Human impact on the Earth's surface

The topic of humans and their impact on the Earth's surface is one that I chose because of its particular interest to me and my deep concern over it. It is quite disturbing to me that we are taking the natural resources we have and destroying them and/or using them as if there is no tomorrow. Unfortunately, there is a tomorrow, and it's almost here. We are beginning to see signs of the problems to come in that we are running out of energy supplies, ozone, fossil fuels, and landfill space. The following is a summary taken from Pickering, Kevin T. and Owen, Lewis A. an introduction to global environmental issues. "Human impact on the Earth's surface" New York: Routledge, 1994. You are encouraged to pursue highlighted links to other places on the World Wide Web, if that particular topic interests you.

The population of the Earth is continuing to increase. With this increasing population, more and more people are depleting and exhausting) what little resources exist. Uncontrolled and excessive use of the natural resources of our world has only created problems for its inhabitants. While there are many examples of man's influence over the natural environment, most of them can be divided into four main categories: exploitation of vegetation, soils, oceans, and landscape resources.

Vegetation

The impact humans can have on the vegetation of the Earth is very important because vegetation is a source of food for the world. However, vegetation is also important as a building material, in manufacturing industries, as a fuel, and as medicine. It wasn't until humans began widespread harvesting of this vegetation that the Earth began to show a negative impact from this change.

The most obvious way that humans impact vegetation is by burning it, both intentionally and accidentally. While fires do occur naturally, those generated by humans can harm the environment by causing danger to animals, properties, and themselves. Long term effects of fire are: clearance of vegetation, soil erosion, flooding, and wind erosion. Small fires only cause limited damage, but repeated, unnatural burning of areas can cause the vegetation to lose its ability to regenerate itself.

Perhaps one of the most publicized ways to destroy the world's vegetation is through deforestation. Humans have been cutting down forests for many years and for many reasons. The most alarming rate of destruction is occurring in the tropical rain forest, where an acre is removed every second. At this rate, the inevitable loss of the rain forest and its ecosystem would disrupt nutrient cycles, especially the oxygen and carbon dioxide cycles. A loss in rain forest would also cause erosion, flooding, and ultimately a loss in biodiversity. Logging is a universal problem, not only affecting the rain forests. Forests are being degraded by loggers taking the best trees, then coming back for more timber before the tree have had a chance to regenerate. Laws governing the maximum acceptable damage to logged forests through selected cuts are hard to enforce as loggers select the trees they want to take and leaves the weak trees for antoher day. By exporting trees to other countries,it is hard for one nation to control how much of its wood is being "chopped". International legislation might be the only way to save the deciduous, boreal, and tropical rain forests that remain.

Another way that humans destroy vegetation is through desertification. Desertification is the spread of desert-like conditions in a semi-arid region, and can be caused by deforestation, bad land management, poor farming techniques, and global climate change. The developing countries of the world, located in the Gobi desert, the Sudan, the Kalahari desert, and the Sahara desert, are particularly subject to this problem, up to 60% affected in some areas. Regions fall prey to desertification when residents change from traditional, subsistence farming methods to crops that can be sold quickly for money. Experts hope that through irrigation and revegetation, desertification can be made a reversible process.

Finally, vegetation is being invaded in many parts of the world by plants that don't belong. Humans, both accidentally and on purpose, introduce new plant species or animals to an environment where they do not have natural enemies. Plants can soon dominate a region and cause great harm, as the Dutch Elm disease fungus did to the elm trees of the United Kingdom in the 1970's. The introduction of goats to Hawaii and the subsequent reduction in plant species illustrates the harm human introduction of animals can have.

Soil

Soil is unique in that it depends on plants and vegetation for its existence, yet plants depend on soil for their support, air, water, and nutrients. Soils are very variable in nature, and there are many factors that can effect the soil's chemical makeup, thereby altering the plant species it can support.

Salinization and lateralization are two major ways in which humans change the chemical content of the soil. Salinization is the accumulation of salt near the surface of the earth due to evaporation, causing restricted plant growth and soil erosion. Salinization is caused by irrigation and abstraction of water from the ground. The effects of salinization are particularly evident in coastal regions such as California and islands such as Long Island, New York. Lateralization, which also changes the chemical content of the soil, is the enrichment of the soil by aluminum and iron oxides. The extent to which lateralization degrades the land is not known, but it can be harmful to countries with increasing populations that rely heavily on the land.

Humans can also cause a change in a soil's structure. Soil structure is important to understand because it affects the soil's ability to retain water, the soil's ability to let water flow through it, the soil's strength, the degree to which a plant can penetrate the soil, and the soil's resistance to erosion. Soil compaction is severe in developed countries where vehicles are common. The compaction of soil retards plant growth and encourages erosion, and, unfortunately, is a hard problem to reverse because it takes years for soil to regain its original structure.

The largest problem that pertains to soil is the erosion of soil, which encompasses water running over the surface, raindrops breaking up the soil, and wind erosion. Many of the factors mentioned earlier, such as salinization, lateralization, and soil compaction, make soil more prone to erosion. There are many consequences of soil erosion: increased likelihood of flooding, landslides, and increased sediment loads leading to silting up of reservoirs. All of these "consequences" of soil erosion usually are referred to as natural events, but, as one can see, humans do play a large part in the cause of natural disasters.

Oceans

So far, this overview of the human impact on the environment has focused on the land. Perhaps it should have focused more on the sea. After all, 2/3 of the earth's surface is covered by water and the biodiversity of the ocean is greater than that anywhere else on the planet. The size of the ocean makes it an easy target for the dumping of waste, including toxic chemicals and nuclear waste.

The ocean is also hurt by overfishing. Since the 1880's, methods have been developed to increase the number of fish that can be caught with less cost. The increased number of fish being caught and the increasing population causes the demand for fish to continually rise. The significant depletion of fish in one area can cause the destruction of marine ecosystems.

Does the size of the ocean mean that it can "absorb" all the waste humans put into it without showing negative effects? NO! Today, many large cities in coastal regions pump their raw sewage straight into the ocean, infecting the fish and plankton that are at the base of our food chain. Each year, the world's beaches and coastal resorts suffer from water pollution caused by untreated sewage, oil, industrial chemicals, and radioactive waste. Because many nations share the ocean as a common resource, the time is coming for international agreements as to how much waste can be put into the world's water supply.

Landscape

Humankind over the past century has radically altered the face of the earth. The cutting and mining away at the surface of the planet and dumping the resulting waste has caused geomorphologists to classify humans as an important land forming agent and refer to us as "geomorphological anthropogenic agents." Many experts regard human activity as an important factor contributing to how we see the landscape today.

Several factors contribute to anthropogenic, or human-caused disfigurement of the land. Mining can cause several problems, especially when the land that is excavated is rich in toxic materials. Underground mining has severe environmental impacts because it contaminates the ground water. Often waste from mining is piled in extraction pits or used as fill, but it can also be carried away by water, ultimately resulting in rivers having to change their course.

Contaminated land is the largest problem we as a race have to deal with. Many countries are slowly learning that we are polluting our own land and effectively "choking ourselves." The United States Government has recognized the problem, and set up the Superfund to try to remedy the problem. Unfortunately, Superfund has been inundated by the amount of hazardous waste sites it is responsible for cleaning and costs often run high due to transaction costs and various other types of legal costs. In the years to come, it will be interesting to see how the people of the world react to the growing environmental concerns. While most of the problems we face as a planet can be traced back to overpopulation, the astounding birth rate cannot be entirely to blame. Ignorance about the effects of our lifestyles, especially here in the United States, is largely to blame. However, there is hope. Improving technology and awareness about the environment will lead to better methods of dealing with waste, erosion, logging, and use of our natural resources. It is possible for people to change, especially when survival is at stake. The governments of today must realize that environmental problems are real and caused largely by humans. Only when countries join together to act as an international unit with a common interest in the environment will significant progress to a sustainable lifestyle be made.


Written by Stephen M. Grimes, December, 1995
grimes@bucknell.edu