Editing IPCC:AR6/WGII/Chapter-11 (section)

==== 11.3.2.1 Observed Impacts ====

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Climate change is having major impacts on the region’s oceans ( ''very high confidence'' ) (Table 11.6) ( [[#Law--2016|Law et al., 2016]] ; [[#Sutton--2019|Sutton and Bowen, 2019]] ). Rising sea surface temperatures (SSTs) have exacerbated marine heatwaves, notably near western Australia in 2011, the GBR in 2016, 2017 and 2020 and the Tasman Sea in 2015/2016, 2017/2018 and 2018/2019 (Table 11.2) ( [[#BoM%20and%20CSIRO--2018|BoM and]] [[#CSIRO--2018|CSIRO, 2018]] ; [[#AMS--2019|AMS, 2019]] ; [[#NIWA--2019|NIWA, 2019]] ; [[#Salinger--2019b|Salinger et al., 2019b]] ; [[#Sutton--2019|Sutton and Bowen, 2019]] ; [[#BoM--2020|BoM, 2020]] ; [[#Salinger--2020|Salinger et al., 2020]] ; [[#Oliver--2021|Oliver et al., 2021]] ). Temperature anomalies ranged from 1.2°C to 4.0°C and durations ranged from 90–250 days (Table 11.2).

'''Table 11.6 |''' Observed climate-change-related changes in the marine ecosystems of Australia and New Zealand. Climate-related impacts have been documented at a range of scales from single-species or region-specific studies to multi-species or community-level changes.

{| class="wikitable"
|-
! Type of change

! Examples

! Climate-related Pressure

! Source

|-
| colspan="4"| '''Australia'''

|-
| Reduced activity and increased energetic demands

| Coral trout ( ''Plectropomus leopardus'' ), one of Australia’s most important commercial and recreational tropical finfish species

| Increased temperature (experimental laboratory study) and ocean warming

| ( [[#Johansen--2014|Johansen et al., 2014]] ; [[#Scott--2017|Scott et al., 2017]] )

|-
| Estuaries warming and freshening

| Australian lagoons and rivers warming and decreasing pH at a faster rate than predicted by climate models

| Warming and reduction in rainfall (leading to reduced flows and therefore being less frequently open to the sea)

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

|-
| Changes in life-history traits, behaviour or recruitment

| Reduced size of Sydney rock oysters (for commercial sale)

| Limited capacity to bio mineralise under acidification conditions

| ( [[#Fitzer--2018|Fitzer et al., 2018]] )

|-
|
| Reduced growth in tiger flathead fish in equatorward range

| Ocean warming

| ( [[#Morrongiello--2015|Morrongiello and Thresher, 2015]] )

|-
|
| 55% of 335 fish species became smaller and 45% became larger as seas warmed around Australia

| Ocean warming (over three decades)

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

|-
|
| Rock lobster display reduced avoidance of predators at 23°C compared to 20°C

| Increased temperature (experimental laboratory study)

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

|-
|
| Analysis of stress rings in cores of corals from the GBR dating back to 1815 found that following bleaching events, the coral was less affected by subsequent marine heatwaves

| Heat events

| ( [[#DeCarlo--2019|DeCarlo et al., 2019]] )

|-
|
| Mortality and reductions in spawning stocks of fishery important abalone, prawns, rock lobsters

| 2011 marine heatwave

| ( [[#Caputi--2019|Caputi et al., 2019]] )

|-
|
| Recruitment of coral on GBR reduced to 11% of long-term average

| Warming-driven back-to-back global bleaching events

| ( [[#Hughes--2019b|Hughes et al., 2019b]] )

|-
|
| Green turtle hatchlings from southern GBR 65–69% female and hatchlings from northern GBR 100% female for last two decades

| Increased sand temperatures

| ( [[#Jensen--2018|Jensen et al., 2018]] )

|-
| New diseases, toxins

| First occurrence of virulent virus causing Pacific Oyster Mortality Syndrome (POMS), up to 90% of all farmed oysters died in impacted areas

| Detected during heatwave

| ( [[#de%20Kantzow--2017|de Kantzow et al., 2017]] )

|-
|
| Mussels, scallops, oysters, clams, abalone and rock lobsters on east coast of Tasmania found to have high levels of Paralytic Shellfish toxins, originating from a bloom of harmful ''Alexandrium tamarense''

| Warming and extension of the East Australian Current

| ( [[#Hallegraeff--2016|Hallegraeff and Bolch, 2016]] )

|-
|
| Range expansion of phytoplankton ''Noctiluca'' , which can be toxic

| Warming and extension of the East Australian Current

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

|-
|
| Mortality of fish following algal blooms in South Australia

| 2013 marine heatwave

| ( [[#Roberts--2019|Roberts et al., 2019]] )

|-
| Changes in species distributions

| Range extensions at the poleward range limit have been detected in: fish, cephalopods, crustaceans, nudibranchs, urchins, corals

| Ocean warming

| ( [[#Baird--2012|Baird et al., 2012]] ; [[#Robinson--2015|Robinson et al., 2015]] ; [[#Sunday--2015|Sunday et al., 2015]] ; [[#Ling--2018|Ling et al., 2018]] ; [[#Nimbs--2018|Nimbs and Smith, 2018]] ; [[#Ramos--2018|Ramos et al., 2018]] ; [[#Smith--2019|Smith et al., 2019]] ; [[#Caswell--2020|Caswell et al., 2020]] )

|-
|
| Contractions in range at the equatorward range edge have been detected in anemones, asteroids, gastropods, mussels, algae

| Ocean warming

| ( [[#Pitt--2010|Pitt et al., 2010]] ; [[#Poloczanska--2011|Poloczanska et al., 2011]] ; [[#Smale--2019|Smale et al., 2019]] )

|-
|
| Australia’s most southern dominant reef building coral, ''Plesiastrea versipora'' , in eastern Bass Strait, increasing in abundance at the poleward edge of the species’ range and in western Australia

| Ocean warming

| ( [[#Tuckett--2017|Tuckett et al., 2017]] ; [[#Ling--2018|Ling et al., 2018]] )

|-
|
| Southwestern Australia fish assemblages—warm-water fish increasing in density at poleward edge of distributions and cool-water species decreasing in density at equatorward edge of distributions; increase in warm-water habitat forming species leading to reduced habitat for invertebrate assemblages

| Combination of increased temperatures and changes in habitat-forming algal species

| ( [[#Shalders--2018|Shalders et al., 2018]] ; [[#Teagle--2018|Teagle et al., 2018]] )

|-
|
| Predicted reduction range of rare W ''ilsonia humilis'' herb in Tasmanian saltmarsh but no change in rest of community

| Wetter and drier climate

| ( [[#Prahalad--2019|Prahalad and Kirkpatrick, 2019]] )

|-
| Changes in abundance

| Shift towards a zooplankton community dominated by warm-water small copepods in southeast Australia

| Ocean warming

| ( [[#Kelly--2016|Kelly et al., 2016]] )

|-
|
| Diebacks of tidal wetland mangroves

| 2015–2016 heatwaves combined with moisture stress

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

|-
|
| Decline in giant kelp in Tasmania, Australia, less than 10% remaining; loss of kelp Australia-wide totalling at least 140,187 hectares

| Ocean warming and change in East Australian Current (lower nutrients)

| ( [[#Wahl--2015|Wahl et al., 2015]] ; [[#Butler--2020|Butler et al., 2020]] ; [[#Filbee-Dexter--2020|Filbee-Dexter and Wernberg, 2020]] )

|-
|
| Regional loss of seagrass in Shark Bay World Heritage Area, western Australia

| High air and water temperatures during 2011 heatwave

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

|-
|
| Increased annual dugong and inshore dolphin mortality across Queensland

| Sustained low air temperature and increased freshwater discharge during high Southern Oscillation Index (SOI) (ENSO) index

| ( [[#Meager--2014|Meager and Limpus, 2014]] )

|-
|
| Predicted equatorward decline and poleward shift of sea urchin in eastern Australia

| Ocean warming

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

|-
|
| Increasing mortality of Australian fur seal pups in low-lying colonies

| Storm surges and high tides amplified by ongoing SLR

| ( [[#McLean--2018|McLean et al., 2018]] ) (Box 11.6)

|-
| Rapid shifts in community composition, structure and integrity

| Community-wide tropicalisation in Australian temperate reef communities; temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of sub-tropical and tropical waters

| Extreme marine heatwaves led to 100-km range contraction of extensive kelp forests

| ( [[#Vergés--2016|Vergés et al., 2016]] ; [[#Wernberg--2016|Wernberg et al., 2016]] )

|-
|
| Ongoing declines in habitat-forming seaweeds

| Climate-driven shift of tropical herbivores

| ( [[#Thomson--2015|Thomson et al., 2015]] ; [[#Nowicki--2017|Nowicki et al., 2017]] ; [[#Zarco-Perello--2017|Zarco-Perello et al., 2017]] ; [[#Wernberg--2016|Wernberg et al., 2016]] )

|-
|
| Dieback of temperate seagrass in Shark Bay, Australia, subsequently replaced by tropical early successional seagrass with seagrass-associated megafauna (sea turtles) declining in health status

| 2011 marine heatwave

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

|-
|
| Increased herbivory by fish on tropicalised reefs of western Australia

| Change in species composition due to ocean warming

| ( [[#Zarco-Perello--2019|Zarco-Perello et al., 2019]] )

|-
|
| No recovery 2 years after coral bleaching and macroalgae mortality in western Australia

| 2011 marine heatwave

| ( [[#Bridge--2014|Bridge et al., 2014]] )

|-
|
| Mass mortality of particular coral species on affected reefs during heatwaves on GBR (Eastern Australia) led to altered coral reef structure and species composition 8 months later.

| 2016 marine heatwave

| ( [[#Hughes--2018c|Hughes et al., 2018c]] )

|-
|
| Community-wide restructuring along GBR 1 year after the 2016 mass bleaching event

| 2016 marine heatwave

| (Stuart- [[#Smith--2018|Smith et al., 2018]] )

|-
| colspan="4"| '''New Zealand'''

|-
| Changes in life-history

| Alteration of shell of pāua (black footed abalone, ''Haliotis iris'' ) under lowered pH (calcite layer thinner, greater etching of external shell surface)

| Lowered pH (experimental laboratory study)

| ( [[#Cummings--2019|Cummings et al., 2019]] )

|-
|
| Decline in maximum swimming performance of kingfish and snapper

| Elevated CO 2 (experimental laboratory study)

| ( [[#Watson--2018|Watson et al., 2018]] ; [[#McMahon--2020|McMahon et al., 2020]] )

|-
|
| Increased mortality and faster growth in juvenile kingfish

| Increased temperature

| ( [[#Watson--2018|Watson et al., 2018]] )

|-
|
| Earlier spawning of snapper in South Island

| 2017–2018 heatwave

| ( [[#Salinger--2019b|Salinger et al., 2019b]] )

|-
| Increase in mortality

| Heat stress mortality in salmon farms off Marlborough, New Zealand, where 20% of salmon stocks died

| 2017–2018 marine heatwave

| ( [[#Salinger--2019b|Salinger et al., 2019b]] )

|-
| Changes in species distributions

| Species increasingly caught further south (e.g., snapper and kingfish)

| Ocean warming and 2017–2018 marine heatwave

| ( [[#Salinger--2019b|Salinger et al., 2019b]] )

|-
|
| Non-breeding distribution of New Zealand nesting seabird (Antarctic prion) shifting south with long-term climate inferred from stable isotopes

| Climate warming

| ( [[#Grecian--2016|Grecian et al., 2016]] )

|-
|
| Less phytoplankton production in Tasman Sea but more on sub-tropical front

| Ocean warming

| ( [[#Chiswell--2020|Chiswell and Sutton, 2020]] )

|-
|
| Loss of bull kelp ( ''Durvillaea'' ) populations in southern New Zealand subsequently replaced by introduced kelp ''Undaria''

| 2017–2018 heatwave when sea and air temperatures exceeded 23°C and 30°C respectively

| ( [[#Salinger--2019b|Salinger et al., 2019b]] ; [[#Thomsen--2019|Thomsen et al., 2019]] ; [[#Salinger--2020|Salinger et al., 2020]] )

|}

Ocean carbon storage and acidification has led to decreased surface pH in the region (Table 11.2), including the sub-Antarctic waters off the East Coast of New Zealand’s South Island ( ''very high confidence'' ) ( [[#Law--2016|Law et al., 2016]] ). The depth of the Aragonite Saturation Horizon has shallowed by 50–100 m over much of New Zealand, which may limit and/or increase the energetic costs of growth of calcifying species ( ''low confidence'' ) ( [[#Anderson--2015|Anderson et al., 2015]] ; [[#Bostock--2015|Bostock et al., 2015]] ; [[#Mikaloff-Fletcher--2017|Mikaloff-Fletcher et al., 2017]] ).

In the estuaries of southwestern Australia, sustained warming and drying trends have caused dramatic declines in freshwater flows of up to 70% since the 1970s and increased frequency and severity of hypersaline conditions, enhanced water column stratification and hypoxia and reduced flushing and greater retention of nutrients ( [[#Hallett--2017|Hallett et al., 2017]] ).

Extensive changes in the life history and distribution of species have been observed in Australia’s ( ''very high confidence'' ) ( [[#Gervais--2021|Gervais et al., 2021]] ) and New Zealand’s marine systems ( ''medium confidence'' ) (Table 11.6) (Cross-Chapter box MOVING SPECIES in Chapter 5). New occurrences or increased prevalence of disease, toxins and viruses are evident ( [[#de%20Kantzow--2017|de Kantzow et al., 2017]] ; [[#Condie--2019|Condie et al., 2019]] ), along with heat stress mortalities and changes in community composition ( [[#Wernberg--2016|Wernberg et al., 2016]] ; [[#Zarco-Perello--2017|Zarco-Perello et al., 2017]] ; [[#Thomsen--2019|Thomsen et al., 2019]] ). Extreme climatic events in Australia from 2011 to 2017 led to abrupt and extensive mortality of key habitat-forming organisms — corals, kelps, seagrasses and mangroves — along over 45% of the continental coastline of Australia ( ''high confidence'' ) ( [[#Babcock--2019|Babcock et al., 2019]] ).

In 2016 and 2017, the GBR experienced consecutive occurrences of the most severe coral bleaching in recorded history ( ''very high confidence'' ) (Box 11.2), with shallow-water reef in the top two-thirds of the GBR affected and the severity of bleaching on individual reefs tightly correlated with the level of local heat exposure ( [[#Hughes--2018b|Hughes et al., 2018b]] ; [[#Hughes--2019c|Hughes et al., 2019c]] ). Mass mortality of corals from these two unprecedented events resulted in larval recruitment in 2018 declining by 89% compared to historical levels ( [[#Hughes--2019b|Hughes et al., 2019b]] ). southern reefs were also affected by warming, although significantly less than in the north ( [[#Kennedy--2018|Kennedy et al., 2018]] ). Coral reefs in Australia are at very high risk of continued negative effects on ecosystem structure and function ( ''very high confidence'' ) ( [[#Hughes--2019b|Hughes et al., 2019b]] ), cultural well-being ( ''very high confidence'' ) ( [[#Goldberg--2016|Goldberg et al., 2016]] ; [[#Lyons--2019|Lyons et al., 2019]] ), food provision ( ''medium confidence'' ) ( [[#Hoegh-Guldberg--2017|Hoegh-Guldberg et al., 2017]] ), coastal protection ( ''high confidence'' ) ( [[#Ferrario--2014|Ferrario et al., 2014]] ) and tourism ( ''high confidence'' ) ( [[#Deloitte%20Access%20Economics--2017|Deloitte Access Economics, 2017]] ; [[#Prideaux--2018|Prideaux and Pabel, 2018]] ; [[#GBRMPA--2019|GBRMPA, 2019]] ). If bleaching persists, an estimated 10,000 jobs and AUD$1 billion in revenue would be lost per year from declines in tourism alone ( [[#Swann--2016|Swann and Campbell, 2016]] ).

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