『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 2 Passage 1阅读练习：Look at the four squares  that indicate where the following sentence could be added to the passage. This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.真题题目及答案解析，TPO/Official 2 Passage 1阅读原文范文音频翻译

托福TPO/Official 2 Passage 1阅读原文Look at the four squares  that indicate where the following sentence could be added to the passage. This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.题目答案及解析-新东方托福官方网校手机版

沙漠大约已经覆盖了地球表面的四分之一，近几十年来，沙漠增长的速度让人警惕。

The deserts, which already occupy approximately a fourth of the Earth’s land surface, have in recent decades been increasing at an alarming pace.

沙漠化就是指类似沙漠的情况向之前没有沙漠存在的地方的扩展。

The expansion of desertlike conditions into areas where they did not previously exist is called desertification.

据估计，还有四分之一的地球表面受到这一进程的威胁。

It has been estimated that an additional one-fourth of the Earth’s land surface is threatened by this process.

沙漠化主要通过以下过程实现：稳定自然植被的消失，以及随之产生的因风力和雨水而不断加速的土壤腐蚀。

Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the subsequent accelerated erosion of the soil by wind and water.

在某些情况下，松散的土壤被完全吹走，只剩下裸露的石质化表层。

In some cases the loose soil is blown completely away, leaving a stony surface.

在另一些情况下，精细颗粒被移走了，而沙砾大小的颗粒堆积起来形成了移动的沙丘。

In other cases, the finer particles may be removed, while the sand-sized particles are accumulated to form mobile hills or ridges of sand.

尽管有些地方还有土壤覆盖，植被的减少通常会导致土壤失去吸收大量水的能力。

Even in the areas that retain a soil cover, the reduction of vegetation typically results in the loss of the soil’s ability to absorb substantial quantities of water.

雨水对松散土壤的冲击会把细小的粘土颗粒冲到土壤空隙中，封闭了土壤，使得水分很难渗透到土壤里。

The impact of raindrops on the loose soil tends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration.

吸水率大大降低，因此流失几率增大，导致侵蚀速率的加快。

Water absorption is greatly reduced, consequently runoff is increased, resulting in accelerated erosion rates.

由于土壤吸水力较低，土壤会逐渐变得干燥，进一步导致了植被的消失，因此形成了土壤逐渐退化的循环。

The gradual drying of the soil caused by its diminished ability to absorb water results in the further loss of vegetation, so that a cycle of progressive surface deterioration is established.

在有的地区，沙漠面积的增加主要是由于气候条件变得更干燥。

In some regions, the increase in desert areas is occurring largely as the result of a trend toward drier climatic conditions.

在过去几千年，持续不断的全球变暖使得一些地方的干旱问题更加严重。

Continued gradual global warming has produced an increase in aridity for some areas over the past few thousand years.

接下来几十年这一进程会加速，如果由空气污染导致的全球变暖显著加剧的话。

The process may be accelerated in subsequent decades if global warming resulting from air pollution seriously increases.

毫无疑问，绝大多数地区的沙漠化不是自然进程，它主要是由人类活动导致的。

There is little doubt, however, that desertification in most areas results primarily from human activities rather than natural processes.

紧邻沙漠的半干旱土地处于脆弱的生态平衡中，它们应对不断增大的环境压力的潜力是有限的。

The semiarid lands bordering the deserts exist in a delicate ecological balance and are limited in their potential to adjust to increased environmental pressures.

人口的增加也给土地带来更大的压力，因为它需要给人们提供食物与燃料。

Expanding populations are subjecting the land to increasing pressures to provide them with food and fuel.

在雨季，土地可能能够应对这些压力。

In wet periods, the land may be able to respond to these stresses.

但是在干旱的季节里，在沙漠边缘地带，存在一个十分普遍的现象：人类对土地施加的压力远远超过了它已经减弱的承载力，因此最终形成了沙漠。

During the dry periods that are common phenomena along the desert margins, though, the pressure on the land is often far in excess of its diminished capacity, and desertification results.

导致沙漠化的主要因素有四个：过渡耕种、过渡放牧、柴火收集与过渡灌溉。

Four specific activities have been identified as major contributors to the desertification processes: overcultivation, overgrazing, firewood gathering, and overirrigation.

随着人口密度的增加，农作物的种植渐渐扩展到了干旱地带。

The cultivation of crops has expanded into progressively drier regions as population densities have grown.

这些地方遭遇大干旱的几率特别高，因此农作物种植失败也是常事。

These regions are especially likely to have periods of severe dryness, so that crop failures are common.

因为种植农作物的前提是把地面的自然植被移除，当农作物种植失败的时候，大片土地裸露出来，没有一丁点植物覆盖，所以更容易遭受风雨侵蚀。

Since the raising of most crops necessitates the prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion.

半干旱地区的自然植被类型主要是草，在这一地区，主要经济活动是家畜养殖。

The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation.

在一个地区过量饲养家畜会导致植被覆盖面积减少，土地被大量践踏和碾碎。

The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil.

随之而来的就是土壤干旱与侵蚀加剧。

This is usually followed by the drying of the soil and accelerated erosion.

在很多国家木柴是做饭与供暖的主要燃料。

Firewood is the chief fuel used for cooking and heating in many countries.

人口增长带来的压力与日俱增，导致木本植物被砍伐，因此很多城市城镇被大片完全没有树木灌木的土地包围。

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.

人们越来越多的使用干动物粪便作为替代燃料，这种做法也破坏了土壤，因为干动物粪便是宝贵的土壤成分调节器，也是植物的营养来源，它却不能再回到土壤里。

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.

最后一个导致沙漠化的人为原因是过度灌溉而引起的土壤盐渍化。

The final major human cause of desertification is soil salinization resulting from overirrigation.

灌溉中的多余的水会下沉到地下水中。

Excess water from irrigation sinks down into the water table.

如果没有排水系统，地下水位会上升，把溶解盐带到土壤表面。

If no drainage system exists, the water table rises, bringing dissolved salts to the surface.

水分蒸发，盐分留了下来并形成白色的结晶层，阻挡空气与水分进入到下面的土壤里。

The water evaporates and the salts are left behind, creating a white crustal layer that prevents air and water from reaching the underlying soil.

沙漠化问题如此严重主要是因为它影响的区域很广泛、影响的人数很多以及扭转或者延缓这一进程特别难。

The extreme seriousness of desertification results from the vast areas of land and the tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process.

一旦土壤因为侵蚀而消失，只有历经几世纪甚至一千年新土壤才会形成。

Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form.

在那些仍有大量土壤的地方，严格执行的土壤保护计划与植被保护计划还有可能扭转现在土壤表层恶化情况的趋势。

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 deterioration of the surface.

The word “threatened” in the passage is closest in meaning to

According to paragraph 3, the loss of natural vegetation has which of the following consequences for soil?

According to paragraph 5, in dry periods, border areas have difficulty

According to paragraph 6, which of the following is often associated with raising crops?

According to paragraph 9, the ground’s absorption of excess water is a factor in desertification because it can

All of the following are mentioned in the passage as contributing to desertification EXCEPT

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

It can be inferred from the passage that the author most likely believes which of the following about the future of desertification?

Look at the four squares  that indicate where the following sentence could be added to the passage. This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Desert Formation The deserts, which already occupy approximately a fourth of the Earth’s land surface, have in recent decades been increasing at an alarming pace. The expansion of desertlike conditions into areas where they did not previously exist is called desertification. It has been estimated that an additional one-fourth of the Earth’s land surface is threatened by this process. Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the subsequent accelerated erosion of the soil by wind and water. In some cases the loose soil is blown completely away, leaving a stony surface. In other cases, the finer particles may be removed, while the sand-sized particles are accumulated to form mobile hills or ridges of sand. Even in the areas that retain a soil cover, the reduction of vegetation typically results in the loss of the soil’s ability to absorb substantial quantities of water. The impact of raindrops on the loose soil tends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration. Water absorption is greatly reduced, consequently runoff is increased, resulting in accelerated erosion rates. The gradual drying of the soil caused by its diminished ability to absorb water results in the further loss of vegetation, so that a cycle of progressive surface deterioration is established. In some regions, the increase in desert areas is occurring largely as the result of a trend toward drier climatic conditions. Continued gradual global warming has produced an increase in aridity for some areas over the past few thousand years. The process may be accelerated in subsequent decades if global warming resulting from air pollution seriously increases. There is little doubt, however, that desertification in most areas results primarily from human activities rather than natural processes. The semiarid lands bordering the deserts exist in a delicate ecological balance and are limited in their potential to adjust to increased environmental pressures. Expanding populations are subjecting the land to increasing pressures to provide them with food and fuel. In wet periods, the land may be able to respond to these stresses. During the dry periods that are common phenomena along the desert margins, though, the pressure on the land is often far in excess of its diminished capacity, and desertification results. Four specific activities have been identified as major contributors to the desertification processes: overcultivation, overgrazing, firewood gathering, and overirrigation. The cultivation of crops has expanded into progressively drier regions as population densities have grown. These regions are especially likely to have periods of severe dryness, so that crop failures are common. Since the raising of most crops necessitates the prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion.  The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation.  The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil.  This is usually followed by the drying of the soil and accelerated erosion.  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 final major human cause of desertification is soil salinization resulting from overirrigation. Excess water from irrigation sinks down into the water table. If no drainage system exists, the water table rises, bringing dissolved salts to the surface. The water evaporates and the salts are left behind, creating a white crustal layer that prevents air and water from reaching the underlying soil. The extreme seriousness of desertification results from the vast areas of land and 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 deterioration of the surface.