts are replaced with grasslands
B.The deserts are expanding
C. the deserts are moving northwards
D. the deserts are being deserted
38. The word “deteriorated ” in paragraph 2means ___.
39. What is the root cause ofdesertification?
C. radical climate change
D. disappearance of rare plant species
40. In order to prevent desertification, theauthor proposes ___.
A. making good use of international aids
B.developing a sustainable agricultural economy
C. gaining international support
D. converting agricultural land into forest