4. Read the following texts to find answers to the questions which precede them:

Why is it vital to preserve rain forests, in the Amazon basin in particular?

Do Latin American countries share the international concern for the Amazon rain forest?

What is the extent of deforestation in the Amazon basin?

Why is the rain forest cut down?

What are the dangerous consequences of continuing deforestation?

International concern about the ecological consequences of continuing deforestation has been growing and was underscored by the United Nations Conference on the Environment and Development ("Earth Summit") held in Rio de Janeiro in 1992.

International calls for conservation of the Amazon basin, in particular, are based on the view that the Amazon basin is a global resource which serves as a control mechanism for the world's climate and as a genetic repository for the future.

The nations of the region, however, tend to look upon such calls as a challenge to "national sovereignty." The extent and rate of deforestation have been subject to continuing controversy. It has been suggested that by 1990 some 10 percent of the Amazon selva may have been cleared for pasture, crops, timber, and firewood. In Brazil deforestation was initiated in the 1960s and became widespread over the next two decades. The same process is going on in Colombia, Ecuador and in Peru. The cultivation of coca for illegal production of cocaine continues to stimulate such activities.

The consequences of continuing deforestation have been much discussed. Rain forests are efficient absorbers of carbon dioxide, besides, scientists believe that the volume of gas released when substantial parts of the forest are cleared and burned may contribute to global warming through the greenhouse effect. Continued conversion of tropical forest to cropland, pasture, or second-growth forest may interrupt the hydrologic cycle and the recycling of soil nutrients; a likely consequence is an increase in the amount of water running off the surface and greater extremes in water levels. The unique gene pool of the Amazon Rain Forest, with perhaps two-thirds of the known organisms of the world, is threatened by continuing deforestation. Particular emphasis has been placed on the threat to biodiversity and the possible loss of as yet unknown and unexploited pharmaceuticals contained in the forest. Finally, at stake is also the survival of many native peoples who, through long residence, have become integrated into the ecosystem of the rain forest and have learned some of its many secrets.

What prompted efforts to develop alternative energy sources?

Why is humanity interested in a more limited use of traditional sources of energy?

Which steps are taken to solve the energy supply problem?

Which factors limit the possible use of alternative energy sources?

Growing concern over the world's ever-increasing energy needs and the prospect of rapidly decreasing reserves of oil, natural gas, and uranium fuel have prompted efforts to develop alternative energy sources. Unreliability of the petroleum fuel supply was dramatically proved during the energy crisis of the 1970s caused by the abrupt reduction of oil shipments from the Middle East to many of the highly industrialized nations of the world. It also has been recognized that the heavy use of fossil fuels has had a disastrous impact on the environment.

Many countries have initiated programs to develop renewable energy technologies that would enable them to reduce fossil-fuel consumption. Fusion devices are believed to be the best long-term option, since their primary energy source would be the hydrogen isotope deuterium abundantly present in ordinary water. Other technologies that are being actively pursued are those designed to make wider and more efficient use of the energy in sunlight, wind, moving water, and terrestrial heat (i.e., geothermal energy). The amount of energy in such renewable and virtually pollution-free sources is large in relation to world energy needs, yet at the present time only a small portion of it can be converted to electric power at reasonable cost.

A variety of devices and systems has been created to better tap the energy in sunlight.

Sophisticated wind turbines have been developed to convert wind energy to electric power. The utilization of wind energy systems grew considerably during the 1980s. For example, more than 15,000 wind turbines are now in operation in Hawaii and California at specially selected sites.

Converting the energy in moving water to electricity has been a long-standing technology. Yet, hydroelectric power plants provide only about 2 percent of the world's energy requirements. Hydroelectric power plants generally require the building of costly dams. Another factor that limits any significant increase in hydroelectric power production is the scarcity of suitable sites for additional installations except in certain regions of the world.

Geothermal energy flows from the hot interior of the Earth to the surface in steam or hot water most often in areas of active volcanism. Geothermal reservoirs with temperatures of 180 C or higher are suitable for power generation. The earliest commercial geothermal power plant was built in 1904 in Larderello, Italy. Geothermal plants have been built in a number of other countries, including El Salvador, Japan, Mexico, New Zealand, and the United States.

What is the primary function of national parks?

What is the difference between a national park and a nature reserve?

How do national parks differ in different countries?

What policy is pursued by national parks as regards tourists?

The establishment of national parks in the United States represented one of the first national efforts to protect wild nature. Yet, in establishing Yellowstone National Park, Congress made clear that it was viewed as "a pleasuring ground" for people and not as an area intended only to safeguard communities of plants and animals. It was not until the formation of the U.S. National Park Service in 1916 that the concept of managing parks so as to maintain their natural qualities was accepted. Nevertheless, the practice of killing predatory animals as "undesirable" elements of wild nature continued in U.S. national parks into the 1930s and lasted in some African national parks as late as the 1960s.

Unlike a strict nature reserve, a national park may be made available for various purposes but usually only for those forms of recreational use that do not create great changes in the natural environment.

National parks usually are selected on the basis of their unique qualities, outstanding natural beauty, unusual geologic formations, or remarkable variety of wild animal or plant life.

In the United States, national parks are dedicated solely to recreational activity. National parks in England may protect cultural as well as natural landscapes, some may be dedicated to the preservation of traditional forms of land use that are disappearing elsewhere. Some national parks, such as in Peru, protect ethnic groups along with their hunting and gathering grounds.Thus, exactly what constitutes a national park varies according to the nations and people involved. The dedication of an area as a national park is everywhere a highly restrictive form of land use, in which all incompatible activities are prohibited. Hunting, logging, mining, commercial fishing, agriculture, and livestock grazing are excluded from most such parks, as are urban and industrial uses not directly related to recreation. There is much debate as to whether tourist facilities should be within or outside national parks. Because of their disruptive effects, the trend is to locate such facilities outside.National parks, at a minimum, require equally extensive boundary demarcation and perhaps policing and patrolling as are necessary for strict nature reserves. They also require the careful planning of trails, roads, and other means of human access. Not only must certain fragile areas be set aside and protected from visitors, but visitor use must be concentrated in those places in which human activities will do a minimum of harm. The trend has been to divide national parks into zones that range from areas of intensive public use to the remotest wilderness or strict nature reserves.

Usually a considerable amount of money and energy must be invested in the planning and management of a national park. This is often beyond the resources of the less developed countries unless international assistance can be provided. Because of their attraction as sites for outdoor recreation and their appeal to tourists, however, national parks often more than pay for themselves in a short period of time. In East Africa, for example, national parks are a major source of foreign exchange of the countries in which they are located because of their unique wild animal life.

Why does the Aral Sea attract ecologists' attention today?

Which causes have led to the remarkable shrinkage of the sea?

Why is the situation with the Aral Sea often called disastrous?

Are any steps taken to save the Aral Sea?

The shallow Aral Sea was formerly the world's fourth largest body of inland water. It lies in the climatically inhospitable heart of Central Asia, to the east of the Caspian Sea. The Aral Sea is of great interest and increasing concern to scientists because of the remarkable shrinkage of its area and volume in the second half of the 20th century. This change is due primarily to the diversion (for purposes of irrigation) of the waters of the Syr Darya and Amu Darya, which flow into the Aral Sea and are its main sources of inflowing water.

The most significant factors affecting the water balance of the Aral Sea are river flow and evaporation, which formerly took out each year about the same amount of water that the rivers brought in. Climate may quite considerably influence the long-term variation in the sea's water level.

In 1960 the surface of the Aral Sea lay 53 m above sea level and covered an area of 68,000 square km. Although the average depth was only about16 m, it descended to a maximum of 69 m off the western shore.

From about 1960 the Aral Sea's water level was systematically and drastically reduced because of the diversion of water from the Amu Darya and Syr Darya rivers for purposes of agricultural irrigation. As the Soviet government converted large acreages of pastures or untilled lands in Uzbekistan, Kazakstan, Turkmenistan, and elsewhere into irrigated farmlands by using the waters of the Amu Darya and Syr Darya, the amount of water from these rivers that reached the Aral Sea dropped accordingly. By the 1980s, during the summer months, the two great rivers virtually dried up before they reached the lake. The Aral Sea began to quickly shrink because of the evaporation of its now-unreplenished waters.By the late 1980s, the lake had lost more than half the volume of its water and had only slightly more than half its former depth. The salt and mineral content of the lake rose drastically because of this, making the water unfit for drinking purposes and killing off the once-abundant supplies of fish. The fishing industry along the Aral Sea was thus virtually destroyed. The ports of Aral in the northeast and Muynoq in the south were now many miles from the lake's shore. The drying up of the lake led to health problems as people in the region breathed toxic dust from fertilizer residue. The contraction of the Aral Sea also made the local climate noticeably harsher, with more extreme winter and summer temperatures.

By 1989 the Aral Sea had receded to form two separate parts, the "Greater Sea" in the south and the "Lesser Sea" in the north, each of which had a salinity almost triple that of the sea in the 1950s. By 1992 the total area of the two parts of the Aral Sea had been reduced to approximately 33,800 square km, and the surface level had dropped by about 15 m. However, plans were made to use less water-intensive agricultural practices in the regions south and east of the lake, thus freeing more of the waters of the Amu Darya and the Syr Darya to flow into the lake and to stabilize its water level. In 1994 Kazakstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan established a joint committee to coordinate efforts to save the Aral Sea and address the health problems of people living in its vicinity.