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No. 83: Ecosystem based approaches to Climate Adaptation – Urban Prospects and Barriers

Zandersen, M., Jensen, A., Termansen, M., Buchholtz, G., Munter, B., Bruun, H.G., Andersen, A. H. 2014. Ecosystem based approaches to Climate Adaptation – Urban Prospects and Barriers. Aarhus University, DCE – Danish Centre for Environment and Energy, 94 pp. Scientific Report from DCE – Danish Centre for Environment and Energy No. 83 http://dce2.au.dk/pub/SR83.pdf


This report presents a study of ecosystem based approaches to climate adaptation in urban areas. It takes the case of green roofs in Copenhagen municipality as a means of creating urban habitats that have the potential to alleviate the negative climate impacts in terms of expected higher rate and volume of surface run off as well as urban heat islands. At the same time, these habitats may also enhance a wider set of benefits derived from ecosystem services such as biodiversity, recreation, mobility, social inclusion and aesthetics.

Ecosystem services are the benefits that people obtain directly or indirectly from ecosystem functions such as the protection from storm surges, air quality regulation, food, fibre and freshwater. Ecosystem-based approaches to adaptation are understood as the use of biodiversity and ecosystem services to help people adapt to the adverse effects of climate change.

Urban areas are characterised by compact built environments and impermeable surfaces that modify energy exchanges and hydrological processes compared to rural and more natural areas. Moreover, urban populations are growing, leading to higher rates of urban sprawl and concentration of people and infrastructures. Cities are therefore especially prone to the negative consequences of changes to the climate system. But by working actively in urban settings with Nature’s capacity to absorb and control negative impacts of climate change, it is increasingly believed that we are capable of creating sustainable resilient cities.

ES.1.1   Objectives

The main objective of this pilot study is twofold: i) to investigate the prospects and conflicts of systematically integrating an ecosystem-based climate change adaptation in the municipality of Copenhagen, where we take the case of ecosystem services provided by green roofs; and ii) to test the feasibility of conducting deliberative valuation using mixed methods to assess preferences for greening residential buildings and areas.

At citizen level, we undertake a deliberative valuation workshop for local inhabitants to test the acceptance and preferences towards green roofs as a multifunctional way of adapting to climate change. The type of outcome can help policy makers better understand motivations and wishes regarding how the city should look like and function, the degree to which they would be willing to undertake action and the role of the municipality in creating incentives.

At policy level, we undertake policy document analysis of Copenhagen plans and strategies and supplement these with interviews with city planners to understand how the green roof policy has developed, barriers and conflicts, the extent to which an ecosystem based approach is integrated in planning and which aspect may promote the inclusion of green roofs as an ecosystem service in the city adaptation policy.

The dual perspective of citizens and city planning gives an example of how mixed method approaches can deliver integrated knowledge of how urban landscapes are perceived and used and what future developments citizens and planners would like to see happen. This study is designed as a pilot study to shed light on these aspects.

ES.1.2   Ecosystem Services from Green Roofs

Green roofs have the potential to provide both private and public benefits. They represent new habitats, where there have not been any for a long period of time (in the case of retrofitting) or where existing habitats have recently been eliminated (in the case of developments on green- or brown fields). The habitats on green roofs are almost exclusively determined by humans and require some level of maintenance. Choices as to the depth of substrate matter and hence the type of vegetation that can be introduced on roofs largely determine the type and quality of ecosystem services provided along with consideration of access for people. Ecosystem services from green roofs range from habitat services that create new habitats for flora and fauna; regulating services such as adaptation to climate change by mitigating urban heat islands and improving surface water run-off under normal everyday rain showers or climate change mitigation by providing alternatives to fossil fuel based transport through popular walking/cycling corridors across urban areas, optimizing solar cell performance or sequestering carbon in vegetation, prolonging the longevity of normal roofs by protection from UV radiation; provisioning services such as urban food production; and cultural services including improving quality of life through improved recreation opportunities, physical and mental well-being, enhancing land values or using greening activities to enhance social inclusion.

ES.1.3   Direct disadvantages of Green Roofs

Despite the potential long list of benefits in terms of ecosystem services from green roofs, there are a number of disadvantages that may answer for the relatively rare occurrence of green roofs in Denmark to date. Quality of installation is one major concern of many stakeholders, given the lack of Danish standards and guidelines, education, research and fairly few years of experience in Denmark. This is also related to the fact that green roofs are not part of traditional Danish building culture. Costs of establishing a green roof is another major obstacle for the large-scale introduction of green roofs in cities. Different types of green roofs place different requirements on the statics of buildings, which may need reinforcement. The roof surface will need proper preparation before several protection and absorption layers are installed with the vegetation layer on top; this demands specific knowhow and materials. Regular maintenance costs adds to the direct costs of green roofs, needing bi-annual removal of unwanted vegetation and leaves, which is far from trivial at roof level. Finally, conflicts of interests with the functioning of green roofs may occur, where rain water harvesting is a preferred option for use in domestic appliances or irrigation, or the statics of a building is not able to carry the weight of both green roof and solar cells.

ES.1.4   Potential for retrofitting green roofs in Copenhagen

Using the National Building Registry (BBR), we conducted a simple analysis of the maximum technical potential of green roofs on flat or nearly flat roof surfaces. Total roof area in the Municipality of Copenhagen represents more than 1300 ha, of which flat roofs take up some 13 % (171 ha). The large majority of flat roof buildings in the municipality are used for commerce, service, transport and public administration (52 %); whereas private housing represents 16 %, regional and state 15 % and municipal institutions about 6%. If, conservatively, we would assume a similar uptake of green roofs on flat roofs in Copenhagen as on the average coverage of green roofs in Germany (where 14 % of the total number of roofs are green), this would represent some 240.000 m2.

ES.1.5   Planning Aspects of Green Roofs in Copenhagen Municipality

Policies and plans begin to mention green roofs in the 2008 ‘Waste Water Plan’, followed by the 2009 ‘Climate Plan’, where green roofs were included as an example of green infrastructure delivering adaptation potential. In 2009, a specific green roof policy was politically decided and later integrated in the 2011 ‘Municipality Plan’, the 2011 ‘Climate Adaptation Plan’ and 2012 ‘Climate Plan 2025’. Local plans and municipal guidelines now incorporate green roofs. The green roof policy requires that all new buildings with a roof slope below 30 degrees should have green vegetation to the extent that this is acceptable in terms of aesthetics and practicality. It is expected from present local plans that about 200.000 m2 of green roofs will be installed on new buildings over the coming years. No qualifications of the green roof requirements exist in terms of the area that vegetation should take up on new roofs, the type or the performance of green roofs. There is no direct financial incentive provided to cover parts of the costs of installing green roofs and also retrofitting green roofs on existing buildings is not included in the policy.

Municipal policies in Copenhagen clearly indicate a growing recognition of ecosystem services in general and of the services that green roofs offer an urban population in particular. Green roofs constitute an element in urban green infrastructure that is increasingly articulated as providing a range of services to the urban population, including aesthetics, more pleasant atmospheres of urban spaces, rain water retention, reduction of heat in buildings and urban spaces and adding to a general greening of the city and a greener urban identity. Thus, green roofs move from ‘merely’ providing patches of urban nature to offer a range of benefits, which in combination are anticipated to make green roofs – as one among several green infrastructure elements – an asset of the future city. Likewise, green roofs are perceived to offer services that will manage some of the future rains and in combination with other climate adaptive measures prepare the city for the impacts of present and future climate changes.

However, the term ecosystem services is absent from the policy discourse. Along with development of the policies to address the city’s overall strategy of climate adaptation, the acknowledgement of green roofs and related ecosystem services progress and become more central. However, measures, standards and initiatives are not very specific while green roofs are often mentioned as examples of a greening of the city or of the benefits (i.e. services) of urban nature.

The acknowledgment of the diversity of ecosystem services provided by green roofs (and also other green infrastructure) makes it possible that green roofs can be considered in relation to other policy areas than climate adaptation, such as climate mitigation, urban design and architecture, common urban identity as an Eco-Metropolis and green growth. Most of these services reflect the city’s conceptualisation of urban sustainability, with emphasis on the natural environmental dimension and the social dimension. Providing more than one service reduces the vulnerability of green roofs in urban development; if developers for budget reasons exclude green roofs from the project, it is not only the aesthetics or water retention that is omitted but a larger range of benefits.

ES.1.6   Citizen Views and Preferences regarding Green Roofs

Citizen views and preferences regarding greening urban space in general and green roofs in particular were investigated during a 3-hour long deliberative valuation workshop with inhabitants of the Øbrohus housing block in Sct. Kjelds neighbourhood in December 2012. Respondents were indirectly asked to reveal their preferences for different characteristics of green roofs that could be envisioned on their building. A monetary valuation was made as to their willingness to accept a monthly rent increase for getting a green roof that they could have access to. 19 individuals participated. The process was built around a convivial setting of coffee/tea and a tasty three-course dinner. The workshop took place in the common rooms of a neighbouring housing block.

The deliberative setting allowed for an integration of the social context of participants and group dynamics, enhancing the reality of the hypothetical choice situations and opening up for learning processes, preference building. The setting gave a common space for individual statements and deliberation of wishes and perceptions regarding the physical surroundings in the neighbourhood in general and in Øbrohus in particular.

Results of the quantitative analysis show a significant preference towards the establishment of a green roof both in session one, where no requirement to pay for the green roof was included and session two, where a monthly rent increase was introduced as a payment vehicle. Introducing the payment vehicle in terms of the monthly rent increase did not change the preference direction. Statistically significant relative preferences remained stable in the two sessions. The most preferred attribute levels in both sessions proved to be the standard sedum-moss green roof combined with solar cells as well and the option to recycle excess rain water in the building. In neither of the two sessions did the stand-alone semi-intensive green roof or high biodiversity indicate any significant preference. The relative importance of the significant attributes roof type and water are fairly balanced with roof type representing 53 % and water 47 %. Average monthly WTPs for options range on average from 145 DKK to 500 DKK, depending on the characteristics of the roof.

ES.1.7   Conclusions

Green roofs represent one example of using Nature’s capacity to help people adapt to the adverse effects of climate change, while potentially also providing a whole variety of other benefits that enhance quality of life and urban sustainability. This is opposed to human-made technical solutions to e.g. increasing temperatures or increasing water run-off, which only provide the one service. Therefore, comparing options that use ecosystem based approaches to e.g. climate adaptation with human made ‘grey’ infrastructures ought to take into account the wider benefits (and disbenefits) of ecosystem services delivered by green infrastructures and permeable surfaces.

If implemented systematically at large scale, green roofs may potentially contribute significantly towards urban sustainability. If, however, we look at individual benefits of green roofs, such as run-off management alone, they may not prove to be economically sound investments. This assessment may very well change when including considerations of enhanced aesthetical values, potential increased property value, recreation opportunities and habitats for biodiversity. Deciding upon systematically implementing green roofs in urban areas (and not uniquely on new buildings) will therefore need to comprise many aspects and involve transdisciplinary cooperation (e.g. between biologists, engineers, architects, planners and economists). Some benefits will accrue to private building owners (e.g. increased private property value or extended longevity of roofs), whereas other benefits may go to different beneficiaries: the neighbourhood and local authority (e.g. reduced risk of flooding and reduced pressure on urban drainage system) and yet other benefits may accrue to the wider society (e.g. establishment of new habitats for biodiversity).

For a large-scale systematic implementation of green roofs in Copenhagen on both existing and new buildings, Copenhagen Municipality could introduce new and/or extend existing policy instruments: i) the current mandate of green roofs through the building code or local plans could be extended to include existing buildings (applicable when large renovations are undertaken) and introduce minimum performance standards and a minimum ratio of green roof to building ground plan; ii) Provide direct financial incentives to compensate for some of the initial and non-negligible installation costs while providing society with a range of desirable public services; iii) make the current indirect financial incentives more flexible by permitting a partial refund of sewage connection fee; and iv) develop performance standards on that give quantifiable advantages of green roof buildings compared to non-green roof buildings. Introduction of green roofs at a larger scale could potentially provide local retention of water, and thus reduced costs for ‘grey’ adaptation measures for the municipality, and would moreover contribute to extension of green spaces, making city spaces more liveable for people. Copenhagen Municipality could choose to mix these policy instruments to create the basis for a truly systematic ecosystem based approach to not only climate adaptation but also to the wider variety of ecosystem services that permeable surfaces and habitat creation can offer in dense urban areas.