The Australia/New Zealand region spans the tropics to mid-latitudes and has varied climates and ecosystems, including deserts, rainforests, coral reefs, and alpine areas. The climate is strongly influenced by the surrounding oceans. Australia has significant vulnerability to the drying trend projected over much of the country for the next 50-100 years (Figure TS-3) because substantial agricultural areas currently are adversely affected by periodic droughts, and there already are large areas of arid and semi-arid land. New Zealand—a smaller, more mountainous country with a generally more temperate, maritime climate—may be more resilient to climate changes than Australia, although considerable vulnerability remains (medium confidence). Table TS-9 shows key vulnerabilities and adaptability to climate change impacts for Australia and New Zealand. [12.9.5]

Table TS-9: Main areas of vulnerability and adaptability to climate change impacts in Australia and New Zealand. Degree of confidence that tabulated impacts will occur is indicated by stars in second column (see Section 1.4 of Technical Summary for key to confidence-level rankings). Confidence levels, and assessments of vulnerability and adaptability, are based on information reviewed in Chapter 12, and assume continuation of present population and investment growth patterns.
Sector	Impact	Vulnerability	Adaptation	Adaptability	Section
Hydrology and water supply	- Irrigation and metropolitan supply constraints, and increased salinization—****	High in some areas	- Planning, water allocation, and pricing	Medium	12.3.1, 12.3.2
	- Saltwater intrusion into some island and coastal aquifers—****	High in limited areas	- Alternative water supplies, retreat	Low	12.3.3
Terrestrial ecosystems	- Increased salinization of dryland farms and some streams (Australia)—***	High	- Changes in land-use practices	Low	12.3.3
	- Biodiversity loss notably in fragmented regions, Australian alpine areas, and southwest of WA—****	Medium to high in some areas	- Landscape management; little possible in alpine areas	Medium to low	12.4.2, 12.4.4, 12.4.8
	- Increased risk of fires—***	Medium	- Land management, fire protection	Medium	12.1.5.3, 12.5.4, 12.5.10
	- Weed invasion—***	Medium	- Landscape management	Medium	12.4.3
Aquatic ecosystems	- Salinization of some coastal freshwater wetlands—***	High	- Physical intervention	Low	12.4.7
	- River and inland wetland ecosystem changes—***	Medium	- Change water allocations	Low	12.4.5, 12.4.6
	- Eutrophication—***	Medium in inland Aus. waters	- Change water allocations, reduce nutrient inflows	Medium to low	12.3.4
Coastal ecosystems	- Coral bleaching, especially Great Barrier Reef—****	High	- Seed coral?	Low	12.4.7
	—More toxic algal blooms?—*	Unknown	—	—	12.4.7
Agriculture, grazing, and forestry	- Reduced productivity, increased stress on rural communities if droughts increase, increased forest fire risk—***	Location-dependent, worsens with time	- Management and policy changes, fire prevention, seasonal forecasts	Medium	12.5.2, 12.5.3, 12.5.4
	- Changes in global markets due to climate changes elsewhere—***, but sign uncertain	High, but sign uncertain	- Marketing, planning, niche and fuel crops, carbon trading	Medium	12.5.9
	- Increased spread of pests and diseases—****	Medium	- Exclusion, spraying	Medium	12.5.7
	- Increased CO2 initially increases productivity but offset by climate changes later—**	Changes with time	- Change farm practices, change industry		12.5.3, 12.5.4
Horticulture	- Mixed impacts (+ and -), depends on species and location—****	Low overall	- Relocate	High	12.5.3
Fish	- Recruitment changes (some species)—**	Uknown net effect	- Monitoring, management	—	12.5.5
Settlements and industry	- Increased impacts of flood, storm, storm surge, sea-level rise—***	High in some places	- Zoning, disaster planning	Moderate	12.6.1, 12.6.4
Human health	- Expansion and spread of vector-borne diseases—****	High	- Quarantine, eradication, or control	Moderate to high	12.7.1, 12.7.4
	- Increased photochemical air pollution—****	Moderate (some cities)	- Emission controls	High	12.7.1

Comprehensive cross-sectoral estimates of net climate change impact costs for various GHG emission scenarios and different societal scenarios are not yet available. Confidence remains very low in the IPCC Special Report on Regional Impacts of Climate Change estimate for Australia and New Zealand of -1.2 to -3.8% of GDP for an equivalent doubling of CO₂ concentrations. This estimate did not account for many of the effects and adaptations currently identified. [12.9]

Extreme events are a major source of current climate impacts, and changes in extreme events are expected to dominate the impacts of climate change. Return periods for heavy rains, floods, and sea-level surges of a given magnitude at particular locations would be modified by possible increases in intensity of tropical cyclones and heavy rain events and changes in the location-specific frequency of tropical cyclones. Scenarios of climate change that are based on recent coupled atmosphere-ocean (A-O) models suggest that large areas of mainland Australia will experience significant decreases in rainfall during the 21st century. The ENSO phenomenon leads to floods and prolonged droughts, especially in inland Australia and parts of New Zealand. The region would be sensitive to a changes towards a more El Niño-like mean state. [12.1.5]

Before stabilization of GHG concentrations, the north-south temperature gradient in mid-southern latitudes is expected to increase (medium to high confidence), strengthening the westerlies and the associated west-to-east gradient of rainfall across Tasmania and New Zealand. Following stabilization of GHG concentrations, these trends would be reversed (medium confidence). [12.1.5.1]

Climate change will add to existing stresses on achievement of sustainable land use and conservation of terrestrial and aquatic biodiversity. These stresses include invasion by exotic animal and plant species, degradation and fragmentation of natural ecosystems through agricultural and urban development, dryland salinization (Australia), removal of forest cover (Australia and New Zealand), and competition for scarce water resources. Within both countries, economically and socially disadvantaged groups of people, especially indigenous peoples, are particularly vulnerable to stresses on health and living conditions induced by climate change. Major exacerbating problems include rapid population and infrastructure growth in vulnerable coastal areas, inappropriate use of water resources, and complex institutional arrangements. [12.3.2, 12.3.3, 12.4.1, 12.4.2, 12.6.4, 12.8.5]

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