At pH 6, freshwater shrimp cannot survive. At pH 5.5, bottom-dwelling bacterial decomposers begin to die and leave undecomposed leaf litter and other organic debris to collect on the bottom. Below a pH of about 4.5, all fish die. Other metal flows into the water from the soils in the surrounding watershed. Most of the frogs and insects also die when the water reaches pH 4.5.
Acid rain harms more than aquatic life.
It also harms vegetation. The forests of the Federal Republic of Germany and elsewhere in Western Europe, for example, are believed to be dying because of acid rain. Scientists believe that acid rain damages the protective waxy coating of leaves and allows acids to diffuse into them, which interrupts the evaporation of water and gas exchange so that the plant no longer can breathe. This stops the plant's conversion of nutrients and water into a form useful for plant growth and affects crop yields. Perhaps the most important effects of acid rain on forests result from nutrient leaching, accumulation of toxic metals and the release of toxic aluminum.