Review
Trade-offs and conflicts between urban climate change mitigation and adaptation measures: A literature review
Introduction
Accommodating more than 50% of the world population, cities account for about 70% of global CO2 emissions and are major contributors to climate change (Division, 2018). Many cities, especially coastal ones are also exposed to a wide range of climate-related risks such as flooding, sea level rise and extreme temperature events. Moreover, as, for instance, population density of risk-prone coastal cities is projected to increase by 25% by 2050, future urbanization may also expose more people to the climate change impacts that are expected to be more frequent and intense (Aerts et al., 2014). Despite the daunting challenges caused by the compounded effects of climate change and rapid urbanization, it is increasingly recognized that cities can offer solutions to curb climate change and its impacts. Such solutions are often developed as part of climate action plans that set forth strategies and targets for adaptation and/or mitigation. Adaptation seeks to reduce vulnerability and enhance coping capacity and is defined by the Intergovernmental Panel on Climate Change (IPCC) as “the process of adjustment to actual or expected climate and its effects” in human and/or natural systems (IPCC, 2014). In contrast, mitigation is focused on the drivers of climate change and is defined by the IPCC as “a human intervention to reduce the sources or enhance the sinks of greenhouse gases (GHGs) (IPCC, 2014). These definitions may imply that adaptation and mitigation are compartmentalized. However, it is argued that the ultimate goal of both is to minimize the undesirable consequences of climate change (Ayers and Huq, 2009). To this end, mitigation mainly focuses on the long-run reduction of risks, while adaptation is aimed at reducing the current risks that exist due to historical emissions and/or because of failure to achieve mitigation targets (Swart and Raes, 2007). Therefore, it can be said that adaptation and mitigation are not mutually independent, as more mitigation can reduce adaptation needs in the long run and more adaptation can lower the mitigation costs through improving coping and adaptive capacities (Endo et al., 2017; Swart and Raes, 2007). In other words, mitigation is needed for successful adaptation and vice versa. This is increasingly recognized in global policy frameworks. For instance, the need for developing action plans that include both mitigation and adaptation mechanisms is underscored in the Paris Agreement (UNFCCC, 2015) and the New Urban Agenda (Habitat, 2017). Similarly, the United Nations Sustainable Development Goals (particularly SDG 11 and SDG 13) recommend adopting integrated plans and policies towards mitigation and adaptation (UNSDG, 2015). Such integrated approaches also contribute to achieving the targets of the Sendai Framework for Disaster Risk Reduction (UNISDR, 2015).
Despite this, traditionally, adaptation and mitigation have been addressed separately in both research and practice. This dichotomous approach is even evident in the assessment reports prepared by the IPCC, where adaptation is addressed by Working Group II and mitigation by Working Group III. This could be explained by the typical understanding that adaptation and mitigation are different in many respects, for instance in terms of spatio-temporal focus and characteristics (Endo et al., 2017; Pasimeni et al., 2019). A summary of major differences mentioned in the literature is presented in Table 1 and is further explained here. An important difference is that actors involved in adaptation and mitigation efforts are often different. Mitigation targets are better defined and more objective and achieving them requires actions from major emitting sectors such as energy, transport, and building. Comparatively, adaptation target are more uncertain and require involvement of a wider range of stakeholders and sectors that may be at the risk of climate impacts (McEvoy et al., 2006; Swart and Raes, 2007). In other words, as adaptation has a short-medium term focus and climate change impacts are more easily and rapidly observed by a wider range of stakeholders. Somehow related to stakeholders, the beneficiaries of mitigation and adaptation can also be different. On the one hand countries and regions that are less vulnerable to climate impacts may not be motivated to contribute to achieving mitigation targets. On the other hand, some regions that historically are less responsible for climate change are disproportionately affected by its impacts. This raises issues related to equity and justice.
Another key difference is that mitigation is typically known as a global responsibility that is taken by nation states following international negotiations. It can offer global benefits in the long run; while also being able to provide immediate local co-benefits such as air pollution reduction. In contrast, adaptation is mainly practiced at local and regional levels and its vulnerability-reduction benefits can become apparent in the near term; although it can also provide medium- and long-term benefits (Landauer et al., 2019). However, it is increasingly recognized that the spatio-temporal scale mismatches are not in absolute terms and both adaptation and mitigation measures can be relevant at different spatial and temporal scales. For instance, spatially, mitigation measures related to low-carbon urban development are implemented at the local level (Berry et al., 2015) and adaptation measures aimed at achieving drought-resilient agriculture systems have consequences beyond the local level and can be coordinated at larger scales (Swart and Raes, 2007). Similarly, absolute differences in temporal scale are also challenged. For example, some adaptation efforts such as ‘building ecological networks’ need longer-term implementation strategies and lead to long-term benefits (Berry et al., 2015; Laukkonen et al., 2009).
The fact that both spatial and temporal scales of adaptation and mitigation measures can be similar has increased the interest in simultaneously addressing them in climate action plans. This interest is also driven by the fact that adaptation and mitigation are closely linked and can complement each other; failure to mitigate will make future adaptation more costly and challenging and better adaptation can reduce the mitigation needs (Berry et al., 2015; Ford et al., 2018). Survey analyses of urban climate action plans in Europe and the US show that the majority of cities consider both mitigation and adaptation (Aylett, 2015; Kalafatis, 2017).
Despite the increasing attention to simultaneous integration of adaptation and mitigation in urban climate action plans, evidence shows that only a small percentage of cities consider different interactions between adaptation and mitigation policies and measures. Co-benefits, synergies, conflicts, and trade-offs are four distinct types of interactions that may occur. Co-benefits occur when implementing an adaptation (mitigation) measure results in ancillary mitigation (adaptation) gains. A synergy refers to a situation when simultaneous implementation of two or more measures produces benefits greater than the sum of individual measures (Grafakos et al., 2019). Trade-offs occur when implementing an adaptation (mitigation) measure has negative effects on mitigation (adaptation) (Berry et al., 2015). In other words, some solutions developed to enable cities perform better under future climate change (i.e., adaptation actions), may have ramifications for the efforts aimed at reducing GHG emissions (i.e., mitigation) and vice versa (Paton et al., 2014). Finally, conflicts refer to situations when two measures are incompatible and their simultaneous implementation is not possible (Landauer et al., 2015).
This study only focuses on trade-offs and conflicts. More attention to these two interactions has been observed in science and policy domains following their recognition in the Paris Climate Agreement (Dovie, 2019). Despite this, there is still limited knowledge about trade-offs and conflicts between urban climate change adaptation and mitigation measures. These interactions warrant further attention to ensure that adaptation and mitigation measures are not counterproductive (Charoenkit and Kumar, 2014). This review also aims to clarify if trade-offs and conflicts are more dominant in some sectors and to provide some insights on how to minimize them. Furthermore, some methodological approaches for identifying and dealing with trade-offs and conflicts will also be discussed. This work builds on the paper by Mia Landauer et al. (2015) that mainly focuses on the cross-sectoral and cross-scale conflicts between mitigation and adaptation policies but does not specifically investigate various trade-offs between different measures at the urban scale.
Next section explains the review methods. Results, including a brief bibliographic analysis of the literature and a synthesis of evidence reported in the literature (on trade-offs and conflicts) are reported in Section 3. Finally, Section 4 concludes the study by discussing some policy implications and highlights gaps that need to be addressed in future research.
Section snippets
Materials and methods
This desktop research involved bibliographic and content analyses of literature focused on trade-offs and conflicts between urban climate change adaptation and mitigation measures. The specific review questions were ‘what is the major focus of the literature and what are the influential papers and journals?’, ‘what sectors and measures involve trade-offs and conflicts?’ and ‘what are possible methods and approaches for identifying and dealing with conflicts and trade-offs?”.
Literature reviewed
Bibliographic analysis
One purpose of the bibliographic analysis was to identify influential journals and documents related to trade-offs and conflicts between adaptation and mitigation. ‘Co-citation analysis by sources’ is a method that can be used to identify most influential journals. It is an analysis used to calculate the number of times two documents are simultaneously cited by other identical documents (Van Eck and Waltman, 2009). Results of this and the other bibliographic analyses presented in this paper can
Conclusions
Cities around the world are increasingly developing action plans to facilitate climate change adaptation and/or mitigation. Improved understanding of interactions between adaptation and mitigation measures is essential for maximizing synergies and minimizing conflicts and trade-offs. The main aims of this paper were to provide more clarity on potential conflicts and trade-offs that may occur and to discuss possible approaches that can be taken to balance adaptation and mitigation.
The
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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