Plant and animal life is sensitive to changes in the chemistry of the environment. For example, scientists have discovered extreme sensitivity in animals and plants that communicate by releasing biochemical compounds called pheromones. Such chemical sensitivity suggests to scientists that organisms may be easily affected by small but sudden changes in the chemistry of air, water, and land. Plants and animals may be able to adapt to changes as they evolve over thousands or millions of years. But in time periods measured in a few decades or even centuries, such changes may prove highly disruptive to many forms of life, including human beings.
Radioactive elements give off radiation that is harmful to plants and animals.
They have been well studied because scientists can measure and track them easily with instruments that detect the radiation they give off. Such radioactive elements as strontium 90 were distributed worldwide in nuclear-bomb testing in the 1950's and early 1960's. Strontium 90 chemically resembles the mineral calcium. Plants and animals absorb and store strontium 90 in tissues where calcium normally accumulates. Small amounts of strontium 90 in the environment are a direct hazard to people.