Acid Rain

Acid rain is rain, snow or fog that is polluted by acid in the atmosphere and damages the environment. Two common air pollutants that acidify rain are sulphur dioxide and nitrogen oxide. When these substances are released into the atmosphere, they can be carried over long distances by prevailing winds and return to earth as acidic rain, snow, fog or dust. When the environment cannot neutralize the acid being deposited, damage occurs.

Acid rain causes direct damage to trees at high elevations, especially the red spruce. Because of acid rain large areas of forests have died. This occurs mainly in the very severe cases of acid rain.

However, forests can be affected in another way, through their soils. Acid rain can easily strip away the nutrients of some soils. In fact, in some areas, the soil has been degraded to the point where its chemistry may have been changed forever.

Acid rain is a problem in eastern Canada because many of the water and soil systems in this region lack natural alkalinity, such as a lime base. Therefore it cannot neutralize acid naturally. Provinces that are part of the Canadian Precambrian Shield, like Ontario, Quebec, New Brunswick and Nova Scotia, are hardest hit because their water and soil systems cannot fight the damaging consequences of acid rain. In fact, more than half of Canada consists of open hard rock areas that cannot neutralize the effects of acid rain. If the water and soil systems were more alkaline, like in Western Canada, they could neutralize the acid rain naturally.

In Western Canada, acid rain is not a problem now, but could always become one if we are not careful. Historically, lower levels of industrialization, combined with natural factors such as eastwardly moving weather patterns and resistant soils have preserved much of Western Canada from the ravages of acid rain. If we monitor the environment carefully and apply strict pollution controls when necessary, we should be able to prevent acid rain from becoming an environmental concern in Western Canada.

However, not all areas in Western Canada are naturally protected. Lakes and soils resting on granite bedrock, for instance, cannot neutralize precipitation. These districts include areas of the Canadian Shield in northeastern Alberta, northern Saskatchewan and Manitoba, and parts of western British Columbia. Lakes in these areas are as defenseless to acid rain as those in northern Ontario. They must be shielded from exposure to acid rain, if not environmental damage could be swift and serious.