Exhaustion of Natural Resources (complete information)

Utilization of natural resources has enormous impact on environmental quality in several ways. Overfishing, overgrazing, and overlumbering, for example, have often so severely depleted natural populations that they can no longer serve as sources of fish, forage, or wood.

Moreover, depletion of their populations lessens the ability of natural ecosystems to recycle air and water and thus purify them of toxic wastes. The use of mineral resources can also adversely affect environmental quality, not only during mining and processing, but also is the use of the products derived from them.

For example, discarded mine residues, or tailings, often produce acid runoffs that poison lakes and streams; offshore oil well blowouts and tanker wrecks pollute the sea; and processing plants produce toxic wastes that contaminate water supplies.

As deposits of a particular mineral become depleted, new technologies for extracting the mineral from lower-grade ores have often proved to be more polluting than traditional methods. The use of manufactured products, such as insecticides and fuels, also often pollutes air, soil, and water. Unfortunately, examples of the adverse effects of resource utilization on ecosystems are numerous.

Fossils Fuels

Coal, natural gas and crude oil, or petroleum, the major fossil fuels, are all derived from organic matter. Most coal was formed during the Pennsylvanian period, 320 to 280 million years ago, from buried vegetation of the great club moss and free fem swamps of that time.

Petroleum is apparently composed of the decomposition products of marine phyto-and zooplankton trapped in the bottom muds of inland seas. Because of their porosity, sandstone and limestone sedimentary rocks are the principal reservoirs of petroleum.

Coal

Following World War II, consumption of coal, once the most widely used fossil fuel, dropped to second and then third place among fossil fuels in many industrialized countries as oil and then natural gas became more readily available.

As oil and gas reseves decline, many expect coal to again become the predominant fuel of industrialized nations. Mining and use of coal, however, have usually extracted a high cost in air and water pollution-including that by acid rain-and landscape destruction by strip mining (open pit mining) and similar practices, in addition to the diseases and accidents associated with mining.

Crude Oil

While the United States has enough coal for several hundred years of expanded energy use, like most oil-producing countries, it is rapidly depleting its crude oil reserves.

Although it is the world’s third largest producer of oil, the United States is estimated to have only about a 20-year supply of readily extractable oil. The world’s known reseves of crude oil are expected to be depleted by the year 2010. Because the world has come to depend so heavily on crude oil, not only for fuel but for such products as lubricants, fertilizers, and plastics, we have become especially conscious of these dwindling petroleum reserves. New interest has also developed in synthetic fuels, or synfuels, such as gasified coal, coal which has been covered to methane or other fuel.

Oil Sand and Oil Shale

Very large deposits of oil sands exist in Canada and some western areas of the United States. Becuase crude oil is less expensive to obtain and process than oil extracted from sands, this resources has not yet been exploited.

Oil shale is a solid that, theoretically, can be profitably processed to separate its gas, oil, and various other fractions, such as sulphur, Oil shale deposits in the United States are 20 times larger than the country’s reserves of oil sands. Despite continuing efforts, however, no satisfactory process has yet been developed to extract shale oil economically.

Environmental problems are also involved, the most serious of which is the possibility that the well water and rivers of several western states would be poisoned by by-products of the extraction process. The use of oil and its products as fuel, especially types containing a substantial amount of sulphur, contributes greatly to air and water pollution.

Uranium

Supplies of uranium ore, upon which the operation of conventional nuclear power plants depends, are severely limited. Conventional reactors, as opposed to breeder or fusion reactors, use uranium-235 (²³⁵U) as fuel. However, the most abundant form of uranium in most uranium ores is uranium-238 (²³⁸U). Uranium-235 makes up only 0.7 per cent of the ore’s uranium fraction.

This means that uranium ore must be enriched, or processed to increase its proportion of ^Z35U to a level at which it can sustain a chain reaction and thus be used as reactor fuel.

At the originally intended rate of expansion of the United States nuclear power industry, severe shortages of domestic uranium ore would have occurred by 1990 or 1995 if reliance on conventional reactor continued; virtual exhaustion of ²³⁵U would have occurred by 2020.

The ²³⁵U ore reserves in the United States amount of only 1.5 million tons; with conventional reactors, by the year 2000, some 2.4 million tons would have been used. Without an eventual switch to breeder- reactor technology or an unlikely breakthrough in the perfection of fusion reactors, nuclear power in the United States was to have had a rather brief history. However, the discovery of several additional world deposits of uranium ore in the early 1980s has extended its life somewhat.

Uranium mining, processing, transport, and use all pose some risks of radioactive pollution of the environment. More serious, however, are the environmental hazards associated with the storage and reprocessing of high level radioactive wastes and the storage of the radioactive components of decommissioned nuclear power plants.

Other Minerals

The question of the adequacy of the world’s supply of mineral resources has long been controversial. Many of the minerals used in industry are nonrenewable or can be recycled only at great expense. The total reserves of many valuable minerals are largely unknown.

The difficulty of estimating mineral reserves is demonstrated by the fact that known reserves of several elements once thought to be inexhaustible were judged to be dwindling dangerously by the late 1960s and early 1970s. By the late 1970s, however, the discovery of several new sources and the development of new methods of ore extraction had radically improved the outlook for several of these elements.

For example, a new process for extracting iron from the ore taconite removed the looming threat of iron shortages in the United States. Also, rich sources of iron and nickel were discovered in the 1960s in Australia and more recently in Brazil. In addition, it was discovered that enormous quantities of manganese, copper, and other minerals are deposited as nodules on the sea floor. Given the present rates of consumption, these nodules contain enough copper to last 6,000 years, enough nicked to last 150,000 years, and enough manganese to last 400,000 years.

For the most part, we have mined the richest ores and are now extracting elements from lower-grade ores through the use of advanced technology.

However, such processes usually raise the cost of the elements, use more water and energy than do traditional methods, and increase rates of pollution. Furthermore, the discovery of new sources and the development of new extraction technologies cannot change the fact that the mineral reserves of our planet are finite.

One of the best ways to meet increased demands for many minerals, while taking into account their-limited supply, is by recycling.

This approach reduces pollution by removing discarded items from the environment and by lessening the need for, and the pollution resulting from, mining and processing ore. Although extracting metals from scrap generates its own pollution and requires considerable energy, the energy efficiency of recycling can be dramatic. For example, the production of aluminium from discarded cans saves up to 95 percent of the energy necessary to extract the same amount of aluminium from ore. Although iron extraction requires large amounts of energy, the production of steel from some scrap iron can save as much as 75 percent of the energy cost of extraction from iron ore. Another way to conserve resources, reduce energy use, and abate pollution is to produce goods that are durable or can be repaired.

Topsoil

It is easy to see why we should conserve short supplies of non­renewable resources. Yet slowly renewable resources need to be guarded just as closely.

Topsoil, for example, that upper portion of the soil from which the roots of food crops absorb their nutrients, is not only essential for growing such crops but tor maintaining natural communities.

It accumulates very slowly-in grasslands, at a rate of only a few inches per century. Without proper protection, however, a single strom can wash or blow away a layer of topsoil several inches deep. Most of this soil is then lost to lakes or oceans.

Topsoil Destruction. Although the loss of the earth’s topsoil is reaching crisis proportions in many parts of the world, it is by no means a modem problem.

From the first gathering of wild crops by primitive nomads, from the first tilling of the soil by ancient farmers, and from the first felling of trees for firewood and building materials, the soil has been abused. Whenever in human history slopes were overgrazed or stands of trees on hillsides were cut or burned away, rains soon began to wash the topsoil into the valley below.

In moderation, woodcutting and grazing need not destroy a forest or the watershed (drainage area) it covers. However, extensive clear- cutting, burning, and over grazing and any cutting of trees on sleep slopes are invariably destructive unless the slopes are replanted at once.

Denuded of trees, a hillside no longer retains rainwater, and lowland springs once fed by the rainwater that percolated through the soil of the forest cease to flow. Moreover, rivers dwindle to a trickle in dry seasons and become destructive, raging torrents that overrun their banks when it rains.

Modern day deforestation and overgrazing are producing a world­wide pattern of topsoil destruction similar to that which centuries ago occurred in most of the Mediterranean countries. Previously wooded, steep mountain slopes have been reduced to bare bedrock in large areas of Greece.

Turkey, North Africa, Spain, Italy, and Yugoslavia. The burgeoning population of Nepal, another example, has been forcing hungry peasants farther and farther up the slopes of the Himalayas in search of cropland. As firewood has become increasingly hard to find in Nepal, even newly planted trees are being used for fuel, as are grasses and other hillside plants.

Destructive landslides, as well as the silting and flooding of lowlands, have been increasing as a result. Thirty-eight per cent of the most densely populated areas of Nepal now consists of abandoned farmland that can no longer grow any crops-an astounding statistic. As wood supplies have declined, people have also begun a more extensive use of cattle dung for fuel. Although always used as fuel to some extent, during formetry was used mostly to fertilize farm soil and to improve its water and nutrient-holding capability.

Similar patterns of soil destruction exist on mountainous slopes elsewhere in the world. In South America, the densest populations have always been in the highlands and plateaus of the Andes. It has always been possible to farm the steep Andean slopes as long as strict rules are observed.

Besides being terraced to control the runoff of rainwater, the land must be allowed to remain follow-that is, return to its natural condition-for 8 to 12 years or more between crops.

Only this extraordinary precaution enables the Andean soil to absorb enough water and its organic content to increase sufficiently so that food crops can be grown on it for a year or two before it is again allowed to lie fallow. When this practice is not observed, the soil’s structure deteriorates, and then water erosion takes a heavy toll.

In the hills of Peru and Columbia, for example, major landslides have become more frequent, floods have worsened, and massive amounts of silt have been carried down into the valleys. As slit fills the rivers, they overflow their banks or change their courses, usually with destructive results. Several multimillion-dollar dams built to produce electric power have become useless within only a few years because their reservoirs are filled with silt.

Topsoil Depletion in the United States. It is widely believed that North American learned long ago to control soil erosion and that the problem on longer exists in Canada and the United States.

Although the causes and means of controlling soil erosion are indeed known to scientists and government agencies, their well-established theories have proved difficult to put into practice.

Overgrazing. The allotment of more animals to a pasture than it can support results in overgrazing. Grass that is continually cropped very closely cannot survive dry periods, and eventually the soil becomes exposed to wind erosion. As a very general rule, it has proved best to remove no more than one-third of the edible productivity of a range in any one year. Such an approach actually improves the range and its cattle during years of adequate rainfall.

It also ensures a reserve of soil, root systems, and moisture that can save the range during drought years. Once extensive overgrazing has occurred in regions with low average rainfall, the transformation of fertile arable land into desert results. Over 10 percent of the world’s deserts have been created by human abuse of crop-and rangeland.

Wind and Water Erosion of Farm Soil. Loss of soil moisture can also be a serious problem for farms in grassland regions; moisture evaporates rapidly from bare soil, especially after it has been tilled.

Harvesting of crops always removes soil moisture. Only if native prairie grasses or other soil-building plants are allowed to grow during occasional fallow years will soil moisture be restored.

Even the best-managed farms, those ultilizing windbreaks of trees, contour cultivation, terracing, and winter crops to hold snow and retard wind erosion lose at least 1 percent of their topsoil each year. Thus, even well-managed farms that are kept in continuous cultivation can be ruined eventually; how soon this happens depends largely on the original depth of the natural topsoil.

Many United States farms are badly treated, despite such terrible experiences as the dust bowl of the 1930s. At the close of the 1970s, many agricultural and economic experts in the United States, responding to soaring wheat prices and a dwindling world food reserve, actually called for fence-to-fence planting of wheat.

While this practice may indeed feed the world’s hungry for a few years and even help control economic inflation, it will eventually produce even greater disasters. Resulting dust bowls could turn the Great Plains into a barren desert unsuitable even for light grazing.

The greatest threat to topsoil in the United States at present is water erosion in the com belt. Most severely affected are southern Iowa, northern Missouri, western Tennessee, western Texas, and the Mississippi basin. Most of the lost topsoil is entering the Mississippi River and being carried into the Gulf of Mexico at an average rate of 15 million tons a minute!

By 1977, about one-third of all land in the United States was being eroded at a rate that was noticeably reducing its productivity. In 1980 and 1981, an estimated 19.2 million hectares (48 million acres)- 10 percent of the total land area-were losing almost 6 tons of topsoil per hectare per year, each year’s loss representing 9 years’ accumulation under the best possible conditions. Much of this erosion is controllable and need not occur.