Many people have tried to define sustainability. One of the most commonly quoted definitions is:
Sustainability is a system of thinking that strives to meet the economic, social and environmental needs of the present without compromising the ability of future generations to meet their own needs. (Brundtland Commission, 1987)
The Natural Step’s definition, developed in Sweden over 20 years ago, says:
In a “sustainable” world, natural and human systems will be regenerative: increasing in health, resilience, diversity, and complexity. It is a world that is getting better all the time for all of its creatures.
The four basic questions used by the Natural Step to assess sustainability are:
Does the action use the least amount of materials from the earth’s crust as possible? (i.e. fossil fuels and metals)
Does it avoid the creation and use of toxic and/or synthetic substances? (i.e. carcinogens, etc.)
Does it avoid degrading all living systems? (i.e. avoid climate change emissions, over-harvesting of fish, timber, etc.)
Does it foster equity so that we can meet basic human needs worldwide?