The Environmentalist 

TL;DR: 10 areas that, a) are characterised by exceptional concentrations of species with high levels of endemism and b) are experiencing unusually rapid rates of depletion are identified, so conservationists can engage in a more systematised response to the challenge of largescale extinctions impending in tropical forests.

TL;DR: By concentrating on these hot-spot areas where needs are greatest and where the pay-off from safeguard measures would be greatest, conservationists can engage in a more systematised response to the challenge of large scale impending extinctions.

TL;DR: A detailed examination of these alternative cultural development models reveals a myriad of possible means by which economic, social, and environmental sustainability might be advanced in practice as mentioned in this paper. But these examples cannot be directly translated to cities in the developed world, they do indicate in a general sense the imaginative policies that any society must foster if it is to achieve "urban sustainability".

TL;DR: A number of apparently viable definitions and models have been advanced; Harvey has provided an analysis of most, and proposed a middle ground as mentioned in this paper. But these works do clearly lie mostly unattended by professionals.