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ECOsystem services for resilient and sustainable cities: an ecohydrological approach for Green Urban Spaces

Periodic Reporting for period 2 - ECO.G.U.S. (ECOsystem services for resilient and sustainable cities: an ecohydrological approach for Green Urban Spaces)

Reporting period: 2017-11-15 to 2018-11-14

Cities and towns are complex social-ecological systems and their successful, and robust governance derives from deep and resilient interactions between social, economic and environmental factors. In this context the environmental infrastructures (in their broad significance, both natural and built, hard or soft) play a key role to maximize the society well-being, and their management must faced with important challenges to find a political and economic equilibrium.
These challenges are generated by a world that is constantly changing both in environmental (i.e. climate local and global changes and interrelated processes), economic (i.e. market globalization, financial shocks, etc...) and social sense (i.e. urbanization, cities and mega-cities growth, country depopulation, etc...).
As a consequence, the governance and the political decisions have to take into account the changing conditions: the necessity of tools able to predict (if possible) the future implication of present choices is nowadays greatly increasing.
As the world’s cities are becoming increasingly overcrowded and polluted, the expansion of land covered by impervious surfaces combined with climate change lead to new challenges for the relationship between people and urban ecosystems. Among the several components of the urban ecotone, green spaces play a significant role providing different ecosystem services. The development of models that embody the impact of human actions on water, energy, carbon and nutrient cycles that characterize the city context is crucial to the determination and quantification of ecosystem services in current and future scenarios. A multidisciplinary approach is thus required to address the problem of making modern cities more livable and resilient.

The work carried out during the second part of the Action, has been devoted in particular: (1) to develop and validate a mathematical model under the framework of the dynamical system theory; (2) to match the ideas and the methodologies provided by Systemic Design theory with the quantification of Ecosystem Services provided by Green Urban Spaces; (3) to the implementation of a new scoring matrix method able to perform a easy-to-use analysis of Water Ecosystem Services provided by Green Urban Spaces and based on real data.
The efforts performed to include all the previous results under the framework of Benefit-relevant indicators (BRIs) analysis can be indicate as the Action conclusion. The BRI is a recently developed concept that “explicitly reflects an ecosystem’s capacity to provide benefits to society, ensuring that ecosystem services assessments measure outcomes that are demonstrably and directly relevant to human welfare” (Olander et al., 2018).
During the second phase of the action (from 15-11-2017 to 14-11-2018) the main scientific outcomes of the project have been: (1) a formal and stylized mathematical model able to capture, in a wide and general sense, complex feedbacks between some actors that are strictly related to governance and well-being in town and cities, i.e. presence of green infrastructure and UGS, their provision of ES and the population that enjoy and benefit from them; and (2) a new scoring matrix method based on a holistic approach in connection with the Systemic Design theory for the evaluation of Water-based Ecosystem Services starting from the Direct Driver influenced by anthropic actions.
In the first case the development of the mathematical model is based on the assumptions proper of the dynamical system theory in connection with the ecohydrological model developed in the Outgoing phase and the theory of optimal stochastic control. The stylized mathematical model is able to capture the key links among the urban green spaces, their provision of ecosystem services and the population that benefits from them. The model variables are the percentage of green urban space able to furnish a certain ecosystem service, the quality of such ecosystem service, and the population that benefits the ecosystem services provided by green urban space. These variables are dynamically related by a set of nonlinear evolution equations that allow us to explore different forms of interactions and feedbacks. The model outcomes have been compared with real situations obtained through a synthesis of extensive data (collected during the Outgoing phase) from cities around the world. The influence of the various parameters and the possibility of shifts of stable solutions to periodic behaviour have been explored along with the role of exogenous inputs (new area acquisition or population immigration) resulting from different political and governance choices.
In the second case the project proposes a new matrix scoring method for the evaluation of Water-based Ecosystem Services related to anthropic direct drivers. The method takes advantages of the outcomes of the ecohydrological model proposed during the Outgoing Phase of the project and the mathematical model proposed at the start of the Return Phase. The related guidelines also include the results of the wide data collection performed during the whole project as well as the new ideas acquired during a deep discussion with experts in Systemic Design approach. Although very simple and certainly suitable for improvement, the method represents a very easy-to-use methodology. The approach lets to include currently available data and without the use of experts’ judgments it assures a very high grade of objectivity.
The results dissemination and exploitation during the whole project have been: production of scientific papers and book chapters, participation to academic courses, seminars and conferences, development of the website of the project, invited speaker in several seminars and conferences, agreements to collaborate with several research centers
Many studies have developed methods for the quantification of ES, e.g. ARIES, EcoServ-Gis, iTreeEco although often not specifically for the urban context. Beside the existing literature, the models developed during the Outgoing Phase of the projects present simple mathematical structures based on stochastic differential equations that link the stochastic and unpredictable nature of rainfall inputs to ecohydrological processes (i.e. evapotranspiration, irrigation, nutrient input and output) and then to a parsimonious formulation for the quantification of key ecosystem services. Also the model developed in the second phase of the action presents a simple mathematical structure based on dynamical system theory that links the evolution of population, space availability within the urban context for green spaces and the quality of the ES provided by green spaces. The proposed model relies on simple yet realistic representations of links between the several actors. Finally the proposed scoring matrix method is particularly suitable for a easy-to-use approach. In particular the method can be usefully adopted during the making-decision process and for the use at a non-academic level. The method lets to reduce the level of subjectivity because it takes advantage of real and available data without the use of experts’ judgments and opinions.
Potential users of the project results can be identified in academics, researchers, public and private institutions, policy makers, experts and practitioners related to GUS management with particular reference to the water management.
Conceptual model at the city scale
Conceptual model at the tree scale