Targeting key factors when adapting cities to climate change - A practical visualization and analysis of urban socio-ecological processes using causal loop diagrams.

We live in an urban century, with projections indicating that by 2050 around 2.4 billion more people worldwide will live in cities. Similarly, urbanization in Europe is expected to increase from 72% in 2015, to 83.7% in 2050, while built-up areas are expected to cover more than 7% of the continent's total surface. At the same time, the effects of climate change are increasingly being noticed in urban settings. These impacts include hydro-meteorological events such as storms, floods, and landslides representing 64% of the damages reported from natural disasters in Europe since 1980, while climatological events, such as extreme temperatures, account for an additional 20%. In this context, Nature-based Solutions (NBS) have gained significant importance for climate change adaptation and mitigation, and are increasingly implemented in urban plans and strategies.

Although the integration of NBS into urban planning instruments is a priority in climate policies, there are still limitations that hinder the decision-making process and particularly the selection of efficient NBS for addressing specific environmental challenges. There is a significant gap in understanding the urban socio-ecological processes and dynamics associated with the regulating ecosystem services of NBS, including the benefits they provide, their quantification, and their valuation for effective integration into urban planning.

This study applies a systems-thinking approach to analyzing climate change impacts on cities by focusing on three key environmental challenges: air pollution; urban heat island effect; and urban flooding and runoff. The ecosystem service processes associated with these environmental challenges were identified and analyzed through a literature review employing a citation-chasing approach, based on relevant articles from the last decade. As a result, three models were designed using causal loop diagrams (CLD), one for each environmental challenge, thereby recognizing the key conditions and drivers of these socio-ecological processes. Key causal connections were then grouped into five domains defined as Climate, People, Water, Soil and Vegetation. Finally, these domains were reviewed and described in terms of their controllable and uncontrollable factors, with an emphasis on identifying priority factors to be integrated into urban adaptation strategies.

These results provide a theoretical framework for supporting the transformation of cities into more resilient environments in response to recurrent climate events. Accordingly, future studies are expected to explore urban environmental issues through an integrated approach, enhancing existing models and tools to support the selection of effective and efficient NBS. This will facilitate informed decision-making and accelerate the transition to climate adaptation.