FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1
2 Cross-Chapter Paper 2: Cities and Settlements by the Sea
3
4 Cross-Chapter Paper Leads: Bruce Glavovic (New Zealand/South Africa), Richard Dawson (United
5 Kingdom), Winston Chow (Singapore)
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7 Cross-Chapter Paper Authors: Matthias Garschagen (Germany), Marjolijn Haasnoot (The Netherlands),
8 Chandni Singh (India), Adelle Thomas (Bahamas)
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10 Cross-Chapter Paper Contributing Authors: Jeroen Aerts (The Netherlands), Sophie Blackburn (United
11 Kingdom), David Catt (USA), Eric Chu (USA), William Solecki (USA), Stijn-Temmerman (Belgium),
12 Gundula Winter (Germany)
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14 Cross-Chapter Paper Review Editor: Soojeong Myeong (Republic of Korea)
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16 Cross-Chapter Paper Scientist: David Catt (USA)
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18 Date of Draft: 1 October 2021
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20 Notes: TSU Compiled Version
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22
23 Table of Contents
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25 Executive Summary..........................................................................................................................................2
26 CCP2.1 Context of Cities and Settlements by the Sea .............................................................................5
27 CCP2.1.1 Introduction and Context ........................................................................................................5
28 CCP2.1.2 Urbanisation in Coastal Systems: Coastal City and Settlement Archetypes ..........................6
29 CCP2.2 Climate Change Risks to Cities and Settlements by the Sea.....................................................8
30 CCP2.3 Adaptation in Cities and Settlements by the Sea .....................................................................11
31 CCP2.3.1 Introduction ..........................................................................................................................11
32 CCP2.3.2 Protection of Coastal Cities and Settlements .......................................................................11
33 CCP2.3.3 Accommodation of the Built Environment ............................................................................13
34 CCP2.3.4 Advance.................................................................................................................................13
35 CCP2.3.5 Retreat...................................................................................................................................14
36 CCP2.3.6 Adaptation Pathways ............................................................................................................14
37 CCP2.4 Enabling Conditions and Lessons Learned ..............................................................................16
38 CCP2.4.1 Enabling Behavioural Change..............................................................................................16
39 CCP2.4.2 Finance .................................................................................................................................17
40 CCP2.4.3 Governance...........................................................................................................................18
41 CCP2.4.4 Enabling Climate Resilient Development for Cities and Settlements by the Sea .................23
42 FAQ CCP2.1: Why are coastal cities and settlements by the sea especially at risk in a changing
43 climate, and which cities are most at risk?...........................................................................................24
44 FAQ CCP2.2: What actions can be taken by coastal cities and settlements to reduce climate change
45 risk? .......................................................................................................................................................25
46 FAQ CCP2.3: Considering the wide-ranging and interconnected climate and development challenges
47 coastal cities and settlements face, how can more climate resilient development pathways be
48 enabled? ................................................................................................................................................... 26
49 References .......................................................................................................................................................28
50
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 Executive Summary
2
3 Cities and settlements by the sea (C&S) are on the frontline of climate change they face amongst the
4 highest climate-compounded risks but are a key source of innovations in climate resilient development
5 (high confidence1) {Sections 6.1, 6.2; Chapter 7, Box 15.2; Cross-Chapter Box COVID in Chapter 7;
6 Cross-Chapter Box SLR in Chapter 3; CCP2.2; SMCCP2.1; WGI Section 12.4.10.2}.
7
8 Much of the world's population, economic activities and critical infrastructure are concentrated near the sea
9 (high confidence), with nearly 11% of the global population, or 896 million people, already living on low-
10 lying coasts directly exposed to interacting climate- and non-climate coastal hazards (very high confidence)
11 {CCP2.1}. Low-lying C&S are experiencing adverse climate impacts that are superimposed on extensive
12 and accelerating anthropogenic coastal change (very high confidence) {WGI Section 12.4.10.2; Sections 6.1,
13 6.2; CCP2.2, SMCCP2.1}. Depending on coastal C&S characteristics, continuing existing patterns of coastal
14 development will worsen exposure and vulnerability (high confidence) {CCP2.1}. With accelerating sea
15 level rise (SLR) and worsening climate-driven risks in a warming world, prospects for achieving the
16 Sustainable Development Goals (SDGs) and charting Climate Resilient Development (CRD) pathways are
17 dismal (high confidence) {CCP2.3, CCP2.4; Chapter 16, 18}. However, coastal C&S are also the source of
18 SDG and CRD solutions because they are centres of innovation with long histories of place-based
19 livelihoods, many of which are globally connected through maritime trade and exchange (medium
20 confidence) {CCP2.4}.
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22 Regardless of climate and socio-economic scenarios, many C&S face severe disruption to coastal
23 ecosystems and livelihoods by 2050 and across all C&S by 2100 and beyond caused by compound
24 and cascading risks, including submergence of some low-lying island states (very high confidence)
25 {CCP2.1; CCP2.2; SROCC SPM, Chapter 4; Section 6.2}.
26
27 There is high confidence that projected climate risks will increase with (i) exposure to climate- and ocean-
28 driven hazards manifest at the coast, such as heat waves, droughts, pluvial floods, and impacts due to SLR,
29 tropical cyclones, marine and land heatwaves, and ocean acidification; (ii) with increasing vulnerability
30 driven by inequity, and (iii) increasing exposure driven by urban growth in at-risk locations. Compounded
31 and cascading climate risks, such as to coastal C&S infrastructure and supply chain networks, are also
32 expected to increase {Section 6.2.7; CCP2.2}. These risks are acute for C&S on subsiding and/or low-lying
33 small islands, the Arctic, and open, estuarine and deltaic coasts (high confidence) {CCP2.2; Table
34 SMCCP2.1}. By 2050, more than a billion people located in low-lying C&S will be at risk from coast-
35 specific climate hazards, influenced by coastal geomorphology, geographical location and adaptation action
36 (high confidence). Between US$7-14 trillion of coastal infrastructure assets will be exposed by 2100,
37 depending on warming levels and socio-economic development trajectories (medium confidence) {CCP2.1}.
38 Historically rare extreme sea level events will occur annually by 2100, with some atolls being uninhabitable
39 by 2050. Coastal flood risk rapidly increases in coming decades, and could increase by 23 orders of
40 magnitude by 2100 in the absence of effective adaptation and mitigation, with severe impacts on coast-
41 dependent livelihoods and socio-ecological systems (high confidence) {SROCC SPM; Chapter 4}. Impacts
42 reach far beyond C&S e.g., damage to ports severely compromising global supply chains and maritime trade
43 with local-global geo-political and economic ramifications. Global investment costs to accommodate port
44 growth and adapt to SLR amount to USD223-768 billion before 2050, presenting opportunities for C&S by
45 the sea to build climate resilience (medium evidence, high agreement) {CCP2.1; CCP2.2; Cross-Chapter Box
46 SLR in Chapter 3}. Severely accelerated SLR resulting from rapid continental ice mass-loss would bring
47 impacts forward by decades, and adaptation would need to occur much faster and at much greater scale than
48 ever done in the past (medium confidence).
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1 In this Report, the following summary terms are used to describe the available evidence: limited, medium, or robust;
and for the degree of agreement: low, medium, or high. A level of confidence is expressed using five qualifiers: very
low, low, medium, high, and very high, and typeset in italics, e.g., medium confidence. For a given evidence and
agreement statement, different confidence levels can be assigned, but increasing levels of evidence and degrees of
agreement are correlated with increasing confidence.
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 A mix of interventions is necessary to manage coastal risks and build resilience over time. An
2 adaptation pathways approach sets out near-term `low-regret' actions that align with societal goals,
3 and facilitates implementation of a locally appropriate sequence of interventions in the face of
4 uncertain climate and development futures, and enables necessary transformation (high confidence)
5 {CCP2.3; Cross-Chapter Box DEEP in Chapter 17, Cross-Chapter Box SLR in Chapter 3}
6
7 A mix of infrastructural, nature-based, institutional and socio-cultural interventions are needed to reduce the
8 multifaceted risk facing C&S, including vulnerability reducing measures, avoidance (i.e., disincentivising
9 developments in high-risk areas), hard- and soft-protection, accommodation, advance (i.e., building up and
10 out to sea) and retreat (i.e., landward movement of people and development) (very high confidence)
11 {CCP2.3}. Depending on the C&S archetype, technical limits for hard protection may be reached beyond
12 2100 under high emission scenarios, with socio-economic and governance barriers reached before then
13 (medium confidence). Hard protection can, however, set up lock-in of assets and people to risks and, in some
14 cases, may reach limits, due to technical and financial constraints, by 2100 or sooner depending on the
15 scenario, local SLR effects and community tolerance thresholds (medium confidence). Where sufficient
16 space and adequate habitats are available, nature-based solutions can help to reduce coastal hazard risks and
17 provide other benefits, but biophysical limits may be reached before end-century (medium confidence).
18 Accommodation is easier, faster and cheaper to implement than hard protection, but limits may be reached
19 by 2100, or sooner in some settings. An adaptation pathways planning approach demonstrates how the
20 solution space can expand or shrink depending on the type and timing of adaptation interventions
21 {CCP1.3.1.2}. As SLR is relentless on human timescales, the solution space will shrink without adoption of
22 an adaptation pathways planning approach (high confidence). Due to long implementation lead times and the
23 need to avoid maladaptive lock-in, especially in localities facing rapid SLR and climate-compounded risk,
24 adaptation will be more successful if timely action is taken accounting for long-term (committed) SLR; and
25 if this is underpinned by sustained and ambitious mitigation to slow greenhouse gas emission rates (high
26 confidence) {CCP2.3; CCP2.4; Cross-Chapter Box SLR in Chapter 3}.
27
28 Individual and collective choices founded on public-centred values and norms, as well as pro-social
29 behaviour, help to foster climate resilient coastal development in C&S (high confidence) {CCP2.4.1}.
30
31 The effectiveness of different approaches (e.g., awareness and education, market-based and legal strategies)
32 is mediated by how well they address contextual and psycho-social factors influencing adaptation choices in
33 coastal C&S (medium confidence). Adaptation options accounting for risk perceptions and aligning with
34 public values are more likely to be socio-culturally acceptable, and consequently facilitate pro-social
35 behavioural change {CCP2.4.1}.
36
37 Locally appropriate institutional capabilities, including regulatory provisions and finances dedicated
38 to maintaining healthy coastal social-ecological systems, build adaptive capacity in C&S by the sea
39 (high confidence) {CCP2.4}.
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41 Implementing integrated multi-level coastal zone governance, pre-emptive planning, enabling behavioural
42 change, and alignment of financial resources with a wide set of values, will provide C&S with greater
43 flexibility to open up the solution space to adapt to climate change (high confidence) {CCP2.4.4}.
44 Insufficient financial resources are a key constraint for coastal adaptation, particularly in the Global South
45 (high confidence). Engaging the private sector in coastal adaptation action with a range of financial tools is
46 crucial to address the coastal adaptation funding gap (high confidence). Considering the full range of
47 economic and non-economic values will improve adaptation effectiveness and equity across C&S archetypes
48 (high confidence). Aligning adaptation in C&S with socio-economic development, infrastructure
49 maintenance, and COVID-19 recovery investments will provide additional co-benefits {CCP2.4.2}. Urgency
50 is also driven by the need to avoid lock-in to new and additional risk, e.g., avoid C&S sprawl into fragile
51 ecosystems and the most exposed coastal localities {CCP2.3}.
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53 Realising global aspirations for climate resilient development depend on the extent to which coastal
54 C&S institutionalise key enabling conditions and chart place-based adaptation pathways to close the
55 coastal adaptation gap, and take urgent action to mitigate greenhouse gas emissions (medium
56 confidence) {CCP2.4, Table CCP2.1}.
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 Since AR5, extensive adaptation planning has been undertaken, but there has not been widespread effective
2 implementation - giving rise to a `coastal adaptation gap' (high confidence). To date, most interventions have
3 been reactive, reliant on protective works alone (high confidence). Effectiveness of alternative interventions
4 differs among C&S archetypes, while their feasibility is influenced by geomorphology, socio-economic
5 conditions as well cultural, political and institutional considerations (very high confidence). Mismatches
6 between adaptation needs and patterns of physical development are commonplace in many coastal C&S,
7 with especially adverse impacts on poor and marginalised communities in the global North and South (high
8 confidence). Overcoming this gap is key to transitioning towards CRD (medium confidence). Under higher
9 warming levels and higher SLR, increasingly dichotomous coastal futures will become more entrenched
10 (medium confidence), with stark differences between more urbanised, resource-rich coastal C&S dependent
11 on hard protection, and more rural, resource-poor C&S facing displacement and migration {CCP2.3;
12 CCP2.4, Chapter 18}.
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14 Coastal adaptation innovators adopt more flexible, anticipatory and integrative strategies, combining
15 technical and non-technical interventions that account for uncertainties, and facilitate effective resolution of
16 conflicting interests and worldviews (limited evidence, high agreement) {CCP2.3; CCP2.4; Chapter 17, 18;
17 Cross-Chapter Box DEEP in Chapter 17}. Moreover, a core set of critical enablers is foundational for C&S
18 to chart CRD pathways. These include building and strengthening governance capabilities to tackle complex
19 problems; taking a long-term perspective in making short-term decisions; enabling more effective
20 coordination across scales, sectors and policy domains; reducing injustice, inequity, and social vulnerability;
21 and unlocking the productive potential of coastal conflict while strengthening local democracy (medium
22 evidence, high agreement) {Table CCP2.1, Table CCP2.2}.
23
24 C&S play a pivotal role in global aspirations to implement the Paris Agreement, advance the SDGs, and
25 foster CRD. Progress towards these ends depends on the extent to which C&S mobilise urgent and
26 transformational changes to institutionalise enabling conditions; close the coastal adaptation gap by
27 addressing the drivers and root causes of exposure and vulnerability to climate-compounded coastal hazard
28 risks; and drastically reduce greenhouse gas emissions (medium confidence) {CCP2.4; Chapter 18}
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30
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 CCP2.1 Context of Cities and Settlements by the Sea
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3 CCP2.1.1 Introduction and Context
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5 This CCP examines the distinctive roles played by Cities and Settlements (C&S) by the sea in vulnerability
6 and coastal hazard risk reduction, adaptation, resilience, and sustainability in a changing climate. The paper
7 builds upon evidence from AR5 (Wong et al., 2014), the Special Report on the Ocean and Cryosphere in a
8 Changing Climate (SROCC) (Magnan et al., 2019; Oppenheimer et al., 2019) and draws material from
9 across WGII AR6 (especially Chapters 3, 6, 9-15). It differs from the sea level rise (SLR) focused analysis of
10 urban areas in SROCC (Section 4.3) through a more integrated assessment that distinguishes between
11 archetypal coastal C&S (CCP2.1.2); sectoral risks to C&S by the sea, (CCP2.2); responses to address these
12 risks (CCP2.3); and enabling conditions and lessons learned (CCP2.4).
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14 We define `cities and settlements' as concentrated human habitation centres, whether small or large, rural or
15 urban (Chapter 6.1.3). We highlight the unique exposure and vulnerability of coastal C&S resulting from
16 rapid urbanisation at the narrow land-sea interface, concentration of economic activity and at-risk people,
17 many with long-standing cultural ties to the coast and dependence on coastal ecosystems that are prone to
18 climate change impacts (high confidence) (He and Silliman, 2019; Lau et al., 2019; Oppenheimer et al.,
19 2019; Sterzel et al., 2020).
20
21 Presently, coastal C&S population exposure to ocean-driven impacts from SLR, and other climate-driven
22 impacts is considerable by any measure (Buddemeier et al., 2008; Barragán and de Andrés, 2015; Kay and
23 Alder, 2017; Haasnoot et al., 2019; McMichael et al., 2020; Sterzel et al., 2020). In 2020, almost 11% of
24 global population 896 million people resided in C&S within the Low Elevation Coastal Zone (LECZ,
25 coastal areas below 10 m of elevation above sea level that are hydrologically connected to the sea) (Haasnoot
26 et al., 2021b), and potentially increases beyond 1 billion by 2050 (Oppenheimer et al., 2019). Infrastructural
27 and economic assets worth US$6,500-US$11,000 billion are also exposed in the 1-in-100-year floodplain for
28 C&S of all sizes (Neumann et al., 2015; Muis et al., 2016; Brown et al., 2018; Andrew et al., 2019; Kulp and
29 Strauss, 2019; Kirezci et al., 2020; Thomas et al., 2020; Haasnoot et al., 2021b; Hooijer and Vernimmen,
30 2021).
31
32 Further, coastal cities located at higher elevations (e.g., Săo Paulo, Brazil), or distantly located inland along
33 tidal-influenced rivers (e.g., the Recife Metropolitan Region, Brazil) also have populations and infrastructure
34 exposed to climate impacts. As such, the inclusion of C&S beyond the LECZ is warranted when assessing
35 climate impacts and associated exposure, vulnerabilities and risks. The coastal zone includes some of the
36 world's largest, most densely populated megacities, as well as the fastest-growing urban areas. However,
37 vast coastal areas are sparsely populated, with population in these regions concentrated in smaller C&S,
38 including along subsiding shorelines and in deltas (Nicholls and Small, 2002; McGranahan et al., 2007;
39 Merkens et al., 2018; Edmonds et al., 2020; Nicholls et al., 2021). From this wider perspective, climate
40 change impacts on the coast directly or indirectly affect a large portion of the global population, economic
41 activity and associated critical infrastructure. Some estimates suggest 23-37% of the global population lives
42 within 100 km of the shoreline (Nicholls and Small, 2002; Shi and Singh, 2003; Christopher Small and
43 Joel E. Cohen, 2004; McMichael et al., 2020).
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45 C&S by the sea are thus on the `frontline' of action to adapt to climate change, mitigate greenhouse gas
46 emissions, and chart climate resilient development (CRD) pathways for several distinct reasons. First, home
47 to a concentrated (and growing) portion of the world's population, many coastal C&S are simultaneously
48 exposed and vulnerable to climate-compounded hazards as well as being centres of creativity and innovation
49 (Glavovic, 2013; Crescenzi and Rodríguez-Pose, 2017; Druzhinin et al., 2021; Mariano et al., 2021;
50 Storbjörk and Hjerpe, 2021). Second, people in C&S by the sea rely on coastal ecosystems, many of which
51 are highly sensitive to climate change impacts that compound non-climate risks and increase the precarity of
52 coastal livelihoods (Lu et al., 2018; He and Silliman, 2019; Thrush et al., 2021). Third, coastal C&S are
53 linked together through a network of ports and harbours that underpin global trade and exchange but are
54 prone to climate change impacts, especially SLR, with significant implications for global CRD prospects
55 (Becker et al., 2018; Christodoulou et al., 2019; Walsh et al., 2019; Hanson and Nicholls, 2020). For these
56 reasons, this paper assesses responses, enabling conditions and lessons learned for addressing climate change
57 in C&S by the sea.
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
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2 CCP2.1.2 Urbanisation in Coastal Systems: Coastal City and Settlement Archetypes
3
4 This assessment uses an archetype framework categorizing coastal C&S according to geomorphological
5 characteristics, urban growth, economic resources, and inequalities (Figure CCP2.1). We use three broadly
6 defined coastal settlement geomorphologies in each row: open coasts (a coast with sediment without river
7 mouths), and two transitional coastal zones with river mouths: estuaries (a wetland receiving sediment from
8 both fluvial and marine sources, which is affected by tide, wave, and river processes), and deltas (a wetland
9 where fluvial sediment is supplied and deposited more rapidly than it can be redistributed by basin processes
10 such as waves and tides) (Bhattacharya, 1978; Barragán and de Andrés, 2015; Kay and Alder, 2017;
11 Haasnoot et al., 2019; Sterzel et al., 2020). Small island C&S are not singled out in this typology because
12 their coastlines often include the geomorphic features listed above, or require a different adaptation approach
13 at larger spatial scales (Haasnoot et al., 2019). Several coastal C&S have a combination of two typologies
14 e.g., Maputo-Matola, Mozambique, and Mumbai, India, having both open and transitional riverine coasts,
15 and can be classed as mixed. We also acknowledge several coastal C&S may have areas sited in
16 mountainous topography that abruptly rise from the coast (e.g., along the Mediterranean), but generally these
17 cities have narrow densely populated coastal shelfs exhibiting these three archetypal categories (Blackburn et
18 al., 2019). Arctic settlements are addressed separately in this CCP.
19
20 Coastal C&S within these geomorphological categories are further distinguished according to higher or
21 lower rates of urban growth and inequality which can be estimated through population growth from
22 national census data, or areal extent of urban development (CEIC); as well as relative urban inequalities
23 estimated by Gini Coefficient data and urban-rural poverty rates (OECD, 2018; OECD, 2020). Combining
24 geomorphological and socio-economic data accounts for urban-rural interconnections and differences; with
25 levels of capital generation, diversity of economic functions and human development indices having
26 previously been used to discern cultural, economic, administrative and political differences between cities
27 and their hinterland (Blackburn et al., 2019; Rocle et al., 2020). For instance, the ecological, cultural and
28 economic footprint of tertiary sectors e.g., coastal tourism associated with the Australian Great Barrier Reef
29 stretches far beyond the nearest onshore settlement of Cairns (Bohnet and Pert, 2010; Brodie and Pearson,
30 2016).
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32 Some caveats are warranted. First, locating a specific city or settlement in a particular archetype does not
33 account for future reclassification due to growth or shifts in development trajectories. Second, significant
34 socio-economic, political and governance variations exist within many C&S, c.f., impoverished informal
35 settlements alongside wealthy neighbourhoods in cities like Cape Town and Săo Paulo (also see Table
36 SMCCP2.1). Third, this archetype framework does not explicitly reveal important interconnections between
37 coastal C&S and their hinterlands, or between particular C&S through maritime trade or other economic,
38 socio-cultural and geopolitical inter-dependencies. Notwithstanding these caveats, these archetypes reveal
39 differentiated physical impacts and socio-economic conditions, as well as the variable challenges and
40 opportunities arising for addressing climate change impacts and projected risk, which, depending on coastal
41 type, C&S size, and resource availability, help to inform efforts to adapt and chart CRD for each archetype
42 (Sánchez-Arcilla et al., 2016; Rocle et al., 2020; Sterzel et al., 2020).
43
44
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 CCP2-7 Total pages: 42
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 Figure CCP2.1: Archetypal C&S affected by ocean, terrestrial, geological, atmospheric and hydrological hazards
2 driven by climate change. Coastal C&S are grouped by physical geomorphology along estuary, deltaic, or open coasts
3 (Barragán and de Andrés, 2015; Kay and Alder, 2017; Haasnoot et al., 2019). C&S are also classified according to
4 relative inequality (e.g., urban Gini coefficient or poverty rates) and growth rates (e.g., recent population growth and
5 increasing density of urban form or built-up area over the past decade) (OECD, 2018; CEIC; OECD, 2020). Settlement
6 types (e.g., informal, low-density or high-density developments) and economic resources (e.g., urban per capita GDP)
7 are also reflected in their respective categories. The bottom map shows the location, 2020 population size, and
8 geomorphological types.
9
10
11 CCP2.2 Climate Change Risks to Cities and Settlements by the Sea
12
13 Coastal C&S are at the forefront of climate risk (FAQ CCP2.1). The dynamic interaction between ocean- and
14 climate-drivers and varied coastal geographies influences the character of coastal risks, including many that
15 are unique to C&S by the sea. The interaction of coastal hazards with exposure and vulnerability is
16 differentiated by coastal archetypes, leading to distinct climate change-compounded risks, and associated
17 responses (Figure CCP2.2; Section 1.3.1.2; Simpson et al. (2021)).
18
19
20
21 Figure CCP2.2: Schematic of how climate- and ocean-drivers (from WGI Chapter 12.4.10.2) and consequential
22 physical impacts on coastal C&S influence risks assessed in (CCP2.2; Figure based on Simpson et al. (2021) and
23 Section 1.3.1.2). These risks to C&S by the sea are shaped and mediated by adaptation interventions aimed at reducing
24 vulnerability and exposure to coastal hazards given settlement archetypes, as well as by expanding the space for
25 responses to risk via enabling conditions assessed in (CCP2.4). Note that exposure to coastal hazard is controlled
26 chiefly by underlying coastal C&S geomorphology, and changes in coastal hazards and urban growth, including
27 population and infrastructure growth; vulnerability is controlled, for example, by socio-economic development and
28 inequality; and responses that shape risks assessed in (CCP2.3) can be enhanced by enabling conditions, including
29 behavioural change, conducive finance, and prudent governance.
30
31
32 Overall, interactions between climatic and non-climatic drivers of coastal change are increasing the
33 frequency and intensity of many coastal hazards, with settlement archetypes and the wider coastal zone
34 subject to escalating risk (high confidence) (Figure CCP2.2; Table SMCCP2.1 for examples of selected
35 coastal C&S). Risks can vary markedly between different archetypes. C&S sited on deltaic and estuarine
36 coasts face additional risks of pluvial flooding compared to open coasts; while greater vulnerabilities arise in
37 coastal settlements with higher inequalities.
38
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 Risks to C&S by the sea were extensively covered in SROCC (Oppenheimer et al., 2019) and also in WGII
2 Chapter 3, 6 and regional chapters; in this paper, specific risks to livelihoods, activities, built environment,
3 and ecosystems are assessed in detail in Supplementary Material SMCCP2.1. The ocean- and climate-impact
4 drivers influencing these risks are assessed in WG1 (Section 12.4.10.2), which include extreme heat, pluvial
5 floods from increasing rainfall intensity, coastal erosion and coastal flood driven by increasing SLR, and
6 tropical cyclone storm surges (high confidence). Further, Arctic coastal settlements are particularly exposed
7 to climate change due to sea ice retreat as well as from permafrost melt (high confidence).
8
9 Without adaptation, risks to land and people in coastal C&S from pluvial- and coastal-flooding will very
10 likely2 increase substantially by 2100 and likely beyond as a result of SLR, with significant impacts even
11 under RCP2.6 (Neumann et al., 2015; Muis et al., 2016; Brown et al., 2018; Nicholls et al., 2018; Kulp and
12 Strauss, 2019; Oppenheimer et al., 2019; Kirezci et al., 2020; Haasnoot et al., 2021b). Across these studies,
13 by 2100, 158-510 million people and US$7,919-US$12,739 billion assets under RCP4.5, and 176-880
14 million people and US$8,813-US$14,178 billion assets under RCP8.5, will be within the 1-in-100-year
15 floodplain (very high confidence). There is medium confidence that accelerated SLR will increase shoreline
16 erosion globally, although biophysical feedbacks will allow many coastlines to maintain relatively stable
17 morphology if room exists to accommodate mangroves in estuarine and deltaic coasts, and beach movement
18 along open coasts (Kench et al., 2015; McLean and Kench, 2015; Perkins et al., 2015; Richards and Friess,
19 2016; CCC, 2017; Duncan et al., 2018; Luijendijk et al., 2018; Mentaschi et al., 2018; Schuerch et al., 2018;
20 Ghosh et al., 2019; Masselink et al., 2020; Toimil et al., 2020; Vousdoukas et al., 2020b). Limiting
21 emissions to RCP2.6 (corresponding to a mean post-industrial global temperature increase of 1.5-2C)
22 significantly reduces future SLR risks (Hinkel et al., 2014; Brown et al., 2018; Nicholls et al., 2018; Schinko
23 et al., 2020). For example, by 2100 the population at risk of permanent submergence increases by 26% under
24 RCP2.6 compared with 53% under RCP8.5 (median values from Kulp and Strauss (2019).
25
26 There is high confidence about regionally differentiated but considerable global sectoral impacts in coastal
27 C&S arising from exposure to hazards. Tangible impacts include damage, loss of life, loss of livelihoods,
28 especially fisheries and tourism (Tessler et al., 2015; Avelino et al., 2018; Hoegh-Guldberg et al., 2018;
29 Seekamp et al., 2019; Arabadzhyan et al., 2020); negative impacts on health and wellbeing, especially under
30 extreme events (McIver et al., 2016; Bakkensen and Mendelsohn, 2019; Bindoff et al., 2019; Pugatch, 2019);
31 and involuntary displacement and migration (Hauer, 2017; Davis et al., 2018; Neef et al., 2018; Boas et al.,
32 2019; McLeman et al., 2021). Intangible impacts include psychological impacts due to extreme events, such
33 as heat-waves, flooding, droughts, and tropical cyclones; heightened inequality in coastal archetypes with
34 systematic gender/ethnicity/structural vulnerabilities; and loss of things of personal or cultural value, and
35 sense of place or connection, including existential risk of the demise of nations due to submergence (Allison
36 and Bassett, 2015; Barnett, 2017; Schmutter et al., 2017; Weir et al., 2017; Farbotko et al., 2020; Hauer et
37 al., 2020; Hoffmann et al., 2020; Bell et al., 2021). Impacts extend beyond the coastal zone, for example
38 disruption to ports and supply chains, with major geopolitical and economic ramifications from the C&S to
39 global scale (very high confidence) (Becker et al., 2018; Camus et al., 2019; Christodoulou et al., 2019;
40 Walsh et al., 2019; Hanson and Nicholls, 2020; Yang and Ge, 2020; Izaguirre et al., 2021; León-Mateos et
41 al., 2021; Ribeiro et al., 2021).
42
43 Many coastal C&S have densely built physical infrastructure and assets that are exposed and vulnerable to
44 climate change-compounded coastal hazards. There is high confidence that SLR, land subsidence, poorly
45 regulated coastal development, and the rise of asset values are major drivers of future risk in all coastal
46 archetypes and, without adaptation, built environment risks, especially in archetypes with high exposure due
47 to rapid growth, are expected to rise considerably in this century across all RCPs (Koks et al., 2019; Magnan
48 et al., 2019; Oppenheimer et al., 2019; Abadie et al., 2020; Nicholls et al., 2021). Archetypes with more
2 In this Report, the following terms have been used to indicate the assessed likelihood of an outcome or a result:
Virtually certain 99100% probability, Very likely 90100%, Likely 66100%, About as likely as not 3366%, Unlikely
033%, Very unlikely 010%, and Exceptionally unlikely 01%. Additional terms (Extremely likely: 95100%, More
likely than not >50100%, and Extremely unlikely 05%) may also be used when appropriate. Assessed likelihood is
typeset in italics, e.g., very likely). This Report also uses the term `likely range' to indicate that the assessed likelihood
of an outcome lies within the 17-83% probability range.
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1 informal settlements are often disproportionally exposed to coastal risks (Roy et al., 2016; Hallegatte et al.,
2 2017; Bangalore et al., 2019).
3
4 There is high confidence that loss of coastal ecosystem services will increase risks to all coastal C&S
5 archetypes that include reduced provisioning of materials and food (e.g., wood, fishery habitat) (Kok et al.,
6 2021), amelioration of coastal hazards (e.g., attenuation of storm surges, waves, and containing erosion)
7 (Section 2.3.2.3; Godfroy et al., 2019; Schoutens et al., 2019; Zhu et al., 2020b), climate change mitigation
8 (through carbon sequestration) (Macreadie et al., 2017; Rovai et al., 2018; Ward, 2020), water quality
9 regulation (nutrient, pollutant and sediment retention and cycling) (Wilson et al., 2018; Zhao et al., 2018),
10 and recreation and tourism (Pueyo-Ros et al., 2018).
11
12 Most studies of coastal C&S focus on adaptation to a single or limited set of risks, but there is high
13 confidence that compound and cascading risks significantly alter C&S risk profiles (Nicholls et al., 2015;
14 Estrada et al., 2017; Edmonds et al., 2020; Eilander et al., 2020; Yin et al., 2020; Ghanbari et al., 2021).
15 Extreme events can lead to cascading infrastructure failures that cause damage and economic losses well
16 beyond the coastal zone (Haraguchi and Kim, 2016; Kishore et al., 2018; Rey et al., 2019; So et al., 2019),
17 and have forced evacuation of C&S and small islands (Look et al., 2019; Thomas and Benjamin, 2020).
18 These risks are exacerbated by non-climate drivers, e.g., compound and cascading impacts arising from
19 exposure to tropical cyclones and COVID-19 that threaten population health and hamper pandemic
20 responses (Salas et al., 2020; Shultz et al., 2020a; Shultz et al., 2020b). There is emerging evidence (low
21 confidence) from individual coastal C&S, and regional case studies (e.g., in Europe, Australia, and the U.S.),
22 illustrating the increasing influence of compound risks on vulnerability due to accelerating climate change
23 (Wahl et al., 2015; Xu et al., 2019; Kirezci et al., 2020).
24
25 Figure CCP2.3 shows that ocean-driven coastal risks to people, land, and infrastructure in East and Southeast
26 Asia are highest compared to other regions, even for low levels of projected SLR. However, risks facing
27 coastal C&S are high across the globe, especially under higher SLR projections (high confidence). Without
28 adaptation, the population at-risk to a 100-year coastal flood increases by ~20% if current global mean sea
29 level rises by 0.15m relative to current levels; this at-risk population doubles at 0.75m rise in mean sea level,
30 and triples at 1.4m. Simultaneously, coastal C&S are projected to experience shoreline retreat, with
31 coastlines having more than 100 m retreat increasing ~165% if current mean sea levels rise between 0.23-
32 0.53 m. Ocean-driven flooding in coastal C&S is also projected to disrupt flights by up to three orders of
33 magnitude per year in selected coastal C&S as mean sea level increases. Typically, larger risks correspond
34 with archetypes associated with higher inequality and high growth rates, especially in deltas, leading to
35 larger vulnerability and exposure respectively under higher warming levels.
36
37
38
39 Figure CCP2.3: Map of coastal C&S risks according to IPCC regions, showing risks to people from a 100-year coastal
40 flood event (*100.000) (Haasnoot et al., 2021b), risks to loss of coastal land (length of coast with more than 100 m
41 retreat) (Vousdoukas et al., 2020b), risks to the built environment (airports at risk indicated by number of flights
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1 disrupted (Yesudian and Dawson, 2021)) and risk to wetlands (± indicates positive or negative area change) (Schuerch
2 et al., 2018). Risks are reported against global mean sea level rise relative to 2020, depending on data availability.
3
4
5 CCP2.3 Adaptation in Cities and Settlements by the Sea
6
7 CCP2.3.1 Introduction
8
9 This section extends SROCC Chapter 4 (Oppenheimer et al., 2019), which focused on SLR, and draws from
10 Chapters 6 and 9-15 to cover all C&S archetypes. Adaptation interventions span psycho-social (e.g.,
11 awareness raising), economic (e.g., insurance), physical (e.g., retreat), technical (e.g., sea walls) and natural
12 dimensions (e.g., wetland restoration) (Nicholls et al., 2015). Adaptation strategies for coastal C&S are
13 typically classified in terms of protect, accommodate, advance, and retreat, which are used below.
14
15 Some coastal cities have adapted to meters of SLR in the past, indicating that adaptation is feasible (Esteban
16 et al., 2020a), but future adaptation options are influenced by variations in projected socio-economic
17 conditions and rates of SLR (Cross-Chapter Box SLR in Chapter 3). To date, interventions are typically
18 implemented reactively in response to extreme events (high confidence); but leading adaptors are
19 increasingly proactive (medium confidence) (Araos et al., 2016; Dulal, 2019; Dedekorkut-Howes et al.,
20 2020), and those that move from previously rigid to more adaptive and flexible solutions, using an adaptation
21 pathways approach that keeps options open in the face of uncertainty, have improved climate risk
22 management (high confidence) (Sections 9.9.4; 10.5; 11.7; 12.5.5; 13.2; 14.7; 15.5; Cross-Chapter Box
23 DEEP in Chapter 17; Walker et al., 2013; Marchau et al., 2019).
24
25 The effectiveness of different strategies and interventions is mediated by physical coastal features for hard
26 adaptation measures, and by the scope and depth of soft adaptation measures, e.g., the coverage extent of
27 social safety nets for urban poor (Section 6.3). Their feasibility is also shaped by socio-economic, cultural,
28 political and institutional factors, e.g., social acceptance of measures (CCP2.2, SMCCP2.2.4). Together,
29 response effectiveness and feasibility shape the solution space for mediating risks (Section 1.3.1.2; Figure
30 CCP2.3; Simpson et al., 2021;), which is achieved chiefly through governance interventions e.g., laws and
31 regulations (Haasnoot et al., 2020). Access to financial resources expands the solution space, most notably
32 for some resource-rich coastal archetypes (CCP2.4.2; Table SMCCP2.1; Sections 3.6, 14.7), but rapid
33 population growth and unfolding climate-driven impacts can increase risks (Haasnoot et al., 2021a)
34 especially for small island and poorer C&S (high confidence) (Section 15.3; Magnan and Duvat (2020).
35
36 CCP2.3.2 Protection of Coastal Cities and Settlements
37
38 CCP2.3.2.1 Hard Engineering Measures
39
40 Hard engineering protection measures are commonly used to reduce coastal flooding, and to drain or store
41 excess water from intense precipitation. Many coastal cities, in particular densely populated and high
42 resource archetypes, have planned and are planning to continue a protection-based strategy, comprising e.g.,
43 breakwaters, sea walls and/or dikes, which could be raised or complemented with large barriers or with
44 `super-levees' enabling construction on top of them (high confidence) (Table SMCCP2.1; Takagi et al.,
45 2016; Haasnoot et al., 2019; Hall et al., 2019; Esteban et al., 2020b)).
46
47 Protection is effective in the short- to medium-term for many coastal cities, and can be cost-effective in the
48 21st Century (section CCP2.4.2), but residual risk remains because protection can fail. Even under RCP8.5,
49 technical limits to hard protection may only be reached after 2100 in many regions, but socio-economic and
50 institutional barriers may be reached before then (Hinkel et al., 2018). With progressive SLR, protection
51 eventually becomes unaffordable and impractical (Strauss et al., 2021). Combining hard engineering
52 measures with nature-based solutions, spatial planning and early warning systems, can help to contain
53 residual risk (Du et al., 2020). Protective works do not prevent salinisation and higher groundwater levels
54 (Alves et al., 2020), and can lead to loss of coastal habitat (Cross-Chapter Box SLR in Chapter 3; Achete et
55 al. (2017); Cooper et al. (2020)). Hard protection measures also create long-term path-dependency as they
56 last for decades and attract new development, locking in impact and exposure as C&S grow, with the
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1 expectation of ongoing protection (Chapter 3; Di Baldassarre et al., 2015; Gibbs, 2016; Griggs and Patsch,
2 2019; Siders, 2019a).
3
4 CCP2.3.2.2 Soft Engineering and Sediment-based Measures
5
6 Sediment-based interventions e.g., beach nourishment, aim to limit coastal erosion and flood risk and have
7 become a widely applied strategy especially in open coast archetypal C&S; in part because there is less
8 impact on adjacent beaches and coastal ecology, and lower construction and maintenance costs compared to
9 hard protection (high confidence) (Parkinson and Ogurcak, 2018). In addition, it is considered a flexible
10 strategy under more rapid SLR conditions (Kabat et al., 2009; Stive et al., 2013), and can be applied in the
11 form of a mega-nourishment strategy wherein natural currents distribute sand along the coast (Stive et al.,
12 2013; de Schipper et al., 2021). However, there are limits to this strategy due to environmental impacts,
13 costs, and the availability of potential and permitted sand reserves which may be unable to keep up with
14 higher rates of SLR (Parkinson and Ogurcak, 2018; Haasnoot et al., 2019; Harris et al., 2021; Staudt et al.,
15 2021). Simultaneously, other socio-economic needs (e.g., damming rivers, or for building and transport
16 infrastructure) may compete for sand as a limited resource (Torres et al., 2017; Bendixen et al., 2019).
17 Regional and global governance provisions (e.g., spatial reservations for sand mining; international
18 frameworks for distribution) could improve long-term feasibility (Torres et al., 2017; Parkinson and
19 Ogurcak, 2018; Bendixen et al., 2019; Haasnoot et al., 2019).
20
21 CCP2.3.2.3 Nature-based Measures
22
23 Nature-based measures, such as retaining mangroves and marshes, have been successful in reducing deaths
24 and damage due to storm surges (high agreement, medium evidence) (Das and Vincent, 2009; Saleh and
25 Weinstein, 2016; Narayan et al., 2017; Triyanti et al., 2017; Hochard et al., 2019; del Valle et al., 2020), and
26 across the USA reportedly provide USD23.2 billion yr-1 in storm protection services (Saleh and Weinstein,
27 2016). They are also a cost-effective strategy (medium confidence) that provide C&S with additional co-
28 benefits through ecosystem services (high confidence) (Cross-Chapter Box NATURAL in Chapter 2;
29 Section 2.2.4; Narayan et al., 2016; Depietri and McPhearson, 2017; Morris et al., 2018; Reguero et al.,
30 2018; Chausson et al., 2020; Du et al., 2020; NIES and ISME, 2020; Reguero et al., 2020; Sudmeier-Rieux
31 et al., 2021).
32
33 Nature-based measures can reduce inland propagation of extreme sea levels (high tides, storm surges) (high
34 agreement) (Godfroy et al., 2019; James et al., 2020; Zhu et al., 2020b), with vertical reduction in water
35 levels ranging from 5-50cm/km behind large mangroves and marshes (Stark et al., 2015; Van Coppenolle
36 and Temmerman, 2020). They also attenuate wind-driven waves and reduce shoreline erosion (high
37 agreement), and this can be as much as 90% over stretches of 10-100 meters for dense mangrove and marsh
38 vegetation (medium evidence) (Li et al., 2014; Möller et al., 2014; Vuik et al., 2016; Vuik et al., 2018;
39 Godfroy et al., 2019; Zhu et al., 2020a) and up to 40% for dunes (Feagin et al., 2019). Coral reefs on average
40 reduce wave energy by 97% (Ferrario et al., 2014). Seagrass meadows attenuate wind waves to a lesser
41 extent, and are only effective in water <0.2 m deep (Ondiviela et al., 2014; Narayan et al., 2016; Morris et
42 al., 2019).
43
44 Within limits, coastal ecosystems can respond to rising sea-level through sediment accretion and lateral
45 inland movement (Kirwan et al., 2016; Schuerch et al., 2018). Nature-based measures have greatest potential
46 in coastal deltas and estuaries, where human populations are exposed but large ecosystems, like mangroves
47 and marshes, can be conserved and restored (Menéndez et al., 2020; Van Coppenolle and Temmerman,
48 2020). Their feasibility depends on physical, ecological, institutional, and socio-economic conditions that are
49 typically locality-dependent (Temmerman and Kirwan, 2015; Arkema et al., 2017); space may not be
50 available in certain places (e.g., intensive urbanization on the shoreline), or these measures may conflict with
51 other human demands for scarce land (Tian et al., 2016). Successful nature-based measures require site-
52 specific knowledge and science-based design, pilot monitoring, and adaptive upscaling (Evans et al., 2017;
53 Nesshöver et al., 2017), and more rigorous understanding of long-term performance, maintenance and costs
54 (Kumar et al., 2021).
55
56 Nature-based measures are increasingly implemented in combination with hard protection measures (Hu et
57 al., 2019; Schoonees et al., 2019; Morris et al., 2020; Oanh et al., 2020). They can reduce dike failure and
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1 increase design life where sediment accretion allows wetlands to respond to SLR (Jongman, 2018; Vuik et
2 al., 2019; Zhu et al., 2020a). There is high agreement that a hybrid strategy combining hard and soft protect
3 strategies is more effective and less costly under many circumstances; and there is limited evidence that
4 technical limits will be encountered with such a strategy for low-lying C&S built on soft or permeable soil or
5 with high exposure to monsoons and river discharges (Spalding et al., 2014; Sutton-Grier et al., 2015; Pontee
6 et al., 2016; Morris et al., 2018; Reguero et al., 2018; Du et al., 2020; Morris et al., 2020; Seddon et al.,
7 2020; Waryszak et al., 2021).
8
9 CCP2.3.3 Accommodation of the Built Environment
10
11 The most effective solution for limiting the growth of climate risks in C&S by the sea is to avoid new
12 development in coastal locations prone to major flooding and/or SLR impacts (very high confidence) (Cross-
13 Chapter Box SLR in Chapter 3; Oppenheimer et al., 2019; Doberstein et al., 2019). For existing C&S
14 accommodation includes biophysical and institutional responses to reduce exposure and/or vulnerability of
15 coastal residents, human activities, ecosystems and the built environment, enabling continued habitation of
16 coastal C&S (Oppenheimer et al., 2019). Next to hard protection, accommodation is the most widely used
17 adaptation strategy across all archetypes to date (high confidence) (Sayers et al., 2015; Olazabal et al., 2019;
18 Le, 2020). Measures include elevation or flood-proofing of houses and other infrastructure (Garschagen,
19 2015; Aerts et al., 2018; Buchori et al., 2018; Jamero et al., 2018; Tamura et al., 2019), spatial planning (e.g.
20 Duy et al. (2018)), amphibious building designs (Nilubon et al., 2016), increasing water storage and/or
21 drainage capacity within C&S (Chan et al., 2018), early warning systems and disaster responses (Hissel et
22 al., 2014), and slum upgrading (Jain et al., 2017; Olthuis et al., 2020).
23
24 Raising land, or individual buildings, can avert flooding and can be done artificially or as nature-based
25 interventions through river diversion and control in estuarine and deltaic archetypes (Nittrouer et al., 2012;
26 Auerbach et al., 2015; Day et al., 2016; Sánchez-Arcilla et al., 2016; Hiatt et al., 2019; Cornwall, 2021).
27 Nature-based land elevation is limited by sediment supply and can address SLR rates of up to 10mm/yr
28 (Kleinhans et al., 2010; Kirwan et al., 2016; IPCC, 2019). It also assumes that existing land-use patterns
29 permit land raising (e.g., in rural or newly developed areas (Scussolini et al., 2017). Artificial land raising
30 can achieve significant elevations and be implemented over a large spatial scale (Esteban et al., 2015;
31 Esteban et al., 2019). Raising land can be cost beneficial for small areas, or where lower safety levels are
32 satisfactory, but protection is usually more economical for larger areas, though both strategies are often
33 combined (Lendering et al., 2020).
34
35 Accommodation measures can be very effective for current conditions and small changes in SLR (Laurice
36 Jamero et al., 2017; Scussolini et al., 2017; Oppenheimer et al., 2019; Du et al., 2020; Haasnoot et al.,
37 2021a), and buy time to prepare for more significant changes in sea level and other climate compounded
38 coastal hazards. However, limits to this strategy occur comparatively soon in some locations, possibly
39 requiring protection in the medium-term, and retreat in the long run and beyond 2100, particularly in
40 scenarios of dramatic SLR (Oppenheimer et al., 2019). For the foreseeable future, accommodation can play
41 an important role in combination with protective measures, to form hybrid interventions, with higher
42 effectiveness than either approach in isolation (Du et al., 2020). Accommodation can play an increasingly
43 important role where hard protection is neither technically nor financially viable; but detailed studies about
44 expected trends of accommodation are lacking (Oppenheimer et al., 2019).
45
46 CCP2.3.4 Advance
47
48 An advance strategy creates new land by building seaward, which can reduce risk for the hinterland and the
49 newly elevated land, either by land reclamation through land-filling or polderisation through planting of
50 vegetation to support natural land accretion (Wang et al., 2014; Sengupta et al., 2018). Advance has occurred
51 in all archetypes (high confidence); from open coasts (e.g., Singapore) and small atolls (e.g., Hulhumalé in
52 the Maldives) (Hinkel et al., 2018; Brown et al., 2020) to cities on estuaries (e.g., Rotterdam) and deltas
53 (e.g., Shanghai Sengupta et al. (2020)), and mountainous coasts (e.g., Hong Kong SAR, China). Earth
54 observations show between 14,000-33,700 km2 of land has been gained in coastal areas over the past 30
55 years, the dominant drivers being urban development and activities like fish farming (Donchyts et al., 2016;
56 Zhang et al., 2017; Mentaschi et al., 2018). Advancing seawards through large floating structures may be a
57 viable option in future (Wang et al., 2019; Setiadi et al., 2020; Wang and Wang, 2020), but is at an
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1 experimental stage, and, so far, only applied in calm water within a city as part of an accommodate strategy
2 (Scussolini et al., 2017; Penning-Rowsell, 2020; Storbjörk and Hjerpe, 2021).
3
4 Advance is seen as an attractive option to adapt to SLR in growing cities that are already densely populated
5 and have limited available land for safe development, with a moderate to high adaptive capacity. But
6 advance can have significant negative impacts on coastal ecosystems and livelihoods, requires substantial
7 financial and material resources and time to build, and may be subject to land subsidence (Jeuken et al.,
8 2014; Garschagen et al., 2018; Brown et al., 2019; NYCEDC, 2019; Oppenheimer et al., 2019; Sengupta et
9 al., 2020; Bendixen et al., 2021).
10
11 CCP2.3.5 Retreat
12
13 Retreat is a strategy to reduce exposure and eventually risks facing coastal C&S by moving people, assets
14 and activities out of coastal hazard zones (Oppenheimer et al., 2019). This includes adaptive migration,
15 involuntary displacement, and planned relocation of population and assets from the coast (Section 7.2.6;
16 Cross-Chapter Box CB-MIGRATE in Chapter 7).
17
18 Planned relocation in coastal C&S with high hazard exposure and climate impacts is already occurring and
19 has been increasing in frequency (medium confidence) (Hino et al., 2017; Mortreux et al., 2018), with some
20 small islands purchasing land in other countries to facilitate movement (Klepp, 2018). In the Arctic, the
21 pressure to relocate away from the coast is expected to rise given the interacting effects of permafrost thaw
22 and coastal erosion. Native villages in Alaska are already relocating (Ristroph, 2017; Ristroph, 2019).
23 Involuntary resettlement may be a secondary effect of large-scale hard coastal protection projects, or inner-
24 city river and canal regulation. In Jakarta, for example, a new giant seawall project involves resettling coastal
25 households along large parts of the coastline (Garschagen et al., 2018).
26
27 Increased migration is to be expected across different climate scenarios, but there is limited evidence and
28 medium agreement about the scale of climate-induced migration at the coast (Oppenheimer et al., 2019)
29 (Chapter 16, RKR on peace). Planned relocation is expected to rise in C&S in response to SLR and other
30 coastal hazards (high agreement, medium evidence) (Siders et al., 2019). Relocation has predominantly been
31 reactive to date, but increased attention is being given to pre-emptive resettlement and the potential pathways
32 and necessary governance, finance and institutional arrangements to support this strategy (Ramm et al.,
33 2018; Lawrence et al., 2020; Haasnoot et al., 2021a). There is limited evidence about the costs of planned
34 relocation and retreat more generally (Oppenheimer et al., 2019).
35
36 Retreat can effectively reduce the exposure of urban residents to coastal hazards and provide opportunity for
37 re-establishment of ecosystems services (very high confidence) (Song et al., 2018; Carey, 2020; Hindsley
38 and Yoskowitz, 2020; Lincke et al., 2020; Lincke and Hinkel, 2021). But there is high confidence that it can
39 sever cultural ties to the coast (Reimann et al., 2018) and can lead to negative and inequitable socio-
40 economic effects for resettled communities if not planned and implemented in ways that are inclusive, just
41 and address cultural, place-attachment and livelihood considerations (Ajibade, 2019; Adger et al., 2020;
42 Carey, 2020; Jain et al., 2021; Johnson et al., 2021), and the rights and practices of Indigenous People
43 (Nakashima et al., 2018; Ristroph, 2019; Mohamed Shaffril et al., 2020). If planned well ahead and aligned
44 with social goals, pathways to managed retreat can achieve positive outcomes and provide opportunities for
45 transformation of coastal C&S (Haasnoot et al., 2021a; Mach and Siders, 2021). There is medium confidence
46 that the availability of suitable and affordable land, and appropriate financing, is a major bottleneck for
47 planned relocation (Alexander et al., 2012; Ong et al., 2016; Hino et al., 2017; Fisher and Goodliffe, 2019;
48 Hanna et al., 2019; Buser, 2020; Doberstein et al., 2020), particularly in very dense mega-urban areas
49 (Ajibade, 2019) and crowded small islands (Neise and Revilla Diez, 2019; Weber et al., 2019; Kool et al.,
50 2020; Lincke et al., 2020)
51
52 CCP2.3.6 Adaptation Pathways
53
54 No single adaptation intervention comprehensively addresses coastal risks and enables CRD. An adaptation
55 pathways approach can facilitate long-term thinking, foresee maladaptive consequences and lock-ins, and
56 address dynamic risk in the face of relentless and potentially high SLR; and frame adaptation as a series of
57 manageable steps over time (Cross-Chapter Box DEEP in Chapter 17; Figure CCP2.4; Haasnoot et al.
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1 (2019)). A portfolio of hard, soft and nature-based interventions can be used to implement strategies to
2 protect, accommodate, retreat, and advance, individually or in combination.
3
4 The strategy, and portfolio of interventions, can be adjusted in response to new information about SLR and
5 other climate risks according to economic, environmental, social, institutional, technical or other objectives.
6 In cases of rapid SLR, it may be necessary to implement a short-term protection strategy to buy time to
7 implement more transformative and enduring strategies (high confidence) (Du et al., 2020; Lawrence et al.,
8 2020; Morris et al., 2020; Haasnoot et al., 2021a). There is high agreement that combining and sequencing
9 adaptation interventions can reduce risk over time (Du et al., 2020; Morris et al., 2020). Phasing
10 interventions can help to spread costs and minimise regret (de Ruig et al., 2019), provided that options are
11 kept open to adjust to changing conditions (Buurman and Babovic, 2016; Haasnoot et al., 2019; Hall et al.,
12 2019).
13
14 Many megacities plan to continue a protection strategy (Table SMCCP2.1). This becomes increasingly
15 costly, institutionally challenging, and requires space possibly facilitated through local relocation. There is
16 high agreement that many C&S are locked-in to a self-reinforcing pathway: coastal defences have a long
17 lifetime and attract people and assets that require further protection (Gralepois et al., 2016; Bubeck et al.,
18 2017; Welch et al., 2017; Di Baldassarre et al., 2018; Jongman, 2018). Transitioning to alternative pathways
19 may involve major transfer and sunk costs (e.g., Gralepois et al. (2016)), but these may prove to be less
20 costly in the long-term. Because of considerable inertia in the built form of cities, such transitions are more
21 likely to be successful and aligned with societal goals if embedded early into C&S planning and
22 development processes that enable transformational change and CRD (Sections 6.4.8; 11.7; 13.11; Box 18.1;
23 Ürge-Vorsatz et al., 2018; Siders 2019b).
24
25 In islands, hybrid options of nature-based (where space and environmental conditions allow) and protect
26 measures (on wealthy, already densely populated islands) could reduce risk for low SLR in the next few
27 decades (Section 15.5). Where feasible, retreat is a compelling option to reduce risk (Figure CCP2.4). With
28 higher rates and levels of SLR in the medium- to long-term, financial, governance and material barriers may
29 differentiate resource-rich islands and more rural islands, leading to a dichotomy between which islands
30 retreat or can rely on protection for a period of time.
31
32
33
34 Figure CCP2.4: Generic adaptation pathways for coastal C&S (a) and the typical solution space with illustrative
35 pathways for three coastal archetypes (b). As risk increases under rising sea levels, solutions need to be combined or
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1 sequenced in order contain risk. Pathways involve different trade-offs. Based on Table SMCCP2.1 - 2.3; Chapters 11
2 and 13, Magnan and Duvat (2020); Lawrence et al. (2020); Haasnoot et al. (2019). Depending on local conditions,
3 archetype and risk tolerance, alternative pathways are needed and possible to contain risk. Dashed lines indicate
4 uncertainty in pathway (a). Dashed and plain borders are used for illustrating various local situations within each
5 archetype (b).
6
7
8 CCP2.4 Enabling Conditions and Lessons Learned
9
10 Here we distil enabling conditions and lessons learned from C&S archetypes adapting to coastal risk (Table
11 SMCCP2.1; Table SMCCP2.2; Sections 6.4; 9.9.4; 10.5; 10.6; 11.7; 11.8; 12.5.5; 13.6.2; 14.7.2; 15.6).
12
13 CCP2.4.1 Enabling Behavioural Change
14
15 Changing behaviours and practices are a critical enabler of adaptation in coastal C&S. Behavioural enablers
16 include using economic, informational, socio-cultural, and psychological incentives to motivate adaptation
17 actions (van Valkengoed and Steg, 2019; Gibbs, 2020): e.g., leveraging Indigenous Knowledge and Local
18 Knowledge (IKLK) and religious beliefs to incentivise adaptation (Hiwasaki et al., 2014; Ford et al., 2015);
19 implementing subsidies/bans to incentivise sustainable aquaculture (Condie et al., 2014; Krause et al., 2020);
20 providing localized flood warnings and forecasts to inform individual risk perceptions and risk management
21 (Bruine de Bruin et al., 2014; Gibbs, 2020), or incentivise risk insurance (Bradt, 2019).
22
23 There is high evidence with medium agreement that public attitudes and perceptions of climate risks
24 significantly influence individual adaptation behaviour across all coastal archetypes (Bradt, 2019; Buchanan
25 et al., 2019; Javeline et al., 2019). Information on climate risks and impacts (e.g., flood warnings, SLR
26 projections) strongly shapes public perceptions of climate risks. It is most effective at incentivising and
27 enabling adaptation behaviour if provided at meaningful spatial and temporal scales, with guidance about
28 how to interpret the information (medium evidence, high agreement) (Gibbs (2020); Cools et al.
29 (2016)). Further, there is medium evidence, high agreement that integrating climate information with existing
30 knowledge systems, such as local norms and beliefs and IKLK, is critical to improve public acceptability and
31 develop context-specific solutions (Ford et al., 2015).
32
33 A second key enabler of coastal adaptation behaviour is self-efficacy or belief in one's capacity to undertake
34 adaptation. There is medium evidence, high agreement that high risk perception is in itself insufficient to
35 motivate people to undertake adaptation (Fox-Rogers et al., 2016; Roder et al., 2019; Gibbs, 2020) and needs
36 to be supplemented with supportive policy and financial provisions to enable adaptation Fox-Rogers et al.
37 (2016).
38
39 Third, there is medium evidence on how trust in state-led, planned adaptation measures can hinder or enable
40 individual adaptation (van Valkengoed and Steg, 2019; Schneider et al., 2020). As an enabler, trust in early
41 warnings can mitigate flood risk by incentivising evacuation (Binh et al., 2020) and high trust can help
42 overcome uncertainty attached to projected climate impacts and/or adaptation decisions (Frederiksen, 2014).
43 As a barrier, low trust can disincentivise adaptation, e.g., willingness to pay for flood insurance (Roder et al.,
44 2019) or public support for managed retreat (Hanna et al., 2020). Paradoxically, high trust in existing
45 adaptation measures can reduce people's perceived need for ongoing adaptation (e.g., levees potentially
46 reducing individual flood-proofing actions). Adaptation decisions also manifest `single-action bias' with
47 modest-cost adaptation actions in the present disincentivising further adaptation (Buchanan et al., 2019).
48
49 Several tools to incentivise adaptation behaviour are being tested around the world e.g., nudges and boosts2
50 are being experimented with to shape individual risk beliefs and demand for flood insurance (Bradt, 2019);
51 ordinances are being used to ban, authorise or limit certain activities (Herrick, 2018); subsidies and financial
52 support being used to incentivise adaptation such as subsidised beach nourishment (McNamara et al., 2015);
53 and zoning restrictions and building codes restrict or guide climate-resilient infrastructural development
54 Schneider et al. (2020). Overall, the literature affirms that behavioural interventions are more readily taken
55 up if they are: aligned with cultural practices, norms, and beliefs; on temporal scales within peoples'
56 planning horizons; and build upon relationships of trust and legitimacy (Donner and Webber, 2014; Herrick,
57 2018; Schneider et al., 2020).
58
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1 CCP2.4.2 Finance
2
3 Lack of financial resources is a key constraint affecting all coastal archetypes (high confidence) (Table
4 SMCCP2.2). Adaptation to coastal hazards is costly the global costs of protecting coastal areas with levees
5 (annual investment and maintenance costs) are estimated at US$1271 billion in 2100 with SLR up to 1.2m
6 (Hinkel et al., 2014). Broadly speaking, it is cost-effective to contain coastal hazard risk in the short- to
7 medium-term in densely populated wealthy localities by using protective works but such measures are
8 unaffordable in dispersed poorer coastal C&S (Lincke and Hinkel, 2018).
9
10 Archetypes with high adaptive capacity may currently have financial resources to meet adaptation needs, but
11 such funding may be unsustainable in the long-term. In Catalonia, while public funds are currently used to
12 finance beach nourishment, these costs will increase with SLR and it is unclear if public finance will remain
13 a feasible source (Hinkel et al., 2018). Even in relatively richer municipalities, financing adaptation is
14 constrained by other urban priorities (Bisaro and Hinkel, 2018). In Europe, shifting responsibilities from
15 national governments to transnational and local actors has resulted in reduced national budgets for coastal
16 adaptation investment and increased pressure on local authorities to raise public funds for adaptation without
17 alienating electoral bases (Bisaro and Hinkel, 2018).
18
19 Locations in the Global South have limited public budgets allocated to coastal adaptation and may rely on
20 international donor aid (Donner et al., 2016; Araos et al., 2017). Such aid is often inconsistent and short-
21 term, which limits long-term maintenance of knowledge, equipment and infrastructure needed to sustain
22 adaptation measures beyond initial funding periods (Weiler et al., 2018; Thomas et al., 2020), with resultant
23 negative consequences in places as different as Kiribati (Donner and Webber, 2014) and Bangladesh (Hinkel
24 et al., 2018). Donor-funded adaptation programs aimed at promoting behavioural change, e.g., through
25 coastal planning or new decision-making systems, require enduring training and institutional capacity, which
26 is difficult to upkeep after aid is depleted. Donor funding is often project-based and there are few avenues
27 available to fund additional permanent and long-term staff needed to bolster climate change institutions.
28 Without funding to support additional staff, existing institutions often lack the human capacity and resources
29 needed for coastal adaptation (Ziervogel and Parnell, 2014).
30
31 C&S in the Global South also face financial challenges in addressing loss and damage due to climate-
32 induced slow-onset and extreme events. Financial support to address both quantifiable damages and non-
33 economic losses through measures such as climate resilient reconstruction after extreme weather events, and
34 national and local level emergency contingency funds, is lacking and has been an issue of contention in
35 international policy arenas (Bahinipati et al., 2017; Wewerinke-Singh and Salili, 2020; Martyr-Koller et al.,
36 2021).
37
38 While coastal adaptation has largely been viewed as the responsibility of governments, private finance is
39 increasingly recognized as necessary to help close the coastal adaptation funding gap (Ware and Banhalmi-
40 Zakar, 2020). Financial arrangements for coastal adaptation measures that align public actor and private
41 investor interests are suitable for a range of budgets, from US$10,000-100 million (Bisaro and Hinkel,
42 2018). Private equity instruments that involve real estate development companies have already been
43 successfully implemented and are most effective in urban areas with high-value real estate development
44 (Chiang and Ling, 2017). Public-private partnership equity instruments that engage construction and real
45 estate developers have been successful for small- to medium-scale infrastructural projects. While public-
46 private partnership bonds and public bonds have potential to align public actors and private investors, such
47 instruments require de-risking of coastal adaptation through enabling economic policy instruments, such as
48 concessional loans (Bisaro and Hinkel, 2018).
49
50 Explicitly identifying the benefits, or goods and services, that are provided by coastal adaptation is critical to
51 supplement limited government funds and engage a broader set of financial tools and actors (Woodruff et al.,
52 2020). Matching goods and services provided by particular adaptation strategies to specific beneficiaries
53 helps identify the range of fair and equitable financial tools. In the Netherlands, public funding through state,
54 regional and local entities have independent tax revenue systems to provide the funding needed to maintain
55 flooding infrastructure (Hinkel et al., 2018).
56
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1 Given the high costs of coastal adaptation, benefit to cost ratios (BCR) are often used to determine the value
2 of investing in adaptation. BCR are high for urbanized coastal areas with high concentrations of assets (13%
3 of the world's coastline), covering 90% of global coastal floodplain population and 96% of assets in the
4 global coastal floodplain (Lincke and Hinkel, 2018). A global assessment shows BCR for investing in flood
5 protection up to ~120 (Tiggeloven et al., 2020). For Europe, at least 83% of flood damages could be avoided
6 by elevating dikes along ~23-32% of Europe's coastline and BCR vary from 8.3 to 14.9, with higher ratios
7 for higher concentration pathways (Section 13.2) (Vousdoukas et al., 2020a). Globally 40% of damages can
8 be reduced with levees of 1m and costs lower than avoided damage (Tamura et al., 2019). For a mix of
9 expensive storm surge barriers, nature-based solutions and flood proofing measures for New York City,
10 Aerts et al. (2014) found BCRs <1 for the current situation, but >2 for a SLR scenario of +1m.
11
12 However, BCR values may be low and adaptation investment may not be financially viable for small coastal
13 settlements, less densely populated poorer coasts, or isolated communities (medium confidence). Considering
14 BCR of protection and coastal migration across a range of SLR and SSP scenarios for the 21st century, a
15 higher BCR was found for protection of only 3% of the global coastline protecting 78% of the coastal
16 population and 92% of global coastal floodplain assets, while for the remaining coasts, coastal migration was
17 estimated to be optimal in terms of economic costs (Lincke and Hinkel, 2021). Considering coastal migration
18 as part of the solution space could lower global costs in investment and maintenance for SLR protection by a
19 factor of 2-4 in the 21st century but would result in large land losses and high levels of migration for South
20 and South-east Asia in particular and, in relative terms, small island nations would suffer most. The need to
21 consider place attachment, community relationships, livelihoods and the spiritual and cultural significance of
22 settlements limit the application of BCR as a tool for coastal adaptation decisions in these contexts (Thomas
23 and Benjamin, 2020). Moreover, there is limited knowledge on trade-offs, including BCR, of alternative
24 adaptation options and pathways at global to regional scale, in particular over the long-term (beyond 2100).
25
26 Even where BCR is high, finance may be inaccessible as it is challenging to convert the long-term benefits
27 of adaptation into the revenue streams that may be needed to initially finance adaptation investments (Hinkel
28 et al., 2018). For example, in Ho Chi Minh City, Vietnam, despite high BCR, high costs of flood protection
29 (US$1.4-2.6 billion) have prevented such adaptation measures from being implemented (Hinkel et al., 2018;
30 Cao et al., 2021). Moreover, drawing from places as distinct as small communities in Fiji (Neef et al., 2018)
31 and Belize (Karlsson and Hovelsrud, 2015), and megacities like New York City and Shanghai (Oppenheimer
32 et al., 2019), BCR provides only a limited view and consideration of feasibility, effectiveness, efficiency,
33 equity, culture, politics and power, and attachment to place, is more likely to foster CRD (high confidence).
34
35 CCP2.4.3 Governance
36
37 An array of climate and non-climate perils (Le Cozannet et al., 2017), present coastal communities and their
38 governing authorities with immense governance and institutional challenges that will get progressively more
39 difficult as sea level rises (high confidence) (Wallace, 2017; Leal Filho et al., 2018; Oppenheimer et al.,
40 2019). Yet a study of public provisions for coastal adaptation in 136 of the largest coastal port-urban
41 agglomerations across 68 countries found no policy implementation in 50% of the cases; in 85% of cases,
42 adaptation actions are not framed by current impacts or future risks; and formal efforts are recent and
43 concentrated in more developed settings (Olazabal et al., 2019; Olazabal and Ruiz De Gopegui, 2021) -
44 underscoring a persistent coastal adaptation gap. Translating these challenges into enabling governance
45 conditions is difficult but instructive lessons are being learned, and summarized (from Table SMCCP2.4) for
46 archetypal C&S in Tables CCP2.1, 2.2.
47
48 We start with a synopsis of governance settings within which coastal adaptation and CRD choices are made,
49 and spotlight factors hindering and enabling translation of adaptation into practice. Then, building upon and
50 extending the SROCC analysis of enablers and lessons learned in responding to SLR (Oppenheimer et al.,
51 2019), we assess key governance challenges, related enablers and lessons learned (Tables CCP2.1, CCP2.2).
52
53 Governance arrangements and practices are embedded in the socio-political and institutional fabric of coastal
54 C&S. Consequently, barriers and enablers for adapting to climate change at the coast, and charting pathways
55 for CRD, reflect more general constraints and opportunities (high confidence) (Meerow, 2017; Rocle and
56 Salles, 2018; Rosendo et al., 2018; Di Giulio et al., 2019; Hölscher et al., 2019; Van Assche et al., 2020;
57 Williams et al., 2020). Local level action is often constrained; 231 cities in the USA report weak leadership,
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1 lack of funding and staffing, and low political will (Fu, 2020). A meta-analysis of coastal municipal planning
2 documents in Australia shows few localities have moved beyond risk assessment (Bradley et al., 2015).
3 Coastal C&S tend to prefer strategies that protect and accommodate existing coastline assets, i.e., a `fix and
4 forget' approach (Gibbs, 2015), rather than enduring proactive adaptation (Cooper and Pile, 2014).
5
6 Many C&S, especially in the Global South, already face high exposure to coastal risks, and development
7 constraints associated with poverty and socioeconomic inequality, lack of transparent resource allocation
8 mechanisms, and low political will (high confidence) (Di Giulio et al., 2019; Nagy et al., 2019; Pasquini,
9 2020; Lehmann et al., 2021). Research from across South America notes inadequate regulatory frameworks,
10 missing data and information, widespread coastal ecosystem degradation, and complex interactions between
11 natural disasters and civil conflict (Villamizar et al., 2017; Nagy et al., 2019). Coastal climate risks in the
12 Global South are often compounded by ongoing land-use management conflicts and other pressures
13 including informal land uses, unregulated and/or inadequate infrastructure/building development, public
14 health priorities such as combating Dengue Fever, inadequate income diversification, low education levels,
15 and political marginalization of communities historically not represented in the urban development process
16 (Barbi and Ferreira, 2014; Salik et al., 2015; Cabral et al., 2017; Goh, 2019). There are also entrenched
17 socio-economic inequalities leading to the maldistribution of adaptation actions and benefits in the Global
18 North (Gould and Lewis, 2018; Keenan et al., 2018; Ranganathan and Bratman, 2019; Yumagulova, 2020;
19 Long et al., 2021).
20
21 To address the myriad governance challenges attributed to low awareness, low skills, scalar mismatches, and
22 high socioeconomic inequality and coastal vulnerability, post-AR5 research highlights enablers of more
23 innovative approaches to bridge capacity, policy, and financial deficits (Reiblich et al., 2019) and facilitate
24 more proactive implementation of coastal adaptation actions (Table SMCCP2.2; Fu, 2020). A survey of
25 NGOs, state and local government across Alaska, Florida, and Maryland in the USA found that perceived
26 risk, uncertainty, and trust in support for climate adaptation varied across two stages of adaptation support
27 for the development of plans and willingness to allocate human and financial resources to implement plans
28 (Kettle and Dow, 2016). To bridge this gap, Cinner et al. (2018) suggest the need to build capacity across
29 five domains: the assets that people can draw upon in times of need; the flexibility to change strategies and
30 interventions; the ability to organize and act collectively; learning to recognize and respond to change
31 (especially as important thresholds are approached); and the agency to determine whether to change or not,
32 and then take prudent action).
33
34 Effective and accountable local leadership can help to mobilize capacities, resources, and climate awareness
35 within coastal C&S. Strong leadership is associated with agenda-setting authorities and the ability to
36 navigate complex institutional interests towards more strategic planning efforts (high confidence) (Ferguson
37 et al., 2013; Anguelovski et al., 2014; Chu et al., 2017; Valdivieso and Andersson, 2018; Fink, 2019;
38 Ndebele-Murisa et al., 2020). Policy leadership can positively influence the motivation and initiative of
39 municipal officers (Lassa and Nugraha, 2014; Wijaya et al., 2020); whilst local leadership is needed integrate
40 coastal management, disaster management and climate adaptation mandates (Rosendo et al., 2018).
41
42 Inclusive decision-making arrangements can enable participation, local ownership, and further equity in
43 crafting coastal adaptation plans and policies (Chu et al., 2016). Inclusion of diverse stakeholders can help
44 improve awareness of adaptation needs; help to bridge existing social inequalities in decision-making about
45 adaption needs, options and outcomes; close the gap between formal and informal institutions, and engage
46 Indigenous forms of decision-making, which often associate climate risks with livelihood, housing, and
47 employment stressors (Ziervogel et al., 2016; Fayombo, 2020). For example, research from Pacific Island
48 States (Nunn et al., 2017) and coastal Arctic zones (Romero Manrique et al., 2018) highlight the need to
49 engage with Indigenous environmental knowledge. Case studies from Indonesia, Philippines, and Timor-
50 Leste show that IKLK and customary laws can support environmental awareness, strengthen social cohesion,
51 and help communities to better respond to climate impacts (Hiwasaki et al., 2015). Research from coastal
52 Cambodia shows that inclusive governance arrangements can target empowerment of the most vulnerable
53 groups to facilitate better adaptation behavior and mainstream adaption knowledge through both formal and
54 informal education at the community level (Ung et al., 2016).
55
56 The law is key to governing climate risks in C&S, including regulating exposure to coastal hazards;
57 facilitating accountable decision-making, funding arrangements, liabilities, and resolving disputes; and
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1 securing human rights (high confidence) (Setzer and Vanhala, 2019; Averill, 2020). But it has limits and can
2 be an adaptation enabler and barrier (Green et al., 2015; Cosens et al., 2017; Craig et al., 2017; DeCaro et al.,
3 2017). Contemporary legal practice has not enabled effective adaptation in part because SLR affects
4 compensable property rights that are secured by the law and which generally trump concerns about public
5 safety, resilience and sustainability (Reiblich et al., 2019). Private property rights can be used as both a
6 sword and a shield to privilege dominant interests, by undermining land use policies, plans and
7 implementation efforts intended to promote integrated coastal management and risk reduction (O'Donnell et
8 al., 2019; Reiblich et al., 2019). Climate change litigation has proliferated over the last decade (Setzer and
9 Vanhala, 2019), addressing, among other things, failures to prepare for or adapt to climate change, and to
10 secure human rights (Peel and Osofsky, 2018). Reflexive and adaptive law that accounts for the distinctive
11 features of coastal hazard risk, and associated governance imperatives, builds coastal C&S adaptive capacity
12 and resilience (high confidence) (Garmestani and Benson, 2013; Cosens et al., 2017; DeCaro et al., 2017).
13 Procedural justice, due process, and use of substantive standards instead of rules, provide legal stability and
14 enable adaptation (Craig et al., 2017). Coastal adaptation efforts are ultimately implemented through C&S
15 actions that are enabled or constrained by prevailing legislative, executive and judicial provisions and
16 practices, which differ significantly across jurisdictions (He, 2018). In practice, the `coastal lawscape' is
17 made up of interconnected cultural-normative, political and legal systems that need to be understood
18 holistically to enable coastal adaptation in C&S (O'Donnell, 2021).
19
20 Tables CCP2.1 and CCP2.2 summarise key insights about key governance challenges facing archetypal
21 coastal C&S around the world, and associated critical enablers and lessons learned to address climate
22 change-compounded coastal hazard risk (based on synthesis of Table SMCCP2.3).
23
24
25 Table CCP2.1: Governance challenges and critical enablers for addressing coastal hazard risk in C&S
Key governance challenges Critical enablers for C&S to address coastal hazard risk
Complexity: Climate change compounds Draw on multiple knowledge systems to co-design and co-produce
non-climatic hazard risks facing coastal more acceptable, effective and enduring responses.
C&S in interconnected, dynamic and Build governance capacity to tackle complex problems.
emergent ways for which there are no
simple solutions.
Time horizon and uncertainty: The Adopt a long-term view but take action now. Keep options open to
future is uncertain, but climate change adjust responses as climate risk escalates and circumstances change
will continue for generations and cannot
be addressed by short-term (e.g., 1-10 Avoid new development commitments in exposed locations. Enable
years) responses alone. managed retreat in most at-risk locations by anticipatory actions, e.g.,
secure funds, legal provisions for buy-outs, resettlement, etc.
Cross-scale and cross-domain Develop networks and linkages within and between different
coordination: Decisions bound by governance scales and levels, and across policy domains and sectors, to
jurisdictional and sectoral boundaries fail improve coordination, build trust and legitimise decisions.
to address linkages within and between
coastal ecosystems and C&S facing Build shared understanding and enable locally appropriate responses
interconnected climate change through experimentation, innovation and social learning.
compounded impacts and risk.
Equity and social vulnerability: Recognise political realities and prioritise vulnerability, justice and
Climate change compounds everyday equity concerns to enable just, impactful and enduring outcomes.
inequity and vulnerability in coastal
C&S, making it difficult to disentangle Strengthen community capabilities to respond to coastal hazard risk,
and address social drivers and root causes using external assistance and government support if necessary.
of risk.
Social conflict: Coastal C&S will be the Design and facilitate tailor-made participation processes, involving
focal point of contending views about stakeholders early and consistently from negotiating responses to
appropriate climate responses; and face implementation.
the challenge of avoiding destructive
conflict and realising its productive Create safe arenas of engagement for inclusive, informed and
potential. meaningful deliberation and collaborative problem-solving.
26
27
28 Table CCP2.2: Lessons learned from efforts to address coastal hazard risk
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Lessons to address governance challenges and unlock Archetypal C&S initiatives, constraints aside
enablers
Complexity: Multiple knowledge systems Seychelles (0.1mill; open coast): Science-policy-
- Reveal dynamic complexity drawing on multiple local knowledge partnerships to co-produce usable
sources of locally relevant evidence information for decision-making.
- Use and integrate local, Indigenous and scientific Dhaka, Bangladesh (21mill; delta): Climate
knowledge change is national priority. Partnering with
- Include marginalised voices and knowledges of Netherlands to develop long-term data plans.
vulnerable groups, women, young people, etc. Jakarta, Indonesia (10.8mill; delta):
- Build shared understanding through storytelling Community-based efforts to foster mutual
- Bridge gaps between science, policy and practice by assistance and self-organisation.
experimenting with novel approaches and working across Utqiagvik (formerly Barrow) Alaska, USA (0.04
organisational, sectoral and institutional boundaries mill; Arctic, open coast): Using local knowledge
and historical precedent of transformative change
Complexity: Governance capacity to integrate local and scientific knowledge.
- Joined-up visionary leadership is key, e.g., cabinet- and Singapore (5.6mill; open coast): Integrated
C&S-level commitments to long-term implementation approach across Ministries committing to long-
- Translate political will into substantial dedicated term adaptation (and mitigation goals) by 2030.
budgets to build government capacity to tackle complex Rotterdam, Netherlands (0.65mill; delta): Delta
problems Programme, supported by law, administrative
- Use flexible approaches to build resilience, e.g., arrangements, and 1bill pa budget to 2029.
independent agency alongside traditional administrative bodies Florianopolis, Santa Catarina island, Brazil
- Counter deadlocks due to short-term priorities and (1.2mill; mixed): Building knowledge hub via
vested interests with long-term perspective, considering public-private-civil society partnerships.
plausible scenarios and incentivising novel solutions Nassau, Bahamas (0.275mill; open coast, small
- Translate national requirements into local action with island): Identifying responsibilities, accessing
enabling provisions for tailored local policy and practice funding, and preparing adaptation plans drawing
- Tackle emergent problems by setting up enduring on evidence-based studies.
monitoring and lesson-learning processes Shanghai (27mill; estuary), China: Contain risk
- Governance arrangements reconcile competing interests by combining long-term planning, political will,
in inclusive, timely and legitimate manner and national and municipal provisions, and
- Make visible and reflect on underlying reasons for technical capability.
policy actions / inaction, including values, attitudes and taken Can Tho City, Vietnam (0.4 mill; delta): Engage
for granted habits influencing problem-solving capability international donors and research community.
Time horizon and uncertainty: Long-term view
- Establish national policies and guidance with long-term Napier (65k), Hawkes Bay (178.6k; open coast),
view (e.g., 100 years) that enables action now New Zealand: National law compels local
- Develop shared medium- (10-50 years) to long-term authorities to take 100-year perspective; 2100
vision (100+ years) Strategy accounts for dynamic complexity and
- Use adaptation pathways approach to make short-term uncertain future through adaptation pathways.
decisions consistent with long-term goals Shanghai, China (27mill; estuary): Plans up to
- Meaningfully involve stakeholders, e.g., involve 2100, strong national and municipal focus on
representatives in decision-making climate change, and access to technical expertise.
- Address power imbalances and human development Dhaka, Bangladesh (21mill; delta): Long term
needs, e.g., in goal-setting and process design adaptation plans through to 2100.
- Reconcile divergent perspectives through tailored
responses Rotterdam, Netherlands (0.65mill; delta): Delta
Programme promotes `living with water', allowing
Time horizon and uncertainty: Avoidance and anticipatory and managing urban flooding.
action Napier (65k), Hawkes Bay, New Zealand
- Avoid development in exposed localities using spatial (178.6k, open coast): Regulatory provisions
plans discourage new development in high-risk
- Use window of opportunity created by extreme events locations; strategy sequences adaptation
- Prepare pre-event plans and tailor risk reduction and interventions. Florianopolis, Santa Catarina
resilience building post-disaster island, Brazil (1.2mill; mixed): Research reveals
- Reveal political pressures and opposition that hamper unregulated ad hoc development in at-risk
efforts to address intolerable risk and unacceptable impacts locations preventing effective adaptation.
Seychelles (0.1mill; open coast, small island):
Cross-scale and cross-domain coordination: Coordination Cross-sectoral and institutional collaboration to
- Collaborative projects involve state and non-state actors improve use of limited financial resources; and
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- Multi-lateral agreements, e.g., between neighbouring community-based and ecosystem-based adaptation
countries, coastal regions and C&S to bridge adaptation and mitigation and improve
- Connect people, organizations and communities coordination.
through boundary spanning organizations Florianopolis, Santa Catarina island, Brazil
- Leadership by central actors with capable teams is key (1.2mill; mixed): Effective local climate action
- Mobilise the capabilities of communities and non-state hampered by governance constraints and weak
actors federal leadership.
- Address policy inconsistencies and clarify roles and Cape Town, South Africa (4.6mill; mixed):
responsibilities Multi-level climate governance advanced at local-
- Secure national and regional resources to support local provincial level, but political turf-battles hamper
efforts national-provincial-local progress.
- Use measures to promote interaction, deliberation and
coordination to manage spill-over effects Cape Town, South Africa (4.6mill; mixed):
- Strengthen linkages between formal (e.g., regulatory) Capable local leaders collaborate with researchers
and informal (e.g., traditions and rituals) institutions, e.g., in municipality-initiated community-based
through information sharing adaptation. Translating plans into action
- Use spatial coordination mechanisms, e.g., land-use challenging given `everyday' vulnerability
planning, to translate national and regional provisions into exacerbated by climate change impacts.
local competencies New York City, USA (23.5mill; mixed): State
and city government work with communities to
Cross-scale and cross-domain coordination: Shared build adaptive capacity and resilience, drawing on
understanding technical capabilities but many challenges.
- Prioritise social learning and shared understanding, e.g.,
accessible information to all, irrespective of education, Cape Town, South Africa (4.6mill; mixed):
language, etc. Adaptation framed by apartheid legacy; focus on
- Account for local history, culture and politics through reducing vulnerability, public safety and securing
engagement, experimentation and innovation critical infrastructure and community assets.
- Generate socio-economic, livelihood and climate- Maputo-Matola, Mozambique (3mill; mixed):
development co-benefits Livelihood opportunities compromised by
- Leverage national and trans-national community and ecological degradation compelling community
local authority networks DIY coping in face of severe poverty and
vulnerability, and weak governance and
Equity and social vulnerability: Address vulnerability institutional capacity, and reliance on donors.
- Expose drivers and root causes of injustice, structural New York City, USA (23.5mill; estuary):
inequity and vulnerability Hurricane Sandy (2012) focused attention on
- Link human development concerns, risk reduction, climate risk and plight of exposed and vulnerable
resilience and adaptation people, and sparked adaptation action.
- Raise awareness and public support for actions that are Monkey River village, Belize (200 people;
just and equitable estuary): Remote Indigenous community capacity
- Understand discriminatory drivers (e.g., on racial to tackle erosion enabled by interventions by
grounds) of coastal land-use patterns and risk researchers, journalists and local NGOs to secure
- Address barriers facing marginalised groups media and political attention after hurricane
- Use inclusive planning, decision-making and damage.
implementation processes that give voice to vulnerable people Accra, Ghana (2.5mill; delta): Household
adaptation mediated by local government flood
Equity and social vulnerability: Community capabilities mitigation efforts; need better early warning and
- Raise vulnerability and risk awareness and maintain local stormwater to prevent flooding.
understanding, build community capability and leverage Lagos, Nigeria (14 mill; open coast): Building
external support by working with professionals, academics, adaptive capacity to overcome `everyday'
local NGOs, journalists and activists vulnerability and poverty severely challenging.
- Secure rights of vulnerable groups through court action Napier (65k), Hawkes Bay, New Zealand
where necessary (178.6k people, open coast): Collaboration
- Integrate traditional community responses with local between local authorities and Indigenous People
government efforts (Mori), involving stakeholders, led to co-designed
- Ensure gender equity, e.g., representation on planning
and decision-making bodies
Social conflict: Tailor-made participation
- Create opportunities for integrative and inclusive
solutions
- Use conflict resolution mechanisms
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- Appoint independent facilitators / mediators and long-term strategy with implementation
involve officials as `bureaucratic activists' to improve commitment.
Manila, Philippines (14mill; open coast): Metro-
inclusivity and iterative and reflexive engagement wide planning and infrastructure provisions that
- Align informal participatory processes with statutory foster climate justice and resilience explored; with
processes and government practices community-based actions.
- Sustain engagement by securing resources for local use,
and aligning activities with political and bureaucratic cycles
- Involve historically disadvantaged and socially
vulnerable groups, e.g., accessible meeting locations / venues,
local languages and culturally appropriate meeting protocols
- Involve local leaders who will champion adaptation and
help mainstream findings into C&S decision-making
- Inclusive processes help address conflict and drivers of
vulnerability, and promote just adaptation
Social conflict: Safe arenas of engagement Napier (65k), Hawkes Bay, New Zealand
- Use flexible and enabling processes based in local (178.6k people, open coast): Active involvement
institutions that are robust and fair, supported by governing of local communities, Indigenous People (Mori)
and research community to co-produce fit-for-
authorities purpose long-term coastal hazard risk strategy.
Rotterdam, Netherlands (0.65mill; delta): Delta
- Attend to local social dynamics and reduce elite Programme institutionalised multi-level adaptation
domination governance with strong accountability
mechanisms.
- Use local and Indigenous knowledge and science Greater London, UK (8.9mill; estuary): Long-
- Use institutional improvisation to address local term provisions for at-risk Thames Estuary,
concerns including major protective works, embedded in
Greater London Spatial Development Plan and
- Use trusted independent facilitators London Climate Change Partnership championed
- Incentivise participation by disadvantaged groups by strategic leadership, and supported by the
- Focus on improving risk literacy, optimism and public and strong technical capability.
capacity for joint problem-solving
- Use joint, collaborative activities to facilitate public
dialogue, and secure institutional support for action
- Enable ongoing deliberation and social learning
- Make continual adjustments as circumstances change,
e.g., build shared understanding about locally relevant
thresholds beyond which alternative courses of action need to
be actioned.
1
2
3 In sum, prospects for addressing climate risk in archetypal coastal C&S around the world depend on the
4 extent to which societal choices, and associated governance processes and practices, address the drivers and
5 root causes of exposure and social vulnerability (very high confidence). Coastal C&S are more able to
6 address these challenges when authorities work with local communities, and vulnerable groups in particular,
7 and with stakeholders from the local to national level and beyond, to chart adaptation pathways that enable
8 sustained reduction in the exposure and vulnerability of those most at risk (very high confidence) (Cross-
9 Chapter Box SLR in Chapter 3; Magnan et al., 2019; Oppenheimer et al., 2019). Unlocking potential
10 enablers for locally appropriate and effective adaptation is difficult because many drivers and root causes of
11 coastal risk are historically and institutionally embedded (high confidence) (Thomas et al., 2019). Charting
12 credible, salient and legitimate adaptation pathways is consequently a struggle in reconciling divergent
13 worldviews, values and interests (Sovacool, 2018; Mendenhall et al., 2020; Bowden et al., 2021a; Bowden et
14 al., 2021b). Unlocking the productive potential of conflict is foundational for transitioning towards pathways
15 that foster CRD (high confidence) (Abrahams and Carr, 2017; Harris et al., 2018; Sharifi, 2020). But this can
16 be especially challenging for low-lying coastal C&S characterised by degraded coastal ecosystems
17 susceptible to climate change impacts as well as pronounced inequity and governance constraints (high
18 confidence) (Esteban et al., 2017; Jones et al., 2020).
19
20 CCP2.4.4 Enabling Climate Resilient Development for Cities and Settlements by the Sea
21
22 The above critical enablers, and lessons learned from around the world, establish a strong foundation for
23 charting pathways for CRD in coastal C&S. These pathways will necessarily vary in different C&S, and
24 synergies and commonalities within different coastal archetypes can be leveraged. Pivotal is recognition of
25 the narrow window of time remaining to translate embryonic risk assessment and adaptation planning into
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 concerted implementation efforts. C&S by the sea could be the centres of innovation that lead the way to
2 advancing SDGs through to 2030, and CRD beyond this decade (see Section 2.1.1).
3
4 This CCP shows that a range of adaptation solutions; hard and soft protection, nature-based measures,
5 accommodate, advance, retreat, and behavioural change will need to be implemented as an integrated and
6 sequenced portfolio of responses if coastal C&S are to contain the adverse risks of climate change (high
7 confidence). The effectiveness and feasibility of any intervention, at a given moment, to reduce a particular
8 climate-compounded coastal hazard risk, or combination of risks, depend upon the settlement archetype;
9 including its geomorphological, cultural, economic, technical, institutional, and political features, and
10 historical development trajectory. Coastal C&S will benefit from developing flexible adaptation pathways -
11 sequences of adaptation strategies and intervention options - to navigate a dynamic solution space that
12 changes in response to climate and other drivers of change, and is also shaped by human development
13 choices, and socio-economic, technological and institutional change.
14
15 There is no silver bullet or panacea. But developing locally appropriate, yet flexible, pathways for CRD will
16 help coastal communities address escalating risks and uncertainty (Cross-Chapter Box DEEP in Chapter 17).
17 Effective pathways are based on robust integrated information about dynamic coastal hazard risk and
18 plausible interventions. However, their successful implementation requires multi-scale governance
19 arrangements and practices able to bridge different administrative and sectoral capacities in the coastal zone;
20 effective and accountable leadership; and inclusive decision-making arrangements to enable participation,
21 manage conflicts and trade-offs; engender local ownership, and promote equity and justice in coastal
22 adaptation plans and policies. Further, the feasibility of adaptation strategies and interventions, especially
23 those entailing changing behaviours and practices, is increased by recognising and incorporating peoples'
24 values and beliefs and Indigenous and Local knowledge systems, as well as the voices of women and
25 vulnerable groups.
26
27 Coastal C&S are on the frontline of observed climate change impacts and future risk (high confidence).
28 Difficult choices will be made as climate- and ocean-driven extremes become more frequent. In the next few
29 decades, many coastal regions and C&S will have the opportunity to take actions to avoid and reduce risk,
30 through incremental as well as more transformative interventions. Under higher levels of global warming,
31 decisions will need to be made faster or respond to higher levels of SLR (high confidence) (Cross-Chapter
32 Box SLR in Chapter 3). This is particularly challenging in coastal C&S characterised by inertia and path-
33 dependency of development choices, with long lead times for adaptation planning and implementation, and
34 the long design life and societal impact of many interventions. Given the risks assessed in coastal C&S, the
35 scale of climate impacts globally will depend to a large extent on whether coastal settlements develop and
36 implement pre-emptive and flexible adaptation pathways, and whether significant and timely reduction in
37 greenhouse gas emissions is achieved in C&S and globally (high confidence).
38
39
40 [START FAQ CCP2.1 HERE]
41
42 FAQ CCP2.1: Why are coastal cities and settlements by the sea especially at risk in a changing
43 climate, and which cities are most at risk?
44
45 Coastal cities and settlements (C&S) by the sea face much greater risk than comparable inland C&S
46 because they concentrate a large portion of global population and economic activity whilst being exposed
47 and vulnerable to a range of climate- and ocean-compounded hazard risk driven by climate change. Coastal
48 C&S range from small settlements along waterways and estuaries, to small island states with maritime
49 populations and/or beaches and atolls that are major tourist attractions, to large cities that are major
50 transport and financial hubs in coastal deltas, and mega-cities and even mega-regions with several coastal
51 mega-cities.
52
53 The concentration of people, economic activity and infrastructure dynamically interact with coast-specific
54 hazards magnifying the exposure of these C&S to climate risks. While large inland cities and coastal
55 settlements can be exposed to climate-driven hazards, such as urban heat islands and air pollution, the latter
56 are also subject to distinctive ocean-driven hazards, such as rising sea levels, exposure to tropical cyclones
57 and storm surges, flooding from extreme tides, and land subsidence from decreased sediment deposition
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 along coastal deltas and estuaries. With climate change increasing the intensity and frequency of hazards
2 under all future warming levels, the risks to lives, livelihoods and property are especially acute in C&S by
3 the sea.
4
5 Coastal cities are diverse in shape, size, growth patterns and trajectories, and access to cultural, financial, and
6 ecosystem resources and services. Along deltaic and estuarine archetypes, cities most vulnerable to a
7 changing climate have relatively high levels of poverty and inequality, in terms access to resources and
8 ecosystem services, and large populations and dense built environments translating into higher exposure to
9 coastal climate risks.
10
11 These climate risks at the coast can also be magnified by compounding and cascading effects due to non-
12 climate drivers directly affecting vulnerable peri- and ex-urban areas inland. These risks include disruption
13 to transport supply chains and energy infrastructure from airports and power plants sited along coastal areas,
14 as occurred in New York City, USA, during Hurricane Sandy in 2012. The impacts can be felt around the
15 world through globalized economic and geopolitical linkages, e.g., through maritime trade and port linkages.
16
17 For open coasts, settlements on low-lying small island states and the Arctic are especially vulnerable to
18 climate change, and sea level rise impacts in particular, well before 2100. While the economic risks may not
19 compare to the scale of those faced in coastal megacities with high per capita GDP, the existential risks to
20 some nations and an array of distinctive livelihoods, cultural heritage, and ways-of-life in these settlements
21 are great, even with modest sea level rise.
22
23 [END FAQ CCP2.1 HERE]
24
25
26 [START FAQ CCP2.2 HERE]
27
28 FAQ CCP2.2: What actions can be taken by coastal cities and settlements to reduce climate change
29 risk?
30
31 Sea level rise responds to climate change over long timeframes and will continue even after successful
32 mitigation. However, rapid global mitigation of greenhouse gases significantly reduces risks to coastal
33 C&S, and crucially buys time for adaptation.
34
35 Appropriate actions to reduce climate change risks on coastal C&S depend on the scale and speed of coastal
36 change interacting with unfolding local circumstances reflecting the hazards, exposure, vulnerability, and
37 response to risks.
38
39 `Hard' protection, like dikes and seawalls, can reduce risks of flooding for several metres of sea-level rise in
40 some coastal C&S. These are most cost-effective for densely populated cities and some islands but may be
41 unaffordable for poorer regions. Although these measures reduce the likelihood of coastal flooding, residual
42 risk remains, and hard protection typically has negative consequences for natural systems. In low-lying
43 protected coastal zones, draining river and excess water will increasingly be hampered, requiring pumping
44 eventually or transferring to alternative strategies.
45
46 Whereas structures can disrupt natural beach morphology processes, sediment-based protection replenishes
47 beaches. These have lower impact on adjacent beaches and coastal ecology and lower costs for construction
48 and maintenance compared to hard structures. Another form of `soft' protection involves establishing,
49 rehabilitating and preserving coastal ecosystems, like marshes, mangroves, seagrass, coral reefs and dunes,
50 providing `soft' protection against storm surges, reducing coastal erosion, and offering additional benefits
51 including food, materials, and carbon sequestration. However, these are less effective where there is limited
52 space in the coastal zone, limited sediment supply, and under higher rates of sea level rise.
53
54 Coastal settlements can `avoid' new flood and erosion risk by preventing development in areas exposed to
55 current and future coastal hazards. Where development already exists, settlements can `accommodate'
56 climate change impacts through, among other things, land use zoning, raising ground or buildings above
57 storm surge levels, installing flood proofing measures within and outside properties, and early warning
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 systems. Improving the capacity of urban drainage, incorporating nature-based solutions within urban areas,
2 and managing land upstream of settlements to reduce runoff from the hinterland, reduces the risk of
3 compound flood events. More radically, land can also be reclaimed from the sea, which offers opportunities
4 for further development but has impacts on the natural system and wider implications for the trajectory of
5 development.
6
7 Coastal risks and impacts such as floods, loss of fisheries or tourism, or salinization of groundwater, require
8 people to change behaviour to adapt, such as diversifying livelihoods or moving away from low-lying areas.
9 Currently most of these practices are reactive and help people adjust to/cope with current impacts. While a
10 critical part of coastal adaptation, changing behaviour is most likely when enabled by supportive policies and
11 financial structures, and alignment with socio-cultural values and worldviews.
12
13 Where risks are very high, or resources are insufficient to manage risks, submergence or erosion of coastal
14 C&S will be inevitable, requiring `retreat' from the coastline. This is the outlook for millions of people in
15 coming decades, including those living in river deltas, Arctic communities, small islands, and low-lying
16 small settlements in poor and wealthy nations. Whilst the impacts of retreat on communities can be
17 devastating, the prospect of many C&S and even whole nations being permanently inundated in coming
18 centuries underscores the imperative for urgent action.
19
20 Crucial to making choices about how to mitigate greenhouse gas emissions, and adapt to climate change in
21 coastal C&S, is to establish institutions and governance practices supporting climate resilient development
22 a mix and sequence of mitigation and adaptation actions - that are fair, just, and inclusive as well as
23 technically and economically effective across successive generations.
24
25 [END FAQ CCP2.2 HERE]
26
27
28 [START FAQ CCP2.3 HERE]
29
30 FAQ CCP2.3: Considering the wide-ranging and interconnected climate and development challenges
31 coastal cities and settlements face, how can more climate resilient development pathways be
32 enabled?
33
34 Coastal C&S are on the frontline of the climate change challenge. They are the interface of three
35 interconnected realities. First, they are critical nodes of global trade, economic activity and coast-dependent
36 livelihoods, all of which are highly and increasingly exposed to climate- and ocean-driven hazards (FAQ
37 CCP2.1). Second, coastal C&S are also sites where some of the most pressing development challenges are at
38 play (e.g., trade-offs between expanding critical built infrastructure while protecting coastal ecosystems,
39 high economic growth coupled with high inequality in some coastal megacities). Third, coastal C&S are also
40 centres of innovation and creativity, thus presenting a tremendous opportunity for climate action through a
41 range of infrastructural, nature-based, institutional, and behavioural solutions (FAQ CCP2.2). Given these
42 three realities of high climate change risks, rapid but contested and unequal development trajectories, and
43 high potential for innovative climate action, C&S are key to charting pathways for Climate Resilient
44 Development.
45
46 Three key levers can enable pathways that are climate-resilient and meet goals of inclusive, sustainable
47 development. One is to enable climate resilient development is flexible, proactive, and transparent
48 governance systems, built on a bedrock of accountable local leadership, evidence-based decision-making,
49 even under uncertainty, and inclusive institutions that consider different stakeholder voices and knowledge
50 systems. Another key enabler is acknowledging the socio-cultural and psychological barriers to climate
51 action and incentivising people to change lifestyles and behaviours that are pro-climate and aligned with
52 community-oriented values and norms. In practice, coastal C&S are experimenting with different strategies
53 to change practices and behaviours, such as using subsidies and zoning policies, tax rebates and public
54 awareness campaigns, to promote individual and collective action. Finally, enabling climate resilient
55 development needs dedicated, short- and long-term financing to reorient current trajectories of unsustainable
56 and unequal development towards climate mitigation and adaptation action that reduces current and
57 predicted losses and damages, especially in highly vulnerable coasts, such as the small island states, the
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FINAL DRAFT Cross Chapter Paper 2 IPCC WGII Sixth Assessment Report
1 Arctic and low-lying C&S. Currently, adaptation finance is concentrated in coastal megacities and tends to
2 be deployed in risk-proofing high-value waterfront properties or key infrastructures. Addressing these
3 finance imbalances (globally, regionally, and sub-nationally) remains a critical barrier to inclusive climate
4 resilient coastal development.
5
6 Notwithstanding the many interconnected challenges faced, from more frequent and intense extreme events
7 to the COVID-19 pandemic, many coastal C&S are experimenting with ways to pivot towards climate
8 resilient development. Critical enablers have been identified and lesson learned which, if translated into
9 practice, will enhance the prospects for advancing the SDGs and charting pathways for Climate Resilient
10 Development that are appropriate to local contexts and foster human well-being and planetary health.
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