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

== 11.6 Key Risks and Benefits ==

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Nine key risks have been identified (Table 11.14) based on four criteria: magnitude, likelihood, timing and adaptive capacity (Chapter 16). Most of the key risks are similar to those in the IPCC AR5 Australasia chapter ( [[#Reisinger--2014|Reisinger et al., 2014]] ), but the emphasis here is on specific systems affected by multiple hazards rather than specific hazards affecting multiple systems. The selection of key risks reflects what has been observed, projected and documented, noting that there are gaps in knowledge, and a lack of knowledge does not imply a lack of risk (11.7.3.3). Key risks are grouped into four categories:

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====== Ecosystems at critical thresholds where recent climate change has caused significant damage and further climate change may cause irreversible damage, with limited scope for adaptation ======

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# 1. Loss and degradation of coral reefs in Australia and associated biodiversity and ecosystem service values due to ocean warming and marine heatwaves (11.3.2.1, 11.3.2.2, Box 11.2).
# 2. Loss of alpine biodiversity in Australia due to less snow (11.3.1.1, 11.3.1.2).

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====== Key risks that have potential to be severe but can be reduced substantially by rapid, large-scale and effective mitigation and adaptation ======

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# 3. Transition or collapse of alpine ash, snow gum woodland, pencil pine and northern jarrah forests in southern Australia due to hotter and drier conditions with more fires (11.3.1.1, 11.3.1.2)
# 4. Loss of kelp forests in southern Australia and southeast New Zealand due to ocean warming, marine heatwaves and overgrazing by climate-driven range extensions of herbivore fish and urchins (11.3.2.1, 11.3.2.2).
# 5. Loss of natural and human systems in low-lying coastal areas due to sea level rise (SLR) (11.3.5, Box 11.6).
# 6. Disruption and decline in agricultural production and increased stress in rural communities in southwestern, southern and eastern mainland Australia due to hotter and drier conditions (11.3.4, 11.3.5, Box 11.3).
# 7. Increase in heat-related mortality and morbidity for people and wildlife in Australia due to heatwaves (11.3.5.1, 11.3.5.2, 11.3.6.1, 11.3.6.2).

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====== Key cross-sectoral and system-wide risk ======

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# 8. Cascading, compounding and aggregate impacts on cities, settlements, infrastructure, supply chains and services due to wildfires, floods, droughts, heatwaves, storms and sea level rise (SLR) (11.5.1.1, 11.5.1.2, Box 11.1, Box 11.4, Box 11.6).

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====== Key implementation risk ======

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# 9. Inability of institutions and governance systems to manage climate risks (11.5; 11.7.1, 11.7.2, 11.7.3).

At higher levels of global warming, adaptation costs increase, options become limited and risks grow. The ‘burning embers’ diagram in Figure 11.6 has four IPCC risk categories: undetectable, moderate, high and very high, with transition points defined by different global warming ranges. The embers are indicative, based on an assessment of available literature and expert judgement (Supplementary Material SM 11.2). Outcomes for low and moderate adaptation have been compared, with the latter including both incremental and transformative options. Illustrative examples of adaptation pathways are shown in Figure 11.7 for low-lying coastal areas and Figure 11.8 for heat-related mortality. These figures highlight thresholds at which adaptation options become ineffective and possible combinations of strategies and options implemented at different times to manage emerging risks and changing risk profiles.

''Caveats:'' (a) key risks are assessed at regional scales, so they do not include other risks for finer scales or specific groups; (b) non-climatic vulnerabilities are held constant for simplicity; (c) the assessment of risk ratings at different levels of global warming is limited by available literature; (d) risks increase with global warming, despite the lack of an IPCC risk rating beyond ''very high'' ; and (e) the feasibility and effectiveness of adaptations options were not assessed due to limited literature (11.7.3.3).

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[[File:a739de97f55c31bdc1a75839b0dd707c IPCC_AR6_WGII_Figure_11_007.png]]

'''Figure 11.7 |''' '''Illustrative adaptation pathway for risk to natural and human systems in low-lying coastal areas due to sea level rise.'''

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[[File:6a005a0dc669bba1c62d22699083838f IPCC_AR6_WGII_Figure_11_008.png]]

'''Figure 11.8 |''' '''Illustrative adaptation pathway for risk of heat-related mortality and morbidity for people and wildlife in Australia due to heatwaves.'''

The New Zealand National Climate Change Risk Assessment ( [[#MfE--2020a|MfE, 2020a]] ) identified the priority risks from climate change for New Zealand based on a literature review and expert elicitation. The top two risks in each of five domains are as follows:

# ''Natural environment''
## risks to coastal ecosystems due to ongoing sea level rise (SLR) and extreme weather events
## risks to indigenous ecosystems and species from invasive species
# ''Human environment''
## risks to social cohesion and community well-being from displacement of people
## risks of exacerbating existing inequities and creating new and additional inequities from distribution impacts
# ''Economy''
## risks to governments from economic costs associated with lost productivity, disaster relief expenditure and unfunded contingent liabilities
## risks to the financial system from instability
# ''Built environment''
## risk to potable water supplies due to changes in rainfall, temperature, drought, extreme weather events and ongoing sea level rise (SLR)
## risks to buildings due to extreme weather events, drought, increased fire weather and ongoing sea level rise (SLR)
# ''Governance''
## risk of maladaptation due to practices, processes and tools that do not account for uncertainty and change over long time frames
## risk that climate change impacts across all domains will be exacerbated, because current institutional arrangements are not fit for adaptation

Not all of these risks feature as key risks for the wider Australasia region; nonetheless, they are reflected across [https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-11 Chapter 11] and remain priorities for New Zealand to address through the National Adaptation Plan, its implementation and monitoring.

Short-term benefits from climate change may include reduced winter mortality, reduced energy demand for winter heating, increased agriculture productivity and forest growth in south and west New Zealand and increased forest and pasture growth in southern Australia, except where rainfall and soil nutrients are limiting (11.3.4, 11.3.6, 11.3.10) ( ''medium confidence'' ).

'''Table 11.14 |''' Key risks from climate change based on assessment of the literature and expert judgement (Supplementary Material SM 11.2). Assessment criteria are magnitude, timing, likelihood and adaptive capacity. Risk drivers are hazards, exposure and vulnerability. Adaptation options describe ways in which risks can be reduced. Confidence ratings are based on the amount of evidence and agreement between lines of evidence.

{| class="wikitable"
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! Key risk

( ''confidence rating'' ) (Chapter reference)

! Consequences influenced by hazards, exposure, vulnerability and adaptation options

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| 1. Loss and degradation of tropical shallow coral reefs and associated biodiversity and ecosystem service values in Australia due to ocean warming and marine heatwaves

( ''very high confidence'' )

(11.3.2, Box 11.2)

| Consequences: Widespread destruction of coral reef ecosystems and dependent socio-ecological systems. Three mass bleaching events from 2016 to 2020 have already caused significant loss of corals in shallow-water habitats across the GBR. Globally, bleaching is projected to occur twice each decade from 2035 and annually after 2044 under RCP 8.5 and annually after 2051 under RCP4.5. A 3°C global warming could cause over six times the 2016 level of thermal stress.

Hazards '':'' Increase in background warming and marine heatwave events degrade reef-building corals by triggering coral bleaching events at a frequency greater than the recovery time. Fish populations also decline during and following heatwave events.

Exposure: Increasing geographic area affected by rate and severity of ocean warming

Vulnerability: Vulnerability to increases in sea temperature is already very high because of other stressors on the ecosystem, including sediment, pollutants and overfishing.

Adaptation options: Minimising other stressors. Efforts on the GBR may slow the impacts of climate change in small sections or reduce short-term socioeconomic ramifications, but they will not prevent widespread bleaching.

|-
| 2. Loss of alpine biodiversity in Australia due to less snow

( ''high confidence'' )

(11.3.1, Table 11.2, Table 11.3, Table 11.4, Table 11.5)

| Consequences : Loss of endemic and obligate alpine wildlife species and plant communities (feldmark and short alpine herb fields) as well as increased stress on snow-dependent plant and animal species.

Hazards : Projected decline in annual maximum snow depth by 2050 is 30–70% (low emissions) and 45–90% (high emissions); projected increases in temperature and decreases in precipitation.

Exposure : Alpine species face elevation squeeze due to lack of nival zone, and alpine environments have restricted geographic extent.

Vulnerability : Narrow ecological niche of species including snow-related habitat requirements; encroachment from sub-Alpine woody shrubs; vulnerability generated by non-climatic stressors including weeds and feral animals, especially horses

Adaptation options : Reducing pressure on alpine biodiversity from land uses that degrade vegetation and ecological condition, along with weed and pest management.

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| 3. Transition or collapse of alpine ash, snow gum woodland, pencil pine and northern jarrah forests in southern Australia due to hotter and drier conditions with more fires

( ''high confidence'' )

(11.2, 11.3.1, 11.3.2, Box 11.1)

| Consequences : If regenerative capacities of the dominant (framework) canopy tree species are exceeded, a long-lasting or irreversible transition to a new ecosystem state is projected with loss of characteristic and framework species, including loss of some narrow-range endemics.

Hazards : Hotter and drier conditions have increased extreme fire weather risk since 1950, especially in southern and eastern Australia. The number of severe fire weather days is projected to increase 5–35% (RCP2.6) and 10–70% (RCP8.5) by 2050

Exposure : Shift in landscape fire regimes to larger, more intense and frequent wildfires over extensive areas (~10 million hectares) of forests and woodlands from longer fire seasons and more hazardous fire conditions and increasing human-sourced ignitions from urbanisation and projected increase in frequency of lightning strikes

Vulnerability : The resilience and adaptive capacity of the forests is being reduced by ongoing land clearing and degrading land management practices

Adaptation options : Increased capacity to extinguish wildfires during extreme fire weather conditions; avoiding and reducing forest degradation from inappropriate forest management practices and land use.

|-
| 4. Loss of kelp forests in southern Australia and southeast New Zealand due to ocean warming, marine heatwaves and overgrazing by climate-driven range extensions of herbivore fish and urchins

( ''high confidence'' )

(11.3.2)

| Consequences : Observed decline in giant kelp in Tasmania since 1990, with less than 10% remaining by 2011 due to ocean warming. Extensive loss of kelp, −140,187 hectares across Australia, loss of bull kelp in southern New Zealand, replaced by the introduced kelp following the 2017/2018 marine heatwave. Further loss of native kelp is projected with warming oceans.

Hazards : Ocean warming and marine heatwave events

Exposure : Coastal waters around Australia and New Zealand

Vulnerability : Giant kelp are already federally listed in Australia as an endangered marine community type. In Australia, kelp forests are vulnerable to nutrient-poor East Australian Current waters pushing further south, warming waters and increased herbivory from range-extending species.

Adaptation options : Minimising other stressors, local restoration and transplantation of heat-tolerant phenotypes.

|-
| 5. Loss of human and natural systems in low-lying coastal areas from ongoing SLR

( ''high confidence'' )

(11.2, 11.3.2, 11.3.5, 11.3.10, 11.4, Table 11.3; Box 11.6)

| Consequences : Nuisance and extreme coastal flooding are already occurring due to SLR. For 0.2- to 0.3-m SLR, coastal flooding is projected to become more frequent, for example, the current 1-in-100-year flood would occur every year in Wellington and Christchurch. For 0.5-m SLR, the value of buildings in New Zealand exposed to coastal inundation could increase by NZD$12.75 billion and the current 1-in-100-year flood in Australia could occur several times a year. For 1.0-m SLR, the value of exposed assets in New Zealand would be NZD$25.5 billion. For 1.1-m SLR, the value of exposed assets in Australia would be AUD$164–226 billion. This would be associated with the displacement of people, disruption and reduced social cohesion, degraded ecosystems, loss of cultural heritage and livelihoods and loss of traditional lands and sacred sites.

Hazards : Rising sea level (0.2–0.3 m by 2050, 0.4–0.7 m by 2090), storm surges, rising groundwater tables.

Exposure : Population growth, new and infill urbanisation, tourism developments in low-lying coastal areas. Buildings, roads, railways, electricity and water infrastructure. Torres Strait Island and remote Māori communities are particularly exposed and sensitive.

Vulnerability : Ineffective planning regulations, reduced availability and increased cost of insurance and costs to governments as insurers of last resort. Inadequate investment in avoidance and preparedness exacerbating underlying social vulnerabilities. Financial and physical capacities to cope and adapt are uneven across populations, creating equity issues.

Adaptation options : Risk reduction coordinated across all levels of government with communities. Statutory planning frameworks, decision tools and funding mechanisms that can address the changing risk. Planning and land use decisions, including managed retreat where it is inevitable. Improved capacity of emergency services, early-warning systems, improved planning and regulatory practice and building and infrastructure design standards. Options that anticipate risk and adjust as conditions change.

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| 6. Disruption and decline in agricultural production and increased stress in rural communities across south western, southern and eastern mainland Australia due to hotter and drier conditions.

( ''high confidence'' )

(11.2, 11.3.4, 11.3.6.3, 11.4.1, Table 11.11, Boxes 11.1, 11.3)

| Consequences : Projected decline in crop, horticulture and dairy production, for example, decline in median wheat yields by 2050 of up to 30% in southwest Australia and up to 15% in southern Australia. Increased heat stress in livestock by 31–42 days per year by 2050. Reduced winter chilling for horticulture. Increased smoke impacts for viticulture. Flow-on effects for agricultural supply chains, farming families and rural communities across southwestern, southern and southeastern Australia, including the MDB.

Hazards : Hotter and drier conditions with constraints on water resources and more frequent and severe droughts in southwestern, southern and eastern Australia.

Exposure : Across southwestern, southern and eastern Australia, many production regions are exposed, including the MDB, which supports agriculture worth AUD$24 billion/year, 2.6 million people in diverse rural communities and important environmental assets containing 16 Ramsar Convention-listed wetlands.

Vulnerability : Existing financial, social, health and environmental pressures on rural, regional and remote communities. Existing competition for water resources among communities, industries and environment and uncertainty about sharing of water under a drying climate.

Adaptation options : Improved governance and collaboration to build rural resilience, including regional and basin-scale initiatives. Improved water policies and initiatives (e.g., MDB plan) and changes in management and technologies. Resilience-focused planning for rural settlements, land use, industry, infrastructure and value chains. Adoption of information, tools and methods to better manage uncertainty, variability and change. Incremental changes in farm management practices (e.g., stubble retention, weed control, water-use efficiency, sowing dates, cultivars). In some regions, major changes may be necessary, for example, diversification in agricultural enterprises, transition to different land uses (e.g., carbon sequestration, renewable energy production, biodiversity conservation) or migration to another area. Flows in waterways based on Indigenous knowledge to protect cultural assets.

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| 7. Increase in heat-related mortality and morbidity for people and wildlife in Australia

( ''high confidence'' )

(11.2, 11.3.1, 11.3.5, 11.3.6, 11.4)

| Consequences : During 1987–2016, natural disasters caused 971 deaths and 4370 injuries, with more than 50% due to heatwaves. Annual increases are projected for excess deaths, additional hospitalisations and ambulance callouts. Heatwave-related excess deaths in Melbourne, Sydney and Brisbane are projected to increase by about 300/year (RCP2.6) to 600/year (RCP8.5) during 2031–2080 relative to 142/year during 1971–2020, assuming no adaptation. Significant heat-related mortality of wildlife species (flying foxes, freshwater fish) has been observed and is projected to increase.

Hazards : Increased frequency, intensity and duration of extreme heat events

Exposure : Pervasive but differentially affecting some wildlife species depending on their thermal tolerances and occupational groups (e.g., outdoor workers) and those living in high exposure areas (e.g., urban heat islands). Health risks multiply with other harmful exposures, for example, to wildfire smoke.

Vulnerability : Lower adaptive capacity for young/old/sick people, those in low-quality housing and of lower socioeconomic status, and areas served by fragile utilities (power, water). Remote locations with extreme heat and inadequate cooling in housing infrastructure (such as remote indigenous communities). For wildlife, impacts of extreme heat events are being amplified by habitat loss and degradation.

Adaptation options : Urban cooling interventions including irrigated green infrastructure and increased albedo, education to reduce heat stress, heatwave/fire early-warning systems, battery/generator systems for energy system security, building standards that improve insulation/cooling, accessible / well-resourced primary health care. For wildlife, removing human stressors, reducing pressures from ferals and weeds, and ensuring suitable habitat.

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| 8. Cascading, compounding and aggregate impacts on cities, settlements, infrastructure, supply chains and services due to extreme events

( ''high confidence'' )

(11.2, 11.3.4, 11.3.5, 11.3.6, 11.3.7, 11.3.8, 11.3.9, 11.3.10, 11.4, 11.5.1, Boxes 11.1, 11.4, 11.6)

| Consequences : Widespread and pervasive damage and disruption to human activities generated by the interdependencies and interconnectedness of physical, social and natural systems. Examples include failure of transport, energy and communication infrastructure and services, heat stress, injuries and deaths, air pollution, stress on hospital services, damage to agriculture and tourism, insurance loss from heatwaves and fires; failure of transport, stormwater and flood-control infrastructure and services from floods and storms; water restrictions, reduced agricultural production, stress for rural communities, mental health issues, lack of potable water from droughts; damage to buildings, roads, railways, electricity and water infrastructure, loss of assets and lives, displacement of people, reduced social cohesion, degraded ecosystems from extreme SLR. Large aggregate costs due to lost productivity and major disaster relief expenditures, creating unfunded liabilities and supply chain disruption, e.g., 2019–2020 Australian fires cost AUD$8 billion. The long-run impact of a 1°C, 2°C or 3°C global warming (relative to 1986–2005) on Australian GDP is estimated at −0.3%/year, −0.6%/year and −1.1%/year respectively, while for New Zealand estimates are −0.1%/year, −0.4%/year and −0.8%/year respectively. Impacts on Māori tribal investments in forestry, agriculture, horticulture, fisheries and aquaculture.

Hazards : Heatwaves, droughts, fires, floods, storms and SLR. This includes cascading and compound events such as heatwaves with fires, storms with floods or droughts followed by heavy rainfall and extreme sea levels.

Exposure : Highly populated areas, rural and remote settlements, traditional lands and sacred sites. Greater urban density and population growth increases exposure in high-risk areas. Different exposure for different hazards, for example, heatwaves: urban and peri-urban areas; fire: peri-urban areas and settlements near forests; floods: people, property and infrastructure from pluvial floods in cities and settlements and fluvial floods on floodplains; storms: buildings and infrastructure in cities and settlements.

Vulnerability : Existing social and economic challenges (e.g., those caused by COVID-19) and socioeconomic and cultural inequalities; competing resource and land use demands across sectors; inadequate planning, policy, governance, decision-making and disaster resilience capacity; and non-climatic stresses on ecosystems. Vulnerabilities generated by interdependencies and interconnectedness of physical, social and natural systems.

Adaptation options : Flexible and timely adaptation strategies that prepare socioeconomic and natural systems for surprises and unexpected threats. Multi-sector coordinated actions that address widespread impacts, redress existing vulnerabilities and building adaptive capacity and systemic resilience. Improved coordination between and within levels of governments, communities and private sector. Greater use of dynamic decision frameworks and suitable economic and social assessment tools. Improved emergency services and early-warning systems; use of climate-resilient standards for buildings and infrastructure. Transformational adaptations (e.g., managed retreat) that can be planned in stages.

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| 9. Inability of institutions and governance systems to manage climate risks

( ''high confidence'' )

(11.2, 11.3.5, 11.3.6, 11.3.7, 11.3.8, 11.3.10, 11.4, 11.5.1, 11.7.2, Boxes 11.1–11.6)

| Consequences : Climate hazards overwhelm the capacity of institutions, organisations, systems and leaders to provide necessary policies, services, resources, coordination and leadership. Failed adaptation at the institutional and governance levels has widespread, pervasive impacts on all areas of society. This includes a reliance on reactive, short-term decision-making that locks in existing exposures, leaves perverse incentives and interconnected and systemic impacts unaddressed and generates high costs and fiscal impacts. This worsens vulnerability and leads to maladaptation, inequities and injustices within and across generations, as well as actions that do not uphold the rights, interests, values and practices of Indigenous Peoples. Resultant failure to take adaptation action generates litigation risk.

Hazards : Increasing frequency, duration, severity and complexity of extreme weather events, droughts and SLR

Exposure : All sectors, communities, organisations and governments

Vulnerability : Fragmented institutional and legal arrangements, under-resourcing of services, lack of dedicated adaptation funding instruments and resources to support communities and local government, uneven capability to manage uncertainty and conflicting values and competing policy and political interests.

Adaptation options : Pre-emptive options that avoid and reduce risks. Redesign of policy and statutory frameworks and funding instruments for addressing changing risks and uncertainties that enable just and collaborative governance across scales and domains. Addressing existing vulnerabilities and capacity, capability and leadership deficits within and across all levels of government, all sectors, Indigenous Peoples and communities. Risk and vulnerability assessment methodologies and decision-making tools that build resilience and address changing risks and vulnerabilities. Co-designed adaptation approaches implemented with communities, including Māori tribal organisations and Australian Aboriginal and Torres Strait Island peoples.

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