Blue Mountains Swamps in the Sydney Basin Bioregion - vulnerable ecological community listing

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. The Blue Mountains Swamps in the Sydney Basin Bioregion is the name given to the ecological community characterised by the species assemblage listed in paragraph 2. All sites are within the Sydney Basin Bioregion.

2. The Blue Mountains Swamps in the Sydney Basin Bioregion is characterised by the following assemblage of species:

3. The total species list of the community is considerably larger than that given above, with many species present in only one or two sites or in low abundance. The species composition of a site will be influenced by the size of the site, recent rainfall or drought condition and by its disturbance (including fire) history. The number of species, and the above ground relative abundance of species will change with time since fire, and may also change in response to changes in fire regime (including changes in fire frequency). At any one time, above ground individuals of some species may be absent, but the species may be represented below ground in the soil seed banks or as dormant structures such as bulbs, corms, rhizomes, rootstocks or lignotubers. The list of species given above is of vascular plant species; the community also includes micro-organisms, fungi, cryptogamic plants and a diverse fauna, both vertebrate and invertebrate. These components of the community are not well documented.

4. The Blue Mountains Swamps community is characterised by a dense mixture of shrubs and sedges, most of which have sclerophyllous foliage. The shrub stratum typically varies from 0.5 m to over 2.0 m tall and is highly variable in cover. The ground stratum may be up to about 1 m tall and is dominated by a dense sward of sclerophyllous sedges and grasses except in patches where these are displaced by a dense cover of taller shrubs. Ferns, forbs and small shrubs are scattered amongst the sedges and grasses. There is considerable local variation within the swamps in species composition and vegetation structure, which is apparently related to local soil properties and fire history (Keith and Benson 1988, Holland et al. 1991). Structure of the vegetation varies from closed heath or scrub to open heath to closed sedgeland or fernland (Specht 1970). Among the frequently occurring large shrub species, Baeckea linifolia, Leptospermum juniperinum and Hakea teretifolia are relatively ubiquitous, while L. grandifolium and Grevillea acanthifolia subsp. acanthifolia occur primarily on deeper, highly organic, frequently waterlogged soils, and L. polygalifolium and Banksia spinulosa are typically found on intermittently waterlogged, shallower sandy soils with a moderate organic content. Small shrubs, including Almaleea incurvata, Epacris obtusifolia and Sprengelia incarnata, are typically more abundant on the less waterlogged soils. The large tussock sedge, Gymnoschoenus sphaerocephalus, and rhizomatous sedges and cord rushes, including Lepidosperma limicola, Ptilothrix deusta, Lepyrodia scariosa and Leptocarpus tenax are generally common throughout the swamps, as are the grasses Entolasia stricta and Tetrarrhena turfosa. Coral ferns, Gleichenia spp., and Drosera binata are typical of frequently waterlogged soils, while other herbs, including Dampiera stricta, Mirbelia rubiifolia and Gonocarpus teucrioides occur in more open vegetation on intermittently waterlogged soils.

5. While no systematic fauna surveys have been carried out across the range of the Blue Mountains Swamps community, a number of vertebrate and invertebrate species listed as threatened in NSW have been recorded as resident or transient in the community. These include the Water Skink (Eulamprus leuraensis), the Giant Dragonfly (Petalura gigantea), the Giant Burrowing Frog (Heleioporus australiacus) and the Red-crowned Toadlet (Pseudophryne australis). The swamps also provide habitat for the Southern Emu Wren (Stipiturus malachurus), Lewin's Rail (Dryolimnas pectoralis) and the Buff-banded Rail (Gallirallus phillippensis), as well as a range of honeyeaters. A number of plant species recorded in the Blue Mountains Swamps community are endemic to the Blue Mountains area (Acacia ptycoclada, Almaleea incurvata, Grevillea acanthifolia subsp. acanthifolia, Notochloe microdon, Olearia quercifolia, Symphionema montanum) and/or threatened in NSW (Carex klaphakei, Eucalyptus copulans, Pultenaea glabra).

6. The Blue Mountains Swamps community is typically associated with the poorly drained headwaters of streams on the predominantly sandstone plateaux of the Blue Mountains. High levels of soil moisture result from the combination of high rainfall (typically exceeding an average of 1000 mm per annum), relatively slow runoff and low subsurface permeability (Young and Wray 2000). The soils typically vary from damp grey-yellow sandy loams to black mineral peats, depending on the level of waterlogging. Upland swamps perform important hydrological functions within the landscape by regulating and sustaining flows, reducing turbidity, and maintaining and enhancing the water quality of discharge streams (Keith et al. 2006). The Blue Mountains Swamps community spans an altitudinal range of approximately 500 to 950 m above sea level. It may occur in low-relief and relatively steep terrain, where examples of the community are sometimes described as 'hanging swamps'. In these latter cases, waterlogging may be exacerbated by seepage moisture on the valley sides that emerges from outcropping strata of water-bearing sandstone, which are underlain by less permeable claystone bands ('aquicludes' of Holland et al. 1991).

7. With increasing elevation, the Blue Mountains Swamps community intergrades with Newnes Plateau Shrub Swamp in the Sydney Basin Bioregion, which is currently listed as an Endangered Ecological Community under the Threatened Species Conservation Act. The transition occurs around Bell and Clarence at approximately 850-950 m above sea level. The Blue Mountains Swamps community typically has less cover of shrubs, a greater cover of sedges (particularly Gymnoschoenus sphaerocephalus) and may occur on steeper terrain than Newnes Plateau Shrub Swamp. The two communities have different suites of Leptospermum species, and Newnes Plateau Shrub Swamp contains several shrub species (e.g. Boronia deanei, Dillwynia stipulifera) and herbs (e.g. Centella asiatica, Geranium neglectum, Velleiea montana) that are absent from, or uncommon in the Blue Mountains Swamps community. Swamps that exhibit intermediate characteristics are collectively covered by the Determinations of these communities and may be diagnosed by detailed consideration of the assemblage of species present at the site.

8. The Blue Mountains Swamps community shares some characteristics with Montane Peatlands and Swamps of the New England Tableland, NSW North Coast, Sydney Basin, South East Corner, South Eastern Highlands and Australian Alps bioregions, which is listed as an Endangered Ecological Community under the Threatened Species Conservation Act. However, this latter community has a lower diversity of sclerophyllous shrub species, a greater diversity of soft-leaved sedges, grasses and herbs, and typically occurs, not on sandstone, but on more fertile substrates than the Blue Mountains Swamps community. The Blue Mountains Swamps community apparently forms part of Temperate Highland Peat Swamps on Sandstone, which is listed as an Endangered Ecological Community under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.

9. Vegetation surveys carried out across the range of the Blue Mountains Swamps community describe a number of related plant assemblages. The Blue Mountains Swamps community includes 'Blue Mountains Sedge Swamps' (map unit 26a) of Keith and Benson (1988), and Benson and Howell (1990); 'Blue Mountains Swamps' (community 13) of Smith and Smith (1996); 'Hanging Swamp' (map unit S) of Douglas (2001); 'Upland Swamps Tea Tree Thicket' and 'Upland Swamps Cyperoid Heath' (map units 27a and 27b, respectively) of NPWS (2003); and those occurrences of 'Blue Mountains - Shoalhaven Hanging Swamps' (map unit FRW130) of Tindall et al. (2004) and Tozer et al. (2006), which are mapped within the Hawkesbury-Nepean catchment. This latter map unit also includes swamps on the Morton plateau within Shoalhaven River catchment, which are not part of the Blue Mountains Swamps community, as they lack species endemic to the Blue Mountains area (paragraph 5) and a number of other species that characterise this community. The Blue Mountains Swamps community belongs to the Coastal Heath Swamp vegetation class of Keith (2004). Together with Newnes Plateau Shrub Swamp, the Blue Mountains Swamps community represents a high altitude expression of this vegetation class, which is typically found on coastal plateaux and sandplains.

10. The Blue Mountains Swamps community has been recorded from the local government areas of Blue Mountains and Wollondilly within the Sydney Basin Bioregion and may occur elsewhere in the Bioregion.

11. The Blue Mountains Swamps community has a total extent of occurrence of less than 2000 km2, bounded approximately by the western Blue Mountains escarpment from Bell to Narrow Neck Peninsula, south to Lacys tableland, the Hawkesbury-Nepean River from Lapstone to Kurrajong in the east, and Mt Wilson in the north. Within this range, the community is currently estimated to occupy an area of approximately 3200 ha (based on mapping by Douglas 2001 and Tindall et al. 2004). The distribution comprises up to 1400 individually mapped swamps, typically 1-2 ha in size, but varying from less than 0.1 ha up to 70 ha, with only 160 swamps larger than 5 ha. These estimates indicate that the geographic distribution of the Blue Mountains Swamps community is in the range of moderately to highly restricted.

12. The geographic distribution of the Blue Mountains Swamps community is unlikely to have been reduced substantially by past land clearing. Approximately two-thirds of the current area of the community occurs within Blue Mountains National Park. While clearing associated with urban, industrial and rural development is unlikely to directly affect a large portion of the remaining third, small-scale clearing associated with residential subdivisions and urban infrastructure has destroyed several swamps between Hazelbrook and Blackheath in recent decades and could threaten other important examples of the community. 'Clearing of native vegetation' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

13. Continuing urbanisation within the Blue Mountains is also likely to threaten the hydrological integrity and ecological function of the swamps through erosion, sedimentation, eutrophication and weed invasion. At present, approximately one-third (ca. 1000 ha) of the community occurs within catchments that are disturbed by urban or industrial development, plantations, rural infrastructure, airstrips, roads, fire trails or utility easements, including more than 250 ha of swamp within Blue Mountains National Park. The expanding area of sealed and partially sealed surfaces associated with urbanisation (e.g. buildings, roads, concourses, etc.) increases the volume and velocity of surface flows discharged into bushland areas, which will affect the Blue Mountains Swamps community where it is part of the hydrological system between the developed areas and streams. These waters carry increased loads of nutrients originating from a variety of sources including fertilised gardens, lawns and golfcourses, industrial infrastructure, leachates and motor vehicles. Expansion and intensification of urban areas is likely to increase nutrient inputs from these sources. The increased velocity, volume and nutrient content of urban runoff are likely to significantly increase rates of erosion, sedimentation and eutrophication, resulting in damage to swamp soils and native vegetation, creating substrates that are susceptible to weed invasion, and transporting weed propagules into the swamps from disturbed areas. The impacts of erosion are likely to be amplified where the swamps occur in steep terrain. 'Alteration to the natural flow regimes of rivers, streams and their floodplains and wetlands' is listed as a Key Threatening Process under the Threatened Species Conservation Act. Given the distribution of the Blue Mountains Swamps community and its catchments in relation to the current urban interface, transport corridors and utility easements, the influx of stormwater, pollutants and nutrients, and the invasion of weeds contribute to a moderate reduction in the ecological function of the community.

14.Problematic weed species in the Blue Mountains Swamps community include the following:

'Invasion and establishment of exotic vines and scramblers' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

15. Degradation of soils and vegetation within the Blue Mountains Swamps community is also associated with certain types of outdoor recreation activity. Overuse of walking trails and unauthorised use of off-road vehicles including trail bikes result in the compaction of swamp soils, physical damage to vegetation and localised concentration of surface water flows that may result in erosion and sedimentation. Degradation by walkers and off-road vehicles has occurred at several locations between Lawson, Medlow Bath and Mt Hay within and outside the Blue Mountains National Park. Threats to the Blue Mountains Swamps community associated with outdoor recreation represent a moderate reduction in the ecological function of the community and are likely to intensify as urban areas continue to expand and with increasing numbers of residents and visitors in the region.

16. Bushfires may sometimes consume the peaty substrate in localised areas of the Blue Mountains Swamps community (Keith 1996). Where this occurs, seed banks and subsoil rhizomes of living plants may be destroyed. Exposure of such soils to heavy post-fire rainfall may result in significant erosion. A localised example of erosion was observed after fires in the Hazelbrook area within Blue Mountains National Park (JL Porter pers. comm.). Physical disturbance to soils and vegetation by machinery, vehicles, hooved animals or walkers is likely to increase the risk of such events. The Blue Mountains Swamps community may also be exposed to disturbances associated with management of bushfire hazard along the urban interface. These may include construction of access tracks and fuel breaks, slashing, mowing and frequent hazard reduction burning. 'High frequency fire resulting in disruption of life cycle processes in plants and animals and loss of vegetation structure and composition' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

17. Groundwater extraction poses a potential future threat to the Blue Mountains Swamps community by altering the hydrological conditions required to maintain its soils and vegetation. The precise nature and timing of impacts will be difficult to predict and will depend on the relationship between swamp hydrology and the aquifers from which water is extracted, as well as the rates of water extraction. Surface infrastructure may also degrade swamp vegetation. There have been recent proposals to utilise the Blue Mountains Swamps community for production of bottled spring water. Proposals to extract groundwater for domestic, industrial or rural use are likely to increase as demand exceeds supply from existing water storages.

18. The dependencies and relationships between the Blue Mountains Swamps community and specialised hydrological conditions may predispose the community to impacts associated with anthropogenic climate change (Hughes 2003). The nature and timing of such impacts are uncertain. Most future climate scenarios for NSW project reduced rainfall (Hennessy et al. 2004a) and, if this eventuates, a delayed contraction of swamps may result (Keith et al. 2006). An increased frequency of extreme weather (Hennessy et al. 2004b) is likely to increase the chance of peat fires and severe erosion events. 'Anthropogenic climate change' is listed as a Key Threatening Process under the Threatened Species Conservation Act.

19. The Blue Mountains Swamps in the Sydney Basin Bioregion is not eligible to be listed as an endangered or a critically endangered ecological community.

20. The Blue Mountains Swamps in the Sydney Basin Bioregion is eligible to be listed as a vulnerable ecological community as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future, as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Amendment Act 2002:

Clause 26

The ecological community's geographic distribution is estimated or inferred to be:

(c) moderately restricted,

and the nature of its distribution makes it likely that the action of a threatening process could cause it to decline or degrade in extent or ecological function over a time span appropriate to the life cycle and habitat characteristics of the ecological community's component species.

Clause 27

The ecological community has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time span appropriate to the life cycle and habitat characteristics of its component species:

(c) a moderate reduction in ecological function,

as indicated by any of the following:

(d) change in community structure

(e) change in species composition

(f) disruption of ecological processes

(g) invasion and establishment of exotic species

(h) degradation of habitat

Professor Lesley Hughes
Chairperson
Scientific Committee

Proposed Gazettal date: 10/08/07

Exhibition period: 10/08/07 - 28/09/07

References:

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Douglas S (2001) Native vegetation mapping of Areas 1 to 5 in Blue Mountains City local government area. Blue Mountains City Council, Katoomba.

Hennessy K, Page C, McInnes K, Jones R, Bathols J, Collins D, Jones D (2004a) Climate change in New South Wales. Part 1: Past climate variability and projected changes in average climate. (CSIRO: Melbourne).

Hennessy K, McInnes K, Abbs D, Jones R, Bathols J, Suppiah R, Ricketts J, Rafter T, Collins D, Jones D (2004b) Climate change in New South Wales. Part 2: Projected change in climate extremes. (CSIRO: Melbourne).

Holland WH, Benson DH, McRae RHD (1991) Spatial and temporal variation in a perched headwater valley in the Blue Mountians: geology, geomorphology, vegetation, soils and hydrology. Proceedings of the Linnean Society of New South Wales 113, 271-295.

Hughes L (2003) Climate change and Australia: Trends, projections and impacts. Austral Ecology 28, 423-443.

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Keith DA, Benson DH (1988) The natural vegetation of the Katoomba 1:100 000 map sheet. Cunninghamia 2, 107-143.

Keith DA, Rodoreda S, Holman L, Lemmon J (2006) Monitoring change in upland swamps in Sydney's water catchments: the roles of fire and rain. Sydney Catchment Authority Special Areas Strategic Management Research and Data Program. Project No. RD07. Department of Environment and Conservation, Sydney.

Smith P, Smith J (1996) Regionally significant wetlands of the Hawkesbury-Nepean River catchment for Sydney Regional Environmental Plan 20, P and J Smith Ecological Consultants, Leura.

Specht RL (1970) Vegetation. In 'The Australian environment'. (Ed. GW Leeper) pp44-67. (CSIRO - Melbourne University Press: Melbourne)

Tindall D, Pennay C, Tozer MG, Turner K, Keith DA (2004) 'Native vegetation map report series. No. 4. Araluen, Batemans Bay, Braidwood, Burragorang, Goulburn, Jervis Bay, Katoomba, Kiama, Moss Vale, Penrith, Port Hacking, Sydney, Taralga, Ulladulla, Wollongong.' NSW Department of Environment and Conservation and NSW Department of Infrastructure, Planning and Natural Resources, Sydney.

Tozer MG, Turner K, Simpson C, Keith DA, Beukers P, MacKenzie B, Tindall D, Pennay C (2006). Native vegetation of southeast NSW: a revised classification and map for the coast and eastern tablelands. Version 1.0. NSW Department of Environment and Conservation, NSW Department of Natural Resources, Sydney.

Young RW, Wray RAL (2000) The geomorphology of sandstones in the Sydney region. In McNally GH and Franklin BJ eds Sandstone city - Sydney's Dimension Stone and other Sandstone Geomaterials.