Planning for sustainable urban green infrastructure for compact cities

Abstract

Urban green infrastructure (UGI), as ambassador and surrogate of nature in city, contributes significantly to ecosystem services, environmental well-being, quality of life, human health, happiness and productivity. Many cities have developed effective strategies and action plans to improve the quantity, quality, spatial spread and pattern of urban green spaces (UGS) in the universal quest for urban sustainability and liveability. Compact cities in developed and developing countries commonly suffer from UGI and UGS shortage, and the nature deficit may be accentuated in land-deficient island cities. The resulting planning blight especially in old city cores and precincts often brings collateral problems of stifling cramped ambience, restricted ventilation and solar access, air pollution and urban heat island effect. The opportunities offered by urban renewal and new developments unfortunately often fail to usher amelioration. Innovative public policies and greening technologies are needed for systematic and long-term improvements. Based on field studies of UGI in over 100 cities and review of the literature and relevant urban ecological concepts, a sustainable greening master plan is proposed. The signature hallmark of naturalistic design is to establish UGS with a high degree of connectivity forming a green network to permeate the city. Preservation and creation of UGS with native species composition, complex biomass structure and rich biodiversity can reinforce the new dimension of UGS design. Heritage trees can receive statutory protection and high-order conservation efforts. Outstanding trees in construction sites deserve augmented protection. Tree transplanting demands substantial enhancement in concepts and skills. Improving roadside tree planting and maintenance offers a cost-effective way to upgrade the streetscape. Ameliorating widespread yet neglected soil limitations could remove a major hindrance to tree growth. Innovative ideas of development right transfer, street pedestrianization, river and canal revitalization, green roofs and green walls could mobilize hitherto underused plantable spaces and surfaces. Greening benefits can be communicated in economic-social terms to complement conventional ecological-environmental emphasis. Bottlenecks in institutional setup and scientific capability should be overcome. The public and the private sectors can work in tandem to insert plantable spaces and amenity vegetation into the urban fabric. Amalgamating natural and social sciences in a multidisciplinary approach, and reinforcing the link between science and public policies, could overhaul and pump-prime greening endeavours.