An economic dimension must necessarily be integrated in the sustainability analysis of nature-based solutions (NBS) to facilitate their deployment in policy, local plans and urban interventions. In this way, valuations of NBS can take into account the trade-offs associated with their implementation making use of a common (monetary) unit. This is why a tool for monetary (further than biophysical) valuations of the ecosystem services supplied by NBS has been developed in Nature4Cities. Such a tool will support the decision making of policy-makers, urban planners and other built environment professionals.
Assessing the benefits, co-benefits and costs of Nature Based Solutions in cities
Mainstreaming Nature Based Solutions (NBS) in cities requires an overall understanding of their economic benefits, co-benefits and costs. However, existing benchmarks established by traditional solutions are not always appropriate to assess the economic sustainability of NBS.
The quantification, valuation and monitoring of ecosystem services (ES), i.e. the benefits that people may obtain from ecosystem functioning, provided by NBS are fundamental components of the assessment of NBS’ socio economic desirability.
The ES relevance for decision making has been widely pushed forward by policy makers, built environment professionals, and researchers with the application of NBS into urban studies. The study of ES helps indeed to internalize natural benefits into the NBS decision-making process, since those benefits are usually not accounted for and treaded as externalities.
Many existing ES assessment methods, models and tools are not cost-effective, and/or provide only qualitative outputs making the operationalization of ES rather challenging. Consequently, generalizable methods, transferable to a broad range of settings, have started to be developed in the form of modelling tools that act as decision support systems (DSS). These can allow decision-makers assessing specific ES supply as well as trade-offs and synergies among ES in a quantitative form and using monetary assessment techniques.
Our web-based tool, called NBenefit$ and developed as a DSS, allows to analyze the costs and benefits of urban NBS and help decision makers addressing several urban challenges at different spatial and temporal scales.
Development of NBenefit$ and lesson learnt from our work
NBenefit$ is based on an integrated modelling framework that runs a “system dynamics” model of NBS, adapting the “Multiscale Integrated Model of Ecosystem Services” (MIMES) to urban systems. Thanks to an extensive critical review of the literature on ES, NBS and urban challenges, we designed a methodology to monetarize the values of ES (benefits) provided by NBS. The proposed methodology then allows comparing these benefits against the life cycle costs of the solution, taking into account market and external costs.
Initially, we collected data on costs and benefits of urban NBS from pilot cities, SMEs working on NBS implementation, and case studies and valuations published in the scientific literature. This allowed to develop a first proof-of-concept model of urban forest, which we applied to a case study in Madrid (Valdebebas Park), Spain, to test its adequacy.
We are currently tailoring the application of such a proof-of-concept model to other areas in Europe, depending on the availability of data required as input for the model. This will support the planning, design, and implementation of NBS in urban contexts other than the investigated area of Madrid.
Credit: Asqueladd, Wikimedia Commons, CC-BY-SA 3.0 License
As a result of our literature review and modelling exercise, many advantages, some limitations and the future activities required to improve our monetary valuation scale were identified.
The proof of concept model suggests that it is feasible to develop a consistent methodology and validate an analytical framework to characterize NBS and assess their economic performance, considering both benefits, co-benefits and possible negative impacts. However, a general lack of context-dependent environmental and economic knowledge for building NBS models and creating realistic management scenarios might hamper the generalization and spreading of the proposed approach. Not surprisingly, data limitations, in particular at the site level, is one of the most relevant challenges in the development of such complex models and decision support systems.
This work further proves that the development and application of a systemic thinking with the use of a system dynamics modelling perspective can certainly foster the multi-stakeholder involvement through participatory processes. Giving evidence on NBS benefits and costs via the use of monetary value scales proves to be attractive for policy and decision makers as well as a scientifically robust approach to support knowledge transfer and enrichment on NBS.
In urban contexts, NBS are part of complex urban interventions that require the collaboration of several built environment professionals like architects, landscape architects, urban designers, environmental engineers or urban planners. To inform the work of these professionals, DSS for NBS need to be integrated early in their workflows with a minimum additional effort from their side. Hence, to advance the operationalization of ES and NBS in urban contexts, user-friendly DSS shall be designed, built, and operated for NBS to support these professionals from early project stages.
Why and how can you use NBenefit$?
NBenefit$ will be incorporated in the Nature4Cities Platform as the operational module allowing to perform socio-economic assessments. The DSS enables predictive simulations and visualization of socio-economic impacts associated with NBS.
Thanks to NBenefit$, you may create spatial and time-dependent scenarios of possible NBS implementation in cities, and then run simulations to quantify the potential biophysical and economic impacts associated with those scenarios (in terms of site-specific biophysical and climatic conditions and land management characteristics), using archetypal NBS (i.e. pre-parameterized models of NBS types, e.g. urban forests, green walls/roofs, urban wetlands, …). After running the tool, you will get information about biophysical impacts (positive and negative) and costs and benefits of different NBS alternatives from early phases in order to advance planning and design stages.
NBenefit$ implements an original modelling approach for the assessment of ES associated with NBS in cities. It allows selecting urban ES, filtering NBS alternatives and visualizing impacts (assessment of biophysical and monetary ecosystem services at different spatial and temporal conditions). More specifically, NBenefit$ employs pre-calculated archetypes and scenarios making use of a system dynamics modelling framework of NBS.
By developing this socio-economic assessment module, Nature4Cities team expects to encourage built environment professionals to integrate NBS evaluation in their early workflows and demonstrate to decision makers the utility of detailed urban monitoring based on ES analysis.
In the long term, our NBenefit$ DSS has the ambition to contribute, with scientific evidences and quantitative figures, to the enhancement of strategies for the sustainable implementation of NBS in cities, and, more generally, to the development of an integrated (European) reference framework on NBS based on robust cost-benefit assessments.
Discover more publications and results on our publications and results page.