Editing IPCC:AR6/WGII/Cross-Chapter-Paper-2 (section)

=== CCP2.3.4 Advance ===

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An advance strategy creates new land by building seaward, which can reduce risk for the hinterland and the newly elevated land, either by land reclamation through landfilling or polderisation through planting of vegetation to support natural land accretion ( [[#Wang--2014|Wang et al., 2014]] ; [[#Sengupta--2018|Sengupta et al., 2018]] ). Advance has occurred in all archetypes ( ''high confidence'' ), from open coasts (e.g., Singapore) and small atolls (e.g., Hulhumalé in the Maldives; [[#Hinkel--2018|Hinkel et al., 2018]] ; [[#Brown--2020|Brown et al., 2020]] ), to cities on estuaries (e.g., Rotterdam) and deltas (e.g., Shanghai [[#Sengupta--2020|Sengupta et al., 2020]] ), and mountainous coasts (e.g., Hong Kong SAR, China). Earth observations show that between 14,000 and 33,700 km 2 of land has been gained in coastal areas over the past 30 years, the dominant drivers being urban development and activities like fish farming ( [[#Donchyts--2016|Donchyts et al., 2016]] ; [[#Zhang--2017|Zhang et al., 2017]] ; [[#Mentaschi--2018|Mentaschi et al., 2018]] ). Advancing seawards through large floating structures may be a viable option in the future ( [[#Wang--2019|Wang et al., 2019]] ; [[#Setiadi--2020|Setiadi et al., 2020]] ; [[#Wang--2020|Wang and Wang, 2020]] ) but is at an experimental stage, and, so far, only applied in calm water within a city as part of an accommodate strategy ( [[#Scussolini--2017|Scussolini et al., 2017]] ; [[#Penning-Rowsell--2020|Penning-Rowsell, 2020]] ; [[#Storbjörk--2021|Storbjörk and Hjerpe, 2021]] ).

Advance is seen as an attractive option to adapt to SLR in growing cities that are already densely populated and have limited available land for safe development, with a moderate to high adaptive capacity. But advance can have significant negative impacts on coastal ecosystems and livelihoods, requires substantial financial and material resources and time to build, and may be subject to land subsidence ( [[#Jeuken--2014|Jeuken et al., 2014]] ; [[#Garschagen--2018|Garschagen et al., 2018]] ; [[#Brown--2019|Brown et al., 2019]] ; [[#NYCEDC--2019|NYCEDC, 2019]] ; [[#Oppenheimer--2019|Oppenheimer et al., 2019]] ; [[#Sengupta--2020|Sengupta et al., 2020]] ; [[#Bendixen--2021|Bendixen et al., 2021]] ).

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