Environmental Impact

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Environmental Impact

The term environmental impact is a legal term introduced by the National Environmental Policy Act of 1969. This act requires federal agencies to conduct studies to determine the possible consequences for the environment of planned activity. Many states have enacted similar legislation. The results of the study are published as an environmental impact statement. These legal documents are often the basis on which an agency decides whether or not to proceed with a project.

All animals interact with their environment, so all animal activity, including human activity, has some environmental impact. However, human impact on Earth's environment far exceeds that of other species. Humans have altered the environment and landscape on a global scale.

Most species inhabit fairly limited regions within Earth's biosphere, but humans occupy every biome. Humans have the advantage of a high level of technology. Technology has enabled humans to create artificial environments that allow survival even in the harshest environments. Technology allows humans to move food and other materials thousands of kilometers from areas where the resources are plentiful to areas where resources are scarce.

Our ability to live just about anywhere in the world comes at a cost to the environment. Most animals require only a few resources to survive, such as air, food, water, and nesting material. These resources are obtained from a relatively small area. In contrast, humans living in highly industrialized nations rely on thousands of products that come from all parts of the world.

The worldwide extent of human activity, the shift to intensive agriculture, the demand for mineral and other resources, and rising standards of living have all created numerous global environmental problems as well as many regional and local environmental problems. These problems are our environmental impact.

There are several significant environmental issues, including the acquisition and use of natural resources, rapid population growth, soil erosion, desertification, diminishing water supplies, deforestation, loss of biodiversity, global warming, and acid rain.

Resource Acquisition

All organisms interact with their environment to acquire and use resources and thus have an impact on their environment. Most of the time, this is a sustainable impact in that resources are replaced at about the same rate as they are removed and waste is produced in amounts that can be easily absorbed by the ecosystem. Consequently, most animals living in a natural environment have no significant long-term environmental impact.

The maximum viable population of a particular species that an environment can support indefinitely is referred to as the carrying capacity. For most organisms, carrying capacity is determined by the ability of an ecosystem to provide resources, such as food, water, and shelter, and its ability to assimilate, dilute, or detoxify wastes.

Early humans interacted with their environment in a sustainable manner, and their environmental impact was localized and short term. However, the development of intensive agriculture (following the invention of the metal plow) beginning about 5,000 B. C. E. allowed humans to increase the carrying capacity of their environment. During this agricultural revolution, humans came to see the environment as something to be tamed and exploited. Farmers were able to produce a surplus of food that could be traded for other goods and services. This trade led to increased urbanization with the development of trade centers.

During the first half of the nineteenth century, the Industrial Revolution made manufactured goods cheap and readily available to everyone. The mechanization of agriculture allowed an even greater rise in food production and increased urbanization. The Industrial Revolution, therefore, expanded the carrying capacity of the environment even more. As methods of resource acquisition developed, including methods of mining, fishing, farming, and logging, humans have had an increasingly significant, and often harmful, impact on the environment.

Population Growth

Many environmentalists consider population growth to be the principal environmental problem facing the world today. Sometime during 1999, world population exceeded 6 billion. If the current rate of population growth continues, the world's population will exceed 10 billion by 2030, and will continue to double about every twenty-five years. A larger population creates a greater demand on energy and other resources to maintain current living standards.


When topsoil is removed, forests are cut down, or grasses are overgrazed, the land can be permanently changed. The process of degrading grassland to infertile conditions is known as desertification. Many grasslands grow in semi-arid regions of the world. These areas average between 25 and 75 centimeters (10 and 30 inches) of precipitation per year. This rain or snow is trapped by a thick layer of humus-rich topsoil. Overgrazing can remove the grass cover, exposing the topsoil to wind and water erosion. Poor farming practices can also expose topsoil. In the 1930s in portions of Texas, Oklahoma, Kansas, and Colorado, overgrazing and poor farming practices combined with extended drought to create dust-bowl conditions. Once the topsoil is lost, it can take hundreds of years to replace.

Diminishing Water Supplies

Water comes from two sources, surface water and ground water. In many parts of the world, there is insufficient surface water to supply the needs of agriculture, so water is pumped from deep wells. Often, the aquifers supplying these wells are recharged only very slowly, if at all. Some of these deep wells pump water that was deposited in the aquifer during the Pleistocene, over 18,000 years ago. Since the climate has now changed, the water cannot be replaced.

Intensive agriculture requires lots of water. Industry, agriculture, and human populations also have a need for abundant supplies of water. Many experts believe the unavailability of sufficient supplies of fresh water will be the most serious long-range problem confronting the United States and many other parts of the world in the years to come.


Deforestation occurs when trees are removed from a forest faster than they can be replaced by natural growth or replanting. Sometimes deforestation is deliberate. When Europeans first arrived, a dense hardwood forest covered much of the eastern United States. Settlers cut down the trees for fuel and building materials and cleared the land for farming.

In tropical regions of the world, the same thing happens today. Trees are removed to open up land for farming. Unfortunately, the soil under tropical forests is poor and lacks essential nutrients due to the heavy rainfall, so the land cannot support agriculture in the long term. After two or three years, the cleared land no longer supports crops and more trees are cut down. Harvesting tropical hardwoods for building materials also contributes to deforestation. The result of clearing land and cutting down hardwoods is an alarming loss of tropical and other forests worldwide.


Worldwide, species are being lost at a rate equal to or greater than at any other time in the history of life on Earth. Entire ecosystems are lost through environmental degradation. The world's tropical forests contain the greatest variety of organisms on Earth. As these forests are cut down for timber or converted to rangeland, there is a great loss of species and diminished biodiversity. Temperate forests and other temperate habitats are also suffering degradation. While it is easy to measure the number of hectares of forest or grassland converted to cornfields or to parking lots, it is much harder to characterize the slow degradation in an ecosystem's structure, function, or composition.

Global Warming

Research strongly indicates that the atmosphere of Earth is gradually warming. The best estimates are that the temperature has increased by 0.5°C (1.0°F) in the last century. This is a small but significant increase. What scientists cannot agree on is what causes global warming. Many researchers are convinced the data show unequivocally that global warming is directly related to the increase in greenhouse gases, such as carbon dioxide. Others feel it may simply be a short-term climactic phenomenon.

Acid Rain

Because acid "rain" may come in the form of rain, snow, fog, or dew, the best term is acid deposition. All rain is slightly acidic. As water falls through the atmosphere, it absorbs carbon dioxide. The carbon dioxide reacts with the water to form carbonic acid. This is normal and healthy. Plants and animals easily tolerate this natural acid rain.

The problem arises when other compounds dissolve in rainwater and make the rain even more acidic. Sulfur dioxide is emitted from power plants that burn high-sulfur coal, and from other sources that burn fuel with a high sulfur content. Sulfur dioxide particles can be carried over long distances by winds and fall to the ground far from where they originated. If the sulfur dioxide dissolves in water in clouds, it forms sulfuric acid. Power plants and automobiles also emit oxides of nitrogen, which can dissolve in water to form nitric and other acids.

Natural precipitation has a pH of about 5.6. The pH of pure water is 7.0. A pH of 5.5 will reduce the ability of trout and salmon to reproduce. If the pH falls below 5.1, several serious effects can occur. Acid rain with a pH below 5.1 can damage buildings and statues, kill fish and aquatic plants, weaken trees, disrupt the nitrogen cycle, and stunt the growth of crops.

There is no escaping the conclusion that human activity has dramatically changed our planet, mostly for the worse. Many of these changes, such as open pit copper mines, are simply unsightly. Other changes, such as air and water pollution, have great potential to do harm to humans and other life. As we struggle with raising the standard of living of people all over the world, it is important to look for techniques of resource extraction and utilization that can minimize the adverse impact human activity has on the environment. All human and animal activity affects the environment in some way, but human activity need not harm our environment.

see also Global Warming.

Elliot Richmond


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Environmental Impact

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Environmental Impact