This section summarizes some key regional concerns regarding vulnerability to climate change and impacts in Australia and New Zealand. They have not been prioritized. Supporting details and references are provided in Sections 12.3 through 12.8.

Drought, Flood, and Water Supply: Climate variability is a major factor in the economies of both countries, principally through the flow-on effects of ENSO-related major droughts on agriculture. Farmers in drought-sensitive parts of both countries will be increasingly vulnerable if interannual droughts occur more frequently or are more intense in the future. Less secure water supplies would accentuate competition between users and threaten allocations for environmental flows and future economic growth. Adelaide and Perth are the main cities with water supplies that are most vulnerable to climate change; increasing salinity in the Murray River is an increasing concern for Adelaide. Any increase in flood frequency would adversely affect the built environment. In New Zealand, floods and landslides are natural hazards that could increase in frequency and severity.

Ecosystem Uniqueness and Vulnerability: Australia and New Zealand have been isolated from the rest of the world for millions of years until relatively recent human settlement. Some species exhibit quite limited ranges of average climate. These two factors leave many of the region's ecosystems vulnerable to climatic change and to invasion by exotic animal and plant species introduced by human activity. This vulnerability has been exacerbated by fragmentation of ecosystems through land-use changes.

Coral Reefs: Australia has one of the greatest concentrations of coral reefs in the world. Rising sea level by itself may not be deleterious. However, the combination of sea-level rise with other induced stresses—notably, increasing atmospheric CO₂ (which leads to a decrease in calcification rates of corals); increasing sea temperatures, leading to coral bleaching; possibly increased riverine outflow events (low salinity and high pollution); and damage from tropical cyclones—may put much of this resource at risk.

Alpine Areas: In Australia, significant warming will raise snowlines, diminish the ski industry, and threaten alpine ecosystems. In New Zealand, snowline changes and the advance or retreat of glaciers also depend on changes in the strength and local orientation of mid-latitude westerlies. Options for relocation of the ski industry are limited by the relatively low altitude of Australia's alpine regions and by rugged terrain and conservation estate regulations in New Zealand.

Agricultural Commodities and Terms of Trade: A major fraction of exports from both Australia and New Zealand are agricultural and forestry products, production of which is sensitive to any changes in climate, water availability, CO₂ fertilization, and pests and diseases. Returns from these commodities could be affected by the projected increase in agricultural production in mid- to high-latitude northern hemisphere countries and resulting impacts on commodity prices and world trade.

Increasing Coastal and Tropical Exposure: Major population and economic growth in coastal areas, especially the tropical and subtropical east coast of Australia, are leading to greatly increased vulnerability to tropical cyclones and storm surges, as well as riverine and estuarine flooding. Rising sea level will accentuate these problems, as would any increase in storm intensities or a more poleward movement of tropical cyclones. Rising sea level also will increase the salinity of estuarine and coastal aquifer groundwater.

Indigenous People: In both countries, indigenous peoples (Aborigines and Torres Straits Islanders in Australia, Maori in New Zealand, as well as Pacific islanders) are among the most disadvantaged members of the population. They generally have lower incomes, and many live in isolated rural conditions or in the sometimes poorly serviced and low-lying margins of large towns and cities. They are more exposed to inadequate water supplies, climatic disasters, and thermal stress and are more vulnerable to an increase in the prevalence of pests and diseases.

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