Question

why should we save natural resources

Answer 1

because they save us

Answer 2

As referred in the name  "natural resources" can't be created by human beings, it should be used judisciouly, we might run out of fuel in next thousand years if we waste natural resources with the same pace. We should conserve our resources, people are totally dependent on this resources. People living in the jungle use woods as their fuel, even their houses are made up of woods. One day because of deforestation those tribes might dissapear.
Talking about urban areas, electricity is produced by burning fossil fuels fuels, people use diesel & petrol in their vehicles.
Life without natural resources will not be possible....we must conserve each an every penny of natural resouces...wastage of any resource must be controlled...