Growth and development in urban ecosystems: A network approach to city organization

Background/Question/Methods Urban ecosystems are intended as the suite of animal and plant species that live in a largely human-built environmental context. The city landscape, the different kinds of boundaries (e.g. political jurisdictions, neighborhoods), the role of time (history, lags and legacies) with their effect on plant and animal dynamics make these environments interesting for ecologists.
One further question relates to the way the human-built environment grows and develops. Are there patterns that constantly repeat and that define typical trajectories of development? Is it possible to identify criteria of organization?
To answer these questions the human environment can be modeled as an ecological flow network in which human activities (industry, agriculture, domestic) become the ecosystem components that exchange flows of various currencies, such as energy, water and so forth. In this paper three different urban ecosystems of Italy are investigated; water is used as main currency and the flow structure produced by water exchanges is investigated by network analysis.

Results/Conclusions

By calculating the reciprocal dependence of compartments, the amount of resource that is involved in cycling, the length of exchange pathways, and the organization of flows, network analysis highlights that human-built environments show characteristic patterns as for growth and development; that such patterns differ from those exhibited by natural ecosystems and that from these patterns criteria for sustainability can be obtained.
The results of this study support the idea that the ecosystem approach provide and interesting conceptual perspective to study urban environments, to understand patterns of organization, and that network analysis is a valuable tool to handle practical questions such as those pertaining sustainbility.