As defined by the "Brundtland Commission" in 1987, sustainability is the ability to "meet the needs of the present without compromising the ability of future generations to meet their own needs". In other words, it describes living within the limits of available natural, physical and social resources and in ways that allow our environment to thrive in perpetuity; a concept that can be summarised as: "enough, for all, forever". Sustainability approaches the issue of resource depletion holistically, unifying Environmental, Economical and Social concerns.