Editing IPCC:AR6/WGII/Chapter-15 (section)

===== Projected Impacts =====

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'''Projected climate and ocean-related changes will significantly affect marine and terrestrial ecosystems and ecosystem services, which will in turn have cascading impacts across both natural and human systems (''' '''''high confidence''''' ''').''' Changes in wave climate superimposed on SLR will significantly increase coastal flooding ( ''high confidence'' ) and low-coastal and reef island erosion ( ''limited evidence, medium agreement'' ). The frequency, extent, duration and consequences of coastal flooding will significantly increase from 2050 ( ''high confidence'' ), unless coastal and marine ecosystems are able to naturally adapt to SLR through vertical growth ( ''low confidence'' ). These changes are a major concern for small islands given that a high percentage of their population, infrastructure and economic assets are located in the low-elevation coastal zone of below 10-m elevation {15.3.3.1.1, 15.3.3.1.2, 15.3.3.1.3, 15.3.3.1.4} .

'''Projected changes in the wave climate superimposed on SLR will rapidly increase flooding in small islands, despite highly contrasting exposure profiles between ocean sub-regions (''' '''''high confidence''''' ''').''' A 5–10-cm additional SLR (expected for ~2030–2050) will double flooding frequency in much of the Indian Ocean and Tropical Pacific, while TCs will remain the main driver of (rarer) flooding in the Caribbean Sea and Southern Tropical Pacific. Some Pacific atoll islands will ''likely'' [[#footnote-000|2]] undergo annual wave-driven flooding over their entire surface from the 2060s–2070s to 2090s under RCP8.5, although future reef growth may delay the onset of flooding ( ''limited evidence, low agreement'' ) {15.3.3.1.1} .

'''Modelling of both temperature and ocean acidification effects under future climate scenarios (RCP4.5 and RCP8.5) suggest that some small islands will experience severe coral bleaching on an annual basis before 2040 (''' '''''medium confidence''''' ''')''' . Above 1.5°C, globally inclusive of small islands, it is projected there will be further loss of 70–90% of reef-building corals, with 99% of corals being lost under warming of 2°C or more above the pre-industrial period. Intact coral reefs, seagrass meadows and mangroves provide a variety of ecosystem services that are important to island communities ( ''high confidence'' ). These include provisioning services, regulating services, cultural services and those that support community resilience ( ''high confidence)'' . If coastal ecosystems are degraded and lost, then the benefits they provide cannot be easily replaced ( ''medium confidence'' ) {15.3.3.1.3, 15.3.3.1.4} .

'''Projected changes in aridity are expected to impose freshwater stress on many small islands, especially SIDS''' '''''(high confidence''''' ''').''' It is estimated that with a warming of 1.5°C or less, freshwater stress on small islands would be 25% less as compared to 2.0°C. While some island regions are projected to experience substantial freshwater decline, an opposite trend is observed for some western Pacific and northern Indian Ocean islands. Drought risk projections for Caribbean SIDS aligned with observations from the Shared Socioeconomic Pathway (SSP) 2 scenario indicate that a 1°C increase in temperature (from 1.7°C to 2.7°C) could result in a 60% increase in the number of people projected to experience severe water resources stress from 2043 to 2071. In some Pacific atolls, freshwater resources could be significantly affected by a 0.40-m SLR. Similar impacts are anticipated for some Caribbean countries with the worst-case scenario (RCP8.5) indicating a 0.5-m SLR by the mid-century (2046–2065) and a 1-m SLR by the end-of-century (2081–2100). SIDS with high projected population growth rates are expected to experience the most severe freshwater stress by 2030 under a 2°C warming threshold scenario {15.3.3.2}

'''The continued degradation and transformation of terrestrial and marine ecosystems of small islands due to human-dominated will amplify the vulnerability of island peoples to the impacts of climate change (''' '''''high confidence''''' ''').''' New studies highlight large population reductions with an extinction risk of 100% for endemic species within insular biodiversity hotspots including within the Caribbean, Pacific and Sundaland regions by 2100 for &gt; 3°C warming {15.3.3.3} . This is ''likely'' to decrease the provision of resources (e.g., potable water) to the millions of people living on small islands, resulting in impacts upon settlements and infrastructure, food and water security, health, economies, culture and migration ( ''high confidence'' ) {15.3.3.2, 15.3.3.3, 15.3.4.1, 15.3.4.2, 15.4.3, 15.3.4.4, 15.3.4.5, 15.3.4.6, 15.3.4.7} .

'''Reef island and coastal area habitability in small islands is expected to decrease because of increased temperature, extreme sea levels and degradation of buffering ecosystems, which will increase human exposure to sea-related hazards (''' '''''high confidence''''' ''')''' . Climate and non-climate drivers of reduced habitability are context specific. On small islands, coastal land loss attributable to higher sea level, increased extreme precipitation and wave impacts and increased aridity have contributed to food and water insecurities that are ''likely'' to become more acute in many places ( ''high confidence'' ). In the Caribbean, additional warming by 0.2°–1.0°C, could lead to a predominantly drier region (5–15% less rain than present day), a greater occurrence of droughts along with associated impacts on agricultural production and yield in the region. Crop suitability modelling on several commercially important crops grown in Jamaica found that even an increase of less than + 1.5°C could result in a reduction in the range of crops that farmers may grow. Most Pacific Island Countries could experience ≥ 50% declines in maximum fish catch potential by 2100 relative to 1980–2000 under both an RCP2.6 and RCP8.5 scenario {15.3.4.3, 15.3.4.4} .

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