Biogeosciences Discuss (preprint)
Nowadays, city planners design urban futures by considering climate change and biodiversity loss. Here, we studied the greenhouse gas fluxes of urban lawns and meadows and linked the observations with plant functional diversity and soil properties. CO2, CH4 and N2O fluxes, as well as plant diversity, were measured in eight lawn–meadow pairs in the Helsinki Metropolitan Area, Finland. Among the sites, an irrigated lawn, a non-irrigated lawn, a young dry meadow and an old mesic meadow were intensively studied especially using manual chamber measurements in 2021–2022. The process-based ecosystem model JSBACH was utilized together with the momentary observations on CO2 exchange to quantify the annual C balance of these intensive study sites. On another hand, the initial dynamics of conversion from lawns to meadows were studied with the six other pairs, where measurements were conducted from 2020 to 2022 and the transformation of half of the sites had been performed in late 2020. We found that lawns are clear sink of carbon, whereas the mesic meadow was more resistant to drought events than a non-irrigated lawn. Moreover, according to our results, the conversion from lawn to meadow did not affect the fluxes of CH4 and N2O. Last, the relation between C and N cycle and plant diversity was unclear and would need further investigations.
Landscape and Urban Planning, Volume 239, November 2023, 104856
Urban green infrastructure can help cities tackle biodiversity loss and support well-being, but also contribute to climate change mitigation. This can be enhanced with green infrastructure policies that favor biodiversity, residential well-being, or climate benefits such as carbon sequestration. However, assessing public support for policies favoring specific green infrastructure outcomes, or potential trade-offs between them, is vital to understanding the social implications that such policies may have upon implementation. This paper presents the results of a public participation GIS (PPGIS) survey (n = 3 237) in Helsinki, Finland, concerning public support for policies favoring diverse climate, biodiversity, and well-being outcomes in green infrastructure. The results of the survey, derived with spatial and aspatial analyses, indicate that urban residents strongly support green infrastructure policies that favor climate benefits such as carbon sequestration, and are more willing to compromise the well-being benefits, rather than the biodiversity, of green infrastructure in favor of climate benefits. The results also reveal how support for policies favoring different green infrastructure outcomes varies spatially across the city, manifesting into priority areas of support for climate, biodiversity, and well-being outcomes. Finally, different ways of valuing and utilizing green infrastructure, and the socio-economic background of the respondents, predict support for policies favoring different green infrastructure outcomes. Our methods and results help take global political targets of mitigating climate change and reversing biodiversity loss into practice in cities in a manner that acknowledges the plurality of understandings on how green infrastructure should be managed, for whom, and most importantly, where.
Environmental Development, Article number: 100899 (2023)
Generally, the carbon neutrality targets of cities underline the role of vegetation especially natural biotopes and ecosystems. City-wide carbon pool assessments have so far focussed on land cover and land use types, with the role of urban trees receiving particularly significant attention. However, the carbon sequestration and storage (CSS) capacity of various vegetation types in urban areas as well as their potential to enhance urban carbon sinks remains largely unexamined. Planning and managing urban green infrastructure (GI) requires a climate-wise strategy of CSS that provides a scalable link between habitats and individual plant species. Therefore, this study focusses on the CSS capacity of urban vegetation through a thematic review and identifies the key elements influencing CSS in cold-climate cities. The study further highlights that the basis for atmospheric carbon sequestration lies in the favourable growth and stomatal functioning of an individual plant. The CSS of individual plants forms the basis for urban GI and the ecosystem services they provide. Moreover, the growth of urban vegetation is affected by diverse urban growing conditions, which are under continuous change as vegetation is managed, used and modified by residents. Although soils are a major storage for carbon, the role of vegetation in transforming carbon from the atmosphere into soil organic carbon is fundamental. In this study, with; the understanding of the key drivers influencing CSS, we define a framework for a; carbon-based vegetation typology and discuss the links between growing conditions and maintenance practices with regard to the CSS capacity of diverse vegetation types. This framework provides a conceptual basis for further interdisciplinary research into the CSS of urban vegetation, for example, for CSS capacity modelling and life cycle assessment of urban vegetation. It also supports climate-wise planning, design and maintenance by formulating practical and science-based recommendations for multi-professional actors engaged in GI.
Scientific Reports 13, Article number: 1720 (2023)
Climate change mitigation requires, besides reductions in greenhouse gas emissions, actions to increase carbon sinks in terrestrial ecosystems. A key measurement method for quantifying such sinks and calibrating models is the eddy covariance technique, but it requires imputation, or gap-filling, of missing data for determination of annual carbon balances of ecosystems. Previous comparisons of gap-filling methods have concluded that commonly used methods, such as marginal distribution sampling (MDS), do not have a significant impact on the carbon balance estimate. By analyzing an extensive, global data set, we show that MDS causes significant carbon balance errors for northern (latitude >60∘) sites. MDS systematically overestimates the carbon dioxide (CO2) emissions of carbon sources and underestimates the CO2 sequestration of carbon sinks. We also reveal reasons for these biases and show how a machine learning method called extreme gradient boosting or a modified implementation of MDS can be used to substantially reduce the northern site bias.
People and Nature, 5(2), 808-825
- Private domestic gardens have immense potential to contribute to urban biodiversity conservation. However, they are divided into small private plots and managed individually by garden owners. Therefore, engagement in wildlife-friendly gardening (WFG), which entails alternative management and design choices, relies on the individual willingness of each garden owner.
- Using an online survey and qualitative walking interviews with garden owners, our study explores individual internal and external factors underlying engagement in WFG. We interpret and reflect on our findings in the context of gardening as a relational practice between people and nature.
- Our findings suggest that motivations for gardening play a central role in how internal and external factors promote or impede WFG. For example, motivations towards organic gardening and learning from nature promote WFG, whereas personal and family care and well-being motivations seem to impede it.
- The perceived and actual garden area, as well as self-reported insufficient knowledge and social norms, covary the most with engagement in WFG. Engagement in WFG relates to people’s relationships with nature, as embodied in social norms of community acceptance and cohesion, and care and respect for nature and others.
- Future research into pro-environmental behaviours in gardens should adopt more relational approaches that go beyond the individual self and take better account of feedback between individual actions and social relations.
Urban Sustainability 3, Article number: 27 (2023)
Managing nature-based solutions (NBS) in urban areas for carbon mitigation and biodiversity outcomes is a global policy challenge, yet little is known about how to both assess and weave diverse knowledge systems and values into carbon-biodiversity trade-off assessments. This paper examines the spatial relationships between biophysical and social values for carbon sequestration potential (measured as carbon dioxide, CO2, flux) and biodiversity in Helsinki, Finland, using integrated valuation. The approach combines methods from carbon sequestration modelling, expert scoring approaches to biodiversity assessment and public participation geographic information systems (PPGIS). Results indicate strong spatial associations between biophysical assessment of CO2 flux and biodiversity priorities, and weaker associations between biophysical and social values. Integration of social and biophysical values leads to multiple pathways for protection of NBS to achieve carbon mitigation and biodiversity outcomes, as well as options for the spatial targeting of education and capacity building programs to areas of local concern.
Urban Forestry & Urban Greening 75, 127682
To address the inter-connected climate and biodiversity crises, it is crucial to understand how multifunctional urban green infrastructure (UGI) is perceived to contribute to carbon neutrality, biodiversity, human well-being, and justice outcomes in cities. We explore how urban residents, including youth, associate carbon-related meanings with multifunctional UGI and how these meanings relate to co-benefits to biodiversity, well-being, and broader sustainability outcomes. Our findings are based on a survey distributed among urban residents of Helsinki, Finland (n = 487) and reveal how carbon-related meanings of UGI manifest at different levels of abstraction, agency, and scale, and incorporate community values and concerns attributed to the planning, features, functions, and transformational dimensions of UGI. Core carbon-related meanings of UGI emphasize either actions towards sustainability, carbon neutrality, biodiversity, or unfamiliarity towards such meanings. Perceived justice concerns and the socio-demographic contexts of the respondents covaried with carbon-related meanings associated with UGI. The results illustrate community perceptions of how it is not only possible, but rather expected, that multifunctional UGI is harnessed to tackle climate change, human well-being, and biodiversity loss in cities. Challenges for implementing the carbon-related benefits of UGI include navigating the different expectations placed on UGI and including residents with diverse socio-economic backgrounds during the process. Our findings contribute to a holistic understanding of how multifunctional UGI can help bridge policy agendas related to carbon neutrality, biodiversity protection, and human well-being that cities can implement when aiming for sustainable, just, and socially acceptable transitions towards a good Anthropocene.
Sustainability, 14(19), 12697, 2022
Urban open spaces (UOS) provide an everyday environment for residents to experience nature. However, the management of UOS—from zoning to construction and maintenance—tends to follow efficient and straight-forward processes lacking use of residents’ experiences. This study first collected the views of management professionals on how participation can best benefit management of UOS. Second, a survey used biodiversity as a case to clarify how the ongoing changes in urban biotopes challenge conventional management of UOS. The results showed that especially in the maintenance phase of current UOS management there is potential to further involve residents in a continuous dialogue and activities to account for local perceptions, including residents’ sensing and emotions raised by UOS. Such involvement may facilitate positive human-nature relations but may require new modes of interaction. We thus propose such adaptive management to foster residents’ contribution to sustainability transition.
Sustainable Cities and Society, vol 84, Sep 2022
Cities are hotspots of anthropogenic activity and consumption. Thus, the consumption-based carbon footprints of their residents are pronounced. However, the beneficial climate impacts attributable to individual residents, such as carbon sequestration and storage (CSS) provided by residential green spaces and housing, have received less attention in the scientific literature. This review article presents an overview of the current research on the urban residential environment’s CSS potential and argues for its inclusion in the so-called carbon handprint potential of individual consumers. The focus of existing research is on developed countries, and in empirical studies the absence of compiling literature presents a clear research gap. Most current potential is estimated to lie within the carbon pools of residential vegetation, soils and wooden construction, with biochar and other biogenic construction materials presenting key future development pathways. The underlying background variables guiding the formation of a residential carbon pool were identified as extremely complex and interconnected, broadly classified into spatial, temporal and socioeconomic factor categories. Our findings suggest that there is significant potential for growth in the residential CSS capacity, but substantial efforts from the scientific community, urban planners and policy-makers, and individual residents themselves are needed to realise this.
CIB World Building Congress - RMIT University, Melbourne, Austraalia Kesto: 27 kesäk. 2022 → 30 kesäk. 2022 https://www.cibwbc2022.org/
Amongst the greatest global environmental challenges of our time are climate change and biodiversity loss. Feedback mechanisms associated with warming climate could also lead to large-scale biodiversity losses worldwide and it would therefore be logical to seek mitigation methods beneficial for both impact categories. However, research on the topic remains relatively scarce. Our study focuses on two key aspects of environmental sustainability, carbon storage capacity and species biodiversity, to determine whether these correlate at different levels of urban density. GIS-datasets are utilized to estimate the carbon storage potential and species diversity across the urban landscape as well as their association at different levels of urban land use intensity. The results highlight the importance of small green spaces at dense urban cores, indicating that in environments where green infrastructure is limited high species diversity and carbon storage are more likely to overlap, whereas at urban fringe the observed relationship is weaker and divergence of the two impact categories becomes more probable. The study draws attention to the role fragmented, limited green spaces play at establishing functioning ecosystems at local scale and provides new information to support the development of sustainable planning and management practices across the urban land use gradient.
Geosci. Model Dev., 15, 1735–1752, 2022
Soil organic carbon (SOC) models are important tools for assessing global SOC distributions and how carbon stocks are affected by climate change. Their performances, however, are affected by data and methods used to calibrate them. Here we study how a new version of the Yasso SOC model, here named Yasso20, performs if calibrated individually or with multiple datasets and how the chosen calibration method affects the parameter estimation. We also compare Yasso20 to the previous version of the Yasso model. We found that when calibrated with multiple datasets, the model showed a better global performance compared to a single-dataset calibration. Furthermore, our results show that more advanced calibration algorithms should be used for SOC models due to multiple local maxima in the likelihood space. The comparison showed that the resulting model performed better with the validation data than the previous version of Yasso.
Biogeosciences, 19, 2121–2143, 2022
Cities have become increasingly interested in reducing their greenhouse gas emissions and increasing carbon sequestration and storage in urban vegetation and soil as part of their climate mitigation actions. However, most of our knowledge of the biogenic carbon cycle is based on data and models from forested ecosystems, despite urban nature and microclimates differing greatly from those in natural or forested ecosystems. There is a need for modelling tools that can correctly consider temporal variations in the urban carbon cycle and take specific urban conditions into account. The main aims of our study were to (1) examine the carbon sequestration potential of two commonly used street tree species (Tilia × vulgaris and Alnus glutinosa) growing in three different growing media by taking into account the complexity of urban conditions and (2) evaluate the urban land surface model SUEWS (Surface Urban Energy and Water Balance Scheme) and the soil carbon model Yasso15 in simulating the carbon sequestration of these street tree plantings at temporal scales (diurnal, monthly, and annual). SUEWS provides data on the urban microclimate and on street tree photosynthesis and respiration, whereas soil carbon storage is estimated with Yasso. These models were used to study the urban carbon cycle throughout the expected lifespan of street trees (2002–2031). Within this period, model performances were evaluated against transpiration estimated from sap flow, soil carbon content, and soil moisture measurements from two street tree sites located in Helsinki, Finland.
The models were able to capture the variability in the urban carbon cycle and transpiration due to changes in environmental conditions, soil type, and tree species. Carbon sequestration potential was estimated for an average street tree and for the average of the diverse soils present in the study area. Over the study period, soil respiration dominated carbon exchange over carbon sequestration due to the high initial carbon loss from the soil after street construction. However, the street tree plantings turned into a modest sink of carbon from the atmosphere on an annual scale, as tree and soil respiration approximately balanced the photosynthesis. The compensation point when street tree plantings turned from an annual source into a sink was reached more rapidly – after 12 years – by Alnus trees, while this point was reached by Tilia trees after 14 years. However, these moments naturally vary from site to site depending on the growing media, planting density, tree species, and climate. Overall, the results indicate the importance of soil in urban carbon sequestration estimations.
Water 2021, 13, 3334
Nature-Based Solutions (NBS) have been proven to effectively mitigate and solve resource depletion and climate-related challenges in urban areas. The COST (Cooperation in Science and Technology) Action CA17133 entitled “Implementing nature-based solutions (NBS) for building a resourceful circular city” has established seven urban circularity challenges (UCC) that can be addressed effectively with NBS. This paper presents the outcomes of five elucidation workshops with more than 20 European experts from different backgrounds. These international workshops were used to examine the effectiveness of NBS to address UCC and foster NBS implementation towards circular urban water management. A major outcome was the identification of the two most relevant challenges for water resources in urban areas: ‘Restoring and maintaining the water cycle’ (UCC1) and ‘Water and waste treatment, recovery, and reuse’ (UCC2). s Moreover, significant synergies with ‘Nutrient recovery and reuse’, ‘Material recovery and reuse’, ‘Food and biomass production’, ‘Energy efficiency and recovery’, and ‘Building system recovery’ were identified. Additionally, the paper presents real-life case studies to demonstrate how different NBS and supporting units can contribute to the UCC. Finally, a case-based semi-quantitative assessment of the presented NBS was performed. Most notably, this paper identifies the most typically employed NBS that enable processes for UCC1 and UCC2. While current consensus is well established by experts in individual NBS, we presently highlight the potential to address UCC by combining different NBS and synergize enabling processes. This study presents a new paradigm and aims to enhance awareness on the ability of NBS to solve multiple urban circularity issues.
Environmental Research Letters
Sustainable forest management and harvested wood products together can create a growing carbon sink by storing carbon in long-lived products. The role of wood products in climate change mitigation has been studied from several perspectives, but not yet from a consumer’s view. In this study, we examine the impact of wooden housing on consumer carbon footprints in Finland. We use the 2016 Finnish Household Budget Survey and Exiobase 2015, a global multi-regional input-output model. The sample size is 3700 households, of which 45% live in a wooden house. We find that residents of wooden houses have a 12(±3)% (950 kg CO2-eq/year) lower carbon footprint on average than residents of non-wooden houses, when income, household type, education of the main income provider, age of the house, owner-occupancy and urban zone are controlled in regression analysis. This is not fully explained by the impact of the construction material, which suggests that the residents of wooden houses may have some features in their lifestyles that lower their carbon footprints further. In addition, we find that an investment in a new wooden house in an urban area has a strong reducing impact on a consumer’s carbon footprint, while investments in other types of housing have a weaker or no reducing impact. Our findings support wooden housing as a meaningful sustainable consumption choice.
Rethinking Sustainability Towards a Regenerative Economy (pp. 115-129). Springer, Cham
The carbon budget for limiting global warming to the targeted 1.5 ° is running out. Cities have a central role in climate change mitigation, as the vast majority of all greenhouse gas emissions occur to satisfy the energy and material needs of cities and their residents. However, cities typically only account for their direct local emissions from transportation, industry, and energy production. This may lead to the so-called low-carbon illusion of cities following from producing little and reporting low emissions, while extensively relying on imported material and energy flows. Consumption-based accounting, or carbon footprinting, enables overcoming this problem by assigning the emissions to the end user regardless of the place of production. However, currently the carbon footprinting methods only capture the harm side, and not the potential positive effects, the restorative or regenerative impacts, caused by green infrastructure, reforestation, and carbon capture and storage, for example. These positive impacts are sometimes called “carbon handprint”. In this chapter, we create a handprint-extended carbon footprinting method to illustrate how restorative and regenerative impacts can be incorporated consistently in the carbon accounting of cities and carbon footprints of consumers. We also link the discussion on regenerative cities with the remaining carbon budgets.
The International Journal of Life Cycle Assessment
Currently, no clear guidance exists for ISO and EN standards of calculating, verifying, and reporting the climate impacts of plants, mulches, and soils used in landscape design and construction. In order to optimise the potential of ecosystem services in the mitigation of greenhouse gas emissions in the built environment, we unequivocally propose their inclusion when assessing sustainability.
We analysed the life cycle phases of plants, soils, and mulches from the viewpoint of compiling standard-based Environmental Product Declarations. In comparison to other construction products, the differences of both mass and carbon flows were identified in these products.
Living and organic products of green infrastructure require an LCA approach of their own. Most importantly, if conventional life cycle guidance for Environmental Product Declarations were to be followed, over time, the asymmetric mass and carbon flows would lead to skewed conclusions. Moreover, the ability of plants to reproduce raises additional questions for allocating environmental impacts.
We present a set of recommendations that are required for compiling Environmental Product Declarations for the studied products of green infrastructure. In order to enable the quantification of the climate change mitigation potential of these products, it is essential that work for further development of LCA guidance be mandated.
In review to Geophysical Research Letters
Water storage plays an important role in mitigating heat and flooding in urban areas. Assessment of the capacity of cities to store water remains challenging due to the extreme heterogeneity of the urban surface. Traditionally, effective storage has been estimated from runoff. Here, we present a novel approach to estimate water storage capacity from recession rates of evaporation during precipitation-free periods. We test this approach for cities at neighborhood scale with eddy-covariance latent heat flux observations from thirteen contrasting sites with different local climate zones, vegetation cover and characteristics, and climates. We find effective water storage capacities to vary between 1.5 and 20 mm corresponding to e-folding timescales of 2.5 to 12 days. According to our results, urban water storage capacity is at least one order of magnitude smaller than the observed values for natural ecosystems, resulting in an evaporation regime characterised by extreme water limitation.
Urban Forestry & Urban Greening, Vol 57, January 2021
Cities have been identified as key actors in climate change mitigation. Nature based carbon sinks have been suggested as a means of mitigating the greenhouse gas emissions of cities. Although there are several studies on the carbon storage and sequestration (CSS) of urban green, the role of residential sites is not fully understood. In addition, the carbon storage of soils is often excluded. Also the implications for planning require more attention. This study estimates the CSS potential of trees and biochar in urban residential yards and identifies effective means to enhance it. Moreover, the study discusses the results at the city scale. The research is based on a case study in Helsinki, Finland, and applies i-Tree planting tool to assess the current and potential life cycle CSS of the case area. The results reveal that trees and the mixing of biochar into growing medium can increase the CSS considerably. The CSS potential of the case area is 520 kg CO2 per resident during 50 years. The added biochar accounts for 65 % of the capacity and the biomass of trees accounts for 35 %. At the city scale, it would lead to 330 000 t CO2 being stored during 50 years. The findings suggest that green planning could contribute more strongly to climate change mitigation by encouraging the use of biochar and the planting of trees, in addition to ensuring favourable growing conditions.