研究生英语听说教程2

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Unit Three Endangered Species vs. Human Needs

Endangered Species vs. Human Needs

Preparing to Read 1. What knowledge do you have about some famous animals on the verge of extinction, as well as why they may soon be extinct? Take the following quiz. Choose the correct answer to each of the questions.

1) Who determines which species are considered endangered? A. WWF — The World Wildlife Fund. B. UN — The United Nations.

C. IUCN — International Union for the Conservation of Nature. 2) How many animal species are endangered worldwide? A. About 300. B. About 1,000. C. About 10,000.

3) What is the number one reason why plants and animals are becoming endangered? A. Habitat destruction. B. Predators (食肉动物). C. Poaching (偷猎). 4) How many species become extinct each day?

A. About thirty. B. About seventy. C. About one hundred. 5) How many pandas are left in the world?

A. About 1,600. B. About 2,500. C. About 3,400. 6) Why are pandas called living fossils? A. Because they are close to extinction. B. Because they are hard to preserve.

C. Because they have been around for 3 million years.

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新视角研究生英语 读说写 2 7) Why is the polar bear an endangered species?

A. People are hunting the bear illegally for its fur. B. Global warming is changing the bear’s habitat.

C. There is not enough fish to eat, because the fish is endangered, too. 8) What food does the oryx (大羚羊) mostly eat? A. Roots. B. Fruits. C. Grass. 9) Why are elephants endangered?

A. Reduced living areas. B. Ivory trade. C. Both.

10) How many South-China tigers are left in the wild?

A. Between 20 and 30. B. Between 100 and 200. C. More than 1,000.

11) By how much has the tiger’s habitat been reduced in the past 100 years? A. 50%. B. 75%. C. 95%.

12) Why is the rhinoceros (犀牛) an endangered species? A. Global warming.

B. Poaching and habitat loss. C. Draught.

13) Where do chimpanzees live?

A. Tropical Rainforest of Africa.

B. Tropical Rainforest of North America. C. Tropical Rainforest of South America. 14) Where do blue whales live?

A. In the cool waters of the Antarctica and South Pole. B. In the Artic regions, particularly, the Artic Circle. C. Near the equator.

15) When is the World Environmental Day? A. March 12. B. June 5. C. October 20.

2. Look at the following picture. Explain how a natural ecosystem works. An Ecosystem at Work 45

Unit Three Endangered Species vs. Human Needs

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Endangered Species vs. Human Needs

by Martha Grace Low

The rate of species dying out is increasing dramatically. It is estimated that 27,000

species become extinct each year, about 3 an hour. Since 1996, scientists calculated that 124 types of amphibians(两栖动物), 1,108 types of birds, 734 types of fish, 1,096 types of mammals, and 253 types of reptiles became endangered. These statistical figures also apply to plants. Once these species become extinct, they will never be seen on Earth again. What caused them to be endangered? Should human beings reflect on their actions? Could we do anything to benefit the future of humanity and all life on Earth? Read the following article taken from Martha Grace Low’s book Thresholds in

Reading published by Heinle & Heinle Publishers and find the answers to these questions.

The most famous endangered species on earth were the dinosaurs. They

died out in one of five “great extinctions” that have occurred in the millions of years since life began on this planet — periods in which, for natural causes, a large percentage of the species that existed simply disappeared. We are now in the middle of a sixth great extinction, but this one has been caused by human activity. Consequently, the importance of preserving species is a popular topic today, particularly in the industrialized world.

But no discussion of endangered species is complete without an

examination of the reasons behind its causes, which are human needs. In

Africa, where the world’s population is growing the fastest, forests are shrinking as people clear lands for homes and farms and cut wood for fuel. Herds of

goats and sheep eat the vegetation, leaving the bare soil to be carried away by wind and water. Humans kill wildlife to protect their crops, and may also kill them for the illegal trade in ivory, rhinoceros horns, furs. In Latin America and Southeast Asia, rainforests are cleared for farmlands and for fuel and timber. The loss of the forest endangers many species of plants and destroys many

animals’ habitats, or natural homes. And in the oceans, fish supplies have been greatly reduced by overfishing and by pollution.

Humans want to survive just as every other species does. We need food,

shelter, and a place to rear our young. So how do our activities endanger other species? Specifically, there are three major ways. We kill off animals directly

in some cases. We may want their meat, bones, skins, tusks, horns, or feathers; or we may want to protect our crops and livestock from them. By overhunting, Euro-Americans endangered the buffalo in North America, and in the

nineteenth century hunters drove to extinction the passenger pigeon1, which

1 passenger pigeon: once the most abundant bird in the early part of the 19th century, lived in huge flocks in eastern North

America. It became extinct when the last known representative of the species — named Martha — died in the Cincinnati Zoo on September 1, 1914. 旅鸽

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新视角研究生英语 读说写 2 6 7 8

was probably the most populous bird species that have ever lived.

Another way that we endanger native life-forms is by introducing foreign species into their habitat. A prime example of this was the introduction of European rabbits into Australia, where they multiplied until they endangered the native species of grazing animals by eating all the vegetation. This became a terrible problem that has finally been brought under some control, though not completely solved.

The most common way that we endanger other species is by destroying

their natural habitats. We do this when we cut down forests, clear land for crops, build towns, dam rivers, drain swamplands of water and then fill them

with dirt for construction, and when we pollute the air, the water, the soil. Most species are habitat-specific; that is, they depend on the particular offerings of a specific environment, and they cannot simply move to the next province or

state and adapt as we can. The greatest diversity of life-forms on our planet are found in the tropical rainforests, yet they are disappearing faster than any other habitat — at the rate of about 50 million acres (20 million hectares) per year. The loss of the rainforest would mean the loss of most of the species that make their homes in them.

But so what? The majority of the animal species on earth are insects and worms anyway, and how important are they to us? And tiny populations of

tropical plants — the world is covered with vegetation, so what difference does it make, how many kinds there are?

Many people’s answer is that every life-form has a right to exist, and that no other reason is needed for preserving it. A more common reason is the beauty of many species. Certain species also provide humans with economic

value. But scientists identify two additional reasons which may not be obvious to most of us.

One of these reasons is that each life-form occupies a special place within its ecosystem — that is, its community of plant and animal life, in combination with the nonliving components of its environment such as the climate, soil, water, and

air. For instance, within a forest the larger trees drop off little twigs and debris, making a layer that holds water in the soil for other plants to use. The roots hold the soil and prevent it from washing away in rainstorms. Whether living or dead, the tree provides shelter for animals and birds and food for insects. As the dead tree rots away, it enriches the soil of the forest floor, enabling other plants to spring up in its place. Such large trees are an example of what we call keystone species2; if they disappeared from their ecosystem, the consequences would be

felt throughout the community of other species living in the forest. “The loss of a keystone species is like a drill accidentally striking a powerline,” says biologist Edward Wilson of Harvard University3. “It causes lights to go out all over.” During the current sixth great extinction, three species of life-forms are dying out every

5

2 keystone species: a species whose presence impacts many other members of the ecosystem 关键物种 3 Harvard University: oldest institution of higher learning in the United States and widely considered one of the most prestigious.

Founded in 1636 in Cambridge, Mass., it was named Harvard College for a Puritan minister, John Harvard (1607–1638), who

bequeathed to the school his books and half of his estate. 哈佛大学 4

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Unit Three Endangered Species vs. Human Needs

hour, or 74 per day, which equals 27,000 each year. Some of these — and we don’ t even know which ones — are undoubtedly keystone species.

Natural ecosystems are characterized by their biodiversity, which means

that a good variety of plant and animal life are present there. In many parts of today’s world, humans have replaced naturally diverse environments with monocultures, in which only one species lives — one that we humans value. A prime example in forested regions of the world is the monocultural “tree

farms” that have been planted after the original forests have been cut down. The character of these tree farms is very different from that of the original forests. In the case of forests, another extremely important reason for preserving

species is illustrated by the Pacific yew tree4, which people used to cut down and never replant because they thought it had no particular value. But recently medical researches discovered that a substance called taxol, produced naturally in the bark of this tree, is an effective medication for treating certain kinds of cancer. Suddenly harvesters began flocking to the forests of the North American

Pacific Northwest5 in search of this tree. If it had become extinct before its value had been discovered, many cancer patients would have died needlessly.

Now, consider for a moment that there are around 1.6 million species that

we have identified on earth (plus uncounted others that we haven’t identified), and most of them have never been studied to see whether they might be able to provide us with food or medicine. About 15 percent of all our medicines are derived from tropical plants, but we have been able to test only about 10 percent of the plants that we know about, and have intensively studied less

than 1 percent. Of the 74 species dying out each day, many of them are tropical plants from the rainforests. In most cases, we don’t even know the value of what we are losing.

If we turn from medicines to food sources, we find that over 50 percent of

today’s global food supply consists of just three grains — wheat, rice, and corn. If climatic changes or a plant disease suddenly threatened one of these grains, many people would starve unless we could find another species to strengthen or replace it. It is dangerous to be so dependent on such a small number of species. We need to preserve a wider variety of food species.

Finally, a very important reason for preserving forestland is that plants produce the oxygen that animals (like us) breathe, and forests produce more of the world’s oxygen than any other environment. Forests also make the air more humid, producing rain; and the loss of forests leads to the process of

desertification — the creation of deserts where little will grow. Many methods of protecting endangered species are being practiced in

different parts of the globe. Legislation is a common method: passing laws

against killing endangered species or destroying their habitat. Worldwide, over 1,200 parks and preserves have been set aside in which wildlife are protected. And certain endangered species are being raised in captivity for later release

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4 the Pacific yew tree: found in the ancient forests of the Pacific Northwest 太平洋紫杉

5 the North American Pacific Northwest: a 400 mile corridor with eight million residents stretches from Eugene, Oregon, through

Seattle, Washington to Vancouver, B.C., Canada 9

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新视角研究生英语 读说写 2 into their wild habitats.

An organization called the World Wildlife Fund6 recommends nine different methods that can be effective in protecting endangered species. They are: 1) Protect habitat

2) Protect individual species

3) Promote ecologically sound development 4) Support scientific investigation 5) Educate the public

6) Train local wildlife professionals

7) Encourage countries to design, fund, and carry out effective conservation activities

8) Monitor the international wildlife trade

9) Influence public opinion and the policies of governments and private institutions.

Only time will tell how effective these attempts will be in slowing the

speed of the current great extinction. And the most important factor in this controversy is the demands of a growing human population for natural resources and living space to serve its own needs.

endanger /In9deIndZ5(r)/ v. cause danger to sb/sth, put in danger 危害，使遭到危险 dinosaur /9daIn5sO:(r)/ n. 恐龙

extinction /Ik9stIOEkSFn/ n. death or destruction of all members 灭绝

preserve /prI9z?:v/ v. keep or maintain sth in an unchanged or perfect condition 保护 n. a place where game or fish is protected and kept for private hunting or shooting 专供私人行猎或捕鱼的保护区

vegetation /8vedZI9teISFn/ n. plants in general 植物 (总称) ivory /9aIvFrI/ n. 象牙

rhinoceros /raI9nás5r5s/ n. 犀牛

rainforest /9reIn9fO:rIst/ n. thick evergreen forest in tropical regions with heavy rainfall 雨林 (热

带地区多雨的茂密常绿森林)

habitat /9h{bIt{t/ n. natural environment of an animal or a plant (动物或植物的) 自然环 境；栖息地

tusk /t?sk/ n. (象、海象、野猪等的) 长牙

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