Acid rain affects animals by changing the pH of their environments. The increased acidity causes anatomical changes, reduces the population of some organisms and may affect reproduction in some species.
National Geographic defines acid rain as any type of precipitation containing high levels of sulfuric and nitric acids. When acid rain reaches the Earth, the acids sink into the soil and enter water systems, such as rivers, lakes and streams. In aquatic ecosystems, acid rain harms animals by increasing the acidity of the water. This increases the amount of aluminum absorbed from the surrounding soil, making the water toxic for aquatic animals. In areas where the pH of the water drops below five, there are fewer crayfish and insects. Increased acidity also affects the growth rate and reproduction capabilities of fish.
Acid rain also has an effect on animals living in the forest. The rain promotes changes in soil pH, making it harder for trees to soak up water. The effects of acid rain also make it harder for trees and other plants to withstand disease, insect damage and temperature changes. When damaged trees and plants die off, there is not as much food available to animals living in the forest ecosystem.