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

=== 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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