Editing IPCC:AR6/WGII/Chapter-10 (section)

===== 10.4.6.4.3 Ecosystem-based adaptation =====

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The literature on urban ecosystem-based adaptation (EbA) [[#footnote-004|9]] , especially across Asia, has grown significantly since AR5 (Demuzere and al., 2014; [[#Yao--2015|Yao et al., 2015]] ; [[#Brink--2016|Brink et al., 2016]] ; [[#Bazaz--2018|Bazaz et al., 2018]] ; [[#de%20Coninck--2018|de Coninck et al., 2018]] ; Ren, 2018). This growing literature reflects the wide recognition that infrastructural adaptation can often have ecological and social trade-offs ( [[#Palmer--2015|Palmer et al., 2015]] ) and need to be complemented by ecosystem-based actions to manage risk more effectively ( [[#Du--2020|Du et al., 2020]] ), build adaptive capacity, and in some cases, meet mitigation and SDGs ( [[#Huang--2020|Huang et al., 2020]] ).

Illustrative examples of EbA in Asian cities include sponge cities in China for sustainable water management, flood mitigation and minimising heatwave impact ( [[#Jiang--2018|Jiang et al., 2018]] ; [[#Yu--2018d|Yu et al., 2018d]] ; [[#Wang--2019a|Wang et al., 2019a]] ; [[#Zhanqiang--2019|Zhanqiang et al., 2019]] ), Singapore’s Active, Beautiful, Clean Waters (ABC Waters) Programme, which uses bio-engineering approaches to protect river channels and prevent localised flooding, improve water quality and create community spaces, and Dhaka’s green roofs and urban agriculture ( [[#Zinia--2018|Zinia and McShane, 2018]] ).

The EbA approaches to manage floods, capture and store rainwater, restore urban lakes and rivers, and reduce surface runoff often blend infrastructural and ecosystem-based approaches. For example, in Tokyo, stormwater management is done by sophisticated underground infrastructure and an artificial infiltration stormwater system ( [[#Saraswat--2016|Saraswat, 2016]] ; [[#Mishra--2019|]] [[#Mishra--2019|Mishra et al., 2019]] ). China’s Sponge City Programme aims to reduce the impacts of flooding through low-impact development measures, urban greenery and drainage infrastructure, such that 80% of urban areas reuse 70% of rainwater by 2020, which would help ensure the resilience of these cities to floods ( [[#Li--2016b|Li et al., 2016b]] ; [[#Stip--2019|Stip et al., 2019]] ).

Case studies on urban EbA also raise equity concerns ( ''medium evidence, medium agreement'' ) such as interventions biased towards suburban areas in Haizhu District, Guangzhou (China) ( [[#Zhu--2019|Zhu et al., 2019]] ); inadequate consideration of low-income, vulnerable populations ( [[#Blok--2015|Blok and Tschötschel, 2015]] ; [[#Meerow--2017|Meerow, 2017]] ; [[#Mabon--2021|Mabon and Shih, 2021]] ); and low familiarity with interventions such as artificial wetlands, water retention ponds as well as green façades and walls can restrict inclusiveness ( [[#Zinia--2018|Zinia and McShane, 2018]] ). Furthermore, urban EbA is constrained by a range of factors such as inadequate institutional structures and processes for connecting different remits and knowledge systems along with trade-offs in land use for different purposes ( [[#Mabon--2021|Mabon and Shih, 2021]] ; [[#Singh--2021b|Singh et al., 2021b]] ).

The EbA interventions are not uniform across Asian cities: in a global study on urban EbA, [[#Brink--2016|Brink et al. (2016)]] found that Eastern Asia, India and Israel report most EbA interventions and that there is variable and ''limited evidence'' on effectiveness and scalability (SM10.5). Using a risk framing (i.e., the extent to which an option reduces risk), urban EbA options in Asian cities score as being ‘low to medium’ effective (see SM10.5); however, when the assessment is expanded to include the ecosystem benefits, economic impacts and human well-being co-benefits of EbA, effectiveness increases. Figure 10.10 shows evidence of the effectiveness of EbA.

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[[File:68388bfd6f5d105824b1a71661789e47 IPCC_AR6_WGII_Figure_10_010.png]]

'''Figure 10.10 |''' '''Evidence of the effectiveness of ecosystem-based adaptation (EbA) using examples of four commonly used EbA options''' '''[[#footnote-000|10]]''' '''.''' Effectiveness is assessed qualitatively based on the evidence (for a full line of sight see SM10.5) and is examined through four framings: potential to reduce risk (e.g., reduced exposure to hazard means to reduce risk); benefits to ecosystems (through improved ecosystem health and high biodiversity); economic benefits (e.g., improved incomes, fewer man-days lost, better livelihoods); and human well-being outcomes (e.g., health, quality of life, etc.). The darker shading signifies high effectiveness and the lightest shade signifies low effectiveness of an EbA option (i.e., the option scores low on the indicator).

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[[#footnote-000-backlink|1]] 10 Assessing the effectiveness of adaptation actions is challenging because of the lack of a clear goal that signifies effective adaptation, varied conceptual framings and metrics used to assess effectiveness, and low empirical evidence on the effectiveness of implemented adaptation actions ( [[#Owen--2020|Owen, 2020]] ; [[#Singh--2021a|Singh et al., 2021a]] ).

For example, urban agriculture is identified as offering multiple benefits such as mitigating emissions associated with food transportation from rural to urban areas, improving food and nutritional security, strengthening local livelihoods and economic development, improved microclimate, soil conservation, improved water and nutrient recycling, and efficient water management ( [[#Padgham--2015|Padgham and Dietrich, 2015]] ; [[#Patil--2019|Patil et al., 2019]] ). However, it can potentially undermine ecosystem services through land-use changes, water overextraction or applying chemical fertilisers ( [[#Ackerman--2014|Ackerman et al., 2014]] ), exposure of smallholders to volatile markets and crops that are not consumed by farming households themselves (thus undermining food security) or increasing the work burdens on women, as well as health externalities (e.g. through use of untreated wastewater, or rearing poultry and livestock in unsanitary conditions). There remain gaps in understanding the differential impacts of urban agriculture at different scales as well as its effectiveness in improving adaptive capacity at scale.

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