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Climate change and variability may create additional pressures on these dynamic coastal ecosystems, potentially having numerous impacts on many sectors, with the potential for major problems over the next few decades and beyond.
Climate change might impact on coastal communities by affecting:
- Water resources, through less supply and greater demand;
- Health, through more heat-related illness;
- Fisheries, as warmer oceans could affect coastal biodiversity;
- Industry, through more energy demand (greater demands during summer for air conditioning as temperatures increase);
- Tourism (affected by changes to the natural environment);
- Insurance (greater liability with extreme weather events);
- Coastal infrastructure, through greater exposure to severe storm events; and
- Associated impacts such as flooding and coastal erosion.
The observed and recorded coastal impacts of climate change around Australia from 1920 to 2000 indicate that there has been a rise in sea level of about 100mm. Long-term, Australian tide gauge records show a more frequent occurrence of extreme sea level events in the second half of the 20th century. There are recordings of increasing saltwater intrusion into northern Australian freshwater swamps since the 1950s.
Long-term beach monitoring in NSW shows linkages between beach erosion and El Nino events and there have been eight mass bleaching events on the Great Barrier Reef since 1979. These were triggered by unusually high sea surface temperatures. The most widespread events of 1998 and 2002 affected up to 50% of the reefs in the Great Barrier Reef Marine Park.
The projected climate change events are likely to be:
- Tropical cyclones becoming more intense;
- Increasing ambient and sea temperature;
- More frequent and intense storm surges;
- Sea levels rising by up to 59cm by the end of this century;
- Risk to coastal communities from sea level rise, storm activity and coastal flooding by 2050; and
- Increased coastal risk and liability could have cost implications for governments and the insurance industry.
Coastal communities, natural ecosystems and water security have been identified as the three sectors in Australia which are most vulnerable to climate change. The largest national vulnerability hotspots include the Great Barrier Reef and Queensland. A Tasmanian study has identified 21% of its coast is at risk from future sea level rise and erosion in the next 50-100 years.
Coast protection costs will increase as sea levels rise. Global average sea levels rose at an average of 1.8mm/yr in the period 1961-2003. The rate was faster from 1993-2003 at 3.1mm/yr. Changes in ice sheet flow from Greenland and Antarctica could increase the upper range of model estimates. Coastlines are likely to be exposed to increasing risks due to climate change and sea level rise, and the effect is likely to be exacerbated by increasing human habitation pressures on coastal areas.
It is likely that corals will experience a major decline due to increased bleaching and mortality due to rising ocean temperatures. Salt marshes and mangroves are likely to be negatively affected by sea level rise.
Between 1991 and 1996 one quarter of Australia's total increase in population was concentrated within three kilometres of the coastline - predominantly within the "sun-belt" locations on the New South Wales and Queensland coasts and in the South-West of Western Australia. This population growth means that the community's exposure to extreme events, notably tropical cyclones, storm surges and flooding of rivers in deltas and other outflow regions, is growing rapidly.
South-West Western Australia has not escaped the effects of climate change. Its temperature is already 0.8°C higher than in 1910; however, the most notable impact is a 10 to 15%t reduction in rainfall since 1975, which has had a major impact on water supplies.
The South-West's mean sea level has increased almost 20 cm (1½ mm/ year) since 1897, which is considered attributable to thermal expansion of the ocean due to global warming. The major impact in Western Australia has been on beach stability and potential inundation of low lying coastal regions under storm conditions.
Sand is eroded from beaches and deposited offshore from waves and higher water levels under storm conditions. A one centimetre rise in mean sea level is normally accompanied by a loss of about one metre of beach.
Worldwide, hundreds of millions of people are vulnerable to flooding due to sea level rise, especially in densely populated and low lying settlements where adaptive capacity is relatively low and which already face other challenges such as tropical storms or local coastal subsidence. The greatest populations at risk are in the mega-delta areas of Asia. The more vulnerable countries are the low lying atoll states of the Pacific. Sea level rise would continue for centuries even if greenhouse gases were stabilised.
The Western Australian Government has an essential role in mitigating greenhouse gas emissions, improving transport strategies, increasing energy efficiency, reducing and off-setting emissions from electricity generation and investing in renewable energy are all strategies vital for the preservation of coastlines throughout the world, Australia and in Western Australia.
The design of NPQ is necessarily dictated by the impacts of climate change. As a community we cannot conclude that we have more pressing shorter term imperatives to deal with. We cannot adopt a view that government carries sole responsibility for the commitment and leadership required to address climate change and its effects on coastal communities.
NPQ will be protected from rising sea levels and storm surges by a seawall standing five metres above mean sea level. The islands themselves will sit three metres above mean sea level and be protected by rock edges, the seawall and a 100m-wide water buffer zone. These design parameters will protect NPQ from a 100-year storm surge event, even after allowing for the worst case effects of rising sea level.
The effect of higher temperatures is likely to be considerably greater on peak energy demand than on net demand, suggesting that there will be a need to install additional generating capacity over and above that needed to cater for underlying economic growth.
The likely impacts on electricity generation from climate change will be:
- Decreased thermal efficiency in power generation;
- A decrease in transmission line efficiency; and
- Changes in demand, especially affecting peak generation capacity required for air conditioning.
NPQ and its 20,000 residents will not require any power from the grid. All power will be sourced from renewable sources of wind, wave and solar energy which will be harvested either within the proposed structure or in the nearby vicinity.
The ultimate public-private partnership will be managing and containing climate change. The challenge for the future is to better understand what influences people's decision-making and to encourage them to change their behaviour based on new beliefs about climate change.
There is a need to bring science, Government and the wider community together, and provide opportunities for people to understand the consequences of different actions, to question their assumptions, conclusions and beliefs, and encourage them to consider different perspectives.
The sustainability principles underpinning NPQ will bring knowledge from various disciplines and groups together to evaluate the problem from different perspectives and provide support for the solution.
Curtin University Sustainability Policy Institute has been commissioned to study NPQ and advise on the adoption of sustainability measures, as part of a larger project it is undertaking to benchmark the terms carbon neutral and carbon free.
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