Some Natural Resources are Limited
You have studied in the beginning of the chapter that some natural resources are exhaustible like fossil fuels, forests, minerals etc. You know that coal and petroleum are fossil fuels. It required the dead organisms millions of years to get converted into these fuels. On the other hand, the known reserves of these will last almost a few hundred years. Moreover, burning of these fuels is a major cause of air pollution. Their use is also linked to global warming. It is therefore necessary that we use these fuels only when absolutely necessary. This will result in better environment,smaller risk of global warming and their availability for a longer period of time. In India, the Petroleum Conservation Research Association (PCRA) advises people how to save petrol/diesel while driving.
Notes
Coal and Petroleum - Notes