Английский язык

Of the 242,000 plant species surveyed by the World Conservation Union – IUCN in 1997, 14 percent, or some 33,000 are threatened with extinction. Some 7,000 are in immediate danger of extinction and another 8,000 are vulnerable to extinction. The principal cause of plant extinction is habitat destruction, often in the form of land clearing for agriculture and ranching, for housing construction, or for the drainage of wetlands for agriculture and construction. Large – scale species migration – propelled by growing trade – is compounding that threat, as is climate change, which could eliminate whole ecosystems in the decades ahead.

The status of animal species is equally worrisome. Of the 9,600 bird species that populate the Earth, two-thirds are now in decline, while 11 percent are threatened with extinction. A combination of habitat alteration and destruction, over – hunting, and the introduction of exotic species is primarily responsible. Of the Earth`s 4,400 species of mammals, of which we are but one, 11 percent are in danger of extinction. Another 14 percent are vulnerable to extinction if recent trends continue. Of the 24,000 species of fish that occupy the oceans and freshwater lakes and rivers, one-third are now threatened with extinction.

The globalization of recent decades is also reducing the diversity of life on Earth. Mushrooming trade and travel have broken down ecological barriers that existed for millions of years, allowing thousands of species – plants insects, and other creatures – to invade distant territories, often driving native species to extinction and disrupting essential ecological processes. Recent "bioinvasion" have forced the abandonment of more than one million hectares of cropland in South America and devastated the fisheries of East Africa`s Lake Victoria.

The presence of chemicals in the environment is affecting the prospects for some animal species as well. In 1962, biologist Rachel Carson warned in Silent Spring that the continuing use of DDT could threaten the survival of predatory bird`s, such as bald eagles and peregrine falcons, because of its effect on eggshell formation. More recently, there is growing concern that a family of synthetic chemicals associated with pesticides and plastics, so-called endocrine disrupters, could be affecting the reproductive process in some species of birds, fish, and amphibians.

The global atmosphere also faces growing stress. As our fossil – fuel – based global economy has expanded, carbon emissions have overwhelmed the capacity of natural systems to fix carbon dioxide. The result it a buildup in CO₂ from roughly 280 parts per million at the beginning of the industrial era to 363 parts per million in 1998, the highest level ever experienced. This buildup of CO₂ and other greenhouse gases is responsible for rising temperatures over the last century, according to leading scientists. The 14 warmest years since record – keeping began in 1866 have all occurred since 1998 is projected to be both the highest ever and the largest annual increase ever recorded.

If the world stays on the present fossil fuel path, atmospheric CO₂ concentrations are projected to reach twice pre – industrial levels as soon as 2050 – and to raise the Eart`s average temperature 1-3,5 degrees Celsius (2-6 degrees Fahrenheit) by 2100. This is expected to bring more extreme climate events, including more destructive storms and flooding, as well as melting ice caps and rising sea levels. A new computer simulation by Britain's Hadley Centre for Climate Change in late 1998 projected major reductions in food production in Africa and the United States as a result of climate change. The Hadley scientists also identify the potential for a «runaway» greenhouse effect after 2050 that could turn areas such as the Amazon and southern Europe into virtual deserts.

The global climate is an essential foundation of natural ecosystems and the entire human economy. If we are entering a new period of climate instability, the consequences could be serious indeed, affecting virtually all of Earth`s ecosystems, accelerating the pace of extinction, and leaving few areas of economic life untouched.

Even in a high – tech Information Age, human societies cannot continue to prosper while the natural world is progressively degraded. Our food crops and medicines are derived from wild plants, and even genetic engineering is based on rearranging the genes that nature has created. Moreover, our crops, industries, and cities require healthy ecosystems to store our water and to maintain a nurturing climate. Like the early residents of Easter Island, we are vulnerable. But them, we can see the problem coming.