Issue121 FLY AW作文组 第三周作业

澄～清UID: 2215483

I am deeply astonished by this assertion, angered by such irresponsible attitude towards the nature and ourselves, and strongly fear it becoming the prevailing opinion. Let us firstly browse some significant data obtained by scientist Edward O. Wilson, “the earth is losing approximately 27000 species per year, translating into astounding 3 species per hour”, which is widely accepted by most biologists. This extraordinary rate of extinction has ever occurred five times before in history of complex life on Earth, known as Mass extinction. The latest one, which occurred more than 65 million years ago, resulted in the demise of 76 percent of all species alive at that time, including the dinosaurs. Look to the past for guidance, if none of preserving actions are not being done now, we, the humans, are the next “dinosaur”.

We have to admit that the species extinction is a natural and ongoing phenomenon. The paleontologists believed that of the hundreds of millions of species that have lived on Earth over the past 3.8 billion years, more than 99 percent are already extinct. Some of this happens as the natural result of competition between species, known as natural selection. One by one extinct and new species appear almost at random as the geological past goes by. more important, the rate of this process is very slow, about five families of organisms per million years. However, today’s extinction, named as the sixth Mass Extinction by biologists, is at the alarming pace. Other five Mass Extinction, over the geological past, were caused by the catastrophic physical disasters, such as climate changes or meteorite impact. But this time, instead of the physical environment, the destroying force is humankind.

Since the invention of agriculture about 10,000 years ago, the human population has increased from approximately 5 million to a full 6 billion people. During that time, especially in the past several centuries, humans have radically transformed the face of planet Earth. We have cleared forests for lumber, pulp, and firewood. We have harvested the fish and shellfish of the world's largest lakes and oceans in volumes that make it impossible to recover fast enough to meet our need. We have run out of the grassland for flocks of sheep and cattle. Furthermore, we polluted this beautiful planet, from the peaks of mountains to the depths of deep-sea vents, from polar ice caps to tropical rain forest, human’s trail pervades all over the world. All these conversion of forests, grasslands, and wetlands for agricultural purposes, coupled with the pollutions and growth of urban centers and the building of dams and canals, highways, and railways, has physically altered ecosystems to the point that extinction of species has reached its current alarming pace. Our activities have greatly accelerated the extinction of species, even ourselves.

The first victim is the ecological diversity and balance of ecosystem. Healthy ecosystems are vital to life, and in turn, the health of ecosystems depend on the continued health and vitality of the individual organisms that composed them. Removing just one species from an ecosystem could damage, even destroy it. For instance, in the late 19th and early 20th centuries, sea otters were hunted to near extinction in many kelp forests off the coast of the Pacific Northwest of the United States and western Canada, causing the entire ecosystem to suffer. Otters eat sea urchins, and when the otters disappeared, the sea urchin population exploded and started to destroy the vast beds of kelp. Without the kelp, other species that lived in the ecosystem, including many species of fish and snails and other invertebrates, began to decline in number. Such subtle relationship between species is always difficult to explore, rendering the effect of species extinction unpredictable and far-reaching. Maybe one day, our offspring find it is our mistake that lead the ruin of human life.

Even if the condition is not as serious as extinction, the protection of biodiversity is still benefit human beings immensely. Scientists have discovered and named only 1.75 million species—less than 20 percent of those estimated to exist. Each of these organisms has unique attributes, some of which may hold the secrets to increase world food supplies, eradicating curing disease. A subspecies of the endangered chimpanzee, for example, has recently been identified as the probable origin of the human immunodeficiency virus, which causes acquired immunodeficiency syndrome (AIDS). But these animals are widely hunted in their west African habitat, and just as researchers learn of their significance to the AIDS epidemic, the animals face extinction. If they become extinct, they will take with them many of the secrets surrounding this devastating disease. Fortunately, these chimpanzee has been preserved, but other three species thoroughly disappeared while I finished this issue, and we even do not know who they are.

Facing with such tough facts, can we continually assert there is no justification for us to exert effort to save endangered species? If we are still indifferent to our friends—animals and plants, our nature, and our beautiful planet, probably, the next extinction one is ourselves.

flycc28UID: 2164453

UPUP~ 越看越像北美的范文...

感叹无限的思路^_^

honeyviolaUID: 2199703

内容挺翔实的，等喜看过后再改改