Why should fossil fuels like coal and petroleum be used judiciously?

There is a need to use fossil fuels like coal and petroleum judiciously because they are formed from the remains of biomass buried in the soil millions of years ago. It is the continuous pressure, heat and time which convert the organic matter into coal and petroleum. Due to the slow and long process of formation of these fuels and the pollution caused by the products of combustion of these fossil fuels it is advisable to use them judiciously.