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UNIT 8
Text A
PRE-READING TASK
Exercise 1
Before reading the passage, try to answer the questions.
1. How many years do you think it takes to double the world population now?
2. What might be the possible solutions to the population explosion in the world?
Now compare your answers with your neighbours'.
The Population Bomb
I. Too many people
1 Figure and numerous facts prove that there are already, and certainly that there will be, too many people. Simply calculating the lengths of time necessary to double the world's population is instructive. Impressively, the time required grows ever shorter: 6 000 years before Christ, 1 000 000 years were necessary to double the population, then about 1 650 years after Christ only 1 000 around the 1850's 200 years, in 1930 80 years. Currently, the world's population doubles every 37 years.
2 What would happen if the population were to continue doubling in volume every 37 years?
3 According to recent calculations, maintaining such a rhythm of growth would result in 60 million billion people on the earth in 900 years, which represents 120 inhabitants per square meter.
4 Optimists believe and often assert that science will indeed find solutions to the problem of overcrowding, namely by providing the means to immigrate to other planets. But this solution is totally impossible. In effect, even if it should become possible, 50 years would be sufficient for the 60 million billion persons to multiply to the point of populating Venus, Mercury, Mars, the Moon and the satellites of Jupiter and Saturn with a density equal to that of the Earth.
II. Food Shortage
5 Today, a good part of humanity suffers from malnutrition or from undernourishment.
6 Some think that the recent scientific discoveries applied to agriculture and known under the name of "green revolution" will resolve the problem. Nothing is less certain. Promoters of the revolution themselves believe that it can offer only a respite of ten or twenty years.
7 In underdevel-oped countries, al-though mostly agri-cultural, the lag in food production in relation to population growth increases more and more. As the crisis worsens these countries will have to import food. But from where?
III. A Dying Planet
8 The world's population explosion is the source of a whole series of environmental deteriorations, which in time can have disastrous consequences.
9 Because the population-food imbalance makes it necessary to increase agricultural production "at any price", methods often harmful to the environment are used without judgment. For example, the construction of huge dams to irrigate hundreds of thousands of acres can in fact provoke catastrophes. Thus, the Aswan Dam currently prevents the deposit of fertile silts brought each year by the flooding of the Nile. The result will obviously be a decrease in the fertility of the Delta lands. Damming the Mekong risks the same consequences for Vietnam and neighbouring countries.
10 Fertilizers, synthetic pesticides, DDT can be devastating, transforming complex ecosystems, necessary for the conservation of the environment, into simple ecosystems.
11 Certain situations are perceived as dangerous only when they become critical enough to cause numerous deaths. Smog is an example. In London in 1952 it caused some 4 000 deaths. This incident provoked an awakening of conscience and resulted in decisions which have proven effective. But smog presents still other dangers: namely, it destroys plants which offer little resistance, and whose oxygen production is indispensable to us, and it changes the earth's thermal equilibrium.
12 For these forms of pollution as for all the others, the destructive chain of cause and effect goes back to a prime cause: "too many cars, too many factories, too many detergents, too many pesticides, more and more trails left by supersonic jets, inadequate methods for disinfecting sewers, too little water, too much carbon monoxide. The cause is always the same: too many people on the earth."
New Words
numerous
a. many 许多的,众多的
instruct
v. 1. 教，教育
2. 通知，向…提供事实情况
instructive
a. 1. 有启发的，有教益的
2. 教育的，指导性的
impressive
a. causing admiration by giving one a feeling of importance 给人以深刻印象的
impressively
ad. 给人以深刻印象地
namely
ad. (and) that is (to say)即，那就是
immigrate
v. to come into a country to make one's life and home there 移居，移入
multiply
v. to increase 增加
populate
v. (of a group) to live in (a particular area) （大批地）居住于，生活于
satellite
n. 1. a heavenly body, moving around a larger one 卫星
2. a man-made object intended to move around the earth, moon, etc. 人造卫星
density
n. 1. 密集，稠密
2. 密度
undernourishment
n. 营养不足
respite
n. ( a short period of) pause or rest, during a time of great effort, pain, or trouble 暂缓，暂停
lag
n. a period of time by which something is slower or later 落后，滞后
worsen
v. to (cause to) become worse 变得更差，恶化
deterioration
n. the state of becoming worse 恶化，变坏
judgment
n. the ability to judge correctly 判断
dam
n. a wall or bank built to keep back water 坝，堤
v. to build a dam across 筑坝
irrigate
v. to supply water to (dry land) 灌溉
acre
n. a measure of land, about 4047 square metres 英亩(≈4047平方米)
provoke
v. to cause 引起
catastrophe
n. a sudden, unexpected, and terrible event that causes great suffering 灾难
fertile
a. (of land) which produces good crops 肥沃的
silt
n. （水流夹带或水底沉积的）泥沙，淤泥
fertility
n. the condition or state of being fertile 肥沃，丰产
delta
（河流的）三角洲
synthetic
a. 1. 合成的
2. 综合的
pesticide
n. 农药，杀虫剂
transformv. to change completely in form, appearance 使改变（性质等）
ecosystem
n. 生态系统
awakening
n. the act of becoming conscious or concerned 觉醒，唤醒
resistance
n. the ability or power of resisting 抵抗力
oxygen
n. 氧，氧气
indispensable
a. that is too important to live without 必不可少的
destructive
a. 破坏性的，毁灭性的
detergent
n. a chemical product used for cleaning 洗涤剂
trail
n. a series of marks left by a person or thing passing by 痕迹
supersonic
a. faster than the speed of sound 超音速的
adequate
a. sufficient 充分的，足够的
inadequate
a. not adequate 不适当的，不充分的
disinfect
v. 消毒，杀菌
carbon
n. 碳
monoxide
n. 一氧化物
Phrases and Expressions
in effect
实际上，实质上
be equal to
等于，比得上
under the name of
名叫，称为
suffer from
遭受
in relation to
与…相比，与…有关，涉及
in time
最终，迟早，及时
at any price
不惜任何代价
Proper Names
before Christ
公元前
Venus
金星
Mercury
水星
Mars
火星
Saturn
土星
the Aswan Dam
阿斯旺水坝
the Nile
尼罗河
the Mekong
湄公河
Vietnam
越南
DDT
滴滴涕（商品名，一种杀虫剂）
Text B
PRE-READING TASK
Exercise 1
Before reading the passage, think about the questions.
1. What would it be like if there were no trees on the earth?
2. Why is it important for us to plant more trees nowadays?
Now read the passage and check your answers with the author's.
Reforest the Earth!
1 Throughout the drought-ridden summer of 1988, the world heard much about how the burning of fossil fuels causes the greenhouse effect (the rapid warming of the earth's atmosphere.) We heard little about how the burning of tropical rain forests also contributes to the greenhouse effect. And still less do we hear about how reforestation of these tropics could help heal an ailing world.
2 The earth constantly maintains 700 billion metric tons of carbon dioxide (CO2) in the atmosphere. Fossil fuels emit another 5.2 billion metric tons of CO2 into the air each year, while the burning of tropical forests emits roughly 1.8 billion metric tons of CO2 -- both contributing to a buildup of carbon dioxide that will soon trigger the greenhouse effect. The CO2 gases trap the heat of the sun in the same way the glass of a greenhouse controls temperature for plants. If the gases become too concentrated, too much heat will collect, resulting in rising temperatures.
3 Of all the carbon dioxide emitted into the atmosphere, only about half accumulates in the skies while the rest disappears into oceans and lakes, vegetation and soil. So out of the 5.2 billion metric tons of CO2 emitted from the burning of fossil fuels and the 1.8 billion metric tons released from the burning of rain forests each year, only 3.5 billion metric tons contributes to global warming.
4 In 1980, 36 000 square miles of forest were burned in the tropics. In 1987, 33 000 square miles of rain forest were burned in Brazilian Amazonia alone. By the year 2020 the figure for tropical-forest emissions of CO2 could climb to another 5 billion metric tons. As a result, the CO2 released into the atmosphere each year would rise to approximately 10.2 billion metric tons.
5 Replanting trees in the tropics could eventually offer a solution to the greenhouse effect. A tree absorbs carbon dioxide through photosynthesis. Plant enough trees (as many as 250 billion) and we could remove much of the additional CO2 building up in the atmosphere. Nowhere in the world are conditions better for growing trees than in the tropics, where year-round warmth and moisture encourage rapid growth. To start a grand-scale tree-growing project in the tropics, however, would require as many as 20 governments in Latin America, Africa, and Asia to stop the rapid destruction of rain forests.
6 How many trees would we need to reforest the earth and stabilize the damage produced by global warming? One acre of a tropical plantation can absorb an annual average of four metric tons of atmospheric carbon. In order to soak up 1 billion metric tons of CO2, we would have to plant 400 000 square miles of new tropical forests. To eliminate the buildup of 3.5 billion metric tons would require planting trees on 1.2 million square miles, an expanse roughly equivalent to all states east of the Mississippi.
7 Where can we find enough space to replant what isn't being otherwise utilized? In the humid tropics forests have been cut down in watershed regions where replanting is urgently needed to stop topsoil from eroding and to prevent flooding. Last year flooding devastated regions in Bangladesh, India, the Sudan, and Thailand. In lowland Southeast Asia deforested lands have degenerated into poor-quality scrub and brush or coarse grasslands, good for little apart from reforestation. In addition, tropical countries urgently need to increase forest cover to adequately expand their fuelwood and commercial timber supplies.
8 At an average cost of $160 per acre, reforesting the tropics would cost $120 billion. This may seem like a high figure, but the global community would be spared much higher greenhouse costs. According to the Environmental Protection Agency, a rise in sea level (just through heating of the ocean surface) would threaten the developed coastal regions of the eastern United States. To protect these shore-lines, seawalls and tidal dams would have to be built at a cost of $10 billion. To improve dams and irrigation systems in the United States could cost an additional $23 billion. In comparison, the Department of Agriculture currently spends $200 million a year on flood-prevention programs. Further costs related to sea level rise and disrupted agriculture in other parts of the world (lush, fertile cropland may turn into desert) would surely turn out to be similarly great.
9 The consequences of the greenhouse effect will be far-reaching and possibly even devastation. If the projections of experts come to pass in the next 50 years, the earth's temperatures will rise between 3°and 9°F. (In polar regions the temperatures may rise as much as 20°F. After a look at the consequences we face as a result of the greenhouse effect, reforesting the earth doesn't seem as unusual as it might have at first. In fact, a program to plant billions of trees throughout the tropics now seems like a very sensible action.
10 Reforesting the earth is not the definitive solution to the warming trend of the greenhouse effect. It is only one way to bring the rising levels of carbon in the atmosphere under control. A worldwide campaign to reforest the earth, however, will improve the quality of our lives, stabilize rising temperatures, and buy time until we find additional solutions to the greenhouse effect.
New Words
reforest
v. to plant again with forest trees 再造林于，重新造林
drought
n. a long period of dry weather, when there is not enough water 干旱
drought-ridden
a. 受干旱困扰
tropical
a. 1. 热带的
2. very hot 酷热的
reforestation
n. 再造林
tropic
n. 1. 热带地区
2. （南或北）回归线
heal
v. to cause to become healthy 治愈
ailing
a. 1. 境况不佳的
2. 生病的，体衰的
metrica. concerning the system of measurement based on the metre and kilogram （采用）公制的，（采用）米制的
dioxide
n. 二氧化物
accumulate
v. to make or become greater in quantity 积聚，堆积
vegetation
n. 1. all the plants in a particular place 植被
2. plant life in general 植物的生长
release
v. to allow to come out; set free 释放，放出
emission
n. 1. the act of emitting 散发，发出
2. something which is emitted 散发物
approximate
a. nearly correct but not exact 大概的
approximately
ad. 大概地，约莫地
photosynthesis
n. 光合作用
moisture
n. 1. water, or other liquids, in small quantities or in the form of steam or mist 湿度，湿气
2. 降雨量
destruction
n. the act of destroying 破坏，毁坏
damage
n. harm, loss 损害，损失
v. to cause harm or loss to 损害，损失
plantation
n. an area of land planted with trees 种植园，种植场
atmospheric
a. of or concerning the earth's atmosphere 大气的，空气的
soak
v. 1. to draw in 吸取,摄取
2. to cause to remain in a liquid 浸湿
eliminate
v. to remove or get rid of 消除，排除
expanse
n. a wide space 广阔区域，大片地区
humid
a. (of air and weather) containing water 潮湿的，湿润的
shed
v. to cause to flow out 使流出
watershed
n. 1. （森林地带的）集水区
2. the high land separating river systems 分水岭
urgent
a. very important, esp. which must be dealt with quickly or first 紧迫的，紧急的
urgentlyad. 紧急地
erode
v. 1. to be or become worn or rubbed away 遭侵蚀，被腐蚀
2. to destroy or wear (sth.) away gradually 侵蚀，腐蚀
devastated
a. that has been devastated 遭破坏的
deforested
a. 被砍伐森林的
degenerate
v. to become worse in quality 衰退，变差
scrub
n. 低矮丛林，密灌丛
coarse
a. not fine, rough 粗的，粗糙的
timber
n. wood for building 木材，原木
threaten
v. 1. to give warning of (something bad) 构成威胁，预示
2. 威胁，恐吓
coastal
a. of or related to the coast 海岸的，近海岸的
irrigation
n. 灌溉
comparison
n. the act or the result of comparing 比较，对照
disrupted
a. that has been or is brought into disorder 被扰乱了的
lush
a. (of plants, esp. grass) growing very well, thickily, and healthily 繁茂的，葱郁的
far-reaching
a. having a wide influence or effect 广泛的，深远的
devastation
n. 破坏
projection
n. something planned, esp. a guess of future possibilities made on the base of experience （根据趋势所作的）预测，估计
polar
a. of, near, like, or coming from lands near the North or South Poles 极地的
definitive
a. that provides a last decision that cannot be questioned 决定性的，最后的
Phrases and Expressions
release from
从…释放出
soak up
吸收，摄取
(be) equivalent to
相当于，与…等同
cut down
砍下，削减，降低
in comparison
比较起来
come to pass
（事情）发生
as a result of
作为…的结果
bring...under control
使…得以控制
Proper Names
Brazilian Amazonia
巴西亚马逊河流域地区
Latin America
拉丁美洲
the Mississippi
密西西比河
Bangladesh
孟加拉国
the Sudan
苏丹
Thailand
泰国
the Environmental Protection Agency
（美国）环境保护局
the Department of Agriculture
（美国）农业部
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