Editing IPCC:AR6/WGII/Chapter-13 (section)

==== 13.4.1.1 Observed Impacts ====

<div id="h3-9-siblings" class="h3-siblings"></div>

Warming continues to be the key climate hazard for European seas (Figure 13.1). Interacting with other climatic and non-climatic drivers, it has detectable and attributable impacts at a wide range of biological and ecological organisational levels (Figure 13.11).

<div id="_idContainer037" class="Figure"></div>

[[File:23c8ea629db1257572940528be9203c7 IPCC_AR6_WGII_Figure_13_011.png]]

'''Figure 13.11 |''' '''Major impacts and risks for marine and coastal ecosystems in Europe for observed and projected 1''' '''.''' '''5°C and 3.0°C GWL''' (Table SM13.4)

Particularly habitat loss in shallow coastal waters and at the coasts themselves, and northward distribution shifts of populations and communities, are evident across all European marine sub-regions ( ''high confidence'' ) (Figure 13.11; Chapter 3). Marine heatwaves have had severe ecological impacts in SEUS ( ''high confidence'' ) (Cross-Chapter Paper 4), threatening sessile benthic biotas and coastal habitats ( [[#Munari--2011|Munari, 2011]] ; [[#Kersting--2013|Kersting et al., 2013]] ; [[#Rivetti--2014|Rivetti et al., 2014]] ; [[#Garrabou--2019|Garrabou et al., 2019]] ). Range contractions, extirpations ( ''medium confidence'' ) ( [[#Smale--2020|Smale, 2020]] ) and species redistributions have been observed ( ''high confidence'' ) in TEUS ( [[#Cottier-Cook--2017|Cottier-Cook et al., 2017]] ) and SEUS ( [[#Castellanos-Galindo--2020|Castellanos-Galindo et al., 2020]] ). Habitat losses, range shifts, species invasions and species thermal preferences have altered community compositions ( [[#Vasilakopoulos--2017|Vasilakopoulos et al., 2017]] ), resulting in the ‘subtropicalisation’ of TEUS and ‘tropicalisation’ of SEUS (Chapter 3; Cross-Chapter Paper 4) and temperature-dependent timing of abundance and reproduction cycles ( [[#Hjerne--2019|Hjerne et al., 2019]] ; [[#Polte--2021|Polte et al., 2021]] ; [[#Uriarte--2021|Uriarte et al., 2021]] ).

Reductions in growth and reproductive success of calcifying species are not yet unambiguously detected and attributed in European seas ( ''medium confidence'' ) (Figure 13.11), as many show resilience ( [[#Kroeker--2010|Kroeker et al., 2010]] ; [[#Wall--2015|Wall et al., 2015]] ). However, fish population sizes are shrinking ( [[#Queirós--2018|Queirós et al., 2018]] ; [[#Ikpewe--2021|Ikpewe et al., 2021]] ), and growth, reproduction and recruitment are negatively impacted ( [[#Lindegren--2018|Lindegren et al., 2018]] ; [[#Goldberg--2019|Goldberg et al., 2019]] ; [[#Hidalgo--2019|Hidalgo et al., 2019]] ; [[#Vieira--2019|Vieira et al., 2019]] ; [[#Denechaud--2020|Denechaud et al., 2020]] ; [[#Maynou--2020|Maynou et al., 2020]] ; [[#Polte--2021|Polte et al., 2021]] ), though positive effects also occur ( [[#Sguotti--2019|Sguotti et al., 2019]] ; [[#Tanner--2019|Tanner et al., 2019]] ). Biodiversity changes depend on region, habitat and taxon ( ''medium confidence'' ) (Figure 13.11) overall resulting in the redistribution of biodiversity in Europe ( [[#García%20Molinos--2016|García Molinos et al., 2016]] ), and biodiversity declines in some sub-regions ( ''high confidence'' ) ( [[#IPBES--2018|IPBES, 2018]] ).

Biological and ecological impacts have cascading effects for marine ecosystem functioning ( [[#Chivers--2017|Chivers et al., 2017]] ; [[#Baird--2019|Baird et al., 2019]] ) and biogeochemical cycling ( [[#Huete-Stauffer--2011|Huete-Stauffer et al., 2011]] ; [[#Munari--2011|Munari, 2011]] ; [[#Kersting--2013|Kersting et al., 2013]] ; [[#Rivetti--2014|Rivetti et al., 2014]] ; [[#Garrabou--2019|Garrabou et al., 2019]] ). In TEUS, increased water-column stratification ( [[#13.1|Section 13.1]] ) and decreasing eutrophication, result in reduced primary production ( ''high confidence'' ) (Figure 13.11; [[#Capuzzo--2018|Capuzzo et al., 2018]] ) and productivity at higher trophic levels ( ''high confidence'' ) ( [[#Free--2019|Free et al., 2019]] ), while in NEUS sea ice decline has resulted in primary production increase by 40–60% ( ''high confidence'' ) (Figure 13.11; [[#Arrigo--2015|Arrigo and van Dijken, 2015]] ; [[#Borsheim--2017|Borsheim, 2017]] ; [[#Lewis--2020|Lewis et al., 2020]] ). Climate-related deoxygenation impacts are small in most European waters ( ''medium confidence'' ) (Figure 13.11), expect for semi-enclosed seas such as the Baltic and Black seas ( [[#Frolov--2014|Frolov et al., 2014]] ; [[#Jacob--2014|Jacob et al., 2014]] ; [[#Reusch--2018|Reusch et al., 2018]] ). Here warming and eutrophication have altered ecosystem functioning ( ''high confidence'' ), reduced potential fish yield and increased harmful algal blooms ( [[#Alekseev--2014|Alekseev et al., 2014]] ; [[#Carstensen--2014|Carstensen et al., 2014]] ; [[#Berdalet--2017|Berdalet et al., 2017]] ; [[#Daskalov--2017|Daskalov et al., 2017]] ; [[#Riebesell--2018|Riebesell et al., 2018]] ; [[#Stanev--2018|Stanev et al., 2018]] ) along with the risks of ''Vibrio'' pathogens and vibriosis ( [[#13.7.1|Section 13.7.1]] ; [[#Baker-Austin--2017|Baker-Austin et al., 2017]] ; [[#Semenza--2017|Semenza et al., 2017]] ). Across all European seas there is only ''low confidence'' of a consistent change in provisioning ecosystem services (e.g., fishing yields) ( [[#13.5|Section 13.5]] ), because of inter-regional variability, but ''high confidence'' in the decrease in regulating services and coastal protection because of the cascading effects of ecosystem impacts (Figure 13.11).

<div id="13.4.1.2" class="h3-container"></div>

<span id="projected-risks"></span>