By the 20th century the human population, due to industrialization, started to have a great impact on the environment and climate, and this is when environmental ethics became an issue. People realized that their treatment of the environment could effect their survival. First it was realized that pollution of water, air, may have a direct effect on human health. Later, science and ecology gathered evidence to show that human activities could harm and even shutdown processes that sustain ecosystems, that ultimately sustain us, and that was the birth of environmentalism. We now find ourselves in a situation similar to what our prehistoric ancestors faced. In order to survive, we MUST develop an environmental ethic, just as our ancestors developed social ethics.