Re-engineering cities as forces for good in the environment

Previous simulation studies, using a case study of the city of Atlanta within the Upper Chattahoochee catchment, Georgia, USA, have shown how it is possible to re-engineer the water infrastructure of a city so as to restore aquatic ecosystem services in a catchment. The results also suggest that such a re-engineered infrastructure might even enable the city to act as a force for good in its environment. Assessing the sustainability of these prospective engineering transitions depends not only upon matters such as the urban ecological footprint, but more centrally on the concept of a system's spectrum of environmental perturbations and on computation of this spectrum for pre- and post-city states. This paper begins by discussing the core concept of the city as a force for good (CFG) and defining the attributes and vital role of the unfamiliar measure of ‘spectrum’. Continuing with the case study of the Atlanta–Chattahoochee city–catchment system, an improved assembly of simulation sub-models was constructed in order to accommodate a change in climate, specified essentially as the difference between a 20-year average of annual precipitation variations across the Chattahoochee catchment for the years 1974–1993 (observed past) and 2020–2039 (forecast future). The outcome of this test is that the sustainability of previously preferred strategies for re-engineering of city wastewater infrastructure in pursuit of CFG is climate-insensitive (i.e. robust under climate change). However, climate change as such has been narrowly and rudimentarily articulated. The paper touches upon assessments geared to the behaviour of the city–catchment system at the margins (extremes) and looks forward to extensive subsequent studies designed to explore these matters much more fully.