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

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dependent species including darling-peas, swainson-peasand a variety of native grasses.Habitat fragmentation is a major threat listed under theFlora and Fauna Guarantee Act 1988 (see Appendix 8). Itoccurs when native vegetation is cleared, leaving habitatremnants separated from other blocks of habitat byareas with little or no habitat value—typically farmland.Such remnants can be characterised by their size andshape, distance to the nearest neighbour remnant andthe land-use of the intervening areas.Habitat fragmentation has a number of impacts uponbiodiversity. Some remnants are too small to supportpopulations of species that have large home ranges,such as barking owls which have home ranges of atleast several hundred hectares. Small remnants may onlybe able to support small populations of other species,making them vulnerable to extinction due to chanceevents. Habitat fragmentation also increases the amountof edge, which is more vulnerable to disturbance,predation and weed invasion. Additionally, fewerpopulations can live in small remnants compared withlarger ones. Thus, continuing fragmentation results in asimplification of the ecological community,disadvantaging specialist species and leading to a declinein ecosystem services.Habitat DegradationHabitat degradation may result from the removal ofparticular elements, leaving it unsuitable for somespecies. Firewood collection on public land within thestudy area is one example. Although the whole forest isnot cleared, the removal of this important element canrender the area unsuitable for many species that requirefallen wood (or coarse woody debris) for protection frompredators and extreme temperatures and as a place toforage (Mac Nally & Horrocks 2002a). Fallen timberloads of more than 40 tonnes per hectare are requiredfor some vertebrates (Mac Nally et al. 2002a). Clearanceof this habitat element is an important process in thedecline of bush stone-curlews, carpet pythons and arange of other threatened species.Road and track networks may reduce richness andabundance of species including invertebrates(Greenslade & Greenslade 1977) and increase the rangeand access for foxes. Recreational activities can alsodegrade habitat. Digging for bardi grubs disturbs thesoil, which promotes weed germination. Power boatingactivities can damage river bank vegetation andcontribute to soil erosion and sedimentation of rivers(see chapter 11).There are many forms of habitat degradation and someof the major ones are described in detail below.Altered Water RegimesThe Murray River has been increasingly regulated withwater diverted for agriculture since Hume Dam was firstconstructed in 1936. The extension to Hume Dam wascompleted in 1961. Regulation remained the same untilDartmouth Dam was commissioned in 1979. There wasan accelerating increase in diversion of water foragriculture from 1961 to 1995 when a cap was imposedon extraction in Victoria. The changes to the waterregimes aimed at providing increased irrigationallocations have changed the river height, flow volumes,flooding frequency, duration and season of flooding (seechapters 3 and 15 for details).Changed water regimes (flow, temperature, andflooding frequency, duration and extent) can greatlyaffect wetlands, floodplains and can greatly change thespecies composition of an area. Densities of the yellowfootedantechinus increase 20-fold after flooding (MacNally & Horrocks 2002), reflecting better survival whenthere are large numbers of invertebrates available(Ballinger & Mac Nally 2005). These population increasesmay also occur among bats (Lumsden et al. 2002) andinsectivorous birds (Chesterfield et al. 1984; Mac Nally etal. 2001). Many bird species require specific floodingconditions for suitable habitat, particularly for breeding(Parkinson et al. 2002).For other species, the water temperature and change offlow speed are important cues that conditions are rightfor breeding. ‘The alteration to the natural temperatureregimes of rivers and streams’ and ‘The alteration to thenatural flow regimes of rivers and streams’ are listed as apotentially threatening process under the Flora andFauna Guarantee Act 1988. For example, the silverperch, a critically endangered species in Victoria, isthought to spawn in late spring and summer after waterflow increases and the temperature rises above 23°C.Cold water released from the bottom of storage weirsmay lead to localised unsuitable habitat as well as theabsence of triggers for breeding. Additionally, eggs maynot be as viable and larvae may not be suited to thelower temperatures. Reduced water temperatures arealso thought to threaten the critically endangered troutcod, the endangered freshwater catfish, Murray cod andMacquarie perch, and the vulnerable golden perch.Water flow and flooding regimes greatly affect aquaticand wetland vegetation. As discussed above, matureriver red gums require flooding every few years. Seeds ofthis species germinate as a result of a disturbance suchas flooding and a new generation grows. Typically, manyof these new seedlings would die during the subsequentflood. With the present flooding regimes, such floodsare only achieved infrequently and this results in forestsof close growing, even age-structured cohorts surviving.These new trees are invading the Moira grasslands thatpreviously persisted when more frequent flooding killedthe juvenile river red gums (Bren 1992).The main threat to wetlands in the study area is waterstorage, regulation and extraction associated withirrigated agriculture. Floodplain wetlands, particularly ofthe Goulburn and Murray Rivers, tend to be flooded lessfrequently, retain water for shorter periods and may beflooded in summer and autumn when river levels arehigh to deliver irrigation water instead of in the naturalseasons for flooding (winter and spring). Hydrologicalthreats on floodplains are exacerbated by flood controllevees in some areas that isolate wetlands fromfloodwaters.Many wetlands in the study area have been cut off fromtheir natural floodplains or catchments and incorporatedinto the water regulation and storage system. Manyformer temporary wetlands (that went through wet anddry cycles) are often now permanently flooded. This haskilled the river red gums and increased rushes such asgiant rush. Other wetlands may be permanently dry as aDiscussion Paper75
esult of being by-passed by irrigation channels. In otherareas, the lack of flooding for many years has weakenedor killed many river red gums (Brett Lane & AssociatesPty Ltd 2005). Other hydrological changes have resultedfrom the use of wetlands as areas to dispose of excessirrigation waters or salinity disposal.A mixed pattern of temporary and more permanentwetlands enables a diverse range of species to inhabitthe floodplains of the study area (Figure 5.19) (Parkinsonet al. 2002). Temporary wetlands are generally shallowwith high light levels and warm temperatures. This leadsto a high diversity and abundance of macroinvertebrateswhich provides a large food resource for wading birdssuch as egrets and spoonbills. Permanent water bodiesmay be of greater value to diving birds such ascormorants and azure kingfishers as the open waterfacilitates fish catching (Parkinson et al. 2002).Figure 5.19 Lake Murphy, near Kerang, floodeddue to an allocation of environmental water.For the four Ramsar sites in the study area, strategicmanagement plans have documented the level of risk tosite values from various activities and processes (DSE2003b, d, e, 2004h). They are summarised in Table 5.7.Although this summary does not assign a risk of grazingto wetlands in the Kerang wetlands, Gunbower forestand Barmah forest, grazing is detrimental to manyspecies, communities and ecological processes in thoseecosystems (Robinson & Mann 1998; Jansen &Robertson 2005).Pest Plants and Animals and PathogensPests and weeds are broadly defined as species that haveundesirable impacts, which may be economic,environmental or social. Pathogens are diseaseproducingorganisms, such as cinnamon fungusPhytophthora cinnamomi, that also have undesirableimpacts. Many of these species, but not all, areintroduced to Australia and their environmental impactsare particularly felt here because of the long prior periodof isolation of the Australian continent.Pest plants and animals are one of the greatest threatsto the integrity of biodiversity in the study area (DNRE2002g). They cause a wide range of impacts on theenvironment including damage to native vegetation,genetic pollution, displacement and loss of native wildlifeand alteration of ecological processes, such as waternutrientcycles and fire regimes. They affect primaryproduction through, for example, direct competition forresources and introduction and spread of diseases thataffect crops and livestock. They may affect amenitythrough preventing access to recreational areas and poserisks to human health (e.g. anaphylaxis as a result of beestings). The seriousness of the threat is underscored bynumerous pest and weed species and processes beinglisted, after rigorous scientific assessment, under theFlora and Fauna Guarantee Act 1988.The Victorian Pest Management—A Framework forAction (DNRE 2002a) provides the broad strategicdirection for pest management in Victoria. Subsidiarydocuments cover specific pests such as foxes, rabbits,wild dogs and weeds (DNRE 2002e, f, g).Significant investment in prevention and control isoccurring on public and private land. The Weeds andPests on Public Land Initiative is a major state governmentprogram to support pest plant and animal control innational parks, state forest and other public land inVictoria. The four-year, $14 million, initiative aims to:• Protect large areas of high value natural assets bypreventing and reducing the impact of weeds andpests;• Improve public land stewardship through a collaborativepartnership approach at the landscape level;• Minimise the movement of weeds and pests acrossthe public/private land interface; and• Engage the community in the management of publiclands;This program operates through on-ground projects inreducing pest plants and animals, increased strategicapproaches to pest management with a pilot study inthe Angahook-Otway region and through an increase inthe Good Neighbour program, which supports privatelandholders by controlling pests and weeds on theborder of public land. The complementary ‘TacklingWeeds on Private Land’ Initiative undertakes widerangingactivities on private land.Significant developments in pest and weed managementinclude taking a ‘biosecurity’ approach, with a focus onpreventing new problems. Large scale, cross-tenure,continuous programs, as demonstrated by the SouthernArk fox control project, also have great potential forimproved outcomes (DNRE 2002d; DSE 2003g). Acooperative approach to tackling pest animals, weedsand pathogens seems to be the most effective. To thisextent, government plays an important role inencouraging cooperation by all those with an interest indealing with pest animals, weeds and pathogens.Deliberate and ignorant introduction and spread ofspecies remains a problem. For example, aquariumspecies are released by often well-meaning people but atgreat risk to the environment. Policing of these activitiesbenefits from community surveillance and reporting.A weed is a plant that requires some form of action toreduce its harmful effects on the economy, environment,human health and amenity (Australian WeedsCommittee 2006). Weeds threaten the productivecapacity of land, water and biodiversity assets in Victoria.It is estimated that they cost Victoria $900 millionannually. Victoria faces new and increasing threats fromweeds (despite the success of current approaches) dueto the number of new species naturalising.76 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
Page 21 and 22: major valleys. The large, older fan
Page 23: ecommending representative areas fo
Page 26 and 27: Box 3.2 Barmah Area GeomorphologyTh
Page 28: 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 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 and 82: Figure 5.27 Cattle on the bank of t
Page 83 and 84: Table 5.8 Comments on fire from exp
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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