Literature review: Impact of Chilean needle grass ... - Weeds Australia

Native temperate grasslands of south-eastern Australia and their conservation status
According to the Australian Native Vegetation Assessment 2001 (Cofinas and Creighton 2001), 60,214 km 2 of the pre-European
area of 589,212 km 2 of tussock grasslands in Australia had been cleared or substantially modifed by grazing by c. 2000. The
category includes grasslands dominated by Astreleba, Sorghum etc., mostly in Queensland (282, 547 km 2 ) and the tussock
grasslands of the dry inland, the largest proportion by far of which was in the north of the continent. Of all the major vegetation
groups, grasslands are among the most affected by clearing in Victoria, ACT and NSW (See Table 9). The Victorian Midlands,
Victorian Volcanic Plains (Victoria and South Australia) and the South East Coastal Plain (Victoria) had less than 30% of their
orginal native vegetation remaining (Cofinas and Creighton 2001).
Table 9. Areal extent (km 2 ) of tussock grasslands in the ACT, NSW and Victoria pre-European settlement and c. 2000. Source:
Cofinas and Creighton (2001).
State/Territory Pre European c. 2000 % remaining
Australian Capital Territory 207 91 44
New South Wales 40,790 19,318 47
Victoria 19,175 614 3
Thus it is the native temperate grasslands along with neighbouring grassy woodlands that are among the most threatened
ecosystems in Australia, and amongst the most inadequately represented in reserves (Lunt 1991, Eddy et al. 1998). Whole
grassland ecosystems have therefore been afford threatened status in south-eastern Australia (Table 10).
Table 10. Threatened grassland communities in south-eastern Australia. CE = critically endangered, E = endangered, U =
unlisted, - = not present
Community ACT NSW Vic References
Natural Temperate Grassland E U Sharp and Shorthouse 1996, ACT Govt 1997
Native Vegetation on Cracking Clay Soils of the
Liverpool Plains (partly Western Slopes Grasslands)
- E - Keith 2004
Natural Temperate Grassland of the Victorian
Volcanic Plain
- - CE DEWHA 2008
In 1971 there were no areas >4,000 ha in conservation reserves (Groves 1979). In the late 1970s the possibility of conserving
moderately large areas seemed remote, because only small remnants were then known to exist (Groves 1979). By the early 1990s
natural temperate grasslands had declined by 99.5% since European settlement (McDougall and Kirkpatrick 1994, Sattler and
Creighton 2002). The 0.5% estimated to remain included remnants in “semi-natural condition” (Kirkpatrick et al. 1995 p. v). By
the late 1990s, in all areas of south-eastern Australia, less than 1% remained of the grasslands and grassy woodlands that once
existed (Lunt et al. 1998). Widespread extinctions occur when habitats are reduced by 90% and extinctions of vertebrates are
continuing to occur in southern Australia in areas where native vegetation is reduced by 70-80% (Traill and Porter 2001).
Existing remnants of southern Australian temperate grassland on public land are mostly small and isolated (Lunt and Morgan
2002). Those on private land are generally larger, but are of lower quality, and all have a history of grazing (Kirkpatrick et al.
1995). Sattler and Creighton (2002) identified the NSW South Western Slopes, Riverina and Victorian Volcanic Plain as
bioregions with the highest priority for improvement of reservation status. These areas cover a high proportion of the land once
occupied by native grasslands.
The extreme fragmentation of the conserved elements (Eddy et al. 1998, Groves and Whalley 2002) means that they are subject
to inundation or impoverishment by the surrounding ‘cultural steppe’, an immature ecosystem with a higher proportion of energy
going into production than into maintenance, rapid accumulation of biomass, reduced litter production, increased excrement
production and reduced species diversity with most species being r strategists (rapid intrinsic rates of population increase, little
food specialisation, etc.) (Matthews1976). Nutrients, biomass, pollutants, exotic organisms, native pests and other ecological
disrupters may be flushed in (Hobbs and Heunneke 1992), while native organisms or their propagules, water, etc. are extracted.
Many environmental changes that may substantially affect the composition and functioning of small remnant grasslands have
rarely received any consideration, including altered climatic regimes, light availability and noise profiles.
Thus ‘fragmentation’ as an outcome of development needs to be contrasted to with the increased connectivity that also results.
Utility infrastructure including power lines, fences, drains and traffic corridors have provided a new network of corridors that
facilitate dispersal of a different set of organisms and allow the movement of a range of non-biological resources between
remaining grassland remnants (Aguiar 2005). A series of small grasslands may nevertheless sustain more diversity than a large
patch with an equivalent total area, because different species may dominate in small patches, there are more edges and
transitional habitats (Hobbs and Heunneke 1992) and a greater liklihood of heterogeneity in disturbance regimes.
Victoria
In simplistic terms, the major plant formations of southern Victoria are determined by geology: heathlands on sands, Eucalyptus
forests and woodlands on sedimentary rocks, and grasslands on clays of volcanic origin (Patton 1935). Victorian grasslands
occur mainly on relatively young geological materials, such as Tertiary volcanics and Pleistocene and Holocene sediments
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