Green spaces and corridors in urban areas
Green spaces in cities provide cooling through shading and enhanced evapotranspiration, thus reducing the urban heat island (UHI) effect that occurs due to the modification of land surfaces and generation of waste heat. Green corridors, i.e. long green spaces in the cities and river-valleys which flow among the cities, can change the micro climate of the area and improve urban ventilation as they create a path for cooler air from outside to penetrate into the more densely built areas, also reducing the UHI. The European Commission aims at mainstreaming green infrastructure into EU policy areas (European Commission, 2013).
In Mediterranean cities, a higher proportion of forest is associated with a lower UHI magnitude (Nastran, Kobal and Eler, 2019). Besides UHI mitigation, green spaces and corridors can have positive effects on the sustainability of the urban landscape and the environmental health of cities. They can provide environmental, economic, recreational, transportation and health benefits. Urban vegetation supports more effective stormwater management (the capacity of vegetated surfaces to retain water and convey it into the ground is an important flood prevention feature that can reduce peak discharges), reduced noise pollution, and improved air quality, urban aesthetics and energy savings. Boosting green urban areas and connecting fragments of green space separated by human activities or structures with ecological corridors is useful for improving biodiversity and animal species dispersal within the urban landscape. Furthermore, the health and wellbeing (happiness, comfort, safety and security) of the urban population is improved by having access to parks, playgrounds or vegetation in public and private places (WHO Europe, 2017).
Despite the numerous benefits, the existing green areas are often threatened by expanding city structures, which fragment the natural areas creating small patches of green spaces amongst buildings and roads. Creating ecological corridors or connections among urban woodlands, gardens or other green spaces can help limit and remediate the negative effects of fragmentation. While the creation of green areas and corridors can be applicable in most urban areas, managing the urban landscape is a complex process subject to conflicting agendas.
Investing in and building up urban green infrastructure requires smart and integrated approaches to land management, urban design and strategic spatial planning, taking local characteristics and spatial distribution of vulnerabilities to climate change into consideration.
Furthermore, the changing climate conditions (i.e. increasing CO2 and air temperature, and changing rainfall conditions) must be well understood in order to select the appropriate species necessary to design plant communities for use in public landscapes, as they have to be adapted to the local environment and to the expected evolution of the climate conditions. Potential side effects, for example from the introduction of exotic species, must also be considered in terms of any negative impacts on the local biodiversity. There may also be positive side effects in using both non-native and native plant species, in terms of reducing the impacts of the climate change, as well as increasing the species diversity and aesthetic value (Alizadeh & Hitchmough, 2018). Initiatives for increasing green areas should follow the ecological restoration guidelines, so as to avoid monotonous plantations with a small number of species which won’t be resilient to disasters. When planning new areas the plan should envisage the list of necessary species divided according to the main layers of vegetation (PAP/RAC, 2020)
In Vitoria-Gasteiz, Spain, the Green Urban Infrastructure Strategy is being implemented through various interventions in different parts of the city: the Green Ring (a series of parks and semi-rural areas surrounding the city), the urban parks and the ecological corridors connecting different elements (such as trees along water streams or tree lined streets), vacant plots and even buildings (Climate-ADAPT, Case studies, 2018).
In Barcelona an integrated approach is undertaken with actions related to flora, fauna and habitats. They act to re-naturalize the city, to broaden the urban green and to retrieve the traditional uses of the urban periphery landscapes. Barcelona is relying on its citizens by using “citizens science” who have participated in producing the Atlas of the nesting birds. Barcelona relies on its citizens when it comes to urban green; they produced guidelines for enhancing biodiversity.
For more information on the use of vegetation on the roofs and facades of buildings to provide cooling in summer and thermal insulation in winter see AO39 Green roofs.
COSTS AND BENEFITS
Studies on costs and benefits suggest these measures have social, ecological and financial benefits. Benefits include increased urban biodiversity, higher environmental qualities in urban areas (e.g., recreational areas, community gardening), reduced vulnerability to heat waves and to floods, increased carbon storage – climate change mitigation and mitigation of air pollution.
Increase in green areas along the coastline may contribute to coastal resilience. If implemented, setback zone may become a new recreational area that may improve citizens’ life quality, city’s touristic offer, as well as result in the increase of the market value of the real estate in the area. In such cases multi-layer green structures should be planned, where those closest to the sea should be salt resistant. (PAP/RAC, 2020)
Success and the impact of these solutions increase if implemented in partnership of public and private sectors with volunteers. The European Green New Deal is expected to bring a number of opportunities for these solutions.
IMPLEMENTATION TIME AND LIFETIME
Finding or acquiring the land to use, taking the necessary administrative and planning steps to convert the land to a green space or green corridor, and actually creating green spaces takes time; however, these green spaces can last indefinitely.
SOURCE FOR MORE DETAILED INFORMATION
Alizadeh & Hitchmough, 2018, ‘A review of urban landscape adaptation to the challenge of climate change’, International Journal of Climate Change Strategies and Management, Vol. 11 No. 2, 2019 pp. 178-194, https://www.emerald.com/insight/content/doi/10.1108/IJCCSM-10-2017-0179/full/pdf?title=a-review-of-urban-landscape-adaptation-to-the-challenge-of-climate-change
Climate-ADAPT, 2018, Case study: Implementation of the Vitoria-Gasteiz Green Urban Infrastructure Strategy, https://climate-adapt.eea.europa.eu/metadata/case-studies/implementation-of-the-vitoria-gasteiz-green-urban-infrastructure-strategy
European Commission, 2013, COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS: Green Infrastructure (GI) — Enhancing Europe’s Natural Capital, https://ec.europa.eu/environment/nature/ecosystems/docs/green_infrastructures/1_EN_ACT_part1_v5.pdf
Nastran, Kobal and Eler, 2019, ‘Urban heat islands in relation to green land use in European cities’, Urban Forestry & Urban Greening, Vol. 37, pp. 33-41, https://www.sciencedirect.com/science/article/pii/S1618866717304806
PAP/RAC, 2020, Coastal Resilience Handbook for the Adriatic.
WHO Europe, 2017, Urban green spaces: a brief for action, https://www.euro.who.int/en/health-topics/environment-and-health/urban-health/publications/2017/urban-green-spaces-a-brief-for-action-2017
EEA, 2012, Urban adaptation to climate change in Europe: Challenges and opportunities for cities together with supportive national and European policies, http://www.eea.europa.eu/publications/urban-adaptation-to-climate-change
GREEN SURGE – Green Infrastructure and Urban Biodiversity for Sustainable Urban Development and the Green Economy – FP7 project, https://cordis.europa.eu/project/id/603567
IEEP, 2012, Green Infrastructure Implementation and Efficiency, https://ieep.eu/publications/green-infrastructure-implementation-and-efficiency