When fossil fuels like coal, oil and petroleum are burned, they give off acidic fumes, including sulphur dioxide and nitrous dioxide. The fumes rise into the air and dissolve in water vapour and droplets in clouds, making sulphuric and nitric acid. Eventually, the vapour and droplets fall as 'acid rain'.
Normal rain is slightly acidic (pH 5&ndash5.6). Acid rain is much more acidic - in some cases as strong as vinegar (pH 3 or less). Where it falls, it makes water in the soil, ponds and lakes acidic. This causes wildlife to suffer. Trees turn brown and sickly and may die. Animals which depend on the trees for shelter become rarer. Nutrients are washed away or broken down. Pondweeds, fish and other waterlife are particularly badly affected.
It is not only wildlife that is affected. Drinking water can be polluted and some kinds of stonework and metalwork can be eaten away.
The widespread effects of acid rain were first noticed in Germany in the 1970s. Now it affects countries all over the world. A major problem is that winds often blow the acid rain hundreds of miles from their source. Thus the areas where acid rain falls are not the areas where the pollution comes from. Pollution from the industrial areas of Britain damages forests in Scotland and Scandinavia. Acids from the MidWest United States are blown into Northwest Canada. More and more regions are beginning to be affected, including South America and Australia.
What can be done? 'Cleaner' forms of energy, such as nuclear power and hydro-electric power, do not contribute towards acid rain. However they in turn have their own problems. Filters can be fitted over power stations and factory chimneys to reduce emissions, however industries can be unwilling to spend money on problems that do not affect them directly.