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

===== 15.3.3.1.4 Marine and coastal ecosystem services =====

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Intact coral reefs ( [[#Woodhead--2019|Woodhead et al., 2019]] ), seagrass meadows ( [[#Hejnowicz--2015|Hejnowicz et al., 2015]] ) and mangroves ( [[#UNEP--2014b|UNEP, 2014b]] ) ( [[#Friess--2016|Friess, 2016]] ) provide a variety of ecosystem services that are key to island communities, including provisioning services (e.g., timber, fisheries, aquaculture), regulating services (e.g., coastal protection, carbon storage, filtering of pollutants), cultural services ( [[#Pascua--2017|Pascua et al., 2017]] ) as well as supporting community resilience ( [[#Förster--2019|Förster et al., 2019]] ). If coastal ecosystems are degraded and lost, then the benefits they provide are also lost ( [[#Oleson--2018|Oleson et al., 2018]] ; [[#Förster--2019|Förster et al., 2019]] ; [[#Brodie--2020|Brodie et al., 2020]] ). In small islands where the risk of loss to ecosystem services is high (Cross-Chapter Box DEEP in Chapter 17), many of these ecosystem services cannot be easily replaced ( ''medium confidence'' ). The beneficial role that coral reefs play in coastal protection through wave attenuation, and therefore enhancing climate resilience in small islands, has been extensively studied (e.g., [[#Elliff--2017|Elliff and Silva, 2017]] ; [[#Harris--2018|Harris et al., 2018]] ; [[#Reguero--2018|Reguero et al., 2018]] ). Indeed, it has been demonstrated that in small islands (such as the Cayman Islands, Grenada, Bahamas) averted damages as a result of protecting intact coral reefs can be considerable when expressed as a percentage of GDP ( [[#Beck--2018|Beck et al., 2018]] ). [[#Ferrario--2014|Ferrario et al. (2014)]] conducted a global meta-analysis including many small islands across the Atlantic, Pacific and Indian oceans and found that coral reefs reduce wave height by an average of 84% (and wave energy by 97%) and that reef crests alone dissipate most of this energy. Based on another meta-analysis of 69 case studies worldwide (wave heights measured before and after the habitat), [[#Narayan--2016|Narayan et al. (2016)]] observed that coral reefs, mangroves and seagrass reduced wave height by 70%, 31% and 36%, respectively (Figure 15.4) and thus perform an essential role in protecting human lives and livelihoods ( ''high confidence'' ). Post-TC studies have provided additional evidence for the protection services offered by coastal ecosystems. On some Caribbean islands (e.g., Saint-Martin/Sint Maarten) where the dense indigenous vegetation belt was preserved, the vegetative structure buffered the waves of TCs Irma and José (2017), reducing the extent of marine inundation and shoreline retreat to a 30-m-wide coastal strip against values &gt;160 m in deforested areas ( [[#Duvat--2019a|Duvat et al., 2019a]] ; [[#Pillet--2019|Pillet et al., 2019]] ). By contrast, the destruction of mangrove ecosystems, even a few trees around the fringes, can accelerate coastal erosion, as exemplified by observations in Micronesia ( [[#Krauss--2010|Krauss et al., 2010]] ; [[#Nunn--2017a|Nunn et al., 2017a]] ).

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'''Figure 15.4 |''' '''Ridge-to-reef interrelated protection services delivered by ecosystems on small islands.''' On small islands, terrestrial, coastal and marine ecosystems are interconnected and interdependent, with each ecosystem contributing towards maintaining the health of the others. Together, these ecosystems provide protection services against natural hazards (including flooding, erosion, landslides, mudflows, glacial melting and sedimentation) to human populations living on islands. As a consequence, the degradation of one or more of these ecosystems significantly reduces the protection services provided by this continuum of ecosystems. Conversely, the protection or restoration of one or more of these ecosystems also provides benefits to the other ecosystems and enhances the protection services provided to island inhabitants. See Box [https://www.ipcc.ch/chapter/15#CCP1.1 CCP1.1] for more details.

As corals, mangroves and seagrasses disappear, so do fish and other dependent organisms that directly benefit industries such as ecotourism and fisheries ( ''high confidence'' ) ( [[#Graham--2015|Graham et al., 2015]] ; [[#Cinner--2016|Cinner et al., 2016]] ). These impacts are sometimes exacerbated by catastrophic events such as tropical storms and marine heatwaves that destroy habitats and hence the resources upon which coastal fisheries depend ( [[#Sainsbury--2018|Sainsbury et al., 2018]] ). There is ''high confidence'' that climate change impacts, together with local human disturbances, will continue to denude coastal and marine ecosystem services in many small islands with serious consequences for vulnerable communities ( [[#Elliff--2017|Elliff and Silva, 2017]] ; [[#Bindoff--2019|Bindoff et al., 2019]] ).

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