Modelling the net environmental and economic impacts of urban nature-based solutions by combining ecosystem services, system dynamics and life cycle thinking: An application to urban forests

Nature-based solutions (NBS) are gaining relevance as sustainable urban actions because of their potential to provide multiple benefits in the form of ecosystem services (ES), and thus mitigate urban challenges. This paper presents an original semi-dynamic modelling framework that simultaneously considers i) ES supply and demand dynamics, ii) negative environmental impacts, externalities, and financial costs derived from NBS, and iii) life cycle NBS impacts beyond the use phase. Compared to other models, it also aims to be valuable for urban planning actions at site level, i.e., for evaluating the net impacts of specific urban NBS projects. To validate the modelling framework, a proof-of-concept model for urban forests is developed and tested for a case study in Madrid (Spain). The modelling framework is split in two interrelated parts: foreground (dynamic modelling) and background (static modelling). In the foreground, the environmental impacts derived from the use phase of an NBS project are quantified considering its spatio-temporal dynamism, by making use of system dynamics. In the background, the environmental impacts derived from the rest of the life cycle phases of the NBS are quantified making use of steady state life cycle impact assessment. The net economic impact of the NBS project, considering both financial values and externalities, is eventually calculated in the background encompassing all the life cycle phases. Results from the case study illustrate how planning, design, and management decisions over the entire life cycle of an urban forest can influence the net environmental and economic performance of this type of NBS. A discussion is provided to inform on how the modelling framework can help moving beyond the state-of-the-art, and how the derived model can be used for sustainability assessments of urban NBS projects

Evaluating the Impact of Nature-Based Solutions: A Handbook for Practitioners

The Handbook aims to provide decision-makers with a comprehensive NBS impact assessment framework, and a robust set of indicators and methodologies to assess impacts of nature-based solutions across 12 societal challenge areas: Climate Resilience; Water Management; Natural and Climate Hazards; Green Space Management; Biodiversity; Air Quality; Place Regeneration; Knowledge and Social Capacity Building for Sustainable Urban Transformation; Participatory Planning and Governance; Social Justice and Social Cohesion; Health and Well-being; New Economic Opportunities and Green Jobs. Indicators have been developed collaboratively by representatives of 17 individual EU-funded NBS projects and collaborating institutions such as the EEA and JRC, as part of the European Taskforce for NBS Impact Assessment, with the four-fold objective of: serving as a reference for relevant EU policies and activities; orient urban practitioners in developing robust impact evaluation frameworks for nature-based solutions at different scales; expand upon the pioneering work of the EKLIPSE framework by providing a comprehensive set of indicators and methodologies; and build the European evidence base regarding NBS impacts. They reflect the state of the art in current scientific research on impacts of nature-based solutions and valid and standardized methods of assessment, as well as the state of play in urban implementation of evaluation frameworks

A system dynamics model of urban forests to assess ES trade-offs and synergies in biophysical and monetary unit.

Oral Presentation Abstract Enhancing urban ecosystem services through the implementation of nature-based solutions (NBS) in cities can support a further integration of environmental objectives into urban planning. However, how to implement NBS to reduce the distance between urban planning and practical urban sustainable management and development remains an open question. In this study, we use a system dynamics framework to analyse the contribution of NBS, specifically urban forests, to address environmental urban challenges. An initial model of urban forest was developed to study i) regulation of temperature and humidity; ii) regulation of chemical conditions; and iii) provision of materials by respectively modelling changes in physiological equivalent temperature, carbon sequestration, and exploitable above ground biomass. The economic benefits (in terms of these services) and costs were then computed under several management and development scenarios representing alternative management types (i.e. trimming, harvesting) and built densities (i.e. low to high built density). As part of the modelling framework, several other ecosystem services, biophysical indicators, and their main socio-environmental factors and processes are identified and related to key urban challenges. The tested model shows the potential of urban forests’ for supplying ecosystem services and identifies different trade-offs on the regulation of chemical conditions and temperature depending on the intensities of wood harvesting and urban conditions (e.g. urban vs periurban), which together with the consideration of costs inform about economic benefits or loss. The use of a system dynamics approach applied to the modelling of NBS shows to be a valuable decision support solution to allow understanding how the concept of ecosystem services can be valuable for the planning and management of green spaces. Keywords: System Dynamics; MIMES; Nature-based Solutions; Ecosystem Services; Monetary Valuatio

A life cycle costing approach to integrate economic valuation in modelling nature-based solutions in cities

Oral Presentation Abstract: Abstract: Nature-based solutions (NBS) are usually described as solutions to societal challenges inspired and supported by nature, which provide social, economic, and environmental benefits. Current NBS assessment toolkits, which assess benefits in the form of ecosystem services (ES), usually do not consider the associated costs during NBS life cycles. Moreover, assessments do not consider changes in ES supply along NBS lifetime, assuming static conditions. In this paper, we present a modelling framework that integrates ES and life-cycle costing (LCC) approaches and considers dynamic conditions to overcome the above mentioned limitations. Based on the modelling framework, a pilot urban forest model is developed and tested in a case study in Madrid (Spain), providing results in biophysical and monetary units. The pilot model assesses two regulation ES classes (regulation of chemical composition of the atmosphere, regulation of temperature and humidity), one provisioning ES class (materials from cultivated plants for direct use or processing), and operational costs due to pruning and management of plant residues. The modelling framework serve as an initial basis for the integration of ES and LCC in the valuation of NBS and similar solutions. Keywords: Nature-based solution, Monetary valuation, Byophysical valuation, Life-cycle thinking, Urban area

Quantification and mapping of regulating and provisioning services in urban areas making use of a system dynamics model

Oral Presentation Abstract: There is a growing evidence that the use of statistical, process-based, and mechanistic models can provide robust information for the quantification and mapping of provisioning and regulating services. These models can allow identification and relation of main factors of biophysical structures and processes, taking into account how the condition of ecosystems or living features (e.g. health conditions of trees) could increase or decrease the supply of ecosystem services (ES). However, they i) usually assume that conditions do not change over time; ii) rarely consider causal loop interactions among biophysical structures, processes and human actions; iii) do not model multiple ES at once. In this research, we present a system dynamics modelling approach to quantify and map several regulation and provisioning services and disservices simultaneously supplied by urban nature-based solutions, which acknowledges temporal changes in the system. To illustrate the approach, we develop and present the results of an urban forest model applied to Valdebebas Park (Madrid, Spain). Five regulating services (carbon sequestration, temperature regulation, air pollutant filtration, and water flow maintenance), one provisioning service (plant material for direct use or processing), and one provisioning disservice (plant residues for landfill or waste treatment) were quantified and mapped in biophysical units. The model includes morbidity dynamics of trees triggered by their location (street vs open spaces), lack of water, and waterlogging, as well as the influence of human management. The results show the potential of system dynamics models to quantify bundles of ES in a spatio-temporally explicit form and their usefulness to inform decision making in urban interventions. Key words: System Dynamics; Nature-based Solutions; Ecosystem Services; Ecosystem Disservices

Modelling Benefits and Costs of Urban Forest: Application to Valdebebas Park (Madrid, Spain)

Oral Presentation Abstract: Process-based models are gaining relevance for the quantification of benefits and costs derived from urban nature-based solutions (e.g. urban forests, green roofs) as a way to inform decision makers. We developed a system dynamics approach to quantify the net environmental and economic benefits of urban nature-based solutions. Based on our system dynamics approach, we present a proof-of-concept model of urban forest to quantify their net economic benefits, which was applied to a zone of Valdebebas Park (Madrid, Spain). The proof of concept model quantifies three ecosystem services (carbon sequestration, temperature and humidity regulation, and potential wood provision) and takes into account investment costs, and two operational costs (re-planting dead trees, and waste treatment of plant residues) in a spatio-temporal explicit form. The model uses a regular grid of cells of 100x100 meters and calculates ecosystem services (benefits) and costs at a monthly temporal resolution. For the application to Valdebebas Park, we modelled the ecosystems services (benefits) and operational costs in the form of biophysical outputs for 50 years. Later, we converted the biophysical outputs into monetary units making use of benefit transfer functions and aggregating outputs into yearly time steps. As part of the model, tree death is included making use of binomial probability functions, which incorporates stochasticity into the model. As a result of the application, advantages and current limitations of the model were discussed as well as its usefulness for decision making. Key words: System Dynamics; MIMES; Nature-based Solutions; Ecosystem Services; Biophysical Valuation; Monetary Valuatio

Spatial optimisation of urban ecosystem services through integrated participatory and multi-objective integer linear programming

Urban ecosystem services (UES) are the benefits supplied by nature to people in urban systems. The supply of UES is threatened because of widespread increasing urbanisation. Modelling scenarios that optimise UES supplies can support sustainable urban planning processes. UES are linked to land use/land cover (LULC) types, which enables the optimisation of UES supply to be based on LULC configurations. However, current modelling approaches are not suitably adapted to the link between UES optimisation and LULC configurations. One possibility to target UES optimal supply is to use mathematical optimisation methods. The objective of this study is to test the combined use of participatory modelling and optimisation models to deliver spatial solutions that maximise UES by optimal urban LULC configurations. An integrated model is built using a multi-objective integer linear programming (MOILP) model along with LULC performance scores to maximise a set of locally supplied UES. This is illustrated with a case study of Lisbon (Portugal) involving the participation of key stakeholders to validate and benchmark the selection of optimisation constraints. Results show land optimally allocated to land cover types with high UES functions combined with a reshuffling and densification of residential land. Thus, the new LULC configuration increased multiple UES supplies while maintaining a level of housing capacity. The model shows clear implications of increasing land cover types whose UES functions are high compared to most other LULC classes. Moreover, incorporating stakeholder participatory modelling offers a transdisciplinary and interdisciplinary scientific contribution intersecting mathematical optimisation, UES, and urban planning

A combination of LCC and ecosystem services assessment making use of system dynamics modelling

Oral Presentation Abstract: In the construction sector, traditional life cycle costing (LCC) is a well-known and robust approach useful to compare the total internal cost of (natural or grey) infrastructure alternatives from their design until their end of life. Two other types of LCC exist:environmental and social . The former, usually applied in combination with LCA, monetarise the cost of environmental externalities and the latterintegrates social externalities. However, it is difficult to take into account positive environmental and/or social externalities only making use of these methods. The combination of LCC with ecosystem services (i.e. the benefits that people obtain from natural elements) could facilitate to account negative and positive environmental and social externalities of solutions such as urban forests, green roofs/walls, or constructed wetlands. Since externalities of natural solutions are changing along time due to the interaction of factors, their valuation also requires use of techniques such as system dynamics models. In this research, we present a methodology that integrates social LCC with ecosystem services assessment, supported on a system dynamics model. This type of methodological integration would be useful for cost-benefit analysis of natural infrastructures where externalities should be considered. The methodology is applied to a pilot case study (a green roof), taking into account three types of costs (investment, operational, and deployment) for an expected operational life of 50 years. The application show the potentiality of blending LCC with ecosystem services assessment and system dynamics for cost-benefit analysis done under a sustainability perspective