Blue Lake

Blue Lake is found in the state of New South Wales (NSW) within Kosciuszko National Park, and is located approximately 3.5 kilometres northwest of Charlottes Pass. Charlottes Pass is the highest township in Australia and is located within the Australian Alps, approximately 215 kilometres southwest of Canberra. Blue Lake is one of only four cirque lakes found on the mainland of Australia. Blue Lake is a clear, deep (up to 28 metres), open, freshwater lake, with a predominantly muddy bottom. The other three lakes, Cootapatamba, Albina, and Club are shallower than Blue Lake and are held entirely by terminal moraines. These four with another glacial lake, Hedley Tarn, make up the alpine lakes, which are the highest lakes on the Australian mainland, being at elevations between 1890 and 2070 metres. Blue Lake was formed by glacial gouging of the granite bedrock. It receives water from Blue Lake Creek originating from Mount Twynam and from snowmelt. The surface of Blue Lake is frozen for approximately four months of the year, it overflows in spring with the snow thaw, and during the remainder of the year the lake level remains stable. The alpine lakes contain the freshest waters in Australia. Blue Lake consists entirely of open water with boulders reaching the lake margin in the east and north east, and the remaining shores being pebbly. Tall alpine herbfield communities surround the north eastern area with wet heaths and grasses abutting the shoreline of the lake. The margins of Hedley Tarn consist of heath, fens and bogs. A number of rare or threatened plants are found within the Ramsar site, including the branched carraway, wedge oschatzia and the snow-wort and it supports the endangered ecological community of montane peatlands and swamps. Threatened animal species found around Blue Lake include the mountain pygmy possum and the broad tooth rat. Historically, indigenous people did not live permanently in the alpine area but probably visited in summer, to perform ceremonies and to collect bogong moths for food. The first official European exploration of the region was undertaken by the Polish explorer, Paul Edmund Strezelecki, who climbed and named Mt Kosciuszko in 1840. Currently, Kosciuszko National Park is the most visited National Park in NSW and Blue Lake is a popular tourist destination for visitors to the National Park. Camping is not permitted within the catchment of Blue Lake

Government evidence of impact of climate change:

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  • Australian Government, Blue Lake Ramsar Site, Ecological Character Description

    Key threats include climate change; cloud seeding; recreation and tourism; bushfires; and erosion and sedimentation.
    Due to its limited distribution and known threats; including climate change and predation by foxes; the broad toothed rat has been listed as vulnerable under the TSCA. 4.3.4 Vulnerable species Litoria verreauxii alpina The alpine tree frog (Litoria verreauxii alpina) is found over about 3500 km throughout the high country of Australia (Osborne et al. 1999) however recent searches indicate that its distribution throughout this region is small.
    Due to the limited distribution of this community and threats from clearing; grazing; trampling; disturbance; peat mining; fires; weed invasion; erosion; sedimentation and climate change; this ecological community has been identified under the TSCA as an endangered ecological community (DEC 2005c). 4.5 Bioregion and biosphere support 4.5.1 Populations representative of the biogeographic region The Blue Lake Ramsar site lies within the Australian Alps biogeographic region according to IBRA; and within the Snowy River Southeast Coast Division according to ADDRB (Appendix 1).
    This leads to reduced evaporation and wind transport of snow; and enables significant snow depths to accumulate and the lake surface to freeze for up to six months of the year (Raine 1982). 5.3 Geomorphology 5.3.1 Geology of the Kosciuszko region The development of the geological features of Kosciuszko National Park may be divided into four periods (Galloway 2004) Ordovician to Lower Devonian (approximately 430 470 million years ago) a period of bedrock formation; followed by prolonged erosion Tertiary (approximately 50 2 million years ago) a period of uplift and continued erosion Pleistocene (approximately the last 2 million years) a period of climatic change that produced glacial and periglacial features; including Blue Lake and Hedley Tarn Holocene (approximately the last 10 000 years) a period of relatively stable climate and geological processes.
    The montane peatlands and swamps of Blue Lake Ramsar site are particularly threatened by climate change; fire; weed invasion; trampling; and sedimentation from nearby eroded slopes (DEC 2005c).
    Fox and cat predation is also a significant threat which is expected to increase with climate change increasing the habitat range favoured by these predators.
    Climate change is likely to allow the perennial blackberry; a declared noxious weed in NSW; to outcompete the mountain plum pine at high altitudes; thereby causing the mountain pygmy possum to lose its habitat niche to other small mammals such as the bush rat.
    Climate change is also likely to directly impact the mountain pygmy possum as it requires a snow depth of at least one metre for insulation during its winter hibernation.
    Climate change also poses a significant threat as decreased snow cover and duration will increase the likelihood of predation by foxes and cats; increase competition from other climatically marginal species; increase the population of foxes; cats; rabbits; hares; and increase weed invasion and fire (Green and Osborne 2003).
    In addition; climate change is predicted to alter the climate and hydrology of the Blue Lake Ramsar site (see section 7.2) and understanding natural water flows and their variability is necessary if the impacts of climate change are to be quantified.
    Table 19 Potential threats; effects and the status of threats Potential threat Threat status Major Climate change (Figure 16) Unknown Cloud seeding (Figure 18) Some potential effects Climate higher air temperatures; less snow cover and duration; increased rainfall Geomorphology soil erosion; morphological changes Hydrology earlier snow thaw; increased run off; increased water flows; absent or shortened freeze thaw cycle; loss of dimictic thermal regime Physico chemical environment increased sedimentation within Blue Lake; reduced water quality Biota establishment of aquatic macrophytes; changes in species composition and abundance of flora and fauna; increased feral animal activity; loss of climatically marginal flora and fauna; earlier migratory bird arrival; weed invasion Climate increased precipitation; increased rainfall; less snow cover and duration; increased atmospheric Agl Hydrology increased run off; increased water flows; increased sedimentation; increased Agl and Ag in water column Physico chemical environment increased Agl in water column and sediments; release of Ag to water column and sediments Biota increased Agin cellular tissue; impacts unknown; loss of snow reliant species and communities; loss of endemic; vulnerable or endangered species and communities; change in species assemblages; increased exposure of fauna to predation; freezing Geomorphology compaction of soil; erosion; reduced visual amenity Hydrology increased sedimentation and litter Physico chemical environment reduced water quality Biota compaction of soil and vegetation; erosion; increased weed invasion; reduced habitat quality and quantity; increased disturbance; increased feral animal activity; loss of endemic; vulnerable and endangered species and communities Hydrology increased run off; increased sedimentation Physico chemical environment reduced water quality Biota loss of vegetation cover Hydrology increased sedimentation Physico chemical environment reduced water quality Biota loss of species and communities Minor Recreation and tourism (Figure 19) Minor Bushfires Minor Erosion and sedimentation Ecological character description 7.2 Climate change Since alpine ecosystems are largely influenced by low temperature conditions; they are considered to be particularly sensitive to climate change (Pickering et al. 2004) and they have been identified as being amongst the most vulnerable systems in Australia (Basher et al. 1998).
    There is little chance for the alpine zone to respond to climate change as the opportunity for species to retreat upward is limited by the relatively low altitude of the Australian Alps (maximum of about 2000 m) (McCarthy et al. 2001).
    Observations of biota changes within these ecotones may provide a good ecological indicator of climate change.
    Furthermore; since human impact is less within alpine environments; the ability to differentiate between climate related changes and other human impacts is enhanced.
    For these reasons; alpine ecosystems and impacts on related components and processes would be important indicators of climate change.
    Records from the Australian Bureau of Meteorology indicate that predictions of climate change are not unfounded due to the consistently drier and hotter conditions occurring since the 1970s.
    Early predictions of climate change on snow conditions in the Australian Alps indicate a dramatic decline in the total area receiving snow and the total amount of snow (Pickering et al. 2004).
    Potential ecological effects on key components and processes at Blue Lake and Hedley Tarn have been summarised in Figure 16 and include (DEC 2006) alterations to catchment hydrology and geomorphologic processes possible extinction of flora and fauna whose climatic ranges are limited to alpine and subalpine regions uphill migration of biota from lower altitudes expansion in the distribution of some plant communities reduction in the extent and species composition of some plant communities change in the mposition and abundance of fauna increase in the diversity; abundance and distribution of weed species uphill extension in the range of feral animals increase in wildfire incidents.
    Blue Lake Ramsar site Increased CO2 and other Greenhouse Gases Climate Higher Air Temperatures Less Snow Cover Duration Increased Rainfall Wind Geomorphology Morphological Change Soil Erosion Habitats Vegetation Community Change Loss of Endangered Communities Change in Species Assemblage Weed Invasion Hydrology Increased Groundwater Less Snow; Earlier Snow Thaw Increased Run off Water Flows Absent Short Freeze Thaw Cycle Loss of Dimictic Thermal Regime Increased Sedimentation Physico Chemical Environment Change in Source of Organic Carbon Reduced Sedimentation Reduced Water Quality Flora Establishment of Aquatic Macrophytes Anemone Buttercup Population Increase Overgrazing by Feral Animals Direct Impact Fauna Change in Species Assemblage Loss of Endangered Vulnerable Species Less Endemic Species Earlier Migratory Biord Arrival Increased Feral Animal Distribution Indirect Impact No Impact Figure 16 Conceptual model of the potential impacts of climate change 7.2.1 Alterations to hydrologic and geomorphologic processes Based on snow data from the Snowy Mountains Hydro electric Authority; it is evident that climate change is already having a negative influence on annual snow cover at Spencers Creek (Figure 17) (Green and Pickering 2002).
    Evidence indicates that some of these mammals have increased altitudinal distribution over the 30 year period prior to 1999; thereby highlighting the potential extension of these species with continued climate change.
    Furthermore; there is a potential decrease in areas of suitable habitat for the broad toothed rat with climate change (Brereton et al. 1995).
    If the drier sites are the typical habitat for the anemone buttercup; it is predicted that this species may respond to climate change by increasing its abundance and extent (Pickering et al. 2004).
    Bog Alpine A reduction in soil moisture associated with climate change is Subalpine likely to promote the replacement of valley bogs by sod tussock Montane grassland species.
    Medium Baseline data of productivity of phytoplankton Impacts of climate change Fauna Undertaken by DECC Medium Needed Low Needed Low Undertaken by DECC Low Implement study on impacts of increased UV radiation on alpine flora Monitor arrival of migratory birds to Blue Lake and Hedley Tarn Monitor changes in visitation patterns of mammals to Blue Lake and Hedley Tarn Establish the physiological requirements for vertebrates; invertebrates and zooplankton Monitor the upstream altitudinal migration of mammals frogs; crustaceans and fish; e.g. trout Establish the effect of Agl on fauna Describe food webs within Blue Lake and Hedley Tarn Collect baseline data on productivity of zooplankton Partly undertaken by DECC Medium Impacts of cloud seeding Needed Low Food web Needed Low Ecological character description Needed Low Baseline data on productivity of zooplankton Detailed fauna census Needed Low Collect detailed fauna data including species assemblage and sightings
    Enhanced greenhouse climate change and its potential effects on selected fauna of south eastern Australia a trend analysis.
    While summer grazing of sheep and cattle and burning of the vegetation to promote fresh regrowth was well established within the region prior to 1944; impacts on Blue Lake and Hedley Tarn were most significant during the drought period of 1890 1901.
    Fire also poses a potential threat as alpine vegetation communities are fire sensitive and often slow to regenerate (NSW NPWS 2002 DEH 2006a) Due to the small population; limited distribution and significant threats; the mountain pygmy possum has been identified as an endangered species under the EPBCA and TSCA a recovery plan has been developed in accordance with the recommendations in the TSCA (NSW NPWS 2002). 5.8.6 Broad toothed rat Mastacomys fuscus The broad toothed rat is described as a tubby; chubby cheeked; compact rodent with a short; wide face and ears.
    Fuel is increasingly dry and available in drought years; thereby making conditions favourable for bushfires.
    However; in extreme drought years environmental conditions change from non drought conditions.
    Fuel is increasingly dry and available in drought years; thereby making conditions favourable for bushfires.