Editing IPCC:AR6/SR15/Chapter-3 (section)

==== 3.4.5.3 Small islands ====

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Qualitative physical observations of SLR (and other stresses) include inundation of parts of low-lying islands, land degradation due to saltwater intrusion in Kiribati and Tuvalu (Wairiu, 2017) <sup>[[#fn:r764|764]]</sup> , and shoreline change in French Polynesia (Yates et al., 2013) <sup>[[#fn:r765|765]]</sup> , Tuvalu (Kench et al., 2015, 2018) <sup>[[#fn:r766|766]]</sup> and Hawaii (Romine et al., 2013) <sup>[[#fn:r767|767]]</sup> . Observations, models and other evidence indicate that unconstrained Pacific atolls have kept pace with SLR, with little reduction in size or net gain in land (Kench et al., 2015, 2018; McLean and Kench, 2015; Beetham et al., 2017) <sup>[[#fn:r768|768]]</sup> . Whilst islands are highly vulnerable to SLR ( ''high confidence'' ), they are also reactive to change. Small islands are impacted by multiple climatic stressors, with SLR being a more important stressor to some islands than others (Sections 3.4.10, 4.3.5.6, 5.2.1, 5.5.3.3, Boxes 3.5, 4.3 and 5.3).

Observed adaptation to multiple drivers of coastal change, including SLR, includes retreat (migration), accommodation and defence. Migration (internal and international) has always been important on small islands (Farbotko and Lazrus, 2012; Weir et al., 2017) <sup>[[#fn:r769|769]]</sup> , with changing environmental and weather conditions being just one factor in the choice to migrate (Sections 3.4.10, 4.3.5.6 and 5.3.2; Campbell and Warrick, 2014) <sup>[[#fn:r770|770]]</sup> . Whilst flooding may result in migration or relocation, for example in Vunidogoloa, Fiji (McNamara and Des Combes, 2015; Gharbaoui and Blocher, 2016) <sup>[[#fn:r771|771]]</sup> and the Solomon Islands (Albert et al., 2017) <sup>[[#fn:r772|772]]</sup> , in situ adaptation may be tried or preferred, for example stilted housing or raised floors in Tubigon, Bohol, Philippines (Jamero et al., 2017) <sup>[[#fn:r773|773]]</sup> , raised roads and floors in Batasan and Ubay, Philippines (Jamero et al., 2018) <sup>[[#fn:r774|774]]</sup> , and raised platforms for faluw in Leang, Federated States of Micronesia (Nunn et al., 2017) <sup>[[#fn:r775|775]]</sup> . Protective features, such as seawalls or beach nourishment, are observed to locally reduce erosion and flood risk but can have other adverse implications (Sovacool, 2012; Mycoo, 2014, 2017; Nurse et al., 2014; AR5 Section 29.6.22) <sup>[[#fn:r776|776]]</sup> .

There is a lack of precise, quantitative studies of projected impacts of SLR at 1.5°C and 2°C. Small islands are projected to be at risk and very sensitive to coastal climate change and other stressors ''(high confidence'' ) (Nurse et al., 2014; Benjamin and Thomas, 2016; Ourbak and Magnan, 2017; Brown et al., 2018a; Nicholls et al., 2018; Rasmussen et al., 2018; <sup>[[#fn:r777|777]]</sup> AR5 Sections 29.3 and 29.4), such as oceanic warming, SLR (resulting in salinization, flooding and erosion), cyclones and mass coral bleaching and mortality (Section 3.4.4, Boxes 3.4 and 3.5). These impacts can have significant socio-economic and ecological implications, such as on health, agriculture and water resources, which in turn have impacts on livelihoods (Sovacool, 2012; Mycoo, 2014, 2017; Nurse et al., 2014) <sup>[[#fn:r778|778]]</sup> . Combinations of drivers causing adverse impacts are important. For example, Storlazzi et al. (2018) <sup>[[#fn:r779|779]]</sup> found that the impacts of SLR and wave-induced flooding (within a temperature horizon equivalent of 1.5°C), could affect freshwater availability on Roi-Namur, Marshall Islands, but is also dependent on other extreme weather events. Freshwater resources may also be affected by a 0.40 m rise in sea level (which may be experienced with a 1.5°C warming) in other Pacific atolls (Terry and Chui, 2012) <sup>[[#fn:r780|780]]</sup> . Whilst SLR is a major hazard for atolls, islands reaching higher elevations are also threatened given that there is often a lot of infrastructure located near the coast ( ''high confidence'' ) (Kumar and Taylor, 2015; Nicholls et al., 2018) <sup>[[#fn:r781|781]]</sup> . Tens of thousands of people on small islands are exposed to SLR (Rasmussen et al., 2018) <sup>[[#fn:r782|782]]</sup> . Giardino et al. (2018) <sup>[[#fn:r783|783]]</sup> found that hard defence structures on the island of Ebeye in the Marshall Islands were effective in reducing damage due to SLR at 1.5°C and 2°C. Additionally, damage was also reduced under mitigation scenarios compared with non-mitigation scenarios. In Jamaica and St Lucia, SLR and extreme sea levels are projected to threaten transport system infrastructure at 1.5°C unless further adaptation is undertaken (Monioudi et al., 2018) <sup>[[#fn:r784|784]]</sup> . Slower rates of SLR will provide a greater opportunity for adaptation to be successful ( ''medium confidence'' ), but this may not be substantial enough on islands with a very low mean elevation. Migration and/or relocation may be an adaptation option (Section 3.4.10). Thomas and Benjamin (2017) <sup>[[#fn:r785|785]]</sup> highlight three areas of concern in the context of loss and damage at 1.5°C: a lack of data, gaps in financial assessments, and a lack of targeted policies or mechanisms to address these issues (Cross-Chapter Box 12 in Chapter 5). Small islands are projected to remain vulnerable to SLR ( ''high confidence'' ).

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