Editing IPCC:AR6/WGIII/Chapter-8 (section)

=== 8.2.3 Coupling Mitigation and Adaptation ===

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There are numerous synergies that come from coupling urban adaptation and mitigation. A number of studies have developed methods to assess the synergies between mitigation and adaptation strategies, as well as their co-benefits ( [[#Solecki--2015|Solecki et al. 2015]] ; [[#Buonocore--2016|Buonocore et al. 2016]] ; [[#Chang--2017|Chang et al. 2017]] ; [[#Helgenberger--2017|Helgenberger and Jänicke 2017]] ). Co-benefits occur when implementing mitigation (or adaptation) measures that have positive effects on adaptation (or mitigation) ( [[#Sharifi--2021|Sharifi 2021]] ). In contrast, the trade-offs emerge when measures aimed at improving mitigation (adaptation) undermine the ability to pursue adaptation (mitigation) targets ( [[#Sharifi--2020|Sharifi 2020]] ). The magnitude of such co-benefits and trade-offs may vary depending on various factors. A systematic review of over 50 climate change articles provides evidence that mitigation can contribute to resilience – especially to temperature changes and flooding – with varying magnitudes, depending on factors such as the type of mitigation measure and the scale of implementation ( [[#Sharifi--2019|Sharifi 2019]] ).

Measures from different sectors that can provide both mitigation and adaptation benefits involve urban planning ( [[#8.4.2|Section 8.4.2]] ), buildings (Sections 8.4.3.2 and 8.4.4), energy ( [[#8.4.3|Section 8.4.3]] ), green and blue infrastructure ( [[#8.4.4|Section 8.4.4]] ), transportation ( [[#8.4.2|Section 8.4.2]] ), socio-behavioural aspects ( [[#8.4.5|Section 8.4.5]] ), urban governance ( [[#8.5|Section 8.5]] ), waste ( [[#8.4.5.2|Section 8.4.5.2]] ), and water ( [[#8.4.6|Section 8.4.6]] ). In addition to their energy-saving and carbon-sequestration benefits, many measures can also enhance adaptation to climate threats, such as extreme heat, energy shocks, floods, and droughts ( [[#Sharifi--2021|Sharifi 2021]] ). Existing evidence is mainly related to urban green infrastructure, urban planning, transportation, and buildings. There has been more emphasis on the potential co-benefits of measures, such as proper levels of density, building energy efficiency, distributed and decentralised energy infrastructure, green roofs and facades, and public/active transport modes. Renewable-based distributed and decentralised energy systems improve resilience to energy shocks and can enhance adaptation to water stress considering the water-energy nexus. By further investment on these measures, planners and decision makers can ensure enhancing achievement of mitigation/adaptation co-benefits at the urban level ( [[#Sharifi--2021|Sharifi 2021]] ).

As for trade-offs, some mitigation efforts may increase exposure to stressors such as flooding and the urban heat island (UHI) effect (see Glossary), thereby reducing the adaptive capacity of citizens. For instance, in some contexts, high-density areas that lack adequate provision of green and open spaces may intensify the UHI effect ( [[#Pierer--2019|Pierer and Creutzig 2019]] ; [[#Xu--2019|Xu et al. 2019]] ). There are also concerns that some mitigation efforts may diminish adaptive capacity of urban poor and marginalised groups through increasing costs of urban services and/or eroding livelihood options. Environmental policies designed to meet mitigation targets through phasing out old vehicles may erode livelihood options of poor households, thereby decreasing their adaptive capacity ( [[#Colenbrander--2017|Colenbrander et al. 2017]] ). Ambitious mitigation and adaptation plans could benefit private corporate interests resulting in adverse effects on the urban poor ( [[#Chu--2018|Chu et al. 2018]] ; [[#Mehta--2019|Mehta et al. 2019]] ).

Urban green and blue infrastructure such as urban trees, greenspaces, and urban waterways can sequester carbon and reduce energy demand, and provide adaptation co-benefits by mitigating the UHI effect ( [[#Berry--2015|Berry et al. 2015]] ; [[#Wamsler--2016|Wamsler and Pauleit 2016]] ; WCRP 2019) ( [[#8.4.4|Section 8.4.4]] , Figure 8.18 and Box 8.2).

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