Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?
Answer:
We commonly think of pollutants as contaminants that make the environment dirty or impure. A vivid example is Sulphur dioxide, a by-product of industrial activity. High levels of Sulphur dioxide cause breathing problems. Too much causes acid rain. Sulphur dioxide has a direct effect on health and the environment. Carbon dioxide, on the other hand, is a naturally occurring gas that existed in the atmosphere long before humans. Plants need it to survive. During the process of photosynthesis, cells use carbon dioxide and energy from the Sun to make sugar molecules and oxygen. The level of atmospheric carbon dioxide in the atmosphere has remained at relatively stable levels. However, human Carbon dioxide emissions over the past few centuries have upset this balance. The increase in Carbon dioxide has some direct effects on the environment. For example, as the oceans absorb Carbon dioxide from the atmosphere, it leads to acidification that affects many marine ecosystems. However, the chief impact from rising Carbon dioxide is warmer temperatures. Rising levels causes an enhanced greenhouse effect. This leads to warmer temperatures which has many consequences. Some effects are beneficial such as improved agriculture at high latitudes and increased vegetation growth in some circumstances. However, the negatives far outweigh the positives. Coast-bound communities are threatened by rising sea levels. Melting glaciers threaten the water supplies of hundreds of millions. Species are becoming extinct at the fastest rate in history.