Vital Forest Graphics

Extent of pollution over Asia

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Source: ABC L[ HS . 2002.

Maximum

Minimum

Forests suffer from air pollution

7 ir pollution takes many forms. In the past sulphur dioxide pol- lution – the result of burning high sulphur coal in the factories of indus- trialized nations – was widespread. Though such pollution has been sharply reduced in much of the west- ern world, it is still a significant pollut- ant in many fast developing countries, particularly China and India. Despite stringent air quality regulations in North America, there are areas where sulphur dioxide is a continuing prob- lem and the cause of widespread dam- age to trees and forests. The Province of British Colum- bia, Canada, is now a major source of natural gas, with the number of gas wells rapidly increasing. Many of these wells have quantities of ‘sour gas’ – gas with significant amounts of hydrogen

Air pollution has had an impact on trees and forests since the early days of the industrial revolution. In some cases the damage has been minor but in others entire forests have been killed. Though the processes causing such damage are well understood, knowledge is generally restricted to a few well-known tree species and lichens. Less understood is the impact of air pollution on birds or animals and its long term effects on ecosystems in general

sulphide. If gas is flared efficiently, few pollutants escape other than carbon dioxide. However it seems that in most cases a wide range of pollutants is pro- duced. These chemical cocktails damage nearby areas. Lichens appear particu- larly sensitive but damage to trees has also been recorded. While emissions from a single site might have little over- all impact, problems are likely to build up as many thousands of wells are sunk (Case, 1980). Extensive forest damage could also occur as a result of the pres- ent exploitation of tar sand oil in the province of Alberta, Canada. The most direct effect of air pollu- tion on forests occurs when trees are exposed to a particular pollutant and, as a result, suffer damage to their foli- age. This generally involves the uptake

50 VITAL FOREST GRAPHICS