Green infrastructure in strategic spatial plans: Evidence from European urban regions

Green infrastructure (GI) is an umbrella term for a strategically planned and managed network of green areas, conservation sites, working lands and water bodies capable of delivering a wide range of benefits for humans and ecosystems (Benedict and McMahon, 2006; Rouse and Bunster-Ossa, 2013). The emergence of the GI concept has been described as form of ecological modernization with potential for reconciling nature protection with economic development goals (Thomas and Littlewood, 2010). There is no clear time and place of origin of the idea of a network of multi-functional green and open spaces (Lennon et al., 2017). Benedict and McMahon (2006) place the roots of this idea in the planning and nature conservation efforts that started in the early 19th century. Nevertheless, the term green infrastructure is rather recent. Wright (2011) described it as emerging from a long period of apparent convergence in theories and practices in different contexts, including nature conservation, US greenways, Garden Cities, New Towns, ecological city and sustainable urbanism. In the United States, the term GI was first used in the 1990s (Benedict and McMahon, 2006). In Europe, GI has been extensively advocated by the European Union through a series of strategies and reports (European Commission, 2010, 2013; Mazza et al., 2011). Countries with long tradition of green space planning, such as the UK, have been particularly keen on adopting the term GI (Mell et al., 2017). Literature from the Global South (Schäffler and Swilling, 2013) and Asia (Byrne et al., 2015) reveal a worldwide growing interest in the topic. Considering that GI has been extensively promoted by both science and policy, and is being supported by a multitude of actors, it is time to look at how much GI planning has been consolidated. Scholars have proposed various principles to incorporate both the ecological and social perspectives into green area planning in order to support the design of a functional GI. Although there is no agreed-upon set of principles (Hansen and Pauleit, 2014), six of them stand out as recognized in most of the studies: coordination, multi-functionality, connectivity, multi-scale planning, diversity and identity. Coordination of GI expansion and management with other domains of spatial planning has been encouraged to better integrate the various planning goals. Coordination with policies on climate change adaptation (Gill et al., 2007), flood prevention and water management (Liao et al., 2017), increasing health and quality of life (Tzoulas et al., 2007), and recreation provision and tourism (EEA, 2014; Kambites and Owen, 2006) are especially relevant for urban settings. Moreover, coordination between the development of green elements and built-up areas has been encouraged for better control and guidance of urban expansion (Kambites and Owen, 2006). Multi-functionality is reflected in the combination of functions fulfilled by the GI which cover social, economic, ecological (Hansen and Pauleit, 2014, Iojă et al., 2014) and cultural aspects (Lafortezza et al., 2013; Lewicka, 2013). Such an intertwining of functions is particularly relevant in urban areas, allowing the limited space to be used more effectively (Ahern, 2007). Supporting the connectivity of the green elements enables the creation of a network that works as a whole and not as separate unrelated parts (Benedict and McMahon, 2006). Connectivity allows ecological processes to be maintained by permitting flows and movement of species (Hansen and Pauleit, 2014). Green infrastructure planning is recommended for addressing issues at multiple scales, from the parcel to urban region to national level, and for considering a high diversity of green elements, including street trees, gardens and parks (Ahern, 2007). Recently, authors have emphasized the need to plan GIs so that they can contribute to creating a sense of place and enhancing the feeling of identity (Hunziker et al., 2007; Roe and Mell, 2013; Rouse and Bunster-Ossa, 2013). Although there are many studies which address GI planning, most of them seek to promote its benefits rather than critically reflect on bridging theoretical consideration with implications for planning practice (Lennon et al., 2017). Thus, it remains unclear how current spatial plans address the green infrastructure. A solid understanding of how the principles are applied in practice would pave the way for theoretically based advances in GI development and support the science − practice knowledge transfer. Furthermore, building this knowledge can be seen as a necessary step towards future comprehensive evaluations and quality assessments of GI planning. In our quest to build a better understanding of the current European approaches to GI planning, we focus on the urban region level (i.e. often refed to as metropolitan area, greater area, city region). While