trends and future of sustainable development - TransEco

Economic sustainabilityThe existence of cities is based on concentration and agglomeration advantages. This means that theproximity of various producers and consumers creates common advantages in comparison to a dispersedsettlement pattern. The advantages can be born at the input side, in the form of shared cost of commonfacilities (e.g. harbour), as well as at the output side in the form of scale effects in markets (more nearbyclients, and less search cost for clients). For business it is also advantageous to have sufficient choice inlabour supply (diversity, no scarcity) and vice versa for workers it is advantageous to have more choice injobs and careers. In turn a large employment base means also a concentration of purchasing power,which attracts an expanding scope of consumer oriented services (retail, education, entertainment, etc.).With all these factors present a more dynamic set of agglomeration advantages emerges, which can leadto further accumulation of population and economic activity. As a consequence at least in some parts ofthe urban area the productivity per acre gets so high that it also significantly pushes up land prices andhence real estate prices. Consequently, a process of selective expulsion (from economic core areas) startsup. In turn this implies that, in absence of further measures, the city starts to expand over an ever largerarea and to show more spatial segregation in functions. Both expansion and segregation stimulatetransport demand, while motorised private road transport gains market share over non-motorisedmodes and public transport. Depending on landscape, climate, hydrology, economic structure, andurban form all kinds of environmental external effects may occur in such an expanding city, e.g.pollution of the air, soils, and water, as well as noise and degradation of natural habitats.There is an ongoing discourse in spatial economics about what constitutes optimal city size (e.g.Arnott, 2004, Capello, 2000, Kanemoto et al., 1996). The number of theoretical and conceptualcontributions is much larger than actual applications to cities (Kanemoto et al., 1996, is a rare example).Furthermore, for a long living system such as a city static optimality is of little value, instead the bestpossible resilient pathway over time is more important.Next to existing economic and geographic models there are also approaches based on physicalconcepts such as material flow analysis (MFA), in which the city is described as a metabolic system (Mollet al., 2005), and entropy models of urban systems (Zhang et al., 2006). These studies indicate that afully fledged treatment of sustainability will probably change the assessment and judgement for manycities, but they stop short of providing an alternative assessment system. Furthermore, these studiesoften focus on one particular aspect, e.g. transport.Since spatial dynamics embodies very complicated processes neither consumers nor producers canfully grasp the longer term consequences of their location choices. When cities start to attain larger sizesand external effects start to become noticeable, a spatial development which is mostly based onindividual private decisions (and interests) has a very high risk to acquire ever more features thatweaken the social and environmental realm of sustainability. In turn the degradation of these realmseventually undermines the economic sustainability, either because problems arise at the input side (lackof natural resources, extra cleaning cost, lack of skilled labour) or at the output side (new emergingsectors choose other cities, skilled workers migrate to better paying regions). In other words themaintenance of agglomeration effects requires also sufficient sustainability in the social andenvironmental realm.38