Special Issue on Green Infrastructure for Urban Sustainability

More than 50% of the world population now lives in urban areas, and the urban population is projected to reach 6.3 billion in 2050, most of which will reside in less developed countries (United Nations 2012). Urban green infrastructure as parks, forests, street trees, green roofs, gardens, and cemeteries is especially in an urbanized world of crucial importance as it is the main carrier of ecosystem services and improves the quality of life for urban residents. For instance, it supports regulating ecosystem services by increasing water infiltration (Haase and Nuissl 2007; Pauleit and Duhme 2000) and has positive impacts on the microclimate regulation (Gill et al. 2007; Hamada and Ohta 2010). Furthermore, urban green provides recreational facilities and offers urban residents the possibility to get in touch with nature (Matsuoka and Kaplan 2008) and supports the local food supply through allotment gardens (Barthel et al. 2013). Green infrastructure as a concept has been developed within the last two decades. It commonly refers to the connective matrices of green spaces that can be found in and around urban and urbanfringe landscapes (Mell 2008) or is simply defined as urban and periurban green space systems (Tzoulas et al. 2007). Due to its provision of numerous complementary ecological, economic, and social benefits, green infrastructure not only enables planners to develop multifunctional, innovative, and sustainable places (Mell 2008), but also promotes ecosystem and human health and wellbeing (Tzoulas et al. 2007) and provides abiotic, biotic, and cultural functions to advance and contribute to urban sustainability (Ahern 2007). Urban green infrastructure is closely related to human wellbeing and biodiversity in urban areas (Gaston 2010; Richter and Weiland 2012) and plays an important part in urban ecology. In recent years, in some published books on urban ecology, urban green was factored into investigations regarding how cities and their sociocultural, economic, and environmental systems can be managed in a way that allows producing sustainable cities (Alberti 2008; Endlicher 2011; Gaston 2010; Niemela et al. 2010; Richter andWeiland 2012). However, urban green mostly plays just a minor part when talking about atmospheric processes such as urban heat islands or climate change (Alberti 2008; Endlicher 2011). The studies on urban green infrastructure also focus on human perception, educational values of urban wilderness as part of urban green or social benefits by urban gardening (Richter and Weiland 2012; Endlicher 2011). However, only a few papers have investigated the recreational services in developing countries (Jim and Chen 2006, 2009). In some regional case studies, for instance, designers have paid more attention to implementing theoretical principles and government requirements in urban planning or landscape architecture, but lack technical support from ecological and geographical perspectives (Li et al. 2005; Jim and Chen 2003). Therefore, it is urgently necessary to improve the research scope and methods linking function, ecosystem services, planning, and the design of urban green infrastructure in the pursuit of urban sustainable development (Mao et al. 2012; Chang et al. 2007).