• Nature4Cities

Citizen Agents behaviors: a precious insight to help policy makers in their NBS projects

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The Nature4Cities project aims to deliver a holistic approach to assess Nature Based Solutions (NBS). Regarding its Environmental Assessment Methodology, Nature4Cities intends to:

- Provide decision support during planning phase of NBS projects for the selection of NBS alternatives with the highest potential benefit.

- Provide Performance evaluation of NBS during their implementation phase.


Modelling citizens behavior regarding NBS


A key objective was to study the impact of citizens behavior on the introduction of new NBS in the urban environment. The benefits of NBS for citizens being largely influenced by the way they use and interact with NBS in leisure and work, we went further than only mapping local air quality and citizen health improvements due to introducing NBS like large parks. We also studied the extent to which citizens of various demographics visit such spaces, given factors like health and income.


To study interactive socio-economic effects of NBS on citizens we provided a novel application of an existing behavioral simulation method: the Agent Based Modelling (ABM). ABM allows for many interactions and possibilities to be modelled, by representing the world from individual objects called “agents”. An agent (as a person) can be simulated with a set of characteristic and a number of “states” that indicate social, economic or other aspects of a person (as long as an understanding exists of how to model the relationship between the characteristic and the behavior that one seeks to model).


The object-oriented approach in ABM allows describing hundreds to thousands or greater number of variation possibilities for citizens. As such ABM is well suited to simulate the impact of Nature Based Solutions on citizens and on the urban environment.

Prior to this project, although ABM was employed to assess behaviors of people of cities. We extended it to the context of NBS projects. In this sense, not only does Nature4Cities create an extension to the field of applicability for ABM, it also introduces a new approach for assessing NBS in a systematic way by allowing to measure citizen interactions with NBS and the impacts of NBS on citizens lives and livelihoods.




A standardized simulation method that can be used for any NBS project


Our aim was to be able to simulate citizen requirements, possible behaviours and resulting perceptions due to implementing NBS, but also their possible actions in the urban context. These simulations are supporting NBS measurement in terms of aspects like wellbeing & health.


We analyzed different types of citizens in a quantitative approach, including vulnerable citizens and social equity. Finally, we addressed the impacts of climate change in relation to specific citizen groups and behaviors.


We developed standardized social and equitability related descriptions of people as agents in the context of NBS, based on aspects of people’s characteristics (e.g age, income, health), activities (travel, work, sleep etc.), behavioral routines (travel model choices), relationships (family, friendships), mental perceptions (wellbeing and motivational factors), and abilities (financial, physical, knowledge). Our work allows describing the characteristics of people as agents in a uniform way across simulation scenarios and their intended inputs and outputs and can be used by future projects for the simulation of NBS. City planners and decision makers will thus get precious help to choose NBS to meet their local challenges.

The ABM method delivers insights for NBS projects in terms of people’s interactions, heterogeneous effects and social and economic dimensions on various benefits and impacts of NBS such as for climate change challenges. It is however needed to consider the organizational hierarchy of responsibilities within the municipality and partner organizations, and the information flow between different stakeholders.


Heat mortality, commercial development, role of private gardens… : a modelling giving insights to policy makers


We developed 10 scenario that define potential models that can be used to study various NBS. These scenarios demonstrate the flexibility of Agent Based Modelling as a modelling framework to simulate a variety of physical, behavioral, economic and social elements.



Then we implemented three of these scenarios in an Agent Based Model, using a multi-criteria analysis and the indicator framework developed by Nature4Cities and datas from our pilot cities.


The simulation results:

- showed substantial variation of the impacts of green roofs across cities on heatwave mortality. In case of Szeged, Alcalá de Henares, and Çankaya Municipality a substantial reduction in mortality was found to occur in case of green roofs for the present and more so for future especially as it becomes hotter across the 21st century. This contrasted with Città Metropolitana di Milano where green roofs had little mitigating impact, because heatwaves had little additional mortality effects in the first place in the simulations.


- provided insights about the number of retail shops that can be sustained based on the purchasing behavior of citizens that walk in parks. In Szeged about 5-6 retail shops emerged on average for about 800 walking citizens. In Alcalá de Henares as well as in Çankaya, about 7 to 9 retail shops emerged for around 1500 walking citizens. The simulation for Città Metropolitana di Milano provided an average number of retail shops of 12 to 14 for a simulated population of 2900 that walks in parks.


- demonstrated that changing the make-up of private gardens from paved to green gardens can have up to a 20% impact on water run-off and catchment in cities with mostly paved gardens and large private garden areas. The typical impact of such changes being in the order of 5% to 10%. The linkage between promotion of changing paved into NBS gardens, and how this affects the water balance was thereby showcased including how qualitative factors of relevance can be incorporated including environmental, social, financial and knowledge related aspects.


The results were showcased to the city partners in in-depth open interviews to assess their usefulness. On overall, the interviewees regard agent-based modelling as a useful and complementary decision-support tool. Especially when the model allows for flexibility in adjusting certain elements, or a comparison between alternative interventions (and thus policy options) is possible. Challenges were also presented including the organizational structure of the municipality, where departments operate in silos, does concerns both access to data and information necessary to develop ABM-models, as well as the day-to-day responsibilities in policymaking. Also developing ABM requires specific expertise which is generally not present in public administration and thus requires hiring external advisors.

The three models developed will be integrated in the Nature4Cities platform to foster the Simplified Urban Assessment Tool. It will also be crossed with the implementation models database that will be a useful tool to provide further alignment with municipal stakeholder processes and how methodologies like ABM can help them in their decision process.


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Copyright © 2017 by Nature4Cities

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730468