A3.4.5 Pollution Impact on Habitat & Species
Trees and Plants
Acid rain can cause severe effects in trees. It does not usually kill 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 slowly released from the soil. Scientists believe that acidic water dissolves the nutrients and helpful minerals in the soil and then washes them away before the trees and other plants can use them to grow. At the same time, the acid rain causes the release of toxic substances such as aluminium into the soil. These are very harmful to trees and plants, even if contact is limited. Toxic substances also wash away in the runoff that carries the substances into streams, rivers, and lakes.
Pollutants can also directly affect trees. Sulphur dioxide impairs a plant’s metabolism. This is indicated by changes in the plant’s physical appearance. The younger and older leaves are more resistant, it is the mid-growth leaves that are more at risk.
The effects of sulphur dioxide are influenced by other biological and environmental factors, including plant type, age, sunlight levels, temperature, humidity and the presence of other pollutants (ozone and nitrogen oxides).
Animals
Animals may be exposed to pollutants through inhaling gases or small particles and by ingesting pollution that is contained in food or water. Soft bodied invertebrates (e.g. earthworms), or animals with thin, moist skin (e.g. amphibians) may also absorb gases through the skin.
The impact that the pollution has on an animal will depend upon a variety of factors including age, gender, condition of health and species.