2. Perspectives on Greening of Cities Through an Ecological Lens

The increasing focus on urban green spaces (UGS) leads to them becoming an important component of the physical makeup of cities. However, it is useful to be mindful that UGS implementation competes for precious land resources in cities, incur carbon and energy footprint, and can have long payback periods for net benefits to be achieved. The net benefits provided by UGS are thus not assured by its mere presence; functional benefits need to be achieved through deliberate design. In particular, it is suggested here that combining design with an understanding of urban ecological knowledge is a useful approach to increase the ecological functions of UGS. A conceptual model using coupled human-ecological function is described to explain how increasing ecological functions of UGS to reduce resource consumption, restore ecological processes and functions, and reduce waste generation can shift the coupled human-ecological function for both humans and the environment. Four principles distilled from conceptual advances in urban ecology and landscape ecology are proposed as a means to bridge scientific knowledge and UGS implementation through design: (1) spatial patterns of UGS across different scales influence the ecological functions of UGS; (2) heterogeneity of UGS determines its resilience to disturbances; (3) urban ecosystems are dynamic; and (4) ecological processes remain important in cities. More application-focused strategies are in turn, derived from these principles, and how these can be applied to UGS are highlighted. It is also suggested that while current scientific knowledge still limits the application of ecological principles in many aspects of UGS design and management, the increasing emphasis on UGS in cities provides good learning opportunities for scientists, practitioners and policy makers to work in concert to enhance the ecological functions of UGS.