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CONSERVATION (Part 3 of 5)   Leave a comment

How Soil Conservation Works

Groups interested in improving farming practices have been around for many years. But the federal government did not get involved in soil conservation until the early 1930s.

Problems that occurred during the 1930s, such as the Dust Bowl, caused people to recognize the need for government leadership in the areas of soil conservation and farming.

  • Agricultural acts passed by lawmakers in 1929 and 1932 provided money to be used for erosion research.

  • In 1933, during the Great Depression, Congress passed a bill that would allow people without jobs to work in erosion control for the government. In this way, soil conservation could be put into practice and the unemployed would have work.

  • The Soil Erosion Service, later renamed the Soil Conservation Service, was created in 1935 as a result of this bill and has been responsible for managing conservation programs.

In 1933 the Soil Erosion Service (soon renamed the Soil Conservation Service) was created as a major division of the United States Department of Agriculture. The Soil Conservation Service has devised a land classification system that offers guidance in the proper use of land. Such factors as slope, type of soil, amount of rainfall, humidity, and vegetation type are considered when determining land use for maximum productivity. Of the eight government-designated land classifications, classes I, II, III, and IV may be used for cultivated crops; however, classes III and IV require skilful management to avoid serious erosion. Classes V through VII can be used for forests and for grazing. Class VIII land, which includes sandy shores and extremely rocky places, is considered suitable only for wildlife or for scenic and recreational purposes.

Covering the ground with plants is one of the key elements in soil conservation. To prove this, the Department of Agriculture experimented with two steep plots of adjacent land one planted with crops and the other thickly covered with grass. The cultivated plot lost 7 inches (18 centimetres) of topsoil in 11 years. By contrast, it was estimated that it would take 34,000 years to lose the same amount of topsoil from the grass-covered plot.

Plant cover tends to hold rainwater where it falls and thus prevents the soil from blowing or washing away. Gullies can be healed in many cases by planting new plants. They provide a tangle of leaves and stems that trap and hold in place part of the soil carried by run-off Another way to heal gullies is to build brush dams across them at regular intervals. Then soil and water running down the gully are caught behind the dams and held in place.

To help prevent the start of erosion, farmers may use a variety of conservation measures:

Contouring. This practice involves ploughing, planting, and cultivating sloping fields around hillsides, with curving furrows horizontal to the hill, instead of furrows running straight uphill and downhill. The curved furrows catch rainfall and allow much of it to soak into the ground. They also catch soil washing down from higher levels.

Strip-cropping. Strips of close-growing plants, such as grasses or clover, are alternated between strips of clean-tilled row crops, such as corn and soy beans The strips of close-growing plants hold water and keep it from eroding the cultivated strip below. These strips are planted on the contour.

Terrace, in geology, stretch of elevated, level land along banks of a river, lake, or ocean; frequently occur in series, one rising above the other; artificial terraces are used effectively in landscape gardening and in agriculture to hold moisture and prevent erosion.

Terracing. On long slopes a low ridge, or terrace, thrown along the outer side of the slope catches soil and rainwater and retards run-off Encouraging plant growth on a terrace will help hold soil.

Listing. In dry regions a Lister plough can be used to throw a ridge of dirt to each side, creating a trough about 18 inches (46 centimetres) wide and 7 inches deep. Crops are planted in the bottom of the trough.

Shelter belts On treeless plains, belts of trees planted at the edges of fields break the force of winds across the fields and reduce wind erosion.

Deep tillage (also called stubble mulching, or primary tillage), method of ploughing to conserve the land.

Deep tillage,stubble mulching. Instead of turning over the soil with a mouldboard plough, a deep-tillage plough breaks the soil below the surface. It leaves the surface vegetation or harvest remains from the previous crop to act as a cover.

Different crops need different substances, called nutrients, to enable them to grow.

Crops get these needed nutrients from the soil. If the same crop is grown in the same field every year, the soil will soon lose nutrients needed by that crop.

Crop rotation is the practice of planting different crops in a field each year or every few years.

With careful planning, crops can be rotated in a way that builds up nutrients in the soil for the next crop. Here’s an example:

Many crops need nitrogen to grow, and they take it from the soil. Other plants, like legumes, take nitrogen out of the air and put it back into the soil. By rotating legumes with other crops, the nitrogen in the soil can be replaced.

Crop rotation. Planting different crops each year on a piece of land keeps the soil productive. One crop can benefit the next. For example, nitrogen is essential for plant growth and is added to the soil by legumes, such as clover, alfalfa, soy beans, and cow peas These combine nitrogen from the air with other elements and store it in the soil through their roots. In a year or two the plants can be ploughed under. This is called green manuring.

After the roots have rotted, other plants that need nitrogen but cannot use nitrogen in the air for example, corn and potatoes can use the stored nitrogen for growth. Rotations are programmed with strip-cropping by shifting the close-growing strips and the tilled strips at fixed intervals.

Water can be polluted by many things. One of these is the topsoil or silt that washes into streams and rivers. This silt washes into streams and rivers from land that has been badly managed.

When silt washes into streams and rivers, two harmful things may happen.

1) Silt that floats in the water limits the amount of air in the water. Fish need air to breathe. When silt limits the air in the water, the fish die.

2) As the movement of water slows down, silt drops to the bottom of the stream beds

There are ways of controlling erosion of silt from land into streams and reservoirs. Conservationists try to make sure that the right steps are taken to prevent the silting of streams.

Cover crops. Land is kept covered in winter and summer with either a growing crop or the residue, such as corn stalks, from the crop previously grown. When cover crops are ploughed under for green manuring, the plant foods added to the soil improve its water-holding capacity and increase its fertility.

Fertilization. Chemical or natural fertilizers replace the soil substances used up by crops.

Erosion on Urban Land

Crop land is not the only soil subject to erosion. The land on which housing and other urban projects are built is particularly susceptible because its protective cover is generally removed.

Mulch, material such as manure, leaves, pulverized earth, placed on surface of soil to retain moisture and to protect plant roots from frost.

To prevent erosion on construction sites, builders should take corrective action. For example, mulches placed on steeply excavated slopes usually prevent soil from washing or blowing away. Straw or fibre netting may be used as mulches. On sites where erosion control is more difficult, hydro seeding can be used. Grass seed, fertilizer, and mulch are power-sprayed on excavated slopes. The quick-growing grass then stabilizes the soil against erosion.


The preservation of wildlife greatly depends upon water and soil conservation. All native plants and animals constitute the wildlife of a region and are a product of the land resources and habitat conditions. But, like humans, wild animals must have food, water, and shelter. Destroying the forests, marshes, ponds, and grasslands destroys their food and water supplies and the places in which they live.

1872: Yellowstone National Park. Although the concept of national parks was first suggested in 1832 by American artist George Catlin, it was not until March 1, 1872, that the first national park in the United States was established by Congress. Yellowstone Park was the beginning of a large system of 49 parks that today can be found in nearly all parts of the country. These parks, as well as other monuments, are managed by the National Park Service.

Once Yellowstone was opened, other countries began setting aside nature preserves similar to America’s national parks. Canada, for example, established a 10-square-mile area of hot springs at Banff, Alberta, in 1885 as a national park. Today there are national parks on all continents, except Antarctica.

Yellowstone is located in parts of three states: north-western Wyoming, southern Montana, and eastern Idaho; it covers 2,219,823 acres (898,329 hectares). Several sub ranges of the Rocky Mountains are in or around the park’s borders: the Snow Mountains, the Gallatin Range, the Absaroka Range, and the Tetons. Several national forests surround Yellowstone. The Grand Canyon of the Yellowstone River is a 19-mile gorge running through the park. Among Yellowstone’s other distinctive features are 10,000 hot springs, including 200 geysers, many of which erupt to heights of 100 feet (30 meters). The most famous geyser is Old Faithful, named for the regularity of its eruptions.

The park is heavily forested, and in 1988 a series of disastrous fires destroyed much of its vegetation and animal life.

Of the original native wildlife of the United States many species are now extinct. These include the passenger pigeon, the Carolina parakeet, the great auk, the Labrador duck, the Pallas cormorant, the dusky seaside sparrow, and the heath hen. Mammals gone forever include the Eastern elk, the Plains wolf, the sea mink, and the Bad Lands bighorn. Many smaller birds and mammals have also become extinct in the wild. Populations of the ivory-billed woodpecker and the California condor no longer exist in the wild in the United States.

The number of moose, caribou, wild sheep and goats, and grizzly and Alaska brown bears grows smaller every year. Much wildlife is now protected by law from over hunting and overfishing. However, if habitat destruction of their natural homes continues, many will be unable to survive.

The United States Fish and Wildlife Service maintains a list of endangered and threatened species of the United States. Environmental concerns for a variety of reptiles, amphibians, small fishes, insects, and molluscs is reflected in the number of species classed as threatened or endangered.

The Endangered Species Act has been effective for preserving some species that seemed destined for extinction. For example, the American alligator had been reduced to a relatively small number by the early 1960s due to illegal hunting for hides and meat. After 20 years of protection, the species recovered to such a large extent in many parts of its range that it led to a relaxation of the laws in the 1980s so that limited hunting was permitted.

Many events can cause a species of animal to become endangered. For example, some animals are killed because people want trophies or desire to wear clothing made from furs and skins.

However, the main reason many creatures have become endangered is because humans are destroying their habitats. Two such habitats are the Florida Everglades and the rain forests of Brazil. Too often, places that are attractive to animals are just as attractive to people, who want to build various facilities.

Unfortunately, nothing can bring back a species that has been lost. Such extinct creatures will only be seen in museums or pictures.

Worldwide, the International Union for Conservation of Nature and Natural Resources keeps track of species threatened with extinction. Endangered species include many of the world’s great cats, whales, certain species of rhinoceros, tapirs, and many other mammals, birds, and reptiles. Housing and other facilities needed by an expanding human population are encroaching on their habitats.

Many species are the victims of the illegal pet trade and of the trade in exotic pelts and skins; the increasing availability of guns and poisons is responsible for the extermination of other species. The African elephant, once common throughout the sub-Saharan region of the African continent, has been greatly reduced in numbers due to illegal poaching for the ivory trade.

Posted 2011/12/21 by Stelios in Education

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ENVIRONMENTAL POLLUTION (Part 1 of 2).   Leave a comment


Industrial Pollution

Efforts to improve the standard of living for humans through the control of nature and the development of new products have also resulted in the pollution, or contamination, of the environment. Much of the world’s air, water, and land is now partially poisoned by chemical wastes. Some places have become uninhabitable. This pollution exposes people all around the globe to new risks from disease. Many species of plants and animals have become endangered or are now extinct. As a result of these developments, governments have passed laws to limit or reverse the threat of environmental pollution.

All living things exert some pressure on the environment. Predatory animals, for example, reduce the population of their prey, and animal herds may trample vast stretches of prairie or tundra. The weather could be said to cause pollution when a hurricane deposits tons of silt from flooded rivers into an estuary or bay. These are temporary dislocations that nature balances and accommodates to. Modern economic development, however, sometimes disrupts nature’s delicate balance. The extent of environmental pollution caused by humans is already so great that some scientists question whether the Earth can continue to support life unless immediate corrective action is taken.

Ecology and Environmental Deterioration

The branch of science that deals with how living things, including humans, are related to their surroundings is called ecology. The Earth supports some 5 million species of plants, animals, and micro-organisms These interact and influence their surroundings, forming a vast network of interrelated environmental systems called ecosystems. The Arctic tundra is an ecosystem and so is a Brazilian rain forest. The islands of Hawaii are a relatively isolated ecosystem. If left undisturbed, natural environmental systems tend to achieve balance or stability among the various species of plants and animals. Complex ecosystems are able to compensate for changes caused by weather or intrusions from migrating animals and are therefore usually said to be more stable than simple ecosystems. A field of corn has only one dominant species, the corn plant, and is a very simple ecosystem. It is easily destroyed by drought, insects, disease, or overuse. A forest may remain relatively unchanged by weather that would destroy a nearby field of corn, because the forest is characterized by greater diversity of plants and animals. Its complexity gives it stability.

Every environmental system has a carrying capacity for an optimum, or most desirable, population of any particular species within it. Sudden changes in the relative population of a particular species can begin a kind of chain reaction among other elements of the ecosystem. For example, eliminating a species of insect by using massive quantities of a chemical pesticide also may eliminate a bird species that depends upon the insect as a source of food.

Such human activities have caused the extinction of a number of plant and animal species. For example, over hunting caused the extinction of the passenger pigeon. The last known survivor of the species died at the Cincinnati Zoo in 1914. Less than a century earlier, the passenger pigeon population had totalled at least 3 billion. Excessive hunting or infringement upon natural habitats is endangering many other species. The great whales and the California condor are among the endangered.

Population Growth and Environmental Abuse

The reduction of the Earth’s resources has been closely linked to the rise in human population. For many thousands of years people lived in relative harmony with their surroundings. Population sizes were small, and life-supporting tools were simple. Most of the energy needed for work was provided by the worker and animals. Since about 1650, however, the human population has increased dramatically. The problems of overcrowding multiply as an ever-increasing number of people are added to the world’s population each year.

The rate of growth of the world’s population has finally begun to slow, after reaching an all-time high of about 2 percent in 1970. In 1987 there were 5 billion people on the planet. The United Nations predicts the population growth rate will decline to 1.5 percent by the year 2000. Even so, there will be 6.1 billion people living on Earth at the beginning of the 21st century twice the number of people living on Earth in 1960.

The booming human population is concentrated more and more in large urban areas. Many cities now have millions of inhabitants. In less developed countries of Asia, Africa, and Latin America, many of these cities are overpopulated because of an influx of people who have left rural homes in search of food, shelter, and employment. Some farmers have been forced off their land by drought and famine.

Environmental pollution has existed since people began to congregate in towns and cities. Ancient Athenians removed their refuse to dumps outside the main part of the city. The Romans dug trenches outside the city to hold garbage and wastes (including human corpses), a practice which may have contributed to outbreaks of viral diseases.

The ancient Romans may have been among the first people to experience the effects of toxic pollution in the form of lead poisoning. Like many other minerals and metals, lead can enter the body with food or drink or may be inhaled with particles of dust. The accumulation of lead in the blood and other tissues can cause severe illness or, in large quantities, death. The Romans used lead to line the inside of bowls and pitchers. It was also used for plates, cups, and spoons. In some areas, it was used in plumbing systems. Some historians believe that the long-term exposure to lead was a major health risk for the Romans.

The adverse effects of pollution became more noticeable as cities grew during the Middle Ages. In Europe, medieval cities passed ordinances against throwing garbage into the streets and canals, but those laws were largely ignored. In 16th-century England, efforts were made to curb the use of coal in order to reduce the amount of smoke in the air again with little effect.

In the 19th century, the Industrial Revolution placed greater pressures on the environment, and pollution changed and increased dramatically. Although industrial development improved the standard of living, there was a great environmental cost.

Air Pollution

Factories and transportation depend on huge amounts of fuel billions of tons of coal and oil are consumed around the world every year. When these fuels burn they introduce smoke and other, less visible, by-products into the atmosphere. Although wind and rain occasionally wash away the smoke given off by power plants and auto mobiles, the cumulative effect of air pollution poses a grave threat to humans and the environment.

Smog, combination of fog and smoke; common in industrial areas.

In many places smoke from factories and cars combines with naturally occurring fog to form smog. For centuries, London, England, has been subjected to the danger of smog, long recognized as a potential cause of death, especially for elderly persons and those with severe respiratory ailments. Air pollution in London originally resulted from large-scale use of heating fuels.

A widespread awareness of air pollution dates from about 1950. It was initially associated with the Los Angeles area. The Los Angeles Basin is ringed for the most part by high mountains. As air sinks from these mountains it is heated until it accumulates as a warm layer that rises above the cooler air from the Pacific Ocean. This results in a temperature inversion, with the heavier cool air confined to the surface. Pollutants also become trapped at surface levels. Because of air-circulation patterns in the Los Angeles Basin, polluted air merely moves from one part of the basin to another part.

Scientists believe that all cities with populations exceeding 50,000 have some degree of air pollution. Burning garbage in open dumps causes air pollution. Other sources include emissions of sulphur dioxide and other noxious gases by electric power plants that burn high-sulphur coal or oil. Industrial boilers at factories also send large quantities of smoke into the air. The process of making steel and plastic generates large amounts of smoke containing metal dust or microscopic particles of complex and sometimes even deadly chemicals.

The single major cause of air pollution is the internal-combustion engine of auto mobiles Gasoline is never completely burned in the engine of a car, just as coal is never completely burned in the furnace of a steel mill. Once they are released into the air, the products of incomplete combustion particulate matter (soot, ash, and other solids), unburned hydrocarbons, carbon monoxide, sulphur dioxide, various nitrogen oxides, ozone, and lead undergo a series of chemical reactions in the presence of sunlight. The result is the dense haze characteristic of smog. Smog may appear brownish in colour when it contains high concentrations of nitrogen dioxide, or it may look blue-grey when it contains large amounts of ozone. In either case, prolonged exposure will damage lung tissue.

The costs of air pollution are enormous. The American Lung Association sites sulphur-dioxide exposure as the third leading cause of lung disease after active and passive smoking. Contaminants in the air also have been implicated in the rising incidence of asthma, bronchitis, and emphysema, a serious and debilitating disease of the lung’s air sac.

pH, quantitative measure of the acidity or basicity of liquid solutions.

In the mid-1970s, people became aware of the phenomenon called acid rain. When sulphur dioxide emissions from electric power plants combine with particles of water in the atmosphere, they fall to ground as acid rain or snow. The acidity or basicity of liquids, including rainfall and snow, is measured by a special scale, called the pH scale. Developed in 1909 by the Danish biochemist S.P.L. Sorensen, the pH scale is used to describe the concentration of electrically charged hydrogen atoms in a water solution. A pH of 7.0 means that the solution is neutral. A pH above 7.0 means the solution is basic; below 7.0 means the solution is acidic. Normal rainwater has a pH of 5.5. The National Center for Atmospheric Research has recorded storms in the north-eastern United States with a pH of 2.1, which is the acidity of lemon juice or vinegar. In Canada, Scandinavia, and the north-eastern United States, acid rain is blamed for the deaths of thousands of lakes and streams. These lakes have absorbed so much acid rain that they can no longer support the algae, plankton, and other aquatic life that provide food and nutrients for fish. Acid rain also damages buildings and monuments. Scientists are concerned that the deaths of thousands of trees in the forests of Europe, Canada, and the United States may be the result of acid rain.

Freon (CFC, or chlorofluorocarbon), various chemical compounds used as refrigerants.

Another new and troubling form of air pollution comes from a variety of chemicals called chlorofluorocarbons, also known as CFCs. These chemicals are used for many industrial purposes, ranging from solvents used to clean computer chips to the refrigerant gases found in air conditioners and ice boxes. CFCs combine with other molecules in the Earth’s upper atmosphere and then, by attaching themselves to molecules of ozone, transform and destroy the protective ozone layer. The result has been a sharp decline in the amount of ozone in the stratosphere. At ground level, ozone is a threat to our lungs, but in the upper atmosphere ozone works as a shield to protect against ultraviolet radiation from the sun. If the ozone shield gets too thin or disappears, exposure to ultraviolet radiation can cause crop failures and the spread of epidemic diseases, skin cancer, and other disasters. In late 1987, more than 20 nations signed an agreement to limit the production of CFCs and to work toward their eventual elimination.

Congress of the United States, legislative branch of the government, composed of Senate and House of Representatives.

Air pollution has been the target of some of the most complicated and far-reaching legislation ever enacted. In 1970, the United States Congress passed legislation aimed at curbing sources of air pollution and setting standards for air quality. A few years later, Congress passed laws designed to phase out the use of lead as an additive in gasoline. Since 1975, the level of lead in the average American’s bloodstream has declined. Further action against the causes of acid rain is continually debated in North America and throughout Europe.

Bhopal,India, capital of Madhya Pradesh state; formerly a Muslim state; ruled 1844-1926 by women (begums, or princesses); Sultan Jahan Begum (1858-1930) did much to advance position of women, education, and medical aid; in 1926 abdicated in favour of son; state acceded to India 1947; disaster in 1984 caused by leak of deadly gas from Union Carbide Corp. plant; pop. 309,285. Circa 1995.

Although the release of toxic chemicals into the atmosphere is against the law in most countries, accidents can happen, often with tragic results. In 1984, in Bhopal, India, a pesticide manufacturing plant released a toxic gas into the air that within a few hours caused the deaths of more than 2,000 people.