Sustainability is the long-term viability of our existence on this planet. Achieving sustainability requires meeting social and economic needs without consuming natural resources faster than they are replenished. When this is achieved, future generations are assured the same freedoms since resources will not run out.
Human life is not currently sustainable because it uses natural resources faster than they are replenished. The unsustainability of our lifestyle comes from an over-reliance on non-renewable resources, including fossil fuels, metals, and minerals. Another issue is damage to water quality, soil quality, and biodiversity. Because of this, future generations are not assured the same quality of life we currently enjoy.