20.4 Human impacts on the environment: pollution

20.4 Human impacts on the environment: pollution

1. Cultivators and settlers

   • After humans became cultivators and settlers (thousands of years ago) the following 'effects' on the environmen gradually became noticable: *The use of tools and the domestication of animals meant  more efficient agriculture. *The greater need for shelter, agricultural land and fuel meant a greater rate of deforestation and desertification. *The careless use of pesticides and fertilisers, together with increasing consumption of fossil fuels, produced problems of pollution. These have been added to by the development of nuclear energy sources.
   • Conservation
     • Humans may also have positive effects- we are able to use our skills and knowledge in conservation. (prevent a valuable resource from being wastefully used)

2. Our demands on the environment

   • Human success, measured as an increase in population size, is largely due to our ability to solve complex problems and modify the environment for our benefit. This places great demands on the environment, causing changes in the atmosphere, the aquatic environment and the land.

3. How humans can upset the balance of populations of other living organisms

   • When humans over-harvest cod for example species that are eaten by cod (increase) in numbers and the species which eat cod may switch to eating other foods). Another example is when humans introduce foreign species to a habitat like, when rabbits where introduced to Australia for hunting but bred very quickly. This reduced grass available for native Australian species.

4. Caused, effects and remedies for pollution

   • Pollution is any effect of human activities that has a harmful effect on the environment. When looking at pollution, you need to consider three key points:  *What is the cause? *What are the effects? *What are the solutions?

5. Pollution of the atmosphere

   • Two big problems with the Earth's atmosphere are:  *The greenhouse effect *The production of acid rain. Burning of fossil fuels has a major effect on the atmosphere. The combustion process oxidises elements and compounds in the fuel.
   • Causes, effects and solutions of acid rain

6. Radioactive pollution

   • 'Radiation' here means ionising radiation (as oposed to other non-ionising radiation, e.g. UV, infra-red, Microwave). Radiation is emitted from radioactive substances as they spontaneously decay and take several forms. The types of most concern are: *alpha particles (a) *beta particles (B) * gamma rays (y).
   • two major ways in which the atmosphere can become polluted by radiation
     • Nuclear power plants
       • Nuclear power plant accidents can endagner life and the surrounding environment if the radioactive core is exposed and meltdown occurs and releases large amounts of radioactivity.
     • Nuclear weapons
       • Nuclear weapon tests that are conducted above ground or under water can release radiation into the atmosphere. A nuclear test is the explosive test of a complete nuclear warhead- some tests in the twentieth century were conducted in areas occupied by soldiers. Exposure to radioactivity frequently leads to various forms of cancer, including leukaemia.

7. Non-biodegradable plastics

   • Plastic is usefull because they protect products (especially foods) from fungi and bacteria. Many plastics are made from large hydrocarbon molecules and cannot be decomposed by normal microbial methods. Because they are so widespread and they are non-biodegradable, they can have severe environmental effects.
   • How they can pollute both aquatic and terrestrial habitats.
     • *They can block the passage of water through drainage channels, leading to waterlogging of soils. This reduces oxygenation and so affects soil fertility. *They can be mistakenly consumed by animals, on both land and water. They block the animal's digestive system and cause many deaths. *They do not allow the passage of oxygen, so when they are present in landfill sites they inhibit natural decomposition of other wastes. *If they are burned in an attempt to remove them they release toxic 'smoky' particles, which can affect breathing and have a long-term effect on health.

8. Pesticides

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