Acid rain is caused by the release of SO₂ (One part sulfur combined with two parts oxygen), principally from burning coal, Sulfur, when mixed with water, mainly rain droplets, becomes sulfuric acid. This is released over lakes and forests. The resulting rains affect trees. Acid runoff gradually displaces water in lakes that infect all kinds of fish that gradually become weak, diseased, and die.

In the northern United States, which relies heavily on the syrup industry, maple trees may soon follow the Dodo bird into history. Maple syrup is already beginning to taste sour from the effects of acid rain. Many other species of trees, such as the elm and the spruce, are also threatened as well as the wildlife, which depend on them.