Answer:
Sustainable development is defined as the principle to meet present need without affecting future generation needs.
Sustainable development is much concerned with the future needs because humans are utilizings the natural resources of the Earth in order to fulfil present needs. But the natural resources of the Earth are non-renewable and will take hundreds or thousands of year to form again, so it is possible that our future generation will unable to consume those natural resources.
Even natural resources cannot be replaced by other resources, example: carbon-based fossil fuel.
Hence, people consuming natural resources in large quantity which can affect future generation needs, as natural resources are non-renewable sources of energy.
