Sustainability is an economic, social, and ecological concept. It is intended to be a means of configuring civilization and human activity so that society and its members are able to meet their needs and express their greatest potential in the present, while preserving biodiversity and natural ecosystems, and planning and acting for the ability to maintain these ideals indefinitely. Sustainability affects every level of organization, from the local neighborhood to the entire globe. With that said how do you specifically define what is sustainable? Economic needs are fairly easy to figure out; ultimately it is do you make a profit or not. Social needs will depend on the society involved and every society is different. There is a difference between urban and rural needs for example much less North Africa, China, and the US. Ecological standards will also vary because it is far from clear how much resilience that an ecosystem has and as a result there will be constant and shifting debate on those standards.