Paneelikeskustelun osallistujat Timo Vesala (Helsingin yliopisto), Ulrika Åkerlund (Boverket, Sweden), Liisa Kulmala (Ilmatieteen laitos), Christopher Raymond (Helsingin yliopisto) ja Miisa Tähkänen (Green Building Council Finland). Keskustelun vetäjänä toimi Tiina Merikoski (Aalto yliopisto). (Kuva: Justine Trémeau)
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Science seminar: Urban green has an important role in mitigating climate change and biodiversity loss and improving well-being

A science seminar ’Towards green and carbon-smart cities’ was held last August at the Helsinki Central Library Oodi as part of the Carbon-Smart Urban Green Festival. At the seminar, the multiple benefits of urban green were discussed and the results of the CO-CARBON project were presented. The seminar was held in English and aimed particularly at the project’s stakeholders (urban planning and landscape professionals), the scientific community, and all those interested in developing climate-smart cities.

Benefits of urban green

The first keynote speaker of the seminar was Professor Timo Vesala from the University of Helsinki, who is also a member of the Finnish Climate Change Panel. In his speech, Vesala highlighted the significant role of densely populated cities as a source of carbon dioxide emissions at the global level. He also emphasised the importance of so-called natural climate solutions, i.e., forests, wetlands, soils and oceans acting as carbon sinks. Human emissions of carbon dioxide are so high that the carbon sequestration capacity of urban green space may seem small in percentage terms. However, according to Vesala, what is more important in the urban context is that, unlike other urban land uses, urban green does not increase carbon emissions, which is why it is essential in climate change mitigation.

In the second keynote speech, landscape architect Ulrika Åkerlund from the Swedish National Board of Housing, Building and Planning (Boverket) discussed the many benefits of urban green, including protection against extreme weather events, health support, biodiversity conservation and climate change mitigation. She also reported on Sweden’s goal to integrate urban green spaces and ecosystem services into planning, building, and urban management in most municipalities by 2025. With this strategy, Sweden aims to meet the requirements of the EU’s Nature Restoration Law for urban areas. Currently, around half of Sweden’s cities have a canopy cover of 30% or more. However, the distribution of urban trees, for example, is still generally uneven between neighbourhoods and should be improved to ensure that everyone has access to the many benefits of urban green. Finally, Åkerlund stressed that now is an important time to act to promote urban green, as it is given high priority on the global political agenda.

Timo Vesala gave the first keynote speech in the seminar (Photo: Anna Pursiainen)

Quantification of carbon sinks to meet carbon neutrality targets

Liisa Kulmala (Finnish Meteorological Institute), Justine Trémeau (Finnish Meteorological Institute) and Minttu Havu (University of Helsinki) started the part of the seminar about the CO-CARBON project results with their presentations on quantification of carbon storage, fluxes and sequestration in urban green infrastructure. Kulmala first gave an overview of carbon sinks in different urban environments. Trémeau then told about a study that compared grassland and meadows, which concluded that grassland is a more stable carbon store than a meadow. However, since meadows are more drought-resistant than grasslands, it is worth to convert grasslands into meadows. Havu reported on SUEWS modelling, which shows that trees are the strongest carbon sinks of urban vegetation in Helsinki, accounting for 40% of all carbon uptake. The modelling can be used to support urban planning and decision-making to achieve carbon neutrality goals.

Liisa Kulmala (photo: Paula-Kaisa Leppänen)

Support from society and communities for urban green

Next, the theme of the presentations changed into implementing multifunctional carbon-smart urban green with co-benefits. Outi Tahvonen and Anna Ryymin (Häme University of Applied Sciences) started the presentations by discussing the national guidelines for building and maintenance of urban green and pointed out their shortcomings. Jussi Lampinen (University of Helsinki) told about research on public support for carbon-smart climate and biodiversity solutions in cities. According to the study, public support in Helsinki varies from moderate to strong depending on the socio-economic context, accessibility of green spaces, and people’s understanding of carbon sequestration, among other factors. The implementation of biodiversity conservation and carbon neutrality objectives should take into account different values, attitudes, and uses of green spaces, as well as different levels of their accessibility. To achieve this, planning needs to apply participatory practices, recognise the linkages between different issues and acknowledge that win-win situations between biodiversity, carbon sequestration, and the social values of green spaces are unlikely to be universal. Ranja Hautamäki (Aalto University) concluded the session with a presentation on the policy recommendations for cities developed in the CO-CARBON project.

Anna Ryymin (left) and Outi Tahvonen (right). (Photo: Justine Trémeau)

The future of urban green

The seminar ended with a panel discussion on how does urban green transform the future cities. The panel began by a discussion on the challenges of climate change mitigation. In their responses, the panelists painted a rather complex picture, including a lack of scientific knowledge, a lack of skills and cross-sectoral cooperation, challenges in policy-making and reconciling different time perspectives, and a lack of clear guidelines and science-based assessment, especially in the business sector.

As a solution to these challenges, the panelists suggested, for example, an effective tool to quantify the area of urban green space and the impacts of its increase in individual construction projects. It would also be important to renew existing systems by learning from good solutions outside Finland. The general political and public attitude should also become more favourable to urban green. The promotion of urban green should also be made an integral part of urban planning and related legislation. Timo Vesala also summed up well in his answer how we cannot always think only about money, but we must accept that we owe a debt to the environment and that paying that debt is of course expensive.

The panelists also discussed how to bridge the gap between science and practice. Miisa Tähkänen, from the business sector, expressed the wish for publications and guides to help non-scientists easily understand how best to promote the green transition. The scientists expressed understanding for this need, but with some hesitation, because it is not always easy to translate the uncertainties of science into a simple language. However, they acknowledged that uncertainty could also be communicated more openly. Christopher Raymond also pointed out that clear nature-based solutions have already been put forward, but that there is often not enough will to change current practices because it is unpleasant and requires difficult decisions.

Finally, the panelists stressed, among other things, that small steps (e.g. using public transport) are important to promote climate action and that no one should strive for perfection. It is also important to protect existing nature and soils as well as to identify areas where nature has suffered and where restoration efforts would be important. There should also be more discussion about equity issues related to urban green and, for example, their relationship to other inequalities between different urban areas. Scientific argumentation and communication should also take into account the public and its interests (e.g., economic) and not always emphasise, for example, only the ecological perspective.

Starting photo: Panelists Timo Vesala (University of Helsinki), Ulrika Åkerlund (Boverket, Sweden), Liisa Kulmala (Finnish Meteorological Institute), Christopher Raymond (University of helsinki) and Miisa Tähkänen (Green Building Council Finland). The panel was chaired by Tiina Merikoski (Aalto University). (Photo: Justine Trémeau)

Text: Johanna Hohenthal

The slides of the seminar presentations are available on festival website.

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