Answer:
Intensive family planning.
Explanation:
The varied developments in medicine, increased standard of living, and minimal or no warfare has tremendously increased the earth's population rapidly. Within a span of hundred years, the human population have increased from 1 billion to about 7 billion today.
Over population has become a huge problem to earth and its environment. People need more resources, so there is rapid draining of earth's natural resources. Similarly, people needs homes and places to live, so chunks of forests and jungles are cleared out for agriculture and urbanization. All these human activities are affecting the ecology drastically.
We need to quickly take up measures before it is too late. The most fundamental pratice to reduce overpopulation would be intensive family planning. Every individual should hold responsible to this practice. Family planning is discretionary to oneself, therefore it should be practiced responsibly.
If we can maintain human population, the consumption and emission of pollution would ultimately decrease too. Thereby, the earth would have better air and more green areas.