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

===== Observations: vulnerabilities and impacts =====

<div id="h4-1-siblings" class="h4-siblings"></div>

'''Anthropogenic climate change has exposed ocean and coastal ecosystems to conditions that are unprecedented over millennia (''' '''''high confidence''''' [[#footnote-005|2]] '''), and this has greatly impacted life in the ocean and along its coasts (''' '''''very high confidence''''' ''').''' Fundamental changes in the physical and chemical characteristics of the ocean acting individually and together are changing the timing of seasonal activities ( ''very high confidence'' ), distribution ( ''very high confidence'' ) and abundance ( ''very high confidence'' ) of oceanic and coastal organisms, from microbes to mammals and from individuals to ecosystems, in every region. Evidence of these changes is apparent from multi-decadal observations, laboratory studies and mesocosms, as well as meta-analyses of published data. Geographic range shifts of marine species generally follow the pace and direction of climate warming ( ''high confidence'' ): surface warming since the 1950s has shifted marine taxa and communities poleward at an average (mean ± ''very likely'' [[#footnote-004|3]] range) of 59.2 ± 15.5 km per decade ( ''high confidence'' ), with substantial variation in responses among taxa and regions. Seasonal events occur 4.3 ± 1.8 d to 7.5 ± 1.5 d earlier per decade among planktonic organisms ( ''very high confidence'' ) and on average 3 ± 2.1 d earlier per decade for fish ( ''very high confidence'' ). Warming, acidification and deoxygenation are altering ecological communities by increasing the spread of physiologically suboptimal conditions for many marine fish and invertebrates ( ''medium confidence'' ). These and other responses have subsequently driven habitat loss ( ''very high confidence'' ), population declines ( ''high confidence'' ), increased risks of species extirpations and extinctions ( ''medium confidence'' ) and rearrangement of marine food webs ( ''medium to high confidence'' , depending on ecosystem). {3.2, 3.3, 3.3.2, 3.3.3, 3.3.3.2, 3.4.2.1, 3.4.2.3–3.4.2.8, 3.4.2.10, 3.4.3.1, 3.4.3.2, 3.4.3.3, Box 3.2}

'''Marine heatwaves lasting weeks to several months are exposing species and ecosystems to environmental conditions beyond their tolerance and acclimation limits (''' '''''very high confidence''''' ''').''' WGI AR6 concluded that marine heatwaves are more frequent ( ''high confidence'' ), more intense and longer ( ''medium confidence'' ) since the 1980s, and since at least 2006 ''very likely'' attributable to anthropogenic climate change. Open-ocean, coastal and shelf-sea ecosystems, including coral reefs, rocky shores, kelp forests, seagrasses, mangroves, the Arctic Ocean and semi-enclosed seas, have recently undergone mass mortalities from marine heatwaves ( ''very high confidence'' ). Marine heatwaves, including well-documented events along the west coast of North America (2013–2016) and east coast of Australia (2015–2016, 2016–2017 and 2020), drive abrupt shifts in community composition that may persist for years ( ''very high confidence'' ), with associated biodiversity loss ( ''very high confidence'' ), collapse of regional fisheries and aquaculture ( ''high confidence'' ) and reduced capacity of habitat-forming species to protect shorelines ( ''high confidence'' ). {WGI AR6 Chapter 9, 3.2.2.1, 3.4.2.1–3.4.2.5, 3.4.2.7, 3.4.2.10, 3.4.2.3, 3.4.3.3.3, 3.5.3}

'''At local to regional scales, climate change worsens the impacts on marine life of non-climate anthropogenic drivers, such as habitat degradation, marine pollution, overfishing and overharvesting, nutrient enrichment and introduction of non-indigenous species (''' '''''very high confidence''''' ''').''' Although impacts of multiple climate and non-climate drivers can be beneficial or neutral to marine life, most are detrimental ( ''high confidence'' ). Warming exacerbates coastal eutrophication and associated hypoxia, causing ‘dead zones’ ( ''very high confidence'' ), which drive severe impacts on coastal and shelf-sea ecosystems ( ''very high confidence'' ), including mass mortalities, habitat reduction and fisheries disruptions ( ''medium confidence'' ). Overfishing exacerbates effects of multiple climate-induced drivers on predators at the top of the marine food chain ( ''medium confidence'' ). Urbanisation and associated changes in freshwater and sediment dynamics increase the vulnerability of coastal ecosystems like sandy beaches, salt marshes and mangrove forests to sea level rise and changes in wave energy ( ''very high confidence'' ). Although these non-climate drivers confound attribution of impacts to climate change, adaptive, inclusive and evidence-based management reduces the cumulative pressure on ocean and coastal ecosystems, which will decrease their vulnerability to climate change ( ''high confidence'' ). {3.3, 3.3.3, 3.4.2.4–3.4.2.8, 3.4.3.4, 3.5.3, 3.6.2, Cross-Chapter Box SLR in Chapter 3}

'''Climate-driven impacts on ocean and coastal environments have caused measurable changes in specific industries, economic losses, emotional harm and altered cultural and recreational activities around the world (''' '''''high confidence''''' ''').''' Climate-driven movement of fish stocks is causing commercial, small-scale, artisanal and recreational fishing activities to shift poleward and diversify harvests ( ''high confidence'' ). Climate change is increasing the geographic spread and risk of marine-borne pathogens like ''Vibrio'' sp. ( ''very high confidence'' ), which endanger human health and decrease provisioning and cultural ecosystem services ( ''high confidence'' ). Interacting climate-induced drivers and non-climate drivers are enhancing movement and bioaccumulation of toxins and contaminants into marine food webs ( ''medium evidence, high agreement'' ), and increasing salinity of coastal waters, aquifers and soils ( ''very high confidence'' ), which endangers human health ( ''very high confidence'' ). Combined climate-induced drivers and non-climate drivers also expose densely populated coastal zones to flooding ( ''high confidence'' ) and decrease physical protection of people, property and culturally important sites ( ''very high confidence'' ). {3.4.2.10, 3.5.3, 3.5.5, 3.5.5.3, 3.5.6, Cross-Chapter Box SLR in Chapter 3}

<div id="Projections:" class="h4-container"></div>

<span id="projections-vulnerabilities-risks-and-impacts"></span>