Implications of Climate Change for Australia's World Heritage ...

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IMPLICATIONS OF CLIMATE CHANGE FOR AUSTRALIA’S WORLD HERITAGE PROPERTIES: A PRELIMINARY ASSESSMENT Rainfall Changes in rainfall and a rise in the basal altitude of the orographic cloud layer are likely to have a significant impact on the natural values of Australia’s World Heritage properties. Most of Australia’s World Heritage properties have experienced a decline in rainfall over the past 35 years. Current CSIRO projections indicate that mean annual rainfall will continue to fall in many regions across Australia. If annual rainfall remains unchanged, evaporation is likely to be higher (CSIRO 2006), resulting in drier conditions. A potential rise in the average basal altitude of the orographic cloud layer due to global warming (Pounds et al. 1999) is an issue of concern for a range of values across a number of World Heritage properties, in particular in the Wet Tropics of Queensland and the Lord Howe Island Group. The orographic cloud layer envelops the mountain summits of these World Heritage properties, and provides an essential source of water for many high-altitude plants and animals by a process known as ‘cloud stripping’ by high-altitude rainforests. Very little is known about the hydrology of cloud stripping and the resulting precipitation derived from this process. However, it is fairly certain that a rise in basal altitude of the orographic cloud layer would exacerbate the effects of long-term drought (Still et al. 1999), resulting in serious consequences for many plant and animal species. Microhylid frogs 9 , for example, rely on cloud mist for their long-term survival. The disappearance of about 20 frog species in the highland forests of Monteverde, Costa Rica, was probably due to changes in the extent of mountain mist following an increase in surface temperature (Pounds et al. 1999). Tropical cyclones and extreme weather events Research has shown that there has been an increase in the destructiveness of cyclones since the 1970s, which correlates with the observed increase in sea surface temperature (Emanuel 2005). Tropical cyclones are common in Kakadu National Park, the Great Barrier Reef and in the Wet Tropics of Queensland. Current projections indicate that cyclones are expected to be less common but more intense (CSIRO 2006), which may inflict greater physical damage to vegetation including the uprooting of trees by destructive winds. High-intensity cyclones may inflict greater damage on certain vegetation types than on others. Eucalyptus trees taller than 9 m are particularly prone to wind damage (Williams & Douglas 1995). The uprooting of trees can also lead to increased erosion during periods of intense rainfall. Invasive species such as climbing vines can also be favoured in the aftermath of tropical cyclones. Increased sea surface temperatures, changes in ocean circulation and ocean acidification The impacts of rising sea surface temperatures and ocean acidification will most likely have catastrophic consequences for marine organisms such as coral and the species dependent on these keystone species, as well as for calcifying organisms such as plankton, sea urchins and coral reef systems (Feely et al. 2004). Acidification takes place via the reaction of dissolved carbon dioxide with water to produce carbonic acid which, in turn, increases acidity. The resulting acidification could prevent calcifying organisms—such as corals, shellfish and some species of phytoplankton—from producing calcium carbonate and thus prevent shell formation. Coral communities around the Lord Howe Island Group (which are the southernmost true coral reefs in the world) and the Great Barrier Reef are likely to be affected if the oceans become more acidic. To date, there have been no experimental studies examining the sensitivity of cold-water coral reef systems, such as those in the Lord Howe Island Group, to CO -induced ocean acidification. However, it is expected that the acidification will affect the recruitment of 2 cold corals more than their warm-water counterparts because the carbonate saturation state is generally lower at higher latitudes than at lower latitudes (i.e. Great Barrier Reef) (The Royal Society 2005). 9 Microhylid frogs lay their eggs on the forest litter and therefore require a constant source of moisture from the cloud stripping process to prevent desiccation of eggs and larvae. 23
IMPLICATIONS OF CLIMATE CHANGE FOR AUSTRALIA’S WORLD HERITAGE PROPERTIES: A PRELIMINARY ASSESSMENT Some scientists (e.g. McMahon et al. 2005; Priddel et al. 2006) have hypothesised that the decline in seabird populations in the Lord Howe Island Group, and of elephant seals at Macquarie Island, may be related to a change in food supply associated with changes in the marine environment in general. In the Pacific region, researchers have associated changes in fish stocks with increased El Niño-Southern Oscillation (ENSO) cycle activity (Bunce et al. 2002). A change in the abundance or availability of food brought about by shifts between two climatic systems, namely the Antarctic Circumpolar Wave (ACW) and the ENSO, could be one explanation for the decline in elephant seal numbers (McMahon et al. 2005). These systems influence the extent of sea-ice retreat (Kwok & Comiso 2002) and the recruitment of krill, which is a source of food for many marine predators (Loeb et al. 1997). However, the connection between global warming and changes in the earth’s climatic systems, such as ENSO, is still ambiguous. According to IPCC (2007), it is unclear how the frequency and intensity of El Niño events will respond to global warming. Chemical and physical changes to the coastal zone The World Heritage properties of Kakadu National Park, Tasmanian Wilderness, Shark Bay, Fraser Island, Lord Howe Island Group, Macquarie Island, Heard and McDonald Islands, Great Barrier Reef and Wet Tropics of Queensland are likely to be affected to varying degrees by sea level rise. Rising sea levels and large storm-surge events pose a significant threat to the integrity of the values of these World Heritage properties. Changes in salinity and physical changes to the coastal zone of some World Heritage properties may have significant implications for terrestrial and marine habitats. Kakadu and Shark Bay will face a more immediate threat from further sea level rise, resulting in an increase in flooding of low lying areas. Remnant mangrove swamps provide evidence of past sea level rise in Kakadu and could aid in predicting future impacts to river systems resulting from rising sea levels. The coastal plains of Kakadu are about 0.2 to 1.2 m above the high-tide water mark (Eliot et al. 1999). Large numbers of buffalo during the mid-1980s accelerated the erosion of levee banks, which led to considerable displacement of alluvium and a subsequent increase in salinity (Cobb et al. 2000). Current projections indicate that sea levels around Kakadu National Park will rise by at least 8 cm, and possibly up to 30 cm, by 2030 (Eliot et al. 1999). A rise in sea level of this magnitude is likely to lead to a further extension of tidal rivers and pose a significant threat to freshwater wetland systems, resulting in a decline in saltwater-sensitive plant species such as melaleuca. It is believed that sea level rise resulting from global warming has already led to changes in Kakadu National Park’s terrestrial ecosystem. For example, aerial studies have shown that over the past 40 years there has been a change in the distribution of mangrove communities (Lucas et al. 2002). Indirect impacts—fire More extreme and more frequent wildfires are likely to have a major impact on fire-sensitive forest communities (i.e. rainforests and alpine forests) and the organisms that they support. The rainforests of the Greater Blue Mountains Area provide a microclimate for primitive plant species with Gondwanian affinities, such as the Wollemi pine (Wollemia nobilis). This species, originally thought to be extinct, is found in only one specific location in the Greater Blue Mountains Area. Although the effect of fire on the Wollemi pine remains largely unknown, catastrophic fire events could threaten remaining stands (DEC 2005). A change in fire regime may affect fire-sensitive conifer species—including Huon pine (Lagarostrobos franklinii), Pencil pine (Athrotaxis cupressoides) and King Billy pine (Athrotaxis selaginoides)—found in montane and subalpine areas of the Tasmanian Wilderness (Parks and Wildlife Service 2004). An increase in the extent and severity of peat fires in World Heritage properties such as Fraser Island and the Tasmanian Wilderness is also of major concern. Extensive peat fires can often burn for weeks. 24
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202 World Heritage property Tempera
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206 World Heritage criteria World H
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