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

== 3.5 Vulnerability, Resilience, and Adaptive Capacity in Marine Social–Ecological Systems, Including Impacts on Ecosystem Services ==

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=== 3.5.1 Introduction ===

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This section assesses the impacts of climate change on ecosystem services (Table 3.25; Chapter 1) and the outcomes on social–ecological systems, building on previous assessments (Table 3.26). [[#3.5.2|Section 3.5.2]] assesses how changes in biodiversity influence ecosystem services. Then Sections 3.5.3 and 3.5.4 assess provisioning services (food and non-food), [[#3.5.5|Section 3.5.5]] assesses supporting and regulating services, and [[#3.5.6|Section 3.5.6]] , cultural services. Where evidence exists, the section evaluates how the vulnerability and adaptive capacity of social–ecological systems govern the manifestation of impacts on each ecosystem service.

'''Table 3.25 |''' Ocean and coastal ecosystem services a

{| class="wikitable"
|-
! Ecosystem service category

! Components

! Ocean and coastal examples

|-
| Provisioning

| Food and feed

| Status of harvested marine fish, invertebrates, mammals and plants.

|-
|
| Medicinal, biochemical and genetic resources

| Existence of, and access to, biological resources that could offer future prospects for development, including marine fish, invertebrates, mammals, plants, microbes and viruses.

|-
|
| Materials and assistance

| Existence of, and access to, minerals, shells, stones, coral branches and dyes used to create other goods; availability of marine organisms to exhibit in zoos, aquariums and as pets.

|-
|
| Energy

| Existence of, and access to, sources of energy, including oil and gas reserves; solar, tidal and thermal ocean energy; and biofuels from marine plants.

|-
| Supporting and regulating

| Habitat creation and maintenance

| Status of nesting, feeding, nursery and mating sites for birds, mammals and other marine life, and of resting and overwintering places for migratory marine life or insects. Connectivity of ocean habitats.

|-
|
| Dispersal and other propagules

| Ability of marine life to spread gametes and larvae successfully by broadcast spawning reproduction, and ability of adults to disperse widely.

|-
|
| Regulation of climate

| Status of carbon storage and sequestration, methane cycling in wetlands, and dimethyl sulphide creation and destruction.

|-
|
| Regulation of air quality

| Status of aquatic processes that maintain and balance CO 2 , oxygen, nitrogen oxides, sulphur oxides, volatile organic compounds, particulates and aerosols.

|-
|
| Regulation of ocean acidification ( [[#3.2.3|Section 3.2.3.1]] )

| Status of chemical and biological aquatic processes that maintain and balance CO 2 and other acids/bases.

|-
|
| Regulation of freshwater quantity, location and timing

| Status of water storage by coastal systems, including groundwater flow, aquifer recharge and flooding responses of wetlands, coastal water bodies and developed spaces.

|-
|
| Regulation of freshwater and coastal water quality

| Status of chemical and biological aquatic processes that retain and filter coastal waters, capture pollutants and particles, and oxygenate water (e.g., natural filtration by sediments including adsorbent minerals and microbes).

|-
|
| Regulation of organisms detrimental to humans and marine life

| Status of grazing that controls harmful algal blooms and algal overgrowth of key ecosystems. Environmental conditions that suppress marine pathogens.

|-
|
| Formation, protection and decontamination of soils and sediments

| Status of chemical and biological aquatic processes that capture pollutants and particles (e.g., adsorption by minerals, microbial breakdown of pollutants).

|-
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| Regulation of hazards and extreme events

| Ability of coastal environments to serve as wave-energy dissipators, barriers and wave breaks.

|-
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| Regulation of key elements

| Status of aquatic processes that maintain and balance stocks of carbon, nitrogen, phosphorus and other elements critical for life.

|-
| Cultural

| Physical and psychological experiences

| Existence of, and access to, recreational opportunities including visiting beaches and coastal environments; and aquatic activities such as fishing, boating, swimming and diving.

|-
|
| Supporting identities

| Existence of, and access to, cultural, heritage and religious activities, and opportunities for intergenerational knowledge transfer; sense of place.

|-
|
| Learning and inspiration

| Existence of educational opportunities and characteristics to be emulated, as in biomimicry.

|-
|
| Maintenance of options

| Existence of opportunities to develop new medicines, materials, foods, and resources, or to adapt to a warmer climate and emergent diseases.

|}

Notes:

(a) Adapted from [[#IPBES--2017|IPBES (2017)]] , with examples made specific to ocean and coastal ecosystems by the authors of Chapter 3

'''Table 3.26 |''' Conclusions from previous IPCC assessments about observed and projected climate impacts on ocean and coastal biodiversity and ecosystem services

{| class="wikitable"
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! Ecosystem service and chapter subsection

! Observed impacts

! Projected impacts

|-
| All ( [[#3.5|Section 3.5]] )

| Climate change has affected marine ‘ecosystem services with regionally diverse outcomes, challenging their governance ( ''high confidence'' ). Both positive and negative impacts result for food security through fisheries ( ''medium confidence'' ), local cultures and livelihoods ( ''medium confidence'' ), and tourism and recreation ( ''medium confidence'' ). The impacts on ecosystem services have negative consequences for health and well-being ( ''medium confidence'' ), and for Indigenous Peoples and local communities dependent on fisheries ( ''high confidence'' ) (1.1, 1.5, 3.2.1, 5.4.1, 5.4.2, Figure SPM.2)’ (SROCC SPM A.8; [[#IPCC--2019c|IPCC, 2019c]] ).

| ‘Long-term loss and degradation of marine ecosystems compromises the ocean’s role in cultural, recreational, and intrinsic values important for human identity and well-being ( ''medium confidence'' ) (3.2.4, 3.4.3, 5.4.1, 5.4.2, 6.4)’ (SROCC SPM B.8; [[#IPCC--2019c|IPCC, 2019c]] ).

|-
| Biodiversity ( [[#3.5.2|Section 3.5.2]] )

| ‘[Climate] Impacts are already observed on [coastal ecosystem] habitat area and biodiversity, as well as ecosystem functioning and services ( ''high confidence'' ) (4.3.2, 4.3.3, 5.3, 5.4.1, 6.4.2, Figure SPM.2)’ (SROCC SPM A.6; [[#IPCC--2019c|IPCC, 2019c]] ).

| ‘Risks of severe impacts on biodiversity, structure and function of coastal ecosystems are projected to be higher for elevated temperatures under high compared to low emissions scenarios in the 21st century and beyond’ (SROCC SPM B.6; [[#IPCC--2019c|IPCC, 2019c]] ).

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| Food provision ( [[#3.5.3|Section 3.5.3]] )

| ‘Warming-induced changes in the spatial distribution and abundance of some fish and shellfish stocks have had positive and negative impacts on catches, economic benefits, livelihoods, and local culture ( ''high confidence'' ). There are negative consequences for Indigenous Peoples and local communities that are dependent on fisheries ( ''high confidence'' ). Shifts in species distributions and abundance has challenged international and national ocean and fisheries governance, including in the Arctic, North Atlantic and Pacific, in terms of regulating fishing to secure ecosystem integrity and sharing of resources between fishing entities ( ''high confidence'' ) (3.2.4, 3.5.3, 5.4.2, 5.5.2, Figure SPM.2)’ (SROCC SPM A.8.1; [[#IPCC--2019c|IPCC, 2019c]] ).

| ‘Future shifts in fish distribution and decreases in their abundance and fisheries catch potential due to climate change are projected to affect income, livelihoods, and food security of marine resource-dependent communities ( ''medium confidence'' ). Long-term loss and degradation of marine ecosystems compromises the ocean’s role in cultural, recreational, and intrinsic values important for human identity and well-being ( ''medium confidence'' ) (3.2.4, 3.4.3, 5.4.1, 5.4.2, 6.4)’ (SROCC SPM B.8; [[#IPCC--2019c|IPCC, 2019c]] ).

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| Non-food consumable provisioning services ( [[#3.5.4.1|Section 3.5.4.1]] )

| Observed impacts on non-food provisioning services not previously assessed.

| ‘Reductions in marine biodiversity due to climate change and other anthropogenic stressors ( [[#Tittensor--2010|Tittensor et al., 2010]] ), such as ocean acidification ( [[#CBD--2009|CBD, 2009]] ) and pollution, might reduce the discovery of genetic resources from marine species useful in pharmaceutical, aquaculture, agriculture, and other industries ( [[#Arrieta--2010|Arrieta et al., 2010]] ), leading to a loss of option value from marine ecosystems’ (WGII AR5 [[IPCC:Wg2:Chapter:Chapter-6#6.4.1.2|Section 6.4.1.2]] ; [[#Pörtner--2014|Pörtner et al., 2014]] )

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| Renewable energy ( [[#3.5.4.2|Section 3.5.4.2]] )

| Observed impacts on ocean renewable energy not previously assessed.

| ‘Ocean renewable energy can support climate change mitigation, and can comprise energy extraction from offshore winds, tides, waves, thermal and salinity gradient and algal biofuels. The emerging demand for alternative energy sources is expected to generate economic opportunities for the ocean renewable energy sector ( ''high confidence'' ), although their potential may also be affected by climate change ( ''low confidence'' ) (5.4.2, 5.5.1, Figure 5.23)’ (SROCC SPM C.2.5; [[#IPCC--2019c|IPCC, 2019c]] ).

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| Habitat creation and maintenance

( [[#3.5.5.1|Section 3.5.5.1]] )

| ‘[Climate] Impacts are already observed on [coastal ecosystem] habitat area and biodiversity, as well as ecosystem functioning and services ( ''high confidence'' ) (4.3.2, 4.3.3, 5.3, 5.4.1, 6.4.2, Figure SPM.2)’ (SROCC SPM A.6; [[#IPCC--2019c|IPCC, 2019c]] ).

‘In polar regions, ice associated marine mammals and seabirds have experienced habitat contraction linked to sea ice changes ( ''high confidence'' )’ (SROCC SPM A.5.2; [[#IPCC--2019c|IPCC, 2019c]] ).

| ‘In the Southern Ocean, the habitat of Antarctic krill, a key prey species for penguins, seals and whales, is projected to contract southwards under both RCP2.6 and RCP8.5 ( ''medium confidence'' ) (3.2.2, 3.2.3, 5.2.3)’ (SROCC SPM B5.3; [[#IPCC--2019c|IPCC, 2019c]] ).

‘Ocean warming, oxygen loss, acidification and a decrease in flux of organic carbon from the surface to the deep ocean are projected to harm habitat-forming cold-water corals, which support high biodiversity, partly through decreased calcification, increased dissolution of skeletons, and bioerosion ( ''medium confidence'' )’ (SROCC SPM B5.4; [[#IPCC--2019c|IPCC, 2019c]] ).

|-
| Climate regulation and air quality

( [[#3.5.5.2|Section 3.5.5.2]] )

| ‘Global ocean heat content continued to increase throughout [the 1951 to present] period, indicating continuous warming of the entire climate system ( ''very high confidence'' )’ (WGI AR6 TS1.2.3; [[#Arias--2021|Arias et al., 2021]] ).

| ‘The increase in global ocean heat content (TS2.4) will ''likely'' continue until at least 2300 even for low-emission scenarios’ (WGI AR6 Box TS.9; [[#Arias--2021|Arias et al., 2021]] ).

|-
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| ‘Land and ocean have taken up a near-constant proportion (globally about 56% yr –1 ) of CO 2 emissions from human activities over the past six decades, with regional differences ( ''high confidence'' )’ (WGI AR6 SPM A1.1; [[#IPCC--2021b|IPCC, 2021b]] ).

| ‘While natural land and ocean carbon sinks are projected to take up, in absolute terms, a progressively larger amount of CO 2 under higher compared to lower CO 2 emissions scenarios, they become less effective, that is, the proportion of emissions taken up by land and ocean decrease with increasing cumulative CO 2 emissions. This is projected to result in a higher proportion of emitted CO 2 remaining in the atmosphere ( ''high confidence'' )’ (WGI AR6 SPM B4.1; [[#IPCC--2021b|IPCC, 2021b]] ).

|-
|
| Observed impacts on marine organisms’ contribution to climate regulation not previously assessed.

| ‘The effect of climate change on marine biota will alter their contribution to climate regulation, that is, the maintenance of the chemical composition and physical processes in the atmosphere and oceans ( ''high confidence'' ) ( [[#Beaumont--2007|Beaumont et al., 2007]] )’

(WGII AR5 [[IPCC:Wg2:Chapter:Chapter-6#6.4.1.3|Section 6.4.1.3]] ; [[#Pörtner--2014|Pörtner et al., 2014]] ).

|-
| Provision of freshwater, maintenance of water quality, regulation of pathogens ( [[#3.5.5.3|Section 3.5.5.3]] )

| Observed climate impacts on salinisation of coastal soil and groundwater not previously assessed.

| ‘In the absence of more ambitious adaptation efforts compared to today, and under current trends of increasing exposure and vulnerability of coastal communities, risks, such as erosion and land loss, flooding, salinisation, and cascading impacts due to mean sea level rise and extreme events are projected to significantly increase throughout this century under all greenhouse gas emissions scenarios ( ''very high confidence'' )’ (SROCC SPM B9.1; [[#IPCC--2019c|IPCC, 2019c]] ).

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| ‘Global warming compromises seafood safety ( ''medium confidence'' ) through human exposure to elevated bioaccumulation of persistent organic pollutants and mercury in marine plants and animals ( ''medium confidence'' ), increasing prevalence of waterborne ''Vibrio'' sp. pathogens ( ''medium confidence'' ), and heightened likelihood of harmful algal blooms ( ''medium confidence'' )’ (SROCC SPM B.8.3; [[#IPCC--2019c|IPCC, 2019c]] ).

| ‘[Risks from marine-borne pollutants and pathogens] are projected to be particularly large for human communities with high consumption of seafood, including coastal Indigenous communities ( ''medium confidence'' ), and for economic sectors such as fisheries, aquaculture, and tourism ( ''high confidence'' ) (3.4.3, 5.4.2, Box 5.3)’ (SROCC SPM B.8.3; [[#IPCC--2019c|IPCC, 2019c]] ).

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| ‘Since the early 1980s, the occurrence of harmful algal blooms (HABs) and pathogenic organisms (e.g., ''Vibrio'' ) has increased in coastal areas in response to warming, deoxygenation and eutrophication, with negative impacts on food provisioning, tourism, the economy and human health ( ''high confidence'' )’ (SROCC [[IPCC:Wg2:Chapter:Chapter-5|Chapter 5]] Executive Summary; [[#Bindoff--2019a|Bindoff et al., 2019a]] ).

| ‘Overall, the occurrence of HABs, their toxicity and risk on natural and human systems are projected to continue to increase with warming and rising CO 2 in the 21st century ( [[#Glibert--2014|Glibert et al., 2014]] ; [[#Martín-García--2014|Martín-García et al., 2014]] ; [[#McCabe--2016|McCabe et al., 2016]] ; [[#Paerl--2016|Paerl et al., 2016]] ; [[#Gobler--2017|Gobler et al., 2017]] ; McKibben et al.; 2017; [[#Rodríguez--2017|Rodríguez et al., 2017]] ; [[#Paerl--2018|Paerl et al., 2018]] ; [[#Riebesell--2018|Riebesell et al., 2018]] ) ( ''high confidence'' )’ (SROCC Box 5.4; [[#Bindoff--2019a|Bindoff et al., 2019a]] ).

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| Regulation of physical hazards

( [[#3.5.5.4|Section 3.5.5.4]] )

| ‘Coastal ecosystems are already impacted by the combination of sea level rise, other climate-related ocean changes, and adverse effects from human activities on ocean and land ( ''high confidence'' )... Coastal and near-shore ecosystems including saltmarshes, mangroves, and vegetated dunes in sandy beaches,...provide important services including coastal protection...( ''high confidence'' )’ (SROCC [[IPCC:Wg2:Chapter:Chapter-4|Chapter 4]] Executive Summary; [[#Oppenheimer--2019|Oppenheimer et al., 2019]] ).

| ‘The decline in warm water coral reefs is projected to greatly compromise the services they provide to society, such as...coastal protection ( ''high confidence'' )...’ (SROCC SPM B.8.2; [[#IPCC--2019c|IPCC, 2019c]] ).

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| Ocean and coastal carbon storage

( [[#3.5.5.5|Section 3.5.5.5]] )

| ‘Recent observations show that ocean carbon processes are starting to change in response to the growing ocean sink, and these changes are expected to contribute significantly to future weakening of the ocean sink under medium- to high-emission scenarios. However, the effect of these changes is not yet reflected in a weakening trend of the contemporary (1960–2019) ocean sink ( ''high confidence'' )’ (WGI AR6 [[IPCC:Wg2:Chapter:Chapter-5|Chapter 5]] Executive Summary; [[#Canadell--2021|Canadell et al., 2021]] ).

| ‘Emission scenarios SSP4-6.0 and SSP5-8.5 lead to warming of the surface ocean and large reductions of the buffering capacity, which will slow the growth of the ocean sink after 2050. Scenario SSP1-2.6 limits further reductions in buffering capacity and warming, and the ocean sink weakens in response to the declining rate of increasing atmospheric CO 2 . There is ''low confidence'' in how changes in the biological pump will influence the magnitude and direction of the ocean carbon feedback’ (WGI AR6 [[IPCC:Wg2:Chapter:Chapter-5|Chapter 5]] Executive Summary; [[#Canadell--2021|Canadell et al., 2021]] ).

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| ‘Mangrove, seagrass, and salt marsh ecosystems offer important carbon storage and sequestration opportunities ( ''limited evidence, medium agreement'' ), in addition to ecosystem goods and services such as protection against coastal erosion and storm damage and maintenance of habitats for fisheries species’ (WGII AR5 Technical Summary).

| ‘…under high emission scenarios, sea level rise and warming are expected to reduce carbon sequestration by vegetated coastal ecosystems ( ''medium confidence'' ); however, under conditions of slow sea level rise, there may be net increase in carbon uptake by some coastal wetlands ( ''medium confidence'' )’ (SROCC Chapter 5; [[#Bindoff--2019a|Bindoff et al., 2019a]] ).

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| Cultural services ( [[#3.5.6|Section 3.5.6]] )

| ‘Climate change impacts on marine ecosystems and their services put key cultural dimensions of lives and livelihoods at risk ( ''medium confidence'' ), including through shifts in the distribution or abundance of harvested species and diminished access to fishing or hunting areas. This includes potentially rapid and irreversible loss of culture and local knowledge and Indigenous knowledge, and negative impacts on traditional diets and food security, aesthetic aspects, and marine recreational activities ( ''medium confidence'' )’ (SROCC SPM B.8.4; [[#IPCC--2019c|IPCC, 2019c]] ).

| ‘Future shifts in fish distribution and decreases in their abundance and fisheries catch potential due to climate change are projected to affect income, livelihoods, and food security of marine resource-dependent communities ( ''medium confidence'' ). Long-term loss and degradation of marine ecosystems compromises the ocean’s role in cultural, recreational, and intrinsic values important for human identity and well-being ( ''medium confidence'' )’ (SROCC SPM B.8; [[#IPCC--2019c|IPCC, 2019c]] ).

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=== 3.5.2 Biodiversity ===

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Climate change is a key agent of biodiversity change in numerous ocean and coastal ecosystems ( ''very high confidence'' ) (Table 3.26; [[#Worm--2021|Worm and Lotze, 2021]] ), and climate change and biodiversity loss reinforce each other ( [[#Pörtner--2021b|Pörtner et al., 2021b]] ). Biodiversity has changed in association with ocean warming and loss of sea ice (Sections 3.4.2.10, 3.4.3.3.3; Section CCP6 2.4.2), SLR ( [[#3.4.2|Section 3.4.2]] ; Cross-Chapter Box SLR in Chapter 3), coral bleaching ( [[#3.4.2.1|Section 3.4.2.1]] ), MHWs (Sections 3.4.2.1–3.4.2.5) and upwelling changes ( ''high confidence'' ) ( [[#3.4.2.9|Section 3.4.2.9]] ). Overlapping non-climate drivers ( [[#3.1|Section 3.1]] ) also decrease ocean and coastal ecosystem biodiversity ( ''very high confidence'' ) ( [[#O’Hara--2021|O’Hara et al., 2021]] ; [[#Pörtner--2021b|Pörtner et al., 2021b]] ). There is ''medium confidence'' that local and regional marine biodiversity losses from climate disrupt ecosystem services provided by specific ocean and coastal species or places (Sections 3.5.3–3.5.6; Figure 3.23; Table 3.26; see Box 3.3; [[#Dee--2019a|Dee et al., 2019a]] ; [[#Hossain--2019|Hossain, 2019]] ; [[#Smale--2019|Smale et al., 2019]] ; [[#Teixeira--2019|Teixeira et al., 2019]] ; [[#Martin--2020|Martin et al., 2020]] ; [[#Pathak--2020|Pathak, 2020]] ; [[#Weiskopf--2020|Weiskopf et al., 2020]] ; [[#Zunino--2020|Zunino et al., 2020]] ; [[#Archer--2021|Archer et al., 2021]] ). However, adaptive capacity varies greatly among ecosystems, and ecological functions sometimes remain, despite changes in species assemblages, as in certain coral reef communities ( [[#Richardson--2020|Richardson et al., 2020]] ). Projected changes in biodiversity due to climate change ( [[#3.4.3.3.3|Section 3.4.3.3.3]] ) are expected to alter the flow and array of ocean and coastal ecosystem services ( ''high confidence'' ) ( [[#Smale--2019|Smale et al., 2019]] ; [[#Cavanagh--2021|Cavanagh et al., 2021]] ; [[#Ruthrof--2021|Ruthrof et al., 2021]] ; [[#Worm--2021|Worm and Lotze, 2021]] ), but data gaps hinder developing projections of ecosystem service changes detailed enough to support decision making ( [[#Rosa--2020|Rosa et al., 2020]] ).

Non-indigenous marine species are major agents of ocean and coastal biodiversity change, and climate and non-climate drivers interact to support their movement and success ( ''high confidence'' ) ( [[#Iacarella--2020|Iacarella et al., 2020]] ). At times, non-indigenous species act invasively and outcompete indigenous species, causing regional biodiversity shifts and altering ecosystem function, as seen in the Mediterranean region ( ''high confidence'' ) (e.g., [[#Mannino--2017|Mannino et al., 2017]] ; [[#Bianchi--2019|Bianchi et al., 2019]] ; [[#Hall-Spencer--2019|Hall-Spencer and Harvey, 2019]] ; [[#Verdura--2019|Verdura et al., 2019]] ; [[#García-Gómez--2020|García-Gómez et al., 2020]] ; [[#Dimitriadis--2021|Dimitriadis et al., 2021]] ). Warming-related range expansions of non-indigenous species have directly or indirectly decreased commercially important fishery species and nursery habitat ( [[#Booth--2018|Booth et al., 2018]] ). Non-indigenous species outperform indigenous species in coastal zones experiencing warming and freshening ( [[#McKnight--2021|McKnight et al., 2021]] ). Non-climate drivers, especially marine shipping in newly ice-free locations ( [[#Chan--2019|Chan et al., 2019]] ), fishing pressure ( [[#Last--2011|Last et al., 2011]] ), aquaculture of non-indigenous species ( [[#Mach--2017|Mach et al., 2017]] ; [[#Ruby--2018|Ruby and Ahilan, 2018]] ) and marine pollution and debris ( [[#Gall--2015|Gall and Thompson, 2015]] ; [[#Carlton--2018|Carlton et al., 2018]] ; [[#Carlton--2018|Carlton and Fowler, 2018]] ; [[#Lasut--2018|Lasut et al., 2018]] ; [[#Miralles--2018|Miralles et al., 2018]] ; [[#Rech--2018|Rech et al., 2018]] ; [[#Therriault--2018|Therriault et al., 2018]] ), promote range shifts and movement of non-indigenous species ( ''high confidence'' ). Non-climate drivers can also intensify the ecological effects of non-indigenous species ( [[#Geraldi--2020|Geraldi et al., 2020]] ). Invasive marine species can alter species behaviour, reduce indigenous species abundance, reduce water clarity, bioaccumulate more heavy metals than indigenous species and inhibit ecosystem resilience in the face of extreme events ( ''medium confidence'' ) ( [[#McDowell--2017|McDowell et al., 2017]] ; Geburzi and McCarthy, 2018; [[#Anton--2019|Anton et al., 2019]] ; [[#Ruthrof--2021|Ruthrof et al., 2021]] ). Risks from invasive species to the sources of other ecosystem services or aquatic goods, including valuable materials, mining activities, shipping or ocean energy installations, have not been evaluated.

Reducing risk to ecosystem functions and services that depend on biodiversity requires an integrated approach that acknowledges the close linkages between the climate and biodiversity crises and common governance challenges ( [[#Pörtner--2021b|Pörtner et al., 2021b]] ). Climate-focused solutions that employ nature-based solutions (NbS), technological interventions and socio-institutional interventions ( [[#3.6.2|Section 3.6.2]] ) can also safeguard biodiversity ( [[#Pörtner--2021b|Pörtner et al., 2021b]] ), which in turn will help ocean and coastal ecosystems adapt to climate impacts as well as help sustain the services they provide to people (Sections 3.5.3–3.5.6).

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=== 3.5.3 Food Provision ===

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Globally, about 17% of humans’ average per capita intake of animal protein in 2017 came from marine and freshwater wild-caught and aquacultured aquatic animals ( [[#Costello--2020|Costello et al., 2020]] ; [[#FAO--2020a|FAO, 2020a]] ). Per capita intake of seafood is 50% or more in some Small Island Developing States (SIDS) ( [[#Vannuccini--2018|Vannuccini et al., 2018]] ), and consumption per capita is 15 times higher in Indigenous Peoples than non-Indigenous Peoples ( [[#Cisneros-Montemayor--2016|Cisneros-Montemayor et al., 2016]] ). Fishery products also supply critical dietary micronutrients worldwide ( [[#3.5.4.1|Section 3.5.4.1]] ; [[#Hicks--2019|Hicks et al., 2019]] ; [[#Vianna--2020|Vianna et al., 2020]] ). Marine and freshwater fisheries and aquaculture provide livelihoods for an estimated 10–12% of the world’s population ( [[#Barange--2018|Barange et al., 2018]] ). Fishing and aquaculture provide women and their families with substantial amounts of food and income ( [[#Harper--2020b|Harper et al., 2020b]] ), because at least 11% of small-scale fishers ( [[#Harper--2020b|Harper et al., 2020b]] ) and up to half of all fishery and aquaculture workers ( [[#FAO--2018|FAO, 2018]] ) are women. This section assesses how climate-driven alterations of the abundance or nutritional quality of food from the sea could affect humans. Aquaculture, catch potential changes and human adaptations to changes in wild and cultured harvests are assessed in [[IPCC:Wg2:Chapter:Chapter-5#5.9|Section 5.9]] .

Ocean and coastal fauna are moving towards higher latitudes globally due to warming ( ''high confidence'' ) ( [[#3.4.3.1|Section 3.4.3.1]] ; Table 3.26), challenging fishers and fisheries management ( ''high confidence'' ) as fishers also move poleward and diversify harvests ( ''medium evidence, high agreement'' ) (Sections 3.4.3.3.3, 5.8.4; Table 3.26; [[#Leitão--2018|Leitão et al., 2018]] ; [[#Liang--2018|Liang et al., 2018]] ; [[#Ottosen--2018|Ottosen et al., 2018]] ; [[#Peck--2018|Peck and Pinnegar, 2018]] ; [[#Pinsky--2018|Pinsky et al., 2018]] ; [[#Erauskin-Extramiana--2019|Erauskin-Extramiana et al., 2019]] ; [[#Free--2019|Free et al., 2019]] ; [[#Gianelli--2019|Gianelli et al., 2019]] ; [[#Scott--2019|Scott et al., 2019]] ; [[#Smith--2019|Smith et al., 2019]] ; [[#Gervais--2021|Gervais et al., 2021]] ). Model hindcasts have identified temperature-associated fisheries reductions worldwide ( [[#Free--2019|Free et al., 2019]] ), and they have implicated overfishing as the primary non-climate driver increasing fishery vulnerability ( [[IPCC:Wg2:Chapter:Chapter-5#5.8.4|Section 5.8.4]] ; [[#Peck--2018|Peck and Pinnegar, 2018]] ; [[#Das--2020|Das et al., 2020]] ). Catch composition is changing in many locations fished by smaller-scale, less-mobile commercial, artisanal and recreational fisheries ( ''high confidence'' ) ( [[#Booth--2018|Booth et al., 2018]] ; [[#Townhill--2019|Townhill et al., 2019]] ; [[#Young--2019b|Young et al., 2019b]] ; [[#Robinson--2020|Robinson et al., 2020]] ; [[#Champion--2021|Champion et al., 2021]] ). Limited exceptions have been noted, with wild harvests in some places remaining stable or increasing (e.g., [[#Arreguín-Sánchez--2019|Arreguín-Sánchez, 2019]] ; [[#Robinson--2019b|Robinson et al., 2019b]] ; [[#Kainge--2020|Kainge et al., 2020]] ). Where possible, fishers are maintaining harvests by broadening catch diversity, traveling poleward and changing gear and strategies ( ''high confidence'' ) ( [[#3.6.3.1.2|Section 3.6.3.1.2]] ; [[#Barange--2018|Barange et al., 2018]] ; [[#Dubik--2019|Dubik et al., 2019]] ; [[#Townhill--2019|Townhill et al., 2019]] ). Fisheries and aquaculture adaptations, including management, are comprehensively assessed in Sections 3.6.3.1.2, 5.8.4 and 5.9.4.

Ocean acidification and deoxygenation caused by climate change are thought to influence fishing and aquaculture harvests, but ''limited evidence'' prevents assessing their present global impact on harvests. Substantial economic losses in the North American Pacific Coast shellfish aquaculture industry in the 2000s assessed in SROCC ( [[#Bindoff--2019a|Bindoff et al., 2019a]] ) and WGII AR5 ( [[#Pörtner--2014|Pörtner et al., 2014]] ) remain the clearest example of human harm from ocean acidification. Technology-based adaptations ( [[#3.6.3|Section 3.6.3]] ) have minimised aquaculture losses from ocean acidification, including early-warning systems to guide hatchery operations and culturing resilient shellfish strains ( [[IPCC:Wg2:Chapter:Chapter-5#5.9.4|Section 5.9.4]] ; [[#Barton--2015a|Barton et al., 2015a]] ). Laboratory studies show that ocean acidification decreases the fitness, growth or survival of many economically and culturally important larval or juvenile shelled mollusks ( ''high confidence'' ) ( [[#Cao--2018|Cao et al., 2018]] ; [[#Onitsuka--2018|Onitsuka et al., 2018]] ; [[#Stevens--2018|Stevens and Gobler, 2018]] ; [[#Griffith--2019a|Griffith et al., 2019a]] ; [[#Mellado--2019|Mellado et al., 2019]] ) and of several valuable wild-harvest crab species ( [[#Barton--2015a|Barton et al., 2015a]] ; [[#Punt--2015|Punt et al., 2015]] ; [[#Miller--2016|Miller et al., 2016]] ; [[#Swiney--2017|Swiney et al., 2017]] ; [[#Gravinese--2018|Gravinese et al., 2018]] ; [[#Tomasetti--2018|Tomasetti et al., 2018]] ; [[#Long--2019|Long et al., 2019]] ; [[#Trigg--2019|Trigg et al., 2019]] ). Ocean acidification alters larval settlement and metamorphosis of fish in laboratory studies ( ''high confidence'' ) ( [[#Cattano--2018|Cattano et al., 2018]] ; [[#Espinel-Velasco--2018|Espinel-Velasco et al., 2018]] ), suggesting possible changes in fish survival and thus fishery characteristics. Deoxygenation can decrease size and abundance of marine species and suppress trophic interactions ( [[#Levin--2003|Levin, 2003]] ), decrease the diversity within marine ecosystems ( [[#Sperling--2016|Sperling et al., 2016]] ) while temporarily increasing catchability and increasing the risk of overfishing ( [[#Breitburg--2018|Breitburg et al., 2018]] ) and decrease the ecosystem services provided by specific fisheries ( [[#Orio--2021|Orio et al., 2021]] ). The chronic effects of deoxygenation on wild fisheries are complex and highly interactive with co-occurring drivers and overall ecosystem responses ( ''medium evidence, high agreement'' ) ( [[#Townhill--2017|Townhill et al., 2017]] ; [[#Rose--2019|Rose et al., 2019]] ). Detecting and attributing marine ecosystem responses to ocean acidification and deoxygenation outside of laboratory studies remains challenging because of the strong influence of co-occurring environmental changes on natural systems ( [[#3.3.5|Section 3.3.5]] ; [[#Rose--2019|Rose et al., 2019]] ; [[#Doo--2020|Doo et al., 2020]] ).

Ocean and coastal organisms will continue moving poleward under RCP8.5 ( ''high confidence'' ) ( [[#3.4.3.1.3|Section 3.4.3.1.3]] ; Figure 3.18), and this is expected to decrease fisheries harvests in low latitudes and alter species composition and abundance in higher latitudes ( ''high confidence'' ) (Table 3.26; Figure 3.23; [[#Asch--2018|Asch et al., 2018]] ; [[#Morley--2018|Morley et al., 2018]] ; [[#Tai--2019|Tai et al., 2019]] ; [[#Erauskin-Extramiana--2020|Erauskin-Extramiana et al., 2020]] ; [[#Shelton--2021|Shelton et al., 2021]] ). Species that succeed in new ranges or conditions may offer opportunities to diversify regional fisheries or aquaculture (Sections 3.6.3.1.2, 5.8.4, 5.9.4; [[#Bindoff--2019a|Bindoff et al., 2019a]] ), or they may outcompete indigenous species and act as invasive species (Sections 3.4.2.10, 3.5.2).

Temperature will continue to be a major driver of fisheries changes globally, but other non-climate factors like organism physiology and ecosystem response ( [[#3.3|Section 3.3]] ) and fishing pressure (Chapter 5), as well as other climate-induced drivers like acidification, deoxygenation and sea ice loss ( [[#3.2|Section 3.2]] ), will play critical roles in future global and local fisheries changes ( ''high confidence'' ). Warming, acidification and business-as-usual fishing policy under RCP8.5 are projected to place around 60% of global fisheries at very high risk ( ''medium confidence'' ) ( [[#Cheung--2018|Cheung et al., 2018]] ). Model intercomparison showed that ocean acidification and protection affect ecosystems more than fishing pressure, and ecological adaptation will significantly determine impacts on fishery biomass, catch and value until approximately 2050 ( ''medium confidence'' ) ( [[#Olsen--2018|Olsen et al., 2018]] ). Ecosystem responses to warming water, fishing pressure, food-web changes, MHWs and sea ice algal populations have been responsible for highly variable or collapsing populations of Northern Hemisphere high-latitude forage fish species including sand lances ( ''Ammodytes'' spp ''.'' ), Arctic cod ( ''Boreogadus saida'' ), capelin ( ''Mallotus catervarius'' ) and herring ( ''Clupea'' spp ''.'' ) ( [[#Lindegren--2018|Lindegren et al., 2018]] ; [[#Steiner--2019|Steiner et al., 2019]] ; [[#Arimitsu--2021|Arimitsu et al., 2021]] ; [[#Suca--2021|Suca et al., 2021]] ). Declining stocks of forage fish are expected to have detrimental effects on seabirds, pelagic fish and marine mammals ( ''medium confidence'' ) ( [[#Lindegren--2018|Lindegren et al., 2018]] ; [[#Steiner--2019|Steiner et al., 2019]] ), which may harm dependent human communities, including Arctic Indigenous Peoples ( ''low confidence'' ) ( [[#Arctic%20Monitoring%20and%20Assessment%20Programme--2018|Arctic Monitoring and Assessment Programme, 2018]] ; [[#Steiner--2019|Steiner et al., 2019]] ). Modelled fishery futures and revenue depend on environmental scenario, fishing-fleet composition and management, and ocean acidification and temperature responses of harvested species ( ''high confidence'' ) ( [[#Punt--2014|Punt et al., 2014]] ; [[#Punt--2015|Punt et al., 2015]] ; [[#Seung--2015|Seung et al., 2015]] ; [[#Fernandes--2017|Fernandes et al., 2017]] ; [[#Rheuban--2018|Rheuban et al., 2018]] ; [[#Tai--2019|Tai et al., 2019]] ; [[#Punt--2020|Punt et al., 2020]] ). Detrimental effects of ocean acidification are projected to begin emerging in specific fisheries by 2030 ( ''limited evidence, high agreement'' ) [(southern Tanner crab ( ''Chionoecetes bairdi'' ) ( [[#Punt--2015|Punt et al., 2015]] ); sea scallop ( ''Placopecten magellanicus'' ) ( [[#Rheuban--2018|Rheuban et al., 2018]] ); Northeast Arctic cod ( ''Gadus morhua'' ) ( [[#Hänsel--2020|Hänsel et al., 2020]] ); Arctic fisheries ( [[#Lam--2016|Lam et al., 2016]] )]. At the same time, projected hypoxic conditions of ~2 mg l –1 of oxygen will be consistently detrimental across taxonomic groups, developmental stages and climate regions ( ''high confidence'' ) ( [[#Sampaio--2021|Sampaio et al., 2021]] ). Ecosystem-based management ( [[#3.6.3.1.2|Section 3.6.3.1.2]] ) shows promise for decreasing risk from interacting climate and non-climate drivers to forage species and fished species.

<div id="3.5.4" class="h2-container"></div>

<span id="other-provisioning-services"></span>
=== 3.5.4 Other Provisioning Services ===

<div id="h2-17-siblings" class="h2-siblings"></div>

<div id="3.5.4.1" class="h3-container"></div>

<span id="non-food-consumable-products"></span>
==== 3.5.4.1 Non-Food Consumable Products ====

<div id="h3-28-siblings" class="h3-siblings"></div>

The interaction of climate and non-climate drivers endangers the supply of non-food consumable products developed from marine organisms ( ''limited evidence, high agreement'' ). This broad class includes nutraceuticals (derived from fish, krill, shellfish, seaweeds and microbes), food preservatives or additives (derived from crustaceans, fish, microalgae and seaweeds, and cyanobacteria), pharmaceuticals (derived from fish, shellfish, microbes, cyanobacteria, corals and sponges) or cosmetic products (derived from sponges, phytoplankton and seaweeds, fish etc.) ( [[#Freitas--2012|Freitas et al., 2012]] ; [[#Dewapriya--2014|Dewapriya and Kim, 2014]] ; [[#Leal--2015|Leal and Calado, 2015]] ; [[#Stengel--2015|Stengel and Connan, 2015]] ; [[#Greene--2016|Greene et al., 2016]] ; [[#Ciavatta--2017|Ciavatta et al., 2017]] ; [[#Gutiérrez-Rodríguez--2018|Gutiérrez-Rodríguez et al., 2018]] ). But biodiversity changes, warming, acidification and non-climate drivers (especially fishing pressure) may decrease the availability of these organisms or the potency of the compounds they produce ( [[IPCC:Wg2:Chapter:Chapter-5#5.7|Section 5.7.5.1]] ; Figure 3.23; Table 3.26; [[#Webster--2012|Webster and Taylor, 2012]] ; [[#Mehbub--2014|Mehbub et al., 2014]] ; [[#Kotta--2018|Kotta et al., 2018]] ; [[#Martins--2018|Martins et al., 2018]] ; [[#Conrad--2021|Conrad et al., 2021]] ). Observed and projected declines and movement of fish stocks due to fishing pressure and climate change impacts ( [[#IPCC--2019b|IPCC, 2019b]] ) have generated concerns that the supply and safety of fish and krill oil for human dietary supplements may decline ( [[IPCC:Wg2:Chapter:Chapter-5#5.7|Section 5.7.5.1]] ; [[#Gribble--2016|Gribble et al., 2016]] ; [[#Lloret--2016|Lloret et al., 2016]] ). This risk can be lowered by technological adaptations ( [[#3.6.2.2|Section 3.6.2.2]] ), such as increasing the use of alternative sources like marine phytoplankton, macroalgae, marine microbes ( [[#Dewapriya--2014|Dewapriya and Kim, 2014]] ; [[#Greene--2016|Greene et al., 2016]] ; [[#Dave--2018|Dave and Routray, 2018]] ; [[#Nguyen--2020|Nguyen et al., 2020]] ) and underutilised resources such as fish, seal, crab and shrimp byproducts ( [[#Dave--2018|Dave and Routray, 2018]] ), and by improving extraction and processing efficiency ( [[#Cashion--2017|Cashion et al., 2017]] ). Climate effects on non-food consumable products could be widespread yet poorly detected, complicating assessment of impacts, risks and vulnerability reduction.

There is ''insufficient evidence'' to develop global projections of future climate impacts on humans through changes in non-food consumable marine products, but specific local examples have been investigated, such as the Arctic ooligan (eulachon; ''Thaleichthys pacificus'' ), a small smelt fish. Ooligan grease has been used by Indigenous Peoples of the North Pacific coast ( [[#Phinney--2009|Phinney et al., 2009]] ) for at least 5000 years to treat stomach aches, colds and skin conditions, and as a traditional food source high in omega-3 fatty acids ( [[#Byram--2001|Byram and Lewis, 2001]] ; [[#Cranmer--2016|Cranmer, 2016]] ; [[#Patton--2019|Patton et al., 2019]] ). Analysis of remains have shown that ooligan could comprise up to 67% of traditional historical fisheries catches ( [[#Patton--2019|Patton et al., 2019]] ). Because ooligan spawning relies on the timing of the spring freshet, and because the species has declined in the past 25 years due to fishing pressure and predation, the species may be at risk from combined climate-induced and non-climate drivers ( ''medium confidence'' ) ( [[#Talloni-Álvarez--2019|Talloni-Álvarez et al., 2019]] ). Projections under RCP2.6 or RCP8.5 estimate reductions by 21 or 31% by 2050 in essential nutrients from traditional seafood for Indigenous Peoples in Canada, relative to 2000, with a modelled nutritional deficit that includes non-traditional dietary substitutions ( [[#Marushka--2019|Marushka et al., 2019]] ).

<div id="3.5.4.2" class="h3-container"></div>

<span id="non-consumable-goods"></span>
==== 3.5.4.2 Non-Consumable Goods ====

<div id="h3-29-siblings" class="h3-siblings"></div>

''Limited evidence'' about climate impacts exists for valuable non-food aquatic materials. Ocean warming and acidification harm red coral ( ''Corallium rubrum'' ) ( [[#Bramanti--2013|Bramanti et al., 2013]] ) and communities hosting black coral ( ''Antipatharian'' spp.), both used for jewellery ( [[#Ross--2020|Ross et al., 2020]] ). While no-take MPAs ( [[#3.6.3.2|Section 3.6.3.2]] ) enhance red-coral structural complexity, they only weakly compensate for warming effects ( [[#Cerrano--2013|Cerrano et al., 2013]] ; [[#Montero-Serra--2019|Montero-Serra et al., 2019]] ). ''Antipatharian'' spp. are not well studied or monitored ( [[#Gress--2018|Gress and Andradi-Brown, 2018]] ). Acidification and warming negatively impact pearl oysters ( [[#Welladsen--2010|Welladsen et al., 2010]] ; [[#Liu--2012|Liu and He, 2012]] ; [[#Liu--2012|Liu et al., 2012]] ; [[#Hoegh-Guldberg--2014|Hoegh-Guldberg et al., 2014]] ; [[#Zhang--2019b|Zhang et al., 2019b]] ). For example, projected climate impacts for 2035 would decrease the average net present value of French Polynesia’s pearl aquaculture industry by 29.1% compared with the present ( [[#Hilsenroth--2021|Hilsenroth et al., 2021]] ). Climate impacts on ornamental species sought by aquarists have not been well studied ( [[#Dee--2019b|Dee et al., 2019b]] ).

Decreasing the vulnerability of renewable-energy installations, particularly wind turbines, to climate risks (Table 3.26; [[#Bindoff--2019a|Bindoff et al., 2019a]] ) could include technological adaptations ( [[#3.6.2.2|Section 3.6.2.2]] ) such as storm ‘survival mode’ settings ( [[#Penalba--2018|Penalba et al., 2018]] ); preparation for hazards such as icing, SLR, drifting sea ice and wave activity ( [[#Neill--2018|Neill et al., 2018]] ; [[#Goodale--2019|Goodale and Milman, 2019]] ; [[#Solaun--2019|Solaun and Cerdá, 2019]] ); and biofouling ( ''medium confidence'' ) (Want and Porter, 2018; [[#Joyce--2019|Joyce et al., 2019]] ; [[#Vinagre--2020|Vinagre et al., 2020]] ), which is expected to increase in response to warming and acidification ( ''medium confidence'' ) ( [[#Dobretsov--2019|Dobretsov et al., 2019]] ; [[#Khosravi--2019|Khosravi et al., 2019]] ; [[#Liu--2020d|Liu et al., 2020d]] ; [[#Lamim--2021|Lamim and Procópio, 2021]] ). Macroalgae and fish-processing byproducts are being tested for biofuel use ( [[#Greene--2016|Greene et al., 2016]] ; [[#Alamsjah--2017|Alamsjah et al., 2017]] ; [[#Saifuddin--2017|Saifuddin and Boyce, 2017]] ; [[#Sakthivel--2018|Sakthivel et al., 2018]] ; [[#Sudhakar--2019|Sudhakar et al., 2019]] ; [[#Nguyen--2020|Nguyen et al., 2020]] ; [[#Ramachandra--2020|Ramachandra and Hebbale, 2020]] ; [[#Tan--2020|Tan et al., 2020]] ), but weather variability could pose financial risk to this sector ( [[#Kleiman--2021|Kleiman et al., 2021]] ).

<div id="3.5.5" class="h2-container"></div>

<span id="supporting-and-regulating-services"></span>
=== 3.5.5 Supporting and Regulating Services ===

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Ocean and coastal regulating services are detailed in Table 3.25. The economic value of all regulating ecosystem services in 2015 was estimated at 29.1 trillion USD, with water- and climate-regulating services contributing the most ( [[#Balasubramanian--2019|Balasubramanian, 2019]] ).

<div id="3.5.5.1" class="h3-container"></div>

<span id="habitat-creation-and-maintenance-and-larval-dispersal"></span>
==== 3.5.5.1 Habitat Creation and Maintenance, and Larval Dispersal ====

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Climate impacts have already altered ocean and coastal habitats ( [[#3.4.2|Section 3.4.2]] ; Table 3.26; [[#Gissi--2021|Gissi et al., 2021]] ) in ways that have led to species range shifts, biodiversity changes, phenology changes and regime shifts ( [[#3.4.3|Section 3.4.3]] ) from the surface ocean to the seafloor ( ''very high confidence'' ) (see Box 3.3; Figure 3.22). Continued ocean and coastal habitat impacts are projected, and their severities will depend on emissions scenario and co-occurring drivers ( [[#3.4.3|Section 3.4.3]] ; [[#Qiu--2019|Qiu et al., 2019]] ) or extremes (e.g., [[#Babcock--2019|Babcock et al., 2019]] ). Warming and physical circulation are projected to change larval dispersal, a habitat-related service ( [[#Bashevkin--2020|Bashevkin et al., 2020]] ), but identifying probable outcomes remains challenging owing to the high variability among species, locations and recruitment ( [[#Schilling--2020|Schilling et al., 2020]] ; [[#King--2021|King et al., 2021]] ; [[#Le%20Corre--2021|Le Corre et al., 2021]] ; [[#Raventos--2021|Raventos et al., 2021]] ). Climate risks to habitat can be decreased by reducing non-climate drivers, preserving ecosystems or restoring habitat (Sections 3.6.2, 3.6.3.2). Risk to larval dispersal cannot be meaningfully addressed at scale by human-implemented adaptations; instead, declines in this service will pressure natural systems to adapt via physiological plasticity or evolution ( [[#3.3|Section 3.3]] ; [[#Bashevkin--2020|Bashevkin et al., 2020]] ).

<div id="_idContainer097" class="Figure"></div>

[[File:4b47d3faf512f2e6f6e91c7717101878 IPCC_AR6_WGII_Figure_3_022.png]]

'''Figure 3.22 |''' '''Observed global influence of climate-induced drivers on ecosystem services.''' Symbols show whether the observed impact of the climate-induced drivers on a group of ecosystem services is positive (beneficial), negative (detrimental) or mixed (usually resulting from location, the presence of interacting drivers or changing effects over time). The ‘observed impact’ indicates the total effect of all climate-induced drivers on a specific ecosystem service, using expert judgement based on summary statements throughout [[#3.5|Section 3.5]] . Tick marks represent the presence of co-occurring drivers non-climate drivers that affect the service. No assessment indicates that not enough evidence is available to assess the direction of impact.

<div id="3.5.5.2" class="h3-container"></div>

<span id="climate-regulation-and-air-quality"></span>
==== 3.5.5.2 Climate Regulation and Air Quality ====

<div id="h3-31-siblings" class="h3-siblings"></div>

Climate regulation by the ocean depends on physical and biogeochemical processes (Sections 3.2–3.4) that create, move, and store heat, water vapour and other climate-active compounds including CO 2 , methane and dimethyl sulphide (WGI AR6 Chapter 6; [[#Szopa--2021|Szopa et al., 2021]] ). Over the 21st century, ocean heat and CO 2 uptake will continue (WGI AR6 SPMB4.1, B5.1; [[#IPCC--2021b|IPCC, 2021b]] ) and sea ice loss from warming will allow some additional CO 2 uptake ( [[#Armstrong--2019|Armstrong et al., 2019]] ), but the ocean will take up a smaller fraction of CO 2 emissions as atmospheric CO 2 concentrations rise ( ''high confidence'' ) (Table 3.26; WGI AR6 SPM B4.1; [[#IPCC--2021b|IPCC, 2021b]] ).

There is ''very limited evidence'' on climate-driven air-quality changes in the coastal zone. Increased humidity decreases the lifetime of ozone and increases particulate matter and indoor mould levels (USGCRP, 2016), potentially affecting near-shore air quality. However, coastal-zone air pollution can enhance coastal-climate impacts by increasing the risk of acid rain, which worsens ocean acidification (nitrogen oxides, sulphur oxides and mercury; [[#Doney--2010|Doney, 2010]] ; [[#Northcott--2019|Northcott et al., 2019]] ).

<div id="3.5.5.3" class="h3-container"></div>

<span id="provision-of-freshwater-maintenance-of-water-quality-and-regulation-of-pathogens"></span>
==== 3.5.5.3 Provision of Freshwater, Maintenance of Water Quality and Regulation of Pathogens ====

<div id="h3-32-siblings" class="h3-siblings"></div>

The salinities of many estuaries, deltas, coastal freshwater aquifers and soils around the world are increasing, and this decrease in water quality is endangering human health and agricultural yields ( ''very high confidence'' ) ( [[#3.4.2.4|Section 3.4.2.4]] ; Table 3.26; [[#Bindoff--2019a|Bindoff et al., 2019a]] ; [[#Bouderbala--2019|Bouderbala, 2019]] ; [[#Rahman--2019|Rahman et al., 2019]] ; [[#Naser--2020|Naser et al., 2020]] ; [[#Rakib--2020|Rakib et al., 2020]] ; [[#Mastrocicco--2021|Mastrocicco and Colombani, 2021]] ). Coastal salinisation is attributed to regionally varying combinations of climate-induced drivers, like SLR and storm-related flooding by seawater, and non-climate drivers, like water withdrawal and land-use changes ( ''very high confidence'' ) ( [[#Islam--2019|Islam et al., 2019]] ; [[#Rahman--2019|Rahman et al., 2019]] ; [[#Paldor--2021|Paldor and Michael, 2021]] ). Monitoring-related adaptations ( [[#3.6.2.2|Section 3.6.2.2.2]] ), including advances in modelling and monitoring, are providing decision-relevant, regional-scale information ( [[#Colombani--2016|Colombani et al., 2016]] ; [[#Mukhopadhyay--2019|Mukhopadhyay et al., 2019]] ; [[#Slama--2020|Slama et al., 2020]] ; [[#Corwin--2021|Corwin, 2021]] ). For example, new projections indicate which drinking-water intake stations on China’s Pearl River Estuary will be unable to meet demands by 2100 due to SLR and drought ( [[#Wang--2021|Wang and Hong, 2021]] ), while others show that SLR effects on seawater intrusion into the coastal aquifer in Kerala, India, under both RCP4.5 and RCP8.5 scenarios are negligible ( [[#Sithara--2020|Sithara et al., 2020]] ). Salinisation-associated changes may disproportionately burden women responsible for securing drinking water and fuel, such as in the Indian Sundarbans ( [[#Mukhopadhyay--2019|Mukhopadhyay et al., 2019]] ). Salinisation will continue to endanger coastal water and soil quality in the future ( ''high confidence'' ) ( [[#Islam--2019|Islam et al., 2019]] ; [[#Paldor--2021|Paldor and Michael, 2021]] ), but the evidence assessed above shows that subsequent impacts to human health and agriculture will depend heavily on regional variations in environment and human behaviour ( ''medium confidence'' ).

Together, climate-induced and non-climate drivers can mobilise toxins and contaminants in ways that harm human and marine species health ( ''very high confidence'' ) (see Box 3.2), and climate change is altering these relationships ( ''high confidence'' ) (Table 3.26; [[#Bindoff--2019a|Bindoff et al., 2019a]] ). Under warming or ocean acidification, marine molluscs exposed to pharmaceuticals via wastewater experience more detrimental biological consequences or greater bioaccumulation ( ''limited evidence, high agreement'' ) ( [[#Costa--2020a|Costa et al., 2020a]] ; [[#Costa--2020b|Costa et al., 2020b]] ; [[#Dionísio--2020|Dionísio et al., 2020]] ; [[#Freitas--2020|Freitas et al., 2020]] ; [[#Kibria--2021|Kibria et al., 2021]] ). Physical circulation, temperature and biogeochemical characteristics ( [[#Bowman--2020|Bowman et al., 2020]] ; [[#Liu--2020a|Liu et al., 2020a]] ; [[#Liu--2020b|Liu et al., 2020b]] ; [[#Sun--2020|Sun et al., 2020]] ; [[#Zhang--2020b|Zhang et al., 2020b]] ) control the ubiquitous oceanic distribution of methylmercury, and ocean acidification- and warming-driven changes in planktonic speciation and interactions can promote additional food-web bioaccumulation of methylmercury ( [[#Tada--2020|Tada and Marumoto, 2020]] ; [[#Wu--2020b|Wu et al., 2020b]] ; [[#Zhang--2020b|Zhang et al., 2020b]] ; [[#Zhang--2021a|Zhang et al., 2021a]] ). Interactions among drivers also matter: temperature plus overfishing increased tissue methylmercury concentrations in Atlantic bluefin tuna from the 1970s to the 2000s more than the decreases in the late 1990s and 2000s from lower environmental mercury levels ( [[#Schartup--2019|Schartup et al., 2019]] ). This appears true for persistent organic pollutants as well, but their bioaccumulation is related more to temperature effects on animal behaviour than on pollutant dynamics ( [[#Houde--2019|Houde et al., 2019]] ; [[#Wagner--2019|Wagner et al., 2019]] ; [[#Kalia--2021|Kalia et al., 2021]] ). By 2100 under RCP8.5, productivity changes and community structure shifts are expected to increase methylmercury concentrations in polar oceans and high-latitude phytoplankton and decrease it in low latitudes ( [[#Zhang--2021a|Zhang et al., 2021a]] ). The estimated average global cost of mercury-related health effects by 2050, mainly from seafood consumption during 2010–2050, will be 19 trillion USD (2020), assuming a 3% discount rate, if methylmercury emissions are not reduced ( [[#Zhang--2021b|Zhang et al., 2021b]] ).

Since previous assessments, evidence has increased that climate impacts, such as warming, extreme weather and SLR, are increasing the geographic spread and risk of marine-borne human pathogen outbreaks, including ''Vibrio'' spp. ( ''very high confidence'' ) (Table 3.26; [[#Bindoff--2019a|Bindoff et al., 2019a]] ; [[#Logar-Henderson--2019|Logar-Henderson et al., 2019]] ; [[#Froelich--2020|Froelich and Daines, 2020]] ; [[#Montánchez--2020|Montánchez and Kaberdin, 2020]] ; [[#Semenza--2020|Semenza, 2020]] ; [[#Ferchichi--2021|Ferchichi et al., 2021]] ). Climate change affects at least 30 human pathogens with aquatic-system infection routes (e.g., ingestion of contaminated water or seafood, or contact with wounds; Table 3.SM.2; Cross-Chapter Box ILLNESS in Chapter 2; [[#Nichols--2018|Nichols et al., 2018]] ). Conditions favourable for ''Vibrio cholerae'' are increasing globally, which raises the risk to humans (Cross-Chapter Box ILLNESS in Chapter 2). Increased storm-related flooding and SLR further increase human encounters with ''Vibrio'' spp. ( [[#Froelich--2020|Froelich and Daines, 2020]] ). Aquatic diseases, particularly ''Vibrio'' spp., have caused large economic losses in aquaculture by decreasing the quality or survival of cultured species ( [[#Lafferty--2015|Lafferty et al., 2015]] ; [[#Novriadi--2016|Novriadi, 2016]] ). Temperature-based model projections show that all Canadian shellfish beds will experience conditions that promote high risk of ''Vibrio'' spp. growth by 2100 for both RCP4.5 and RCP8.5 scenarios ( [[#Ferchichi--2021|Ferchichi et al., 2021]] ). Climate-induced drivers may increase ''Vibrio'' spp. loads in seafood species: laboratory-simulated heatwaves increase ''Vibrio'' spp. abundance in Pacific oyster ( ''Crassostrea gigas'' ) ( [[#Green--2019|Green et al., 2019]] ) and simulated ocean acidification increases hard clam ( ''Mercenaria mercenaria'' ) susceptibility to ''Vibrio'' spp. infection ( [[#Schwaner--2020|Schwaner et al., 2020]] ). Projected increases in temperature, extreme and variable rainfall conditions, coastal flooding and SLR ( [[#3.2|Section 3.2]] ; Cross-Chapter Box SLR in Chapter 3) strongly increase the risk of frequent and severe aquatic human pathogen outbreaks in ocean and coastal areas that will continue to harm human health and cause economic losses ( ''high confidence'' ) (Cross-Chapter Box ILLNESS in Chapter 2; [[#Froelich--2020|Froelich and Daines, 2020]] ; [[#Semenza--2020|Semenza, 2020]] ; [[#Ferchichi--2021|Ferchichi et al., 2021]] ). [[#3.6.3.1.5|Section 3.6.3.1.5]] assesses human adaptations to increasing risk of marine-borne pathogens.

Climate-driven changes in temperature, salinity (from ice melt and precipitation changes), deoxygenation and ocean acidification can alter dynamics of infectious diseases that target ocean and coastal species by increasing hosts’ susceptibility or pathogens’ abundance or virulence ( ''high confidence'' ) ( [[#Burge--2020|Burge and Hershberger, 2020]] ; [[#Byers--2021|Byers, 2021]] ). Coral and urchin diseases have increased over time driven by warming-related declines in organism recovery and survival or immunity ( ''medium confidence'' ) ( [[#Cohen--2018|Cohen et al., 2018]] ; [[#Tracy--2019|Tracy et al., 2019]] ). Seagrass and sea star wasting disease outbreaks have occurred under combinations of ocean warming or MHWs and non-climate drivers (e.g., eutrophication, bottom trawling), but attribution of these outbreaks to specific drivers is still not resolved ( [[#Harvell--2019|Harvell et al., 2019]] ; [[#Jakobsson-Thor--2020|Jakobsson-Thor et al., 2020]] ; [[#Krause-Jensen--2021|Krause-Jensen et al., 2021]] ). Disease outbreaks threaten marine biodiversity, species that create habitat or dampen wave action, and keystone species ( [[#Harvell--2020|Harvell and Lamb, 2020]] ). Attributing observed changes in marine disease patterns to climate remains extremely difficult owing to interacting climate and non-climate drivers ( [[#Burge--2020|Burge and Hershberger, 2020]] ) and lack of baseline data ( [[#Tracy--2019|Tracy et al., 2019]] ). Projected increases in the frequency, duration and intensity of warming events would reduce survival and recovery of some species from hot events, reduce immunity of other species to pathogens, extend poleward ranges of some pathogens and increase infection risk when host species congregate in scarce habitat ( [[#Cohen--2018|Cohen et al., 2018]] ). Pathogens that target ocean and coastal organisms may themselves be sensitive to future climate conditions or subsequent ecosystem changes, which challenges development of projections ( [[#Cohen--2018|Cohen et al., 2018]] ; [[#Burge--2020|Burge and Hershberger, 2020]] ).

New examples have illustrated how toxic HABs interfere with regulating, provisioning ( [[#3.5.3|Section 3.5.3]] ) and cultural ecosystem services ( [[#3.5.6|Section 3.5.6]] ) in interconnected ways ( ''limited evidence, high agreement'' ). A massive toxic ''Pseudo-nitzschia'' spp. bloom in 2013–2016 along the USA West Coast triggered Dungeness crab, rock crab and razor clam fishery closures to protect human consumers (Sections 3.6.2, 3.6.3.1.5; [[#McCabe--2016|McCabe et al., 2016]] ), and this disproportionately harmed fishers, especially small-vessel owners, and fishing-support service industries, primarily through lost revenue ( [[#Ritzman--2018|Ritzman et al., 2018]] ; [[#Moore--2019|Moore et al., 2019]] ; [[#Trainer--2019|Trainer et al., 2019]] ; [[#Jardine--2020|Jardine et al., 2020]] ; [[#Moore--2020a|Moore et al., 2020a]] ). Toxic ''Alexandrium'' spp. blooms promoted by climate-driven coastal extremes (e.g., MHWs, stratification, runoff) in Tasmania, Australia, in 2012 and Chile in 2016 caused fish kills, shellfish product recalls, substantial economic losses, and human sickness and death ( [[#Trainer--2019|Trainer et al., 2019]] ). The Chile event caused an estimated loss of 800 million USD in the farmed salmon industry ( [[#Díaz--2019|Díaz et al., 2019]] ) and resulted in a series of large, long-lasting regional protests calling for national aid ( [[#Delgado--2019|Delgado et al., 2019]] ). New evidence, however, suggests that the perceived global increase in harmful algal blooms results from better monitoring and more detrimental bloom impacts, rather than a climate-linked mechanism ( [[#Hallegraeff--2021|Hallegraeff et al., 2021]] ).

Natural and engineered systems have long been used effectively to manage precipitation and wastewater safely (see Box 4.5), and maintaining and enhancing them is a key nature-based adaptation strategy for coastal communities ( [[#3.6.2.3|Section 3.6.2.3]] ; Cross-Chapter Paper 2). Estimated values of water purification and stormwater management provided by coastal ecosystems are in the hundreds to thousands of USD per hectare [e.g., 272 Euro per 0.01 km 2 yr –1 from the Mediterranean’s sandy coastline ( [[#Hérivaux--2018|Hérivaux et al., 2018]] ); 1100–2800 USD per 0.01 km 2 yr –1 from the state of Maryland, USA ( [[#Campbell--2020b|Campbell et al., 2020b]] ); 600 USD per 0.01 km 2 yr –1 in Zhuzhou City, China ( [[#Zhan--2020|Zhan et al., 2020]] )]. Both wild and cultured organisms also provide filtration services. Seagrasses’ ability to purify water is well recognised by coastal residents and ocean resource users in tropical and temperate locations ( [[#Ambo-Rappe--2019|Ambo-Rappe et al., 2019]] ; [[#Quevedo--2020|Quevedo et al., 2020]] ; [[#Heckwolf--2021|Heckwolf et al., 2021]] ; [[#McKenzie--2021a|McKenzie et al., 2021a]] ). Globally, aquacultured shellfish remove an estimated 49,000 tonnes of nitrogen and 6000 tonnes of phosphorus from coastal waters, worth a potential 1.20 billion USD, and they may help improve existing engineered wastewater treatment systems ( [[#van%20der%20Schatte%20Olivier--2020|van der Schatte Olivier et al., 2020]] ). Climate change, especially episodic extreme rains and RSLR ( [[#Romero-Lankao--2014|Romero-Lankao et al., 2014]] ), is challenging management and design of wastewater and stormwater systems ( ''high confidence'' ) ( [[#Flood--2011|Flood and Cahoon, 2011]] ; [[#Trtanj--2016|Trtanj et al., 2016]] ; [[#Hummel--2018|Hummel et al., 2018]] ; [[#Kirshen--2018|Kirshen et al., 2018]] ; [[#Nazarnia--2020|Nazarnia et al., 2020]] ; [[#Reznik--2020|Reznik et al., 2020]] ; [[#McKenzie--2021b|McKenzie et al., 2021b]] ) and the integrity of coastal landfills ( [[#Beaven--2020|Beaven et al., 2020]] ). Without substantial adaptation that addresses projected wastewater management challenges and community needs ( [[IPCC:Wg2:Chapter:Chapter-4#4.2.6|Section 4.2.6.1]] ; [[#Kirshen--2018|Kirshen et al., 2018]] ; [[#Kirchhoff--2019|Kirchhoff and Watson, 2019]] ; [[#Kool--2020|Kool et al., 2020]] ; [[#Nazarnia--2020|Nazarnia et al., 2020]] ; [[#Hughes--2021|Hughes et al., 2021]] ), coastal water quality in many areas will decrease because of more frequent or severe releases of untreated wastes ( ''high confidence'' ) ( [[#Flood--2011|Flood and Cahoon, 2011]] ; [[#Hummel--2018|Hummel et al., 2018]] ; [[#Hughes--2021|Hughes et al., 2021]] ; [[#McKenzie--2021b|McKenzie et al., 2021b]] ), and this will have harmful consequences for human and coastal ecosystem health ( ''high confidence'' ) ( [[IPCC:Wg2:Chapter:Chapter-4#4.2.6|Section 4.2.6.1]] ; Cross-Chapter Box ILLNESS in Chapter 2; [[#Bindoff--2019a|Bindoff et al., 2019a]] ).

<div id="3.5.5.4" class="h3-container"></div>

<span id="regulation-of-physical-hazards"></span>
==== 3.5.5.4 Regulation of Physical Hazards ====

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Coastal ecosystems physically protect people and property from storms and flooding, and climate change threatens this protection function (Figure 3.22; Table 3.26). Increasingly detailed models show how warm-water coral reefs ( [[#Reguero--2019|Reguero et al., 2019]] ; [[#Storlazzi--2019|Storlazzi et al., 2019]] ; [[#Reguero--2021|Reguero et al., 2021]] ) mangroves ( [[#Blankespoor--2017|Blankespoor et al., 2017]] ; [[#Menéndez--2020|Menéndez et al., 2020]] ; [[#Trégarot--2021|Trégarot et al., 2021]] ) and wetlands ( [[#Sun--2020|Sun and Carson, 2020]] ) prevent billions of US dollars of direct and indirect damage to private and public property and shield millions of people from flooding each year. Protection by mangroves provides more economic benefits in higher-income nations and shields more people in lower-income nations ( [[#Menéndez--2020|Menéndez et al., 2020]] ). Seagrasses ( [[#James--2020|James et al., 2020]] ; [[#James--2021|James et al., 2021]] ), kelp ( [[#Morris--2020b|Morris et al., 2020b]] ; [[#Zhu--2020|Zhu, 2020]] ), suspended shellfish aquaculture ( [[#Gentry--2020|Gentry et al., 2020]] ; [[#Zhu--2020a|Zhu et al., 2020a]] ), oyster reefs ( [[#Chowdhury--2019|Chowdhury et al., 2019]] ), coastal wetlands ( [[#Möller--2019|Möller, 2019]] ; [[#Keimer--2021|Keimer et al., 2021]] ) and sandy coastlines ( [[#3.4.2.6|Section 3.4.2.6]] ) [[#Hérivaux--2018|Hérivaux et al., 2018]] ) also measurably decrease wave energy. Non-climate drivers [e.g., invasive species ( [[#James--2020|James et al., 2020]] ), sediment-supply changes ( [[#Ganju--2019|Ganju, 2019]] ; [[#Ladd--2019|Ladd et al., 2019]] ; [[#Ilia--2020|Ilia, 2020]] ), erosion and storm damage ( [[#Mehvar--2019|Mehvar et al., 2019]] ; [[#Bacopoulos--2021|Bacopoulos and Clark, 2021]] )], acting together with climate-induced drivers and associated impacts [e.g., SLR (Cross-Chapter Box SLR in Chapter 3), changes in plant biodiversity ( [[#3.5.2|Section 3.5.2]] ; [[#Lee%20Smee--2019|Lee Smee, 2019]] ; [[#Silliman--2019|Silliman et al., 2019]] ; [[#Schoutens--2020|Schoutens et al., 2020]] ), MHWs ( [[#3.4.3|Section 3.4.3.7]] ) and acidification ( [[#3.4.2.1|Section 3.4.2.1]] )], compromise physical protection by coastal ecosystems ( ''very high confidence'' ). (See Cross-Chapter Box SLR in [https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-3 Chapter 3] and Sections 3.6.3.1 and 3.6.3.2.2 for assessment of adaptations that address this ecosystem service.)

<div id="3.5.5.5" class="h3-container"></div>

<span id="regulation-of-carbon-cycling-in-ocean-and-coastal-ecosystems"></span>
==== 3.5.5.5 Regulation of Carbon Cycling in Ocean and Coastal Ecosystems ====

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Current and future total carbon storage and cycling in the ocean are governed by past and future CO 2 emissions trajectories (Table 3.26), but regional ocean and coastal carbon stocks and cycling vary over time and space due to processes being altered by climate, including ocean circulation, sea ice cover, coastal upwelling and thermal stratification ( [[#3.2.2.3|Section 3.2.2.3]] ); ocean primary production and export (Sections 3.2.3, 3.4.4); and marine ecosystem biodiversity ( ''high confidence'' ) ( [[#3.5.2|Section 3.5.2]] ; Figure 3.22). Quantifying regional carbon fluxes and stocks is still challenging and relies on indirect measures (e.g., [[#Fennel--2019|Fennel et al., 2019]] ; [[#Clay--2020|Clay et al., 2020]] ), especially in coastal ecosystems where drivers interact. Carbon cycling and storage co-occurs with other regulating services such as habitat provision, water-quality maintenance and coastal protection ( [[#Ouyang--2018|Ouyang et al., 2018]] ), particularly in vegetated coastal ecosystems (see Box 3.4). Adaptations to support regional carbon cycling and storage generally focus on area-based management and conservation ( [[#3.6.3.2|Section 3.6.3.2]] ), but interventions to enhance ocean carbon storage are being explored for mitigation (WGIII AR6 Chapter 7).

<div id="box-3.4" class="h2-container box-container"></div>

'''Box 3.4 | Blue Carbon Ecosystems'''
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Climate change and other anthropogenic drivers, including eutrophication, land-use changes and overexploitation, directly and indirectly threaten blue carbon ecosystems (Annex II: Glossary). Commonly considered blue carbon ecosystems include vegetated coastal ecosystems (Sections 3.4.2.3–3.4.2.5), whose mangroves, salt marshes and seagrass beds host rooted, vascular plants known to store large amounts of carbon for long periods and to be amenable to management ( [[#Lovelock--2019|Lovelock and Duarte, 2019]] ). Other ocean and coastal taxa, including rooted or floating macroalgae (e.g., non-vascular multicellular kelp or seaweed genera such as ''Macrocystis'' spp., ''Sargassum'' spp. or ''Laminaria'' spp. ( [[#Filbee-Dexter--2020|Filbee-Dexter and Wernberg, 2020]] ), phytoplankton and even pelagic fauna (e.g., finfish or whales; [[#Chami--2019|Chami et al., 2019]] ), have also been proposed as blue carbon ecosystems. Terrestrial vascular-plant-derived material can also carry and store significant amounts of carbon in marine environments ( [[#Cragg--2020|Cragg et al., 2020]] ). There is increasing evidence about the coverage and carbon content of macroalgal, planktonic and faunal taxa, but ''low agreement'' about their long-term carbon-storage potential and manageability ( [[#Alongi--2018b|Alongi, 2018b]] ; [[#Wernberg--2018|Wernberg and Filbee-Dexter, 2018]] ; [[#Lovelock--2019|Lovelock and Duarte, 2019]] ; [[#Ortega--2019|Ortega et al., 2019]] ; [[#Pfister--2019|Pfister et al., 2019]] ; [[#Queirós--2019|Queirós et al., 2019]] ; [[#Filbee-Dexter--2020a|Filbee-Dexter et al., 2020a]] ; [[#Gallagher--2020|Gallagher, 2020]] ; [[#Mariani--2020|Mariani et al., 2020]] ; [[#Thorhaug--2020|Thorhaug et al., 2020]] ; [[#van%20Son--2020|van Son et al., 2020]] ; [[#Bach--2021|Bach et al., 2021]] ; [[#Bayley--2021|Bayley et al., 2021]] ; [[#Cavanagh--2021|Cavanagh et al., 2021]] ; [[#Frontier--2021|Frontier et al., 2021]] ; [[#Martin--2021|Martin et al., 2021]] ; [[#Pedersen--2021|Pedersen et al., 2021]] ; [[#Weigel--2021|Weigel and Pfister, 2021]] ). This section focuses on the array of ecosystem services and adaptation opportunities provided by vegetated coastal blue carbon ecosystems, where consensus and evidence are most abundant. Mitigation potential of blue carbon ecosystems is assessed with land-based mitigation options in WGIII AR6 [[IPCC:Wg2:Chapter:Chapter-7#7.4|Section 7.4]] .

Carbon storage and burial in mangroves, salt marshes and seagrass meadows (see Table Box 3.4.1) help regulate ocean and coastal carbon cycling and may contribute to nature-based mitigation, although regional estimates vary widely based on climatic and edaphic conditions (WGIII AR6 [[IPCC:Wg2:Chapter:Chapter-7#7.4|Section 7.4]] ). In addition, coastal vegetated ecosystems provide substantial and interdependent regulating, provisioning and cultural ecosystem services. These services include: (a) disproportionately high biodiversity per unit area ( [[#Pörtner--2021a|Pörtner et al., 2021a]] ); (b) abundant habitat ( [[#3.5.5.1|Section 3.5.5.1]] ) and nurseries for aquatic, terrestrial, aerial and microbial species; (c) natural filtration of waste and stormwater runoff into the coastal ocean (Sections 3.5.5.3, 4.2.7; Cross-Chapter Box ILLNESS in Chapter 2); (d) coastal protection ( [[#3.5.5.4|Section 3.5.5.4]] ; [[#Ouyang--2018|Ouyang et al., 2018]] ; [[#Quevedo--2020|Quevedo et al., 2020]] ); (e) food and natural materials (Sections 3.5.3, 3.5.4); and (f) support for tourism, livelihoods and cultural activities ( [[#3.5.6|Section 3.5.6]] ). Global estimates of services provided by coastal blue carbon ecosystems depend on the quality of available mapping, which is currently best developed for mangroves ( [[#Macreadie--2019|Macreadie et al., 2019]] ), and improving for salt marshes and seagrasses ( [[#McOwen--2017|McOwen et al., 2017]] ; [[#McKenzie--2020|McKenzie et al., 2020]] ; [[#Young--2021|Young et al., 2021]] ).

'''Table Box 3.4.1 |''' Estimates of organic carbon storage and burial rates in mangroves, salt marshes and seagrass meadows a

{| class="wikitable"
|-
!
! Mangroves

! Salt marshes

! Seagrass meadows

|-
| Carbon stocks (MgC ha –1 )

| 856 ± 64.2 [79–2208] ( [[#Kauffman--2020|Kauffman et al., 2020]] )

| 317.2 ± 38.2 [27–1900] ( [[#Alongi--2018c|Alongi, 2018c]] )

| 139.7 [9.1–628] ( [[#Fourqurean--2012|Fourqurean et al., 2012]] ; [[#Alongi--2018d|Alongi, 2018d]] )

|-
| Carbon burial rate (g C m –2 yr –1 )

| 194 ± 30 [6.2–1722] ( [[#Wang--2020|Wang et al., 2020]] )

| 168 ± 14 [1.2–1167.5] ( [[#Wang--2020|Wang et al., 2020]] )

| 220.7 ± 40.2 [–2094 to 2124] ( [[#Alongi--2018d|Alongi, 2018d]] )

|-
| Global carbon burial rate (TgC yr –1 )

| 41 ( [[#Wang--2020|Wang et al., 2020]] )

| 12.63 ( [[#Wang--2020|Wang et al., 2020]] )

| 35.31 ( [[#Alongi--2020|Alongi, 2020]] )

|-
| Global areal coverage (Mha)

| 13.7 ( [[#Richards--2020|Richards et al., 2020]] )

| 5.5 ( [[#McOwen--2017|McOwen et al., 2017]] )

| 16 ( [[#McKenzie--2020|McKenzie et al., 2020]] )

|}

(a) Estimates are the mean ± 95% confidence interval, where available (indicating the ''extremely likely'' range) and range. Carbon stocks for mangroves include above- and below-ground storage up to 3 m depth (sampling period 2007–2017). The estimates for salt-marsh and seagrass stocks are soil stocks up to 1 m depth (observations spanning 1983–2016 for salt marshes and until 2016 for seagrass meadows). Date ranges for the burial rates are: 1989–2020, 1975–2020 and 1956–2016 for mangroves, salt marshes and seagrass meadows, respectively.

Coastal vegetated ecosystems are vulnerable to harm from multiple climate-induced and non-climate drivers, and together these have reduced wetland area globally ( ''high confidence'' ) ( [[#3.4.2.5|Section 3.4.2.5]] ) and endangered the services provided by these ecosystems ( ''high confidence'' ). Loss of coastal vegetated ecosystems changes biodiversity (Sections 3.5.2, 3.4.2.3–3.4.2.5; [[#Numbere--2019|Numbere, 2019]] ; [[#Parreira--2021|Parreira et al., 2021]] ), increases risk of damage and erosion from SLR and storms (Sections 3.4.2.3–3.4.2.5; Cross-Chapter Box SLR in Chapter 3; [[#Galeano--2017|Galeano et al., 2017]] ) and impacts provisioning (Sections 3.5.3–3.5.4; [[#Li--2018b|Li et al., 2018b]] ; [[#Maina--2021|Maina et al., 2021]] ). These changes also strongly determine the quantity and longevity of blue carbon storage ( ''high confidence'' ) ( [[#Macreadie--2019|Macreadie et al., 2019]] ; [[#Lovelock--2020|Lovelock and Reef, 2020]] ). Specific site characteristics and ecosystem responses to climate change will determine future local blue carbon storage or loss ( ''high confidence'' ) (see Table Box 3.4.2). For instance, poleward migration of mangroves to areas dominated by salt marshes is expected to increase carbon storage ( [[#Kelleway--2016|Kelleway et al., 2016]] ); however, this change in the dominant vegetation and associated faunal changes can modify carbon stocks and sequestration, as well as other ecosystem services ( [[#Martinetto--2016|Martinetto et al., 2016]] ; [[#Kelleway--2017|Kelleway et al., 2017]] ; [[#Smee--2017|Smee et al., 2017]] ; [[#Macreadie--2019|Macreadie et al., 2019]] ; [[#Macy--2019|Macy et al., 2019]] ). Landward range expansion of mangroves, marshes and seagrass in response to gradual RSLR can enhance carbon sequestration ( [[#3.4.2.5|Section 3.4.2.5]] ; Cross-Chapter Box SLR in Chapter 3; [[#Macreadie--2019|Macreadie et al., 2019]] ), but coastal squeeze can limit this ( [[#Phan--2015|Phan et al., 2015]] ; [[#Schuerch--2018|Schuerch et al., 2018]] ) and RSLR can either submerge and bury or erode and release stored blue carbon ( [[#3.4.2.5|Section 3.4.2.5]] ; [[#Macreadie--2019|Macreadie et al., 2019]] ; [[#Lovelock--2020|Lovelock and Reef, 2020]] ). Gains and losses of mangrove habitat area (and therefore carbon storage) projected for nations under RCP4.5 and RCP8.5 depend primarily on the combination of SLR rate, adaptation scenario (including coastal development) and island or continental status ( [[#Lovelock--2020|Lovelock and Reef, 2020]] ). The influence of warming, MHWs and acidification on seagrass meadows ( [[#Kendrick--2019|Kendrick et al., 2019]] ; [[#Strydom--2020|Strydom et al., 2020]] ), and associated coralligenous reefs ( [[#Zunino--2019|Zunino et al., 2019]] ), suggests that future warming and especially MHWs will cause more widespread loss of services from these ecosystems ( [[#3.4.2.5|Section 3.4.2.5]] ). Loss of blue carbon ecosystems will not only halt carbon storage but also release stored carbon: emissions after 2000 due to global mangrove deforestation have been estimated at 23.5–38.7 Tg Cyr –1 ( [[#Ouyang--2020|Ouyang and Lee, 2020]] ). Mitigation estimates for avoided conversion and restoration of coastal wetlands and the implications of the impacts of climate change are assessed in WGIII AR6 [[IPCC:Wg2:Chapter:Chapter-7#7.4|Section 7.4]] .

<div id="_idContainer093" class="Box_Header-continued"></div>

Box 3.4

To date, initiatives aiming to restore coastal wetland ecosystems primarily address ecosystem characteristics other than carbon storage ( [[#Herr--2017|Herr et al., 2017]] ; [[#de%20los%20Santos--2019|de los Santos et al., 2019]] ; [[#Lovelock--2019|Lovelock and Duarte, 2019]] ; [[#Friess--2020a|Friess et al., 2020a]] ). But recovery of coastal vegetated ecosystems is expected to bring back the full suite of ecosystem services they provide, not just carbon storage ( ''medium confidence'' ) ( [[#Marbà--2015a|Marbà et al., 2015a]] ; [[#Burden--2019|Burden et al., 2019]] ; [[#Friess--2020a|Friess et al., 2020a]] ), making coastal restoration a low-risk action that offers both adaptation and mitigation benefits ( [[#Steven--2020|Steven et al., 2020]] ; [[#Gattuso--2021|Gattuso et al., 2021]] ). Successful restoration requires using appropriate plant species in suitable environmental settings ( [[#Wodehouse--2019|Wodehouse and Rayment, 2019]] ; [[#Friess--2020a|Friess et al., 2020a]] ) with favourable geomorphology and biophysical conditions ( [[#Cameron--2019|Cameron et al., 2019]] ; [[#Ochoa-Gómez--2019|Ochoa-Gómez et al., 2019]] ) and considering social, economic, policy and operational constraints ( [[#3.6.3.2.2|Section 3.6.3.2.2]] ; Cross-Chapter Box NATURAL in Chapter 2), now and in the future ( ''high confidence'' ) ( [[#Duarte--2020|Duarte et al., 2020]] ; [[#Lovelock--2020|Lovelock and Reef, 2020]] ). Nevertheless, restored spaces may not store carbon at rates equal to those of undisturbed spaces ( [[#Yang--2020|Yang et al., 2020]] ), and it may take decades to determine or achieve carbon-storage outcomes of restoration ( [[#Sasmito--2019|Sasmito et al., 2019]] ; [[#Duarte--2020|Duarte et al., 2020]] ; [[#Oreska--2020|Oreska et al., 2020]] ). Integration improves efforts to restore or conserve coastal wetland ecosystems to accomplish both adaptation and mitigation outcomes ( [[#Steven--2020|Steven et al., 2020]] ). Government-led conservation of blue carbon ecosystems as part of national and subnational climate strategies (e.g., [[#Friess--2020a|Friess et al., 2020a]] ; [[#Kelleway--2020|Kelleway et al., 2020]] ; [[#Wedding--2021|Wedding et al., 2021]] ) benefits from coordination with private activities, such as incentivising conservation with payments for ecosystem services ( [[#Muenzel--2018|Muenzel and Martino, 2018]] ; [[#Friess--2020a|Friess et al., 2020a]] ). Moreover, successful area-based protection measures consider both environmental and social issues ( [[#3.6.3.2|Section 3.6.3.2]] ). Continued integration and alignment of policies at international to local levels ( [[#3.6|Section 3.6.5]] ) will also support achieving the adaptation and mitigation benefit of blue carbon spaces ( [[#Friess--2020a|Friess et al., 2020a]] ; [[#Steven--2020|Steven et al., 2020]] ; [[#Wu--2020a|Wu et al., 2020a]] ).

'''Table Box 3.4.2 |''' Examples of vegetated blue carbon ecosystem carbon-storage gains and losses in response to climate-induced drivers, and key actions contributing to maintained and/or increased carbon storage a

{| class="wikitable"
|-
!
! Mangroves

! Salt marshes

! Seagrasses

|-
| ''Sea level rise''

|
|-
| Landward expansion by vegetation

| +C

| +C

| +C

|-
| Coastal squeeze

| −C

| −C

| −C

|-
| Loss of low-lying or submerged land or vegetation

| −C

| −C

| −C

|-
| Human adaptation to increase accommodation space

| +C

| +C

|
|-
| ''Extreme storms''

|
|-
| Erosion, loss of area, subsidence

| −C

| −C

| 0 to −C

|-
| Enhanced sedimentation

| +C

| +C

| +C

|-
| Vegetation damage and mortality

| −C to +C

|
| −C

|-
| ''Warming''

|
|-
| Increased productivity

| +C

|
| +C

|-
| Vegetation mortality

|
| −C

|-
| Increased decomposition of soil

| −C

| −C to +C

|
|-
| Poleward expansion of mangroves

| +C

| −C

|
|-
| Poleward expansion of seagrasses

|
| +C

|-
| Poleward expansion of bioturbators

| ∆C

|
|-
| Change in dominant species

| ∆C

|
|-
| ''Rising concentrations of atmospheric CO'' 2

|
|-
| Increased productivity of some species

| ∆C

| ∆C

| +C

|-
| Biodiversity loss

|
| −C

|-
| ''Altered precipitation''

|
|-
| Vegetation mortality

| −C

|
|-
| Reduced productivity

| −C

| −C

|
|-
| Increased productivity

| +C

|
| +C

|-
| Increased remineralisation

| −C

| −C

|
|-
| Low-salinity events

|
| 0 to −C

|-
| ''Key actions to sustain blue carbon storage''

|
|-
| Protect ecosystems

| X

| X

| X

|-
| Develop alternative livelihoods

| X

|
|-
| Provide space for landward migration

| X

| X

|
|-
| Restore hydrological connections

| X

| X

|
|-
| Maintain or restore sediment supply

| X

| X

|
|-
| Restore ecosystems

| X

|
| X

|-
| Plant indigenous species

|
| X

|
|-
| Reduce nutrient inputs

|
| X

|}

(a) ‘+C’ indicates potential positive effects on blue carbon stocks, ‘−C’ indicates potential negative effects, ‘0’ indicates no effects and ‘∆C’ indicates positive potential or negative effects. Effects on carbon stocks are from [[#3.4.2.5|Section 3.4.2.5]] , [[#Macreadie--2019|Macreadie et al. (2019)]] , [[#Lovelock--2020|Lovelock and Reef (2020)]] and [[#Wang--2020|Wang et al. (2020)]] . Key actions to sustain blue carbon storage are from [[#Duarte--2020|Duarte et al. (2020)]] and [[#Wedding--2021|Wedding et al. (2021)]] .

<div id="_idContainer094" class="Box_Header-continued"></div>

Box 3.4

<div id="3.5.6" class="h2-container"></div>

<span id="cultural-services"></span>
=== 3.5.6 Cultural Services ===

<div id="h2-19-siblings" class="h2-siblings"></div>

Cultural services provided by ocean and coastal ecosystems help maintain psychological well-being, cultural development, human identities, educational opportunities and reserves that could support development of future goods or activities (Table 3.25). Most recent studies of ocean and coastal cultural services simply detail local benefits using replicable methods (e.g., [[#Drakou--2018|Drakou et al., 2018]] ; [[#Folkersen--2018|Folkersen, 2018]] ; [[#Förster--2019|Förster et al., 2019]] ; [[#Lau--2019|Lau et al., 2019]] ; [[#Pouso--2019|Pouso et al., 2019]] ; [[#Weitzman--2019|Weitzman, 2019]] ; [[#Yang--2019|Yang et al., 2019]] ), focusing on diverse ocean and coastal environments and ecosystems ( [[#Jobstvogt--2014|Jobstvogt et al., 2014]] ; [[#Balzan--2018|Balzan et al., 2018]] ; [[#Drakou--2018|Drakou et al., 2018]] ; [[#Ingram--2018|Ingram et al., 2018]] ; [[#Pouso--2018|Pouso et al., 2018]] ; [[#Zapata--2018|Zapata et al., 2018]] ; [[#Ghermandi--2019|Ghermandi et al., 2019]] ; [[#Pouso--2019|Pouso et al., 2019]] ; [[#Tanner--2019|Tanner et al., 2019]] ; [[#Turner--2019|Turner et al., 2019]] ; [[#Ortíz%20Liñán--2021|Ortíz Liñán and Vázquez Solís, 2021]] ). Cultural ecosystem services may directly benefit from marine development activities, such as marine aquaculture (e.g., [[#Alleway--2018|Alleway et al., 2018]] ), and indirectly benefit from marine activities that increase biodiversity (e.g., [[#Causon--2018|Causon and Gill, 2018]] ). Cultural services are generally quantified using interviews and revealed-preference or stated-preference valuation ( [[#National%20Research%20Council--2005|National Research Council, 2005]] ; [[#Sangha--2019|Sangha et al., 2019]] ), but people often are especially reluctant to evaluate cultural ecosystem services in monetary terms, given the spiritual and community linkages to these services ( [[#Oleson--2018|Oleson et al., 2018]] ).

Additional evidence since previous assessments (Table 3.26) confirms that climate-change impacts on ocean and coastal cultural ecosystem services have already disrupted people’s place-based emotional attachments and cultural activities ( ''limited evidence, high agreement'' ) (Figure 3.22). Bleaching and mortality of corals in the Great Barrier Reef have induced measurable ‘reef grief’, a type of solastalgia, among reef visitors and researchers ( [[#Conroy--2019|Conroy, 2019]] ; [[#Curnock--2019|Curnock et al., 2019]] ; [[#Marshall--2019|Marshall et al., 2019]] ). The mental health of people in Tuvalu ( [[#Gibson--2020|Gibson et al., 2020]] ), Alaska ( [[#Allen--2020|Allen, 2020]] ) and Honduras ( [[#Kent--2020|Kent and Brondo, 2020]] ) have suffered from both the experience of climate impacts on ocean and coastal ecosystems (e.g., SLR and changes in fisheries and wildlife), and the anticipation of more in the future. The climate-associated MHWs and harmful algal bloom events in 2014–2016 in the US Pacific Northwest ( [[#Moore--2019|Moore et al., 2019]] ) prevented seasonal razor clam harvests culturally important to Indigenous Peoples and the local community ( [[#3.5.5.3|Section 3.5.5.3]] ; [[#Crosman--2019|Crosman et al., 2019]] ). Sea level rise and storm-driven coastal erosion endanger coastal archaeological and heritage sites around the world ( ''very high confidence'' ) (Hoque and Hoque, 2008; [[#Carmichael--2018|Carmichael et al., 2018]] ; [[#Reimann--2018|Reimann et al., 2018]] ; [[#Elliott--2019|Elliott and Williams, 2019]] ; [[#Ravanelli--2019|Ravanelli et al., 2019]] ; [[#Anzidei--2020|Anzidei et al., 2020]] ; [[#Chemeli--2020|Chemeli et al., 2020]] ; [[#García%20Sánchez--2020|García Sánchez et al., 2020]] ; [[#Harkin--2020|Harkin et al., 2020]] ; [[#Hil--2020|Hil, 2020]] ; [[#Rivera-Collazo--2020|Rivera-Collazo, 2020]] ).

Disruptions in ocean and coastal ecosystem services partly attributable to climate change have also caused economic losses ( ''limited evidence, high agreement'' ). Water-quality deterioration over 24 years in a temperate bay in the USA due to nutrient enrichment and warming caused 0.08–0.67 million USD per decade in lost recreational shellfish revenues ( [[#Luk--2019|Luk et al., 2019]] ). In southwestern Florida, where nutrient enrichment, lake hydrology, and rainfall conditions control cyanobacterial HAB formation ( [[#Havens--2019|Havens et al., 2019]] ), toxic HAB events deterred visitors and recreation, leading to lodging and restaurant revenue losses ( [[#Bechard--2020|Bechard, 2020]] ), decreased domestic and international arrivals and overall visitor spending (a 99 million USD loss from August to October 2018; [[#Scanlon--2019|Scanlon, 2019]] ), and lost recreational spending from loss of boat-ramp access (a 3 million USD economic loss from June to September 2018; [[#Alvarez--2019|Alvarez et al., 2019]] ). In Cornwall, England, HABs from 2009 to 2016 disrupted residents’ sense of place, identity and well-being by interrupting recreational and economic activities, and by creating feelings of uncertainty and unease around the safety or dependability of future ocean-related activities ( [[#Willis--2018|Willis et al., 2018]] ). Increasingly abundant ''Sargassum'' spp. floating macroalgae from the central Atlantic Ocean and Caribbean Sea, whose proliferation has been attributed to high sea surface temperatures and nutrient enrichment ( [[#Wang--2019a|Wang et al., 2019a]] ), has substantially disrupted beach tourism in the Caribbean and Mexico and imposes millions of dollars of clean-up costs annually on affected beaches ( [[#Milledge--2016|Milledge and Harvey, 2016]] ).

Observed disruption of ocean and coastal cultural services by climate impacts, plus increasingly severe and widespread projected climate-change impacts on ocean and coastal ecosystems, imply that the risk to cultural ecosystem services will remain constant or even increase ( ''medium confidence'' ) (Figure 3.22; Table 3.26). Recent studies assert that cultural ecosystem services are at risk from climate change ( ''high confidence'' ) ( [[#Singh--2019a|Singh et al., 2019a]] ; [[#Koenigstein--2020|Koenigstein, 2020]] ). However, ''limited evidence'' and complex social–ecological interactions (e.g., [[#Ingram--2018|Ingram et al., 2018]] ) challenge development of specific projections. For instance, the little auk ( ''Alle alle'' ) in the North Water Polynya is traditionally harvested by Indigenous Inughuit for food and community-wide celebrations and seasonal activities, but harvests are threatened to an undetermined degree as the seabird competes for food with recovering bowhead whale ( ''Balaena mysticetus'' ) populations and northward range shifts of capelin ( ''Mallotus villosus'' ) due to warming ( [[#Mosbech--2018|Mosbech et al., 2018]] ). [[#3.6|Section 3.6]] assesses the cultural implications of implemented human adaptations.

<div id="3.6" class="h1-container"></div>

<span id="planned-adaptation-and-governance-to-achieve-the-sustainable-development-goals"></span>