Urban Green Infrastructure: An Introduction

Published: 18th October 2018 15:00Last Updated: 22nd October 2018 12:27

Introduction: What is green infrastructure?

Green infrastructure (or blue-green infrastructure) refers to human-managed and natural systems that provide services to society and ecosystems’ (Cole et al. 2017). Green infrastructure draws attention to the importance of the natural environment and ecological functions in urban land-use planning by integrating a network of natural and semi-natural areas into the urban fabric. This promotes the multifunctionality of land and the health of ecosystems, which provide a myriad of benefits – including environmental, social, climate change adaptation and mitigation, and biodiversity. Green infrastructure is different from low-carbon infrastructure in that green infrastructure focuses on nature-based solutions and ecosystem-based adaptation and mitigation measures within cities.


Fig. 1 Examples of green infrastructure. Courtesy of the EU Environment Commission.

The main areas green infrastructure can be used to target are stormwater (e.g. wetlands and green roofs), storm surges (e.g. dune cordons), heat stress (e.g. tree cover), biodiversity (e.g. habitat corridors), food production (e.g. bees for pollination), air quality (e.g. urban forests), water (e.g. reedbeds) and soils (e.g. vegetated verges). Studies indicate that well-functioning green infrastructure can increase urban resilience against extreme weather- and climate-related events such as landslides, floods, storm surges, and droughts (Tzoulas, 2007; Gaffin, Rosenzweig, & Kong, 2012; Depietri & McPhearson, 2017). Green infrastructure can also be part of the mix of measures to reduce urban greenhouse gas emissions. Moreover, green infrastructure aims to increase the overall physical and emotional well-being of urban communities. Green infrastructure is often less expensive than grey infrastructure and provides more co-benefits. The challenges associated with green infrastructure, especially encountered in developing country contexts with high urbanization rates, high levels of informality and poverty and under-resourced governments, are competing land development pressures (including increasing local municipal rates base), informal/illegal land occupations, and the regular maintenance requirements (i.e. expertise, budgets and local government mandates).

Key Terminology

  • Ecosystem-based adaptation (EbA) – the use of biodiversity and ecosystem services to help people to adapt to the adverse effects of climate change (CBD, 2008)
  • Green infrastructure multifunctionality – Green infrastructure can perform a number of functions and provides several benefits for the same spatial area (EEA, 2015, p.12)
  • Nature-based solutions (NbS) – inspired and supported by nature and use, or mimic, natural processes. They are multifaceted, functional, flexible and offer an abundance of co-benefits, while stimulating the local economy by increasing opportunities for revenues from sustainable practices (ICLEI, 2018).

A brief list of green infrastructure and case studies

Permeable pavements, SUDS & rain gardens

Impervious surfaces such as pavement are known to increase surface runoff, leading to poorer water quality and increased risk for flash and lasting floods. Thus, increasing the permeability of urban surfaces can better regulate stormwater drainage. Permeable pavements allow for vehicular and pedestrian traffic but also provide for infiltration of rainwater into the soil and, depending on the topography, the groundwater table below. Ideally, permeable pavements are also made of high albedo pavement (lighter colours) that reflect sunlight that is typically absorbed by typical impervious pavements made up of tar. Sustainable urban drainage systems (SUDS) also work to improve stormwater drainage and water quality. Increasing green space along roadways acts as a natural filter for water coming off road surfaces. Rain gardens provide an alternative to hardscaping garden space by incorporating native vegetation that increases filtration of rainwater into groundwater.

Case Studies:

Urban forests

These include urban parks, street trees, landscaped boulevards, gardens, river and coastal promenades, greenways, river corridors, wetlands, nature preserves, shelterbelts of trees, and working trees (e.g. trees that provide windbreaks, riparian buffers, alley cropping, silvopasture)  at former industrial sites (USFS, n.d.). Urban forests can decrease energy use (notably for air conditioning) and reduce the urban heat island effect through shading and the cooling effects of evapotranspiration. Furthermore, they improve air quality. All of these effects can improve physical public health, but also emotional health.

Case Studies:

Natural or constructed wetlands

Historically, cities developed along coasts, deltas, and rivers due to the ease of transport. Wetlands chiefly occur in the same areas, however, significant wetland destruction (i.e. draining wetlands to avoid flooding and allow for property development) often accompanies rapid urbanisation. Wetlands are natural rainwater buffers and also act as natural water filters. They are also an important habitat for birds, amphibians, and insects. Thus, protection of natural wetlands is of crucial importance to building urban resilience. Further, mimicking wetlands through constructed wetlands is another alternative to reap the benefits of wetlands in areas where they may not naturally exist or have been completely destroyed.

Case studies:

Green buildings

Green buildings encompass a whole range of green infrastructure considerations such as green roofs, green walls, geothermal heating and cooling, passive design, and rainwater collection.  Green roofs and walls can reduce surface water runoff for better stormwater management. Further, they aid in improving air quality and reducing the urban heat island effect, thereby reducing the need for air conditioning and reducing emissions associated with fossil fuel sources of electricity. They can also provide important amenity spaces for people, and spaces to grow food.

Case Studies:

Urban wildlife corridors

These are ‘habitats that are typically long relative to their width, and they connect fragmented patches of habitat. They can vary greatly in size, shape, and composition. The main goal of corridors is to facilitate movement of individuals, through both dispersal and migration, so that gene flow and diversity are maintained between local populations. By linking populations throughout the landscape, there is a lower chance [of] extinction and greater support for species richness.’ (Conservation Corridor, 2018).

Case Studies

Allotments, small holdings, and orchards

These contribute not only to urban food production and community engagement but also provide habitat for pollinating insects. Wildflower meadows have also proliferated in response to dwindling pollinator populations.

Case Studies:

An eco-corridor into Beijing's Olympic Forest Park. Courtesy of Landscape Performance Series.

Useful Articles & Literature

 

References

  • CBD. (2008) Report of the first meeting of the second ad hoc technical expert group on biodiversity and climate change. Convention on Biological Diversity: 17-21.
  • Cole, L., McPhearson, T., Herzog, C., & Russ, A. (2017) Urban Green Infrastructure. In: Environmental Education Review.
  • Conservation Corridor. (2018) ‘Corridor FAQ.’ Conservation Corridor. Available online from: https://conservationcorridor.org/the-science-of-corridors/ [Accessed 14 September 2018].
  • Depietri, Y. & McPhearson, T. (2017) “Integrating the grey, green, and blue in cities: Nature-based solutions for climate change adaptation and risk reduction,” in Kabisch, N., Korn, H., Stadler, J., Bonn, A. (Eds), Nature-based Solutions to Climate Change in Urban Areas: Linkages Between Science, Policy, and Practice, Springer.
  • European Environment Agency (2015) Exploring nature-based solutions: The role of green infrastructure in mitigating the impacts of weather- and climate change-related hazards. EEA Technical report No 12/2015. Available online from: https://www.eea.europa.eu/publications/exploring-nature-based-solutions-2014 [Accessed 14 September 2018]
  • Gaffin, S., Rosenzweig, C., Kong, A. (2012) Adapting to climate change through urban green infrastructure. Nature: Climate Change 2: 704.
  • ICLEI (2018) Resilient Cities Report 2018. [Accessed 14 September 2018]
  • Tzoulas, K., Korpela, K., Venn, S., Yli-Pelkonen, V., Kazmierczak, A., Niemela, J., James, P. (2007) Promoting Ecosystem and Human Health in Urban Areas using Green Infrastructure: A LIterature Review. Landscape and Urban Planning 81: 197-178.
  • USFS (n.d.) Urban Forests. Available online from: https://www.fs.fed.us/managing-land/urban-forests [Accessed 14 September 2018].
 

Further resources

Comments

We have recently published a collection of urban forestry stories from cities around the world and a number of them are about climate change mitigation:  You can find the book at:

http://www.fao.org/3/I8838EN/i8838en.pdf

For more information about our activities please visit:

http://www.fao.org/forestry/urbanforestry/en/