5 existiNg eNvirONmeNt 5.1 ComponeNts of biodiversity, ecOlOgical and physical eNvirONmeNtal PrOcesses The study area (Figure 1) includes predominantly agricultural land adjacent to highly urbanised areas. Most land within the study area can be considered highly altered from its ‘natural state’, with consequent impacts on biodiversity and ecological processes, due to its land-use history. The changed ecological processes resulting from land-use change reported by numerous authors (see Pickett et al. 2001, Whitford et al. 2001, Dale et al. 2005 and Theobald et al. 2005) have historically occurred over much of the study area. Those with significant effects on biodiversity include changes in vegetation structure and composition; local species extinctions and fragmentation of habitat; changes in species abundances including the introduction of new species; and the alteration of disturbance regimes. The surrounding catchments have been highly modified. Water quality into Westernport Bay is often poor because of extreme modification to catchment hydrology and the establishment of intensive agriculture. There is very little connectivity of habitat within the current Urban Growth Boundary. The Port Phillip and Westernport catchment, within which Melbourne is located, scored poorly for four out of five biodiversity indicators in the Catchment Condition report (PPWCMA 2006). 5.2 listeD aND NOmiNateD cOmmuNities uNDer the ePbc act Five ecological communities listed, or nominated for listing, under the EPBC Act were identified from the Commonwealth’s Protected Matters Search Tool as potentially occurring within the study area. These are: > Natural Temperate Grassland of the Victorian Volcanic Plain; > Grassy Eucalypt Woodland of the Victorian Volcanic Plain; > Temperate Lowland Plains Grassy Wetland; > White Box-Yellow Box-Blakely’s Red Gum Grassy Woodland and Derived Native Grassland; and > Gippsland Red Gum Grassy Woodland and Associated Native Grassland. This assessment determined that White Box-Yellow Box-Blakely’s Red Gum Grassy Woodland and Derived Native Grassland and Gippsland Red Gum Grassy Woodland and Associated Native Grassland do not occur within the study area. Delivering Melbourne’s newest sustainable CoMMunities – strategiC iMpaCt assessMent report 65 Natural Temperate Grassland on the Victorian Volcanic Plain, Grassy Eucalypt Woodland of the Victorian Volcanic Plain and Temperate Lowland Plains Grassy Wetland are considered to have a moderate or high likelihood of occurring within the study area. These communities are described in more detail below. 5.2.1 Natural temPerate grassland of the victorian volcanic Plain Natural Temperate Grassland of the Victorian Volcanic Plain is native grassland of Kangaroo Grass (Themeda triandra), Wallaby-grass (Danthonia spp.) and other perennial tussock-forming grasses interspersed with an array of native herbs and sub-shrubs. Natural Temperate Grassland covered the vast majority of the Victorian Volcanic Plain, stretching from the Yarra River in Melbourne almost to the South Australian border. At least 95 per cent of its original extent has now been cleared or patches have been severely degraded, primarily for agriculture, but also for urban development. As a result it is listed as a critically endangered ecological community under the EPBC Act. The original, pre-European and current extents of around 870,000ha and 65,000ha respectively are shown in Figures 2 and 3. More information about this type of grassland can be found in Department of the Environment, Water, Heritage and the Arts (2008). The EPBC-listed grassland community ‘Natural Temperate Grassland of the Victorian Volcanic Plain’ is essentially identical to Victoria’s Western Basalt Plains Grassland listed as a threatened community under the Victorian Flora and Fauna Guarantee Act 1988 (FFG Act). It also corresponds to Plains Grassland and Creekline Tussock Grassland ecological vegetation classes, which have a conservation status of endangered within the Victorian Volcanic Plains bioregion. Refined maps of native grassland and other native vegetation within and to the west of the study area, including the OMR/E6 Transport Corridor and Regional Rail Link are shown in Figures 5 and 6. Remnants of native grassland persist in the study area, mostly in the Melbourne West Investigation Area, but also in smaller areas within the Melbourne North Investigation Area (Figures 7 and 8). Scattered remnants of this ecological community also occur within the OMR/E6 Transport Corridor and the Regional Rail Link. The final ground-truthed maps (Figures 5–8) are considered very reliable maps of the extent of Natural Temperate Grassland in the study area. Apart from being a critically endangered ecological community, Natural Temperate Grassland provides habitat for several species of plant and animal threatened at a national (and state) level. Several of these are discussed in this report, including Golden Sun Moth (critically endangered), Striped Legless Lizard (vulnerable), Grassland Earless Dragon (endangered), Spiny Rice-flower (critically endangered) and Plains-wanderer (vulnerable). 66 Delivering Melbourne’s newest sustainable CoMMunities – strategiC iMpaCt assessMent report 5.2.2 Grassy eucalyPt woodland of the victorian volcanic Plain Grassy Eucalypt Woodland of the Victorian Volcanic Plain is an open eucalypt woodland with a predominantly grassy understorey. The ecological community exhibits a degree of natural variation in appearance and composition across its range, due to variations in rainfall and landscape features such as changes in elevation, drainage patterns and the presence of rocky outcrops. It is most commonly dominated by River Red Gum (Eucalyptus camaldulensis), but this can become Grey Box (E. microcarpa) or Yellow box (E. melliodora) on drier sites, and Manna Gum (E. viminalis) or Swamp Gum (E. ovata) on damper sites. In some areas, this community can have an association with or include stony knolls. Grassy Eucalypt Woodland of the Victorian Volcanic Plain is an ecological community that was listed under the EPBC Act on 25 June 2009 as critically endangered. Grassy Eucalypt Woodland of the Victorian Volcanic Plain has a similar former range to the Natural Temperate Grassland of the Victorian Volcanic Plain and is likely to have extended from Melbourne to near Hamilton in south-west Victoria. It was always somewhat more restricted than Natural Temperate Grasslands of the Victorian Volcanic Plain, being confined to more friable soils on the basalt plains and rarely occurring on the true cracking clays. The EPBC-listed community ‘Grassy Eucalypt Woodland of the Victorian Volcanic Plain’ incorporates Victoria’s Volcanic Plains (River Red Gum) Grassy Woodland, which is listed as threatened under the FFG Act (Scientific Advisory Committee, 2004). This also correlates with Plains Grassy Woodland, the relevant ecological vegetation class which has a conservation status of endangered within the Victorian Volcanic Plains bioregion. The Commonwealth Department of Environment, Water, Heritage and the Arts has drafted advice that defines eligible stands of this vegetation type based on condition of the vegetation. In essence, for a stand to qualify as the listed community, it must be at least 0.5ha in size and have at least 50 per cent of its perennial ground layer made up of native species; or if it is more degraded, it must have a density of at least three large (>70cm diameter at breast height) trees per hectare. Department of Sustainability and Environment mapping, revised following the formal listing of Grassy Eucalypt Woodland, almost certainly represents an overestimate of the extent of the listed community. Following an additional program of ground-truthing this vegetation type, it was clear that some of the area mapped includes areas with very poor understorey condition. Without additional access to private property to determine Delivering Melbourne’s newest sustainable CoMMunities – strategiC iMpaCt assessMent report 67 this precisely, a precautionary approach was taken where all areas with suitable tree cover and considered potentially able to support the necessary understorey component were included. However, where areas were confirmed not to be the listed community (generally due to absence of any native understorey), these were excluded from the mapping. There were only relatively small areas where this was the case. Using Department of Sustainability and Environment’s modelled vegetation mapping, the original (pre-European) extent of Grassy Eucalypt Woodland is shown in Figure 10. The current extent of Grassy Eucalypt Woodland is shown in Figures 7 and 8. Within the study area, grassy woodlands of the Victorian Volcanic Plain are found scattered through the Melbourne North Investigation Area and adjoining precincts inside the existing Urban Growth Boundary, and including in the Sunbury area. The largest concentration of remnants is found in the south-east of the Melbourne North Investigation Area, with some more consolidated patches in the south-west and along Merri Creek, where there are many adjoining stony knolls. The ecological community also occurs within the OMR/E6 Transport Corridor. Generally the quality of the understorey appears similar throughout the Investigation Area, however this will be the subject of further detailed investigation. Beyond the Investigation Area, the community occurs more extensively to the east towards Whittlesea and to the west (generally as discrete stands) toward Gisborne. The