Biology human impact

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Biology human impact

Topic 4.5 - Human Impact

4.5.1 Outline the two local or global examples of human impact causing damage to an ecosystem or the biosphere. One example must be the increased greenhouse effect.

The greenhouse effect is a naturally occuring phenomena in the ecosystem of the planet. It is simply the accumulation of carbon dioxide and other gases such as methane in the atmosphere, which traps heat from the sun's radiation and raises planetary temperatures. Recently, however, increased industry and burning of fossil fuels have caused the release of excessive amounts of carbon dioxide into the atmosphere. The planet is now enveloped by a layer of carbon dioxide far thicker than would be there naturally, which allows the sun radiation to enter our atmosphere, but prevents it from going out. This causes the trapping of heat into our atmosphere, and the consequent gradual increase in temperature around the world, hence global warming. This effect is called the greenhouse effect, since the layer of carbon dioxide around our planet has similar effects to the glass walls of a greenhouse in causing increased temperature inside.

The ozone layer is present at about 20 Km above the surface of the earth. It absorbs ultra violet light that radiates from the sun, thus protecting us from the harmful effects of these radiations. Increased industry in the last 20 years or so, have caused the breaking of ozone molecules into oxygen, resulting in a hole in this protective layer. The chemicals responsible for this effect are a group of chlorofluoro carbons (CFCs) that are used in refrigeration, aerosol cans and other types of industry. These compounds are very light and they escape to the upper layers of the atmosphere, reaching the ozone layer and destroying it. A hole in the ozone layer is most prominent over the Antarctic.

4.5.2 Explain the causes and effects of the two examples in 4.5.1, supported by data.

The greehouse effect is largely a result of human industry and machinery, including automobiles and other vehicles that emit significant amounts of carbon dioxide from the burning of fossil fuels. Its effects have included an increase in global temperature by several degrees over the past decade, a melting of glacial deposits across the globe, and the recent thinning of Artic and Anartic pack ices; all of the effects reported as the much-publicized global warming. Many scientists predict more drastic changes in temperature and environment in the future if current warming patterns continue. Ozone depletion, as previously mentioned, is due to chemicals called CFCs being released into the atmosphere. CFCs, or chlorofluorocarbons, are a compound of chlorine, fluorine and carbon, as the name would suggest. They are found in refrigerants and a variety of aerosol containers. When these compounds are released into the atmosphere, by the action of spraying a can of hair spray, for example, they react with and break apart double-bonded oxygen molecules (ozone). One molecule of CFC can destroy thousands of ozone molecules; thus their large-scale release into the atmosphere during the 1980's and early 1990's was very damaging. The result was the opening of a large hole in the ozone layer (the atmospheric layer responsible for deflecting UV radiation from the sun harmful to most organisms) which was centered over Anartica. For several years the hole moved throughout the Southern Hemisphere, often exposing countries such as Austrailia to dangerously high amounts of UV radiation. Today the hole still exists, but since the banning of the production or use of CFCs it has shrunk considerably due to the repair of the ozone by natural causes.

4.5.3 Discuss measures which could be taken to contain or reduce the impact of the two examples, with reference to the functioning of the ecosystem.

The best method currently agreed upon to resolve the greenhouse effect issue is a twofold proposal. The first involves attempts to reduce the production of greenhouse gases by international treaties on the amount of gases emitted, such as the Kyoto Treaty, the use of alternative fuel and energy sources that emit little or no greenhouse gases, and improved filtering for industrial and automotive gases already produced. The second involves allowing the environment to stabilize this problem itself. This includes checking the destruction of forests and other photosynthetic environs and organisms, as these naturally regulate the amount of carbon dioxide in the atmosphere.

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