Since the emergence of widespread concerns over environmental degradation in the 1960s, a great deal of work has been put into the concept of environmental 'sustainability'. More recently, economic and social sustainability have been adopted as additional and interrelated concerns. Sustainability is now a broad multi-focal agenda, and terms such as 'triple bottom line' and 'sustainable development' are being used interchangeably. As a result, 'sustainability' is in danger of carrying so many implications and nuances that in order for it to be properly understood it must be defined whenever it is used.