The Regional Impacts of Climate Change

Other reports in this collection Vulnerability Assessments and Case Studies

In Australia, vulnerability assessments were carried out for Cocos (Keeling) Island (an Australian Territory), Geographe Bay in Western Australia, and Kiribati in response to the first version of the IPCC Common Methodology (IPCC, 1991). This led to recommendations for changes to the Common Methodology (McLean and Mimura, 1993).

Meanwhile, a major vulnerability study was carried out by the Port of Melbourne Authority (1992) on the impact of projected greenhouse changes on the 3,000 km of the Victorian coast. Quantitative assessment was carried out for selected beaches for 0.3- and 0.5-m rises in mean sea level, without considering other changes. The largest recession rates were indicated for beaches west of Cape Otway, due to the relatively fine sand and more severe wave conditions. Shoreline recession rates also were significant in parts of Port Phillip Bay and the Gippsland Lakes, due to generally narrower beaches. Detailed assessments identified beaches, barriers, estuaries, mudflats, swamps, and sedimentary cliffs that are particularly vulnerable.

A series of nine case studies initiated by the Australian Department of the Environment, Sport and Territories (DEST) on coastal vulnerability to climate change and sea-level rise was undertaken during 1994 and 1995 (Waterman, 1996). Impacts considered included sea-level rise, temperature and rainfall variation, changes in storm intensity and frequency, and saltwater intrusion into surface and groundwater supplies. Case studies were undertaken for Mackay, Queensland; Batemans Bay, New South Wales; Gippsland Lakes and Port Phillip Bay, Victoria; South Arm, Hobart, Tasmania; Northern Spencer Gulf, South Australia; Perth, Western Australia; and the Darwin and Alligator Rivers regions in the Northern Territory. Emphasis in the studies was placed on the wider socioeconomic, environmental, aesthetic, and cultural aspects, as well as strategies for integration of vulnerability assessment into coastal management and planning processes. The main aim in most of the studies, however, was to test the methodology rather than to produce definitive assessments of the vulnerability in the regions.

The studies found that vulnerability to climate change is difficult to determine in the context of the inherent variability of natural systems and the impacts of development on the coastal zone. In addition, the effects of change are poorly understood, and the implications for coastal management are not well appreciated by the wider community. The researchers concluded that community consultation, along with serious attempts to address the complex jurisdictional issues concerning coastal management, was essential.

Several of the studies, such as those for Port Phillip Bay and Hobart, noted the high degree of variability in potential impacts, even over distances of a few kilometers. The basis for identifying vulnerable areas was a geomorphological study that identified the main coastal landforms. At the broadest scale of generalization, the whole coast of Australia has been categorized by Chappell et al. (1996) according to several overlapping geomorphological and greenhouse hazard criteria, partly based on the work of Bird (1988, 1993) and Thom (1984). High wave energy coasts in the southern parts of the west and east of the continent are vulnerable to shifts in wave direction and energy, especially on beach coasts. Across most of northern Australia, rising sea level and changes in tropical cyclone activity are the greatest threats, whereas the Great Barrier Reef may benefit in some respects from moderate sea-level rises.

Severe limitations applied in quantitatively assessing likely impacts in the DEST case studies because of the wide range of uncertainty in the scenarios for sea-level rise, temperature and rainfall changes, and changes in storm intensity and frequency. Moreover, even in well-studied areas-such as the Alligator Rivers region in the Northern Territory, where rapid changes (such as saltwater intrusion into the Kakadu freshwater flood plains) (Knighton et al., 1991; Woodroffe and Mulrennan, 1993) have occurred in historical times-processes of natural change are not well understood. Nevertheless, it is clear that Kakadu National Park, which is a World Heritage Area and major tourist attraction as well as Aboriginal hunting and fishing grounds, would be almost totally transformed into mangrove forest by a sustained 1-m rise in mean sea level.

In several of the areas studied, towns such as Port Augusta, Port Pirie, Lakes Entrance, and Mackay have experienced partial flooding from the sea due to extreme events in the recent past, so they are very vulnerable to effects of sea-level rise. This was highlighted for Mackay by Smith and Greenaway (1994), who note a high sensitivity of flood damage to any change in the climatology of storm surges.

Potential vulnerability to health effects, particularly due to increases in standing water (see Section, also were noted. The study of the Perth metropolitan coastline noted the natural "breakwater effect" of the offshore reef system and concluded that "climate change, natural or greenhouse-induced, appears to be more important to future changes ... than projected rises in mean-sea level." Saltwater penetration into the coastal aquifer also is an issue in the Perth region, as it is in some other coastal aquifers (Ghassemi et al., 1991).

Small, low-lying coastal and island communities are particularly vulnerable to sea-level rise and changes in climatic forcing of extreme events. These communities include several of the Torres Strait islands (Mulrennan, 1992), the Australian territory of Cocos (Keeling) Islands, and several Aboriginal coastal communities across northern Australia. Unlike cities such as Darwin, these small communities usually do not abide by strict building codes or have evacuation procedures. Development of such codes and procedures therefore is necessary for effective adaptation.

The DEST project (Waterman, 1996) identified a number of issues concerning how policy and management decisions are made about the effects of climate change and sea-level rise by authorities and groups in coastal areas. Common methodological elements that should form part of a region-specific approach to vulnerability assessment were identified. Specific recommendations included capacity-building at governmental and community levels, including awareness raising; the development of a better appreciation of insurance, legal, and land-use planning implications, including professional and public liability; the development of a guide to best practice in integrated coastal zone management; and the development of benchmarks, monitoring programs, and databases for coastal zones.

In New Zealand, there has been no comprehensive national assessment of coastal vulnerability to climate and sea-level changes. Nonetheless, under the Resource Management Act (RMA) of 1991, local authorities are obligated to ensure the "avoidance or mitigation of natural hazards," including coastal flood and erosion hazards. Subsequent legal rulings have confirmed that future sea-level rise should be taken into account in coastal hazard analyses in connection with resource consent (permit) procedures as specified under the RMA. Furthermore, the New Zealand Coastal Policy Statement (Department of Conservation, 1994), which contains policies aimed at achieving the single purpose of the RMA (the "sustainable management of natural and physical resources"), includes specific reference to the possibility of a "rise in sea level" and its impacts on the subdivision, use, and development of the coast.

As a consequence of this policy framework, numerous coastal hazard studies have been commissioned by local authorities and developers in New Zealand for planning, policy development, and environmental impact assessment purposes. On the whole, these analyses-mostly in the form of unpublished consultants' reports-suggest that a considerable portion of the existing built environment of the New Zealand coast would be endangered by a future rise in sea level of the order of 0.5-1 m, especially along sandy beach and dune coasts. Where development pressures are high, such as in the Bay of Plenty, the potential increase in vulnerability is large unless adaptive measures are taken.

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