Why do we need to manage our resources?
Everything that we use or consume - food, clothes, vehicles, tools, petrol, furniture, medicines, books, toys, and the infrastructure of electricity, roads bridges, and buildings are obtained from resources on this earth. The only thing one gets from outside is the sun's energy and even this is converted by the biotic components of the environment and by physical and chemical based processes on the earth before one makes use of it.
The recent concerns about the environment and natural resources have arisen because of the increasing awareness of the finite nature. What appeared as to be plentiful earlier, clean water and air, fuel energy, land for food, forests and trees are becoming increasingly scarce. If one depletes them too fast, without the possibility of their regeneration, one will be creating untold misery for oneself and for the future generations