This presents a compelling challenge for those engaged in efforts to create long-term, comprehensive solutions designed to reverse the unsustainable patterns of growth that America’s cities have experienced over the past five decades. What incentives can be created to encourage sustainable behavior? Conversely, how can we ask those living in impoverished conditions today not to seek to replicate the lifestyles of those living in more upscale, “greener” neighborhoods, thus placing even greater stress on fragile and finite ecosystem services? Under such circumstances, should researchers—and particularly scientists—assume advocacy roles, or is it their job to simply present the data and facts and to leave it at that, especially when the data and facts indicate that there is no clear cut strategy for addressing the competing problems that are being faced?

The truth is that science can help address this dilemma, but it simply cannot begin to resolve problems of choice, circumstance and lifestyle. That’s because the challenges involving the temporal and spatial aspects of sustainability (which is where the broad, often abstract, principles of sustainability are turned into concrete measures) are ultimately political and social issues, and not scientific ones—unless, of course, nature intervenes to transform time-bound and place-based challenges into existential risks that necessitate a truly global response.