With global deforestation, the recovery ability of our ecosystem is diminishing. We have less forest to 'eat up' the carbon dioxide we breathe out. Together with our extensive consumption of fossil fuels, industry-generated carbon dioxide accumulates, and the greenhouse effect is made worse. Warmer weather results in more frequent forest fires and loss of more forests.
People also set fire to forests to clear land for agriculture. Intentional and accidental forest fires (e.g. from a burning cigarette); and human-made pollutants from factories, power plants and transportation put a burden on clean air and often pose longer-term effects on the biosphere. Pollutants from power plants and transportation are more or less the same as those from forest fires. Factories, depending on the chemicals they use, emit air pollutants that can be toxic, damaging to the stratospheric ozone or add to the greenhouse effect. The refrigerants in air-conditioning, a must in many cities and modern buildings, damage the stratospheric ozone as well as contribute to the greenhouse effect.
Background radiation is a natural occurrence, but the extra amount of radiation, as a result of the diminished filtering effect of our ozone protection layer, also falls into the category of pollution. Likewise, radon emission from rocks and soil is a natural occurrence, but the accumulation of such radioactive gases and particulates due to poor ventilation or use of materials that contain high radon results in pollution.
You may by now be able to distinguish between natural occurrence and pollution, and between natural and human-made pollution. You may have found that the damage from natural pollution can be extensive, but that such occurrences are infrequent, localized and rather short-term, apart from catastrophic events such as the impact of meteoroids.
How about the air pollution in Hong Kong? It is time for an activity.
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