Scientists have discovered that air pollution from burning of fossil fuels is the major cause of acid rain. The main chemicals in air pollution that create acid rain are nitrogen oxides and sulfur dioxide. Acid rain usually forms in the clouds where sulfur dioxide and nitrogen oxides react with water' oxygen, and oxidants. This forms a mild solution of sulfuric and nitric acid. Besides rain, snow, fog and other forms of precipitate containing these mild acids fall to the earth are all called acid rain.
Acid rain influences the forests.
Over years, many foresters watched some forests grow slowly. The leaves and needles turn brown and fall off when they should be green and health. The main reason is acid rain. Acid rain does not kill the trees directly. It is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowing released from soil.