Our world is made up of interconnected systems. When one element changes, the entire system is affected, and nature must absorb the change or be thrown out of balance. People often cause these environmental chain reactions through negative actions such as dumping chemical waste, but sometimes they are caused by a good idea. It might start with a plan to get rid of disease-causing insects or to fertilize soil to grow more crops. An environmental chain reaction can affect an area as small as a pond in a city park or as big as the whole planet. Nature requires a delicate balance, and it often takes just one small action to have far-reaching effects.