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

=== 15.5.4 Ecosystem-Based Measures ===

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Small islands have focused increasingly on EbA approaches and other nature-based solutions that bring benefits both for the ecosystems and communities (Figure 15.7; [[#Giffin--2020|Giffin et al., 2020]] ). There is ''robust evidence'' on implementation of EbA approaches across small islands, yet ''medium agreement'' on the exact benefits of these activities ( [[#Mercer--2012|Mercer et al., 2012]] ; [[#Doswald--2014|Doswald et al., 2014]] ; [[#Nalau--2018a|Nalau et al., 2018a]] ) given the difficulties in quantifying benefits and the absence of monitoring and evaluation frameworks ( [[#Doswald--2014|Doswald et al., 2014]] ). Traditionally, EbA activities, especially at national and regional scales, have predominantly focused on restoring or conserving coastal and marine ecosystems (e.g., coral reefs, mangrove forests and seagrass meadows), with less emphasis on the services provided by natural inland forests ( [[#Mercer--2012|Mercer et al., 2012]] ). Incorporation of forests is, however, increasing, in most cases as components of ridge to reef (Figure 15.4) (or Disaster Risk Reduction) projects ( ''limited'' to ''medium evidence'' ), and is geared towards integrated watershed management to establish downstream water security, erosion control and ultimately to protect the health of coral reef ecosystems ( [[#Förster--2019|Förster et al., 2019]] ).

Additionally, some islands are constructing climate-smart development plans such as improved management of existing and newly established protected areas, restoration of riparian zones, urban forests/trees, sub-urban and peri-urban home gardens, and improved agroforestry practices towards increasing resilience to changing climate conditions, wildfires as well as decreasing food insecurity (e.g., [[#Pedersen--2016|Pedersen et al., 2016]] ; [[#McLeod--2019|McLeod et al., 2019]] ). Paired terrestrial and marine protected areas (MPAs) have shown that forest conservation and rehabilitation yield better outcomes for coral health as forests stabilise soils and prevent erosion and sequester groundwater pollutants ( ''limited'' to ''medium evidence, high agreement'' ) ( [[#Carlson--2019|Carlson et al., 2019]] ). The success of protected areas is, however, undermined by weak governance due in part to limited financial resources which undermine management and the enforcement of regulations governing activity within them ( [[#Schleicher--2019|Schleicher et al., 2019]] ).

Since the 1990s, artificial reefs have been increasingly used in small islands to support reef restoration and reduce beach erosion, especially in the Caribbean region (e.g., Dominican Republic, Antigua, Grand Cayman, Grenada) and Indian Ocean (Maldives, Mauritius) ( [[#Fabian--2013|Fabian et al., 2013]] ; [[#Reguero--2018|Reguero et al., 2018]] ). They have been more or less successful in reducing the destructive impacts of extreme events, depending on their technical characteristics and the local context. For example, while it resisted the waves generated by hurricanes Georges and Mitch in 1998, the artificial reef (Reef Ball breakwater type) implemented at Gran Dominicus Resort, Dominican Republic, did not prevent significant beach erosion. By contrast, the coral reef restoration project implemented to ‘build a beach’ on the resort island of Ihuru, North Malé Atoll, Maldives, was successful as it enabled beach expansion and prevented the erosive impacts of the 2004 Indian Ocean tsunami on the beach ( [[#Fabian--2013|Fabian et al., 2013]] ).

Over the past decades, beach nourishment has been implemented in small islands either to reduce beach erosion (e.g., in tourist areas) or to protect critical human assets (e.g., roads) that are highly exposed to storm waves. It has been increasingly used to maintain beaches in the islands of the Maldives ( [[#Shaig--2011|Shaig, 2011]] ) and in Barbados ( [[#Mycoo--2014b|Mycoo, 2014b]] ). However, islands have limited sand stocks, and sediment extraction can aggravate risks and/or accelerate ecosystem degradation if implemented without the necessary precautions.

In designing and implementing EbA, IKLK have high relevance especially amongst Pacific small islands as many communities are remote and still rely on ecosystems for their livelihoods ( [[#Nalau--2018b|Nalau et al., 2018b]] ; [[#Narayan--2020|Narayan et al., 2020]] ). In Fiji, IKLK have informed EbA projects by identifying native species suitable for strengthening the coastal environment to reduce coastal erosion and flooding in the villages ( [[#Nalau--2018b|Nalau et al., 2018b]] ). Whole-of-island approaches, like Lomani Gau in the Gau Island in Fiji, try to foster integrated management practices in small islands that are based on shared governance of resources and on understanding the interlinkages between sectors and ecosystems ( [[#Remling--2016|Remling and Veitayaki, 2016]] ). In the Caribbean, EbA approaches are somewhat absent in national and regional programmes and plans, yet at the local scale EbA strategies are used increasingly with implementation mostly led by NGOs ( [[#Mercer--2012|Mercer et al., 2012]] ).

EbA approaches have many benefits but also face several challenges and limits. Biophysical limits can make some EbA and nature-based solutions ineffective: coral reefs are ''unlikely'' to withstand increased temperatures, reducing the effectiveness of coral reef-based EbA options under higher temperature scenarios ( [[#Barkdull--2018|Barkdull and Harris, 2018]] ; [[#Cornwall--2021|Cornwall et al., 2021]] ). Likewise, many other coastal and marine ecosystems, such as mangroves, face severe limitations with increasing sea levels and other climate impacts ( [[#Morris--2018|Morris et al., 2018]] ; [[#Thomas--2021|Thomas et al., 2021]] ).

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