What is sustainability?
Sustainability is based on a simple principle: Everything that we need for our survival and well-being depends, either directly or indirectly, on our natural environment. Sustainability creates and maintains the conditions under which humans and nature can exist in productive harmony, that permit fulfilling the social, economic and other requirements of present and future generations.
Sustainability is important to making sure that we have and will continue to have, the water, materials, and resources to protect human health and our environment.
— U.S. Environmental Protection Agency