Urbanization is a major trend of the twenty-first century. This trend provides opportunities and causes social, economic, and environmental challenges, such as an unsustainably high ecological footprint, low environmental quality in often poorly planned and built urban settlements, and climate change, which will severely impact urban areas.
Urban green infrastructure (UGI) is considered as a promising approach to successfully address these challenges by the development of networks of green and blue spaces that provide multiple benefits to human society and enhance urban biodiversity. Green infrastructure emerged as a planning concept in the US in the 1990s in response to the challenges of ecological fragmentation and degradation of sprawling cities. It is considered as a natural life support system for environmental, social, and economic sustainability (Benedict and McMahon 2002). The concept marks a shift from a conservationist approach that separates nature from urban. Moreover, UGI may include the entire range of green and blue spaces from natural and near-natural forests and wetlands, the many different kinds of human designed green spaces such as parks, gardens, and tree plantings in streets and derelict lands, and even incorporating the technical greening of buildings through green façades and green roofs (Cvejic et al. 2015).
The principles of multifunctionality, connectivity, integration and social inclusion were highlighted as being central to UGI in the EU funded research project GREEN SURGE (2013-2017), within which I was a member of the research group working on UGI planning (see. table 1). None of these principles is entirely new but I believe it is the consideration of all of these together, which makes UGI innovative.
I became acquainted with the term of UGI in the early 2000s when working as an academic in the UK. With a background in the German approach to landscape planning and landscape ecology, and after having been involved in a European Union funded scientific network that explored “green structure planning” (Werquin et al. 2005), I was first hesitant to use this new term because it seemed to adopt a reductionist perspective on green and blue spaces as engineered solutions. Indeed, the risk of pursuing a technocratic approach to planning by UGI should not be ignored and has been rightly highlighted by some scholars (e.g. Lennon 2015).
However, despite this potential limitation, I became convinced that urban green infrastructure offers a perspective on urban landscapes that can promote collaboration between disciplines, notably ecology, environmental sciences, architecture, urban planning, engineering of technical infrastructures, social sciences, and not least policy-makers, in the quest for more integrated planning, design and management of urban areas. Urban areas have been conceptualized as complex systems where social, ecological, and technological processes are inextricably linked and innovations in any of these three domains drives urban change (McPhearson et al. 2016). In my view, UGI is particularly well equipped to address such complexity and to offer various perspectives for practical applications.
Our research has focused on consolidating and further developing UGI as a concept for the strategic planning of UGI in addition to exploring its potentials for climate change mitigation and adaptation. Both strands of enquiry have resulted in extensive guidance for urban planning and landscape architecture (Hansen et al. 2017a, 2017b, Lang 2018).
Even in densely built inner city areas, UGI has the capacity to offset the negative impacts of climate change by reducing heat stress and storm water runoff. However, results showed that by 2050, an increase from a current 9% to 20–25% projected crown cover would be required to maintain current thermal conditions on hot summer days (Zölch et al. 2016). Adding this amount of green will require a complete rethinking of open spaces and their above and belowground uses. New mobility concepts will be needed to strongly reduce space demand for car-based mobility as well as a change of engineered infrastructures towards hybrid green, blue, and grey infrastructures.
In conclusion, I believe that the concept of UGI can contribute to the transformation of urban areas towards more sustainability, the well-being of humans, plants and animals and climate resilience. It has the potential to transcend the separation of nature and urban, green and grey, and thus to relieve the tensions between the compact and the green city model. To fulfill this promise, UGI forces us to fundamentally rethink urban structures regarding their open spaces and their functions. To make this happen, new approaches to governance of urban areas are necessary that are able to overcome sectorial silos within administrations, while also deeply engaging with the public.
Benedict, Mark A. and Edward T. MacMahon. 2002. Green Infrastructure, Smart Conservation for the 21st Century. Renewable Resources Journal, 20: 12–17.
Cvejić, Rozalija, Klemen Eler, Marina Pintar, Špela Železnikar, Dagmar Haase, Nadja Kabisch, and Michael Strohbach. 2015. A Typology of Urban Green Spaces, Ecosystem Provisioning Services and Demands. EU FP7 Project GREEN SURGE, Deliverable D3.1. Accessed March 19, 2016. https://www.e-pages.dk/ku/1334/html5/.
Hansen, Rieke, Emily Rall, Eleanor Chapman, Werner Rolf, and Stephan Pauleit. 2017a. Urban Green Infrastructure Planning. A Guide for Practitioners. EU FP7 Project GREEN SURGE Deliverable 5.3. Accessed September 12, 2020. https://www.e-pages.dk/ku/1340/html5/.
Hansen, Rieke, Werner Rolf, Stephan Pauleit, DennisBorn, Robert Bartz, Ingo Kowarik, Katharina Lindschulte and, Carlo W. Becker. 2017b. Urban Green Infrastructure. A foundation of attractive and sustainable cities. Pointers for Practice. Bonn: Federal Agency for Nature Conservation.
Lang,Werner, Stephan Pauleit, Julia Brasche, Georg Hausladen, Johannes Maderspacher, Rupert Schelle, and Teresa Zölch. 2018. Guidelines for climate-oriented communities in Bavaria. Recommendations from the project Climate protection and green infrastructure in cities at the Centre for Urban Ecology and Climate Adaptation. Munich: Technical University of Munich. Accessed September 12, 2020. https://www.zsk.tum.de/fileadmin/w00bqp/www/_my_direct_uploads/Guideline_English_final-komprimiert.pdf.
Lennon, Mick. 2015. “Green infrastructure and planning policy, a critical assessment.” Local Environment 20 (8): 957-980.
McPhearson, Timon, Steward T. A. Pickett, Nancy B. Grimm, Jari Niemelä,, Marina Alberti, Thomas Elmqvist, Christiane Weber, Dagmar Haase, Jürgen Breuste, and Salman Qureshi. 2016. “Advancing Urban Ecology toward a Science of Cities.” BioScience, 66 (3): 198-212.
Werquin,Ann Caroll,Bernard Duhem, Gunilla Lindholm, Bettina Oppermann, Stephan Pauleit, and Sybrand Tjallingii. 2005. Green structure and urban planning. Final Report. COST Action C11. Luxembourg: Office for Official Publications of the European Communities.
Zölch, Teresa, Johannes Maderspacher, Christine Wamsler, and Stephan Pauleit. 2016. “Using green infrastructure for urban climate-proofing: An evaluation of heat mitigation measures at the micro-scale.” Urban Forestry and Urban Greening, 20(1): 305–316.