Discussion Paper - Part A - Victorian Environmental Assessment ...

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Grazing may also: reduce the capacity for riparian zonevegetation to act as a nutrient ‘filter’; compact soil; andincrease erosion where bare soil has been exposed,therefore increasing sediment input into waterways(Figure 5.27).Alternatively, domestic stock grazing can positivlyaffect the environment if applied in a strategic manner.Grazing cattle and sheep for a limited time in springcan help to reduce weeds by restricting seed set andflowering in certain annual species. Low-level sheepgrazing is applied in grasslands such as Terrick TerrickNational Park to maintain an open habitat preferredby many threatened flora species.The limited studies that have been undertaken todetermine the effectiveness of different grazingstrategies for maintaining and enhancing biodiversitysuggest that intermittent grazing provides the bestbiodiversity outcomes by creating vegetationheterogeneity through both time and space (Dorrough etal. 2004). Continuous and intensive grazing can cause asignificant loss of habitat value through speciesselectivity, changes to vegetation structure and impactson habitat values (e.g. Chesterfield 1986; Jansen &Healey 2003). However, a varied vegetation structure canhave less useable forage and therefore has not generallybeen favoured by graziers (Dorrough et al. 2004). Thismismatch in land management objectives is one of themain impediments to the introduction of strategicgrazing management with biodiversity conservation as aprimary objective across parts of the public land estate.Changes due to intensive grazing may be irreversible inthe short to medium term, and a significant allocation ofresources may be required to restore native vegetation.In particular, damage to stream frontages is significant.A site’s ability to recover from grazing damage dependson stocking density, soil type, geomorphology andtopography and is therefore highly variable (Robertson &Rowling 2000; Martin et al. 2006). There may be asubstantial time lag between the time of revegetationand the re-establishment of animal populations (Vesk &Mac Nally 2006)In addition to domestic stock grazing on public landwithin the study area, there are native grazers(kangaroos and wallabies) and feral grazers (feral cattle,rabbits, hares, fallow deer, feral horses/brumbies, goatsand pigs). When in large populations, these additionalgrazers contribute to over-grazing of vegetation. Thehard-hoofed feral cattle, brumbies and goats alsocontribute to trampling, soil compaction and erosion.Climate Change, Greenhouse and BiolinksClimate change, both natural and due to increased levelsof greenhouse gases in the atmosphere, is described inchapter 4. This section looks specifically at the potentialeffects of climate change on biodiversity. Climate changerepresents a major new threat to biodiversity andecosystem services for the 21st century with somepredicting mass extinctions (Thomas et al. 2004).Climate change is predicted to change the distribution,configuration and abundance of species and ecosystemservices.The types of species most at risk from greenhouseeffects have been divided into six categories (Mansergh& Bennett 1989; Brereton et al. 1995):• Genetically impoverished and/or localised populations• Poor dispersers and annual plants• Specialised species, especially those dependent onmature vegetation, e.g. superb parrot• Peripheral or disjunct populations• Coastal species• Montane and alpine speciesThe implications of climate change on the flora andfauna of river red gum ecosystems require furtherstudies, especially for invertebrates. In theory, globalwarming could affect invertebrates by increasing thedevelopmental rate of species, thus resulting in moregenerations each year for some species. This could occurboth for herbivorous insects and for their naturalenemies. Another possibility is that insects from coolerregions of the river red gum range could be displaced byspecies better adapted to warmer temperatures. Thiscould promote invasive invertebrate species currentlyonly found further north. The knowledge base regardingthe invertebrate fauna on river red gums is inadequateto allow further speculation.Modelled responses of fauna to climate change insoutheastern Australia has lead to the identification ofclimatic refugia (areas where species will experience aclimate similar to the present) and a series of biolinkzones in Victoria (Bennett et al. 1992; Brereton et al.1995), which have since been recognised in governmentpolicy (DCE 1992b). Biolink zones are areas that willmaximise the capacity for species to “move”, recoloniseand reconfigure as they adapt to climate change (seeMansergh et al. 2005). The Murray River and associatedriparian vegetation and wetlands have been identified asa key sub-continental scale “biolink”.A National Action Plan (NAP) has been developed forAustralian biodiversity in response to greenhouse climatechange (NRMMC 2004). In strategy action 5.1 (p. 27)the NAP seeks to implement “strategies to reduce thephysical barriers to movement to facilitate the migrationand dispersal of terrestrial species and communities thatare vulnerable to climate change”. The River Red GumForests study area has been identified as a major link,provided by its contiguity in linking different habitatzones (DCE 1992b; Brereton et al. 1995). However,vegetation conditions could be improved to maximisethe river red gum’s value as a biolink (ARIER et al. 2004).Further, recommended actions of the NAP include to“identify and implement opportunities to re-establishnative vegetation and enhance habitat for vulnerablespecies on private land through revegetation, vegetationmanagement and land-use change program”. Thevarying width of native vegetation (in both NSW andVictoria) along the rivers provide opportunities toimprove the area as a biolink.FireFire (see chapter 4) is vital for many Australianecosystems and shapes the composition and distributionof plant and animal communities across Victoria. Plantshave adapted to fire over millions of years and havevarious survival mechanisms. Some trees with thick barkmay lose their canopy but survive the fire and grow new<strong>Discussion</strong> <strong>Paper</strong>85
Table 5.8 Comments on fire from explorers’ journals.Explorer (year)AreaExtractHamilton HumeWilliam Hovell(1824-25)Ovens River &Goulburn River‘All the country from where we started this morning is all burning inevery direction and the bush is all on fire….the blacks….’. (Hovell1921:343)‘…all the country around us appears to be on fire…’.(Hovell 1921:359)‘The country is on fire in all directions. This appears to be the season forburning the old grass to get new.’ (Hovell 1921:361)Thomas Mitchell(1836)Charles Sturt(1838)Loddon RiverMurray River (nearjunction withEdwards River)Murray River(general)‘Fire, grass, kangaroos, and human inhabitants, seem all dependant oneach other for existence in Australia….. Fire is necessary to burn thegrass and form those open forests’. (Mitchell 1969:412)‘….. under a dark wood of gum trees scathed by fire to their very tops.’(Sturt 1838 cited in Sturt 1899:138)‘When timber was again seen it was like the reeds, blackened by nativeconflagrations. Huge trunks and leafless limbs lay one across another onground as black as themselves.’ (Sturt 1838 cited in Sturt 1899:143)‘The reeds had been burnt by the natives and in burning had set fire tothe largest trees and brought them to the ground.’ (Sturt 1838)shoots from buds on the surface of the trunk andbranches. Individual plants in other species may die butproduce prolific seed, which take advantage of post-firelight, moisture and nutrients. A substantial proportion ofnative plant and animal species are dependent on firefor their continued survival and propagation. The lifehistory characteristics (also termed ‘vital attributes’; seebelow Noble and Slatyer (1980)) of individual plant andanimal species determine their tolerance to fire. Differenthabitats and their resident species, such as grasslands,heathlands, woodlands and rainforests all have theirown tolerances to fire.Fire regimes are classified by frequency (interval betweenfires), intensity, season, and scale. Inappropriate fireregimes are fires occurring at frequencies, intensities,seasons, and scales that lie outside the ecological andphysiological tolerances of resident plants and animals.The interplay of fire with plant and animal species andcommunities is complex, and inappropriate fire regimesare now recognised as a potential threat to sustainableecosystems and biodiversity conservation under the Floraand Fauna Guarantee Act 1988 (Scientific AdvisoryCommittee 2003).Native animals survive fire through mobility, shelter, andsurvival in unburnt areas. Although many individualanimals are killed, populations survive and generallyrecolonise burnt areas as they recover. Sometimes,species in isolated small populations occupying a narrowecological niche, such as the mountain pygmy-possum,may be at risk in a major fire.Studies of charcoal records from sediment cores indicatethat fire has played a role in shaping the landscapessurrounding the Murray River (C. Kenyon unpublished).Extracts from the journals of early European explorers(see Table 5.8) and overlanders suggest that lowintensityfires were a frequent occurrence in the RiverRed Gum Forests study area (Mac Nally & Parkinson2005). An early settler in the Barmah region noted thatIndigenous people set fire to the region approximatelyevery five years (Curr 1883). Table 5.8, reproduced fromMac Nally (2005), compiles extracts from the journals.Unfortunately these reports do not refer specifically toriverine forests. It is likely that wildfires started bylightning, also occurred in riverine forests.Current knowledge suggests that while river red gumsaplings are fire-sensitive (Dexter 1978), large trees aregenerally able to survive low intensity fires (Mac Nally &Parkinson 2005). The Arthur Rylah Institute is currentlycurating and managing DSE’s Vital Attributes database.This project includes interim recommendations in relationto the maximum and minimum fire intervals for differentvegetation types (Cheal & Carter 2006). According tothis data, riverine woodlands and forests are flammableonly occasionally (i.e. after seasons with extended86 River Red Gum Forests Investigation 2006
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2 GeologyGeology underpins the dive
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Figure 2.2 Schematic diagram of fol
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et al. 2000). This Selwyn Block is
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Figure 2.4 Murray Basin during the
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quartz sand and gravel beds, carbon
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Box 3.1 River MeandersRivers rarely
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lakes by flooding from Chalka Creek
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major valleys. The large, older fan
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ecommending representative areas fo
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Box 3.2 Barmah Area GeomorphologyTh
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4 Climate andHydrological SystemsAu
Page 31 and 32: Figure 4.1 Annual anomalies (based
Page 33: such as messmate have a thick prote
Page 36: Natural Hydrology of the River Murr
Page 39: Table 4.3 Stream flow in major Vict
Page 42 and 43: GroundwaterHydrology also relates t
Page 44 and 45: FloodplainsThe floodplains of the R
Page 46 and 47: 5 BiodiversityBiodiversity is impor
Page 48 and 49: Ecosystem Assessment 2005). Species
Page 51: Figure 5.2 Hairy darling-pea on a r
Page 57 and 58: Figure 5.5 A common blue-tongued li
Page 59: Threatened VertebratesBased on cons
Page 64 and 65: Figure 5.8 Mature river red gum on
Page 66 and 67: Figure 5.12 Tangled lignum at Mulcr
Page 68 and 69: Egrets generally only breed in livi
Page 70 and 71: which is essential habitat for some
Page 72 and 73: dependent species including darling
Page 74: Table 5.7 Summary of risk levels to
Page 77 and 78: Figure 5.22 Koala in a river red gu
Page 79 and 80: Examples include the larvae of leaf
Page 81: Figure 5.27 Cattle on the bank of t
Page 85 and 86: 6 Indigenous LandAssociationsThis c
Page 89 and 90: Table 6.1 Summary of area in Victor
Page 91 and 92: waters. The Joint Body is funded to
Page 93 and 94: Consultative ManagementConsultative
Page 95 and 96: 7 Non-IndigenousHistoryThe resource
Page 97 and 98: Figure 7.2 Murray Downs homestead (
Page 99 and 100: Reception Centre established in 194
Page 101 and 102: and rural water supply became the r
Page 103: FisheriesThe collapse of the Murray
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