[素材库] [观点]是否有必要保护濒危物种 [复制链接]

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发表于 2004-4-2 12:15:53 |只看该作者 |倒序浏览

Since life began on this planet, countless creatures have come and gone rendered extinct by naturally changing physical and biological conditions.

If extinction is part of the natural order, and if many other species remain, some people ask: "Why save endangered species? What makes these animals and plants so special that money and effort should be spent to conserve them?"

Congress answered these questions in the preamble to the Endangered Species Act of 1973, stating that endangered species of fish, wildlife, and plants "are of aesthetic, ecological, educational, historical, recreational, and scientific value to the Nation and its people." In this statement, Congress was summarizing a number of convincing arguments made by scientists, conservationists, and others who are greatly concerned by the disappearance of unique creatures.
Unfortunately, we cannot attribute the accelerating decline of our wild animals and plants to "natural" processes. Biologists know that today's dangers to wildlife most often result from habitat degradation, environmental pollution, the introduction of exotic (non-native) organisms, and exploitation—all generally as a direct result of human activities.

Although conservation efforts have begun in recent years, mankind is still exterminating entire species at an ever-increasing rate. Since the Pilgrims landed at Plymouth Rock in 1620, more than 500 species, subspecies, and varieties of our nation's plants and animals have become extinct—lost forever. By contrast, during the 3,000 years of the Pleistocene Ice Age, all of North America lost only about three species every 100 years. The situation today is even worse in other parts of the world.

The Benefits of Natural Diversity
No creature exists in a vacuum. All living things are part of a complex, delicately balanced network called the biosphere. The earth's biosphere is composed of ecosystems, which include plants and animals and their physical environment. The removal of a single species within an ecosystem can set off a chain reaction affecting many other species. It has been estimated, for example, that a disappearing plant can take with it up to 30 other species, including insects, higher animals, and even other plants. The full significance of extinction is not always readily apparent; much remains to be learned, and the full long-term impacts are difficult to predict.

Contributions to Medicine
Each living thing contains a unique reservoir of genetic material that has evolved over eons of time. This material cannot be retrieved or duplicated if lost. So far, scientists have partially investigated only a small fraction of the world's species and have begun to unravel a few of their chemical secrets to determine, among other things, possible benefits to mankind. No matter how small or obscure a species, it could one day be of direct aid to all of us. It was "only" a fungus that gave us penicillin, and certain plants have yielded substances used in drugs to treat heart disease, cancer, and a variety of other illnesses. At least a quarter of all prescriptions written annually in the United States contain chemicals discovered in plants and animals. If these organisms had been destroyed before their chemistries were known, their secrets would have died with them.

Contributions to Agriculture
Many seemingly insignificant forms of life are beginning to show important utilitarian benefits in areas such as agriculture. Some farmers are beginning to use insects and other animals that compete with or prey on certain crop pests, as well as using plants containing natural-toxin compounds that repel harmful insects. These are called "biological controls," and in many cases they are a safe, effective, and less expensive alternative to synthetic chemicals.
Thomas Jefferson wrote that "the greatest service which can be rendered any country is to add a useful plant to its culture, especially a bread grain." It has been estimated that there are almost 80,000 species of edible plants, of which fewer than 20 produce 90 percent of the world's food. If underutilized species are conserved, they could help to feed growing populations. One grain native to the Great Lakes States, Indian wild rice, is superior in protein to most domesticated rice, and its increasing commercial production is earning millions of dollars annually. Crossing it with a related but endangered species, Texas wild rice, could perhaps result in a strain adaptable to other regions. Plant collectors are now seeking out remaining wild strains of many common crops, such as wheat and corn, for work on new hybrids more resistant to crop diseases, pests, and marginal climatic conditions.
Other Uses
Industry is also increasingly making use of wild plants. Two species in particular that show important potential are the jojoba and the guayule. The jojoba produces an oil with many unique properties that are suitable for a variety of industrial processes. In the past, the only comparable oil was derived from the sperm whale, but overharvesting brought this great marine mammal to the brink of extinction. The guayule is a shrub containing high amounts of natural rubber, as well as a resin rich in other valuable substances. Both plants grow in the deserts of the southwestern United States, giving economic value to lands not suitable for other agricultural purposes. Both could provide domestic sources of products that would otherwise have to be imported.
Environmental Monitors
Many individual species are uniquely important as indicators of environmental quality. The rapid decline in bald eagles and peregrine falcons was a dramatic warning of the dangers of DDT—a strong, once widely used pesticide that accumulates in body tissues. (Its effect on these birds was to hamper fertility and egg-hatching success.) In another example, certain plants, such as the eastern white pine, are good indicators of excess ozone, sulfur dioxide, and other air pollutants. Species like these can alert us to the effects of some contaminants before more damage is done.

Intrinsic Value
Aside from the more utilitarian reasons for preserving endangered species, many people believe that every creature, after adapting for thousands or even millions of years to fit a constantly changing environment, has an intrinsic value. Exterminating other forms of life is not only shortsighted, but wrong—especially since the species could never be replaced. Mankind would also lose; being accustomed to diversity in nature, the quality of human life would be diminished.
This text of this article was excerpted and adapted from the U.S. Department of the Interior brochure, "Why Save Endangered Species" and is not protected by copyrights belonging to the Alaska Department of Fish and Game.