Our way of life is placing an increasing burden on the planet.
The increasing stress we put on resources and environmental systems such as water, land and air cannot go on forever. Especially as the world's population continues to increase and we already see a world where over a billion people live on less than a dollar a day.
A definition of sustainable development is: 'development which meets the needs of the present without compromising the ability of future generations to meet their own needs' - Globally we are not even meeting the needs of the present let alone considering the needs of future generations.