Europe is warming twice as fast as other continents1, posing substantial social and environmental risks2, particularly for cities where about 75% of European people live3. European cities face an adaptation gap, despite planning for adaptation for decades4 and both institutional and financial support. According to UNEP5:VI, an adaptation gap is “the difference between actually implemented adaptation and a societally set goal, determined largely by preferences related to tolerated climate change impacts and reflecting resource limitations and competing priorities”. Conceptualizing and operationalizing this gap remains challenging, mainly because of difficulties in defining adaptation and measuring its baselines, progress, and goals6. Moreover, what is socially acceptable depends on the context and may change with socio-ecological, technological, and political conditions in the future5,7.
Few empirical studies have assessed the adaptation gap using a clear methodological approach and set of defined proxies. Specifically in urban contexts, studies on single8 and large-scale U.S. American cities9 have quantified the adaptation gap using climate models and government reports to juxtapose estimated adaptation needs and adaptation progress. These studies rely on the idea that the main gap in adaptation exists between potential adaptation options in planning documents and the actual implementation of adaptation actions on the ground8,10. One of the most elaborate studies to date involved structured expert judgment to evaluate possible dimensions where adaptation gaps manifest, such as potential and actual levels of risk knowledge, planning, action, capacities, evidence on risk reduction, and long-term strategic pathways. The study was applied across 61 local case studies globally11 and represents a breakthrough in the field of adaptation tracking. However, challenges remain in defining societally accepted goals and impact levels. Moreover, existing research falls short of elucidating strategies for effectively reducing the adaptation (implementation) gap.
In this study, we contribute to these discussions focusing on the “internal adaptation policy consistency” question. Based on a European large-scale study on local adaptation planning and its progress12, we demonstrate how a series of consistency checks applied to adaptation plans could theoretically and methodologically advance the evaluation of the adaptation (implementation) gap and, most importantly, help reduce it.
‘Consistency’ refers to the utilization of a consistent and operational conceptualization of adaptation’13:847, which is needed to ensure that any documented difference in adaptation over time and space14 is not a function of definitional inconsistency. ’Internal consistency’15 refers to the same level of rigorousness in defining adaptation but within the adaptation plans themselves. We argue that the origins of an adaptation gap go back to the adaptation planning process, identifiable through specific indicators in adaptation documentation.
Plan quality studies often serve as indicators of adaptation progress12,16–18, utilizing the adaptation management cycle as a theoretical foundation. We contend that only through rigorous19, credible17 and frequently updated planning routines genuine adaptation progress can be assessed. This is because shifting baselines, targets, and concurrent societal processes complicate comparisons across different environmental states6,20. Moreover, we argue that the adaptation management cycle has so far been framed too narrowly: as sequential stages rather than a series of interconnected decisions essential for addressing climate vulnerabilities and enhancing local adaptive capacities. There is substantial theory and evidence showing that linking goals and actions is crucial in policymaking21,22. While ‘coherency’ is typically discussed regarding alignment among policy domains, governmental levels, or organizations23–25, there appears to be a significant gap in the analytical understanding of internal consistency within the adaptation planning domain.
We argue that alignment of adaptation planning phases is crucial to successfully plan for and achieve adaptation outcomes12, as inconsistencies may lead to an adaptation gap. Previous research has highlighted misalignments between adaptation objectives and actions 26. However, other inconsistencies can also indicate an adaptation gap. We identify five key forms of consistency12: consistency between risks of hazards and adaptation goals (C1), between sectoral risks and adaptation measures (C2), between risks for vulnerable groups and related measures (C3), between measures for vulnerable groups and related monitoring and evaluation (M&E)(C4), and between risks for vulnerable groups and participation (C5). We use data from a sample of 167 European cities that allow for the analysis of C1 to 5, reported below (Fig. 1).
Across C1 to C5 (Fig. 1, bottom left), European cities show the highest consistency in C2 with 52% of plans fully aligning sectoral risks with adaptation measures. The lowest consistency is observed in C5, where only 1% of plans effectively involve vulnerable groups in plan development. This translates into an adaptation gap of 70%, indicating that more than two-thirds of plans are misaligned, with significant discrepancies particularly in planning for social climate vulnerabilities.
Looking at individual items within C1 to C5, cities exhibit the highest consistency in C2, aligning environmental risks with respective adaptation measures such as improving urban greenery and biodiversity (83% of plans for this item; respective brown bar in Fig. 1) and aligning risks in the water sector with respective actions (80% of plans). Conversely, cities falter in social vulnerability-related items, such as planning for gender- and ethnicity-related risks (rosé bars of C3 in Fig. 1; between 41% and 100% inconsistency), and in including vulnerable groups such as the elderly, children, low-income and ethnic communities in plan development (rosé bars of C5 in Fig. 1; between 92% and 100% inconsistency). Moreover, cities see challenges of including these groups in monitoring and evaluation (M&E) of measures (rosé bars of C4 in Fig. 1; between 81% and 100% inconsistency, respectively), highlighting significant gaps in inclusivity and targeted actions.
The analysis also reveals that many adaptation goals and measures lack preceding risk assessments, (the grey part of bars visible in C1, C2), particularly in sector-specific planning where 49% of decisions are made without risk consideration, compared to 52% that are risk-assessed. Notably, in the environment domain, 92% of plans fail to consider environmental risks before planning measures. This not only illustrates the interdependencies between sectors and urban functions—where the effects of measures may impact different sectors—but also risks leading to maladaptation27,28, sunk costs, or ineffective adaptation efforts. This widespread discrepancy underscores the need for more rigorous and integrated risk assessment processes in adaptation planning..
Spatial variations of consistency forms unearth regional disparities of a potential adaptation gap across European cities (Fig. 2). Northern European and UK cities show low scores of C1, suggesting high potential adaptation gaps due to misalignments between risk oof hazards and adaptation goals. Conversely, Eastern European cities exhibit lower scores in C3, C4, and C5, which focus on the sensitivities of vulnerable groups, including their risks and impacts, focused measures, monitoring, and participation. Interestingly, Eastern European adaptation plans are more recent, typically post-2018, whereas those in the UK and Northern Europe are older. This suggests that newer plans increasingly neglect the needs of vulnerable groups, revealing that merging different consistency metrics can mask significant regional differences (Fig. 2, bottom left panel).
We acknowledge uncertainties due to the varying thoroughness in documenting the adaptation process, such as risk assessment and participation processes, and in executing outlined measures and actions, monitoring and evaluation. Moreover, we assume that an identified risk indicates a societal goal to reduce it, though the preferred extent of reduction remains unspecified. Future research would benefit from utilizing high-quality adaptation plans with more explicit goals, allowing for a more precise assessment of the quantitative adaptation gap. However, conceptual challenges persist with cascading and complex risks where measures in one sector impact other sectors. These situations often require quantitative modeling of impact networks.. The strength of our methodology, however, lies in the application and quantification of readily accessible, qualitative data.
Our analysis reveals that 70% of adaptation plans in European cities exhibit inconsistencies, minimizing the adaptation potential of those plans and explaining the current adaptation gap. A significant portion of these discrepancies arises from insufficient consideration of social vulnerability, specifically in planning to implement measures for vulnerable groups, and their involvement in plan development and evaluation processes. This oversight raises equity and justice concerns. Many cities across Europe12 and the US29 continue to struggle with planning for just urban transitions. Our study provides a practical reference point and guidance for addressing these issues. We strongly recommend that decision-makers focus on enhancing internal consistency in future adaptation plans to narrow the existing adaptation gap.