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

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Cats and dogs carry disease and prey on native wildlife,including small mammals, birds and reptiles. Cats occurin domestic, farm (semi-domestic) and feral populations.In domestic situations, sterilisation and the use ofenclosures can reduce the impacts of cats on theenvironment. Methods of effectively controlling feral catshave proven elusive although research is currentlyunderway at both the state and national level.Figure 5.24 Damage to eucalypt leaves by the gumleaf skeletoniser.Feral pigs are particularly deleterious in wetlandenvironments where they root up the ground vegetation,leading to increases in soil erosion, sedimentation ofwaterways and weed invasion. They pose a significantrisk to livestock as potential carriers of disease.Feral cattle and horses (brumbies) pug wetlands andaccess points to water, trample vegetation andcontribute to soil erosion (see grazing, above).Exotic fish were brought to Victoria by Europeansettlers in the late 1800s to stock waterways with edibleand familiar species for angling. More recentlyintroduced exotic aquarium fish are further upsetting theecology of rivers and streams. Some introduced fish havebecome dominant, reducing native fish species bycompeting aggressively for food and for space. Exoticfish also introduce new diseases, parasites andpathogens with the potential to wipe out any nativespecies susceptible to new pathogens.Carp are recognised as a serious vertebrate pest andhave expanded rapidly in distribution and abundance todominate waterways in the Murray-Darling Basin andsoutheastern Australia (Koehn et al. 2000). They are thelargest and most visible introduced fish species and havereceived much public and political attention. Barmahforest has been identified as a potential recruitmentzone for carp (Stuart & Jones 2006) and although carpnumbers have reduced in some areas over the pastdecade (Nicol et al. 2004) they remain an abundantlarge fish species, comprising 80 percent of the biomassin 1999-2001 (Stuart & Jones 2002). Commercialharvesting of adult carp in Moira Lake has variedbetween 76 tonnes in 2001 to less than 20 tonnes inrecent years (King 2005). A National Carp ManagementStrategy and local carp action plans influencemanagement.Figure 5.23 Gum leaf skeletoniser on askeletonised leaf.Locally overabundant native animals, while notclassified as pests, can inflict significant damage on thelocal environment. For instance, overabundantkangaroos can severely overgraze landscapes, reducingthe forage and habitat available for other native species.In the last financial year (2005-2006) five permits wereissued for the destruction of 120 western greykangaroos and 14 permits for 250 eastern greykangaroos were issued in Loddon, Gannawarra andCampaspe Shires and Swan Hill Rural City Council (DSE,unpublished data). Overabundant koala populations inVictoria have, in some instances, killed the preferredfood trees in an area with many koalas dying as aconsequence. The koala (Figure 5.22) population onUlupna Island (Barmah State Park) is at very high levelsand may need future management to preserve thehealth of both the forest and the koala population.Additionally, small populations of native animals maybecome nuisances in recreational areas. For example,birds that are fed in picnic grounds often become lesswary of people and will pester them for food whileother species may force entry into camp tents. Othernative species are agricultural pests. For example, in thestudy area, cockatoos and corellas eat crops and flocksof small birds such as silvereyes can reduce grapeharvests.Invertebrate PestsSome species that are becoming more widespread inVictoria include Portuguese millipedes, Argentine antsand European wasps. Argentine ants have been found intowns along the Murray River and European wasps alsooccur there. There is the danger of other speciesinvading the riverine system, especially in the face ofclimate change. The main contenders are exotic speciesof tramp ants such as the red imported fire ant and thebig-headed ant. The former is currently located inQueensland (with at least one incursion into Victoria thatwas destroyed) and the latter occurs along the coast ofNew South Wales.A wide range of insect species damage river red gumforests to varying degrees. The majority of these insectpests cause damage on an infrequent basis with theimmediate effects generally short-term and localised.<strong>Discussion</strong> <strong>Paper</strong>81
Examples include the larvae of leaf-feeding sawflies andlarvae of the leaf-mining leafblister sawfly (Farrow 1996;Phillips 1996; Elliot et al. 1998). While the causes ofsuch outbreaks are not fully understood, factors such asavailability of food resources, prevailing climaticconditions, foliage nutrient conditions, age status ofindividual host trees and stands, and population statusof predator species all appear to play a role (Collett2001).Observations over many years in Victoria have identifiedtwo insect species causing significant economic andaesthetic damage to wide areas of river red gum forest.These species are the gum leaf skeletoniser and the redgum basket lerp psyllid. These outbreaks either occurregularly causing defoliation damage or on an infrequentwidespread basis causing significant by defoliation.The gum leaf skeletoniser (Figure 5.23) is a defoliatinginsect native to eastern Australia, capable of causingsevere damage to foliage on river red gum in nativeforests, roadside plantings and plantations (Farrow1996). It lays eggs in young leaves where the younglarvae feed on the upper and lower surface leaf tissueavoiding the oil glands and veins, thereby creating a“skeleton” (Figure 5.24) (Elliot et al. 1998). The firstsignificant outbreaks were recorded in 1933 (DCFL1986). Subsequently, large outbreaks occurred regularlyat decade intervals in 1944 and 1957 along the MurrayFigure 5.25 Feral honeybees in a tree hollow atHeywood Lake in northwest Victoria.River (Harris 1974) culminating in a major defoliationevent in 1975 when more than 40,000 ha of river redgum forest was stripped of leaves in the Murray andGoulburn Valleys (Harris et al. 1977; DCFL 1986). Sincethen, several smaller localised outbreaks have occurredwith the most significant being along the Goulburn Rivernear Shepparton in the mid-1990s. Outbreaks of gumleaf skeletoniser appear to be linked to a lack offlooding. Populations were lower on sites with nearbyfloodwaters while flooded sites had negligiblepopulations of gum leaf skeletoniser (Harris 1972). Itseems likely that increasing length and severity ofdrought, coupled with increased demands on availablewater resources, may further increase the incidence ofsuch outbreaks.The red gum basket lerp is a sap-feeding psyllid insectnative to south-eastern Australia. It lays eggs on thesurface of mature leaves and, once hatched, the larvaeconstruct a shell (known as a ‘lerp’) from starch derivedfrom the host plant, defoliating the leaf in the process.The lerp probably protects the psyllid insect frompredation and desiccation during hot weather. Red gumbasket lerp are most active during summer whenattacked foliage dries rapidly. By late summer trees canbe totally defoliated. Some affected trees die while oldertrees produce epicormic shoots, which can affect timberquality (Collett 2001). Extensive areas of river red gumhave occasionally been defoliated by large populationsof lerps near Orbost (1950s), in the Seymour-Euroa area(1950s), Lakes Entrance (1980s and 90s), Mansfield(1940s and 50s) and in plantations around Sheppartonand western Melbourne (Collett 2001). Hot weather,high soil moisture, absence of flowering and variationsin leaf chemistry (e.g. phenolic feeding inhibitors) haveall been associated with psyllid outbreaks (Morgan1984).Further research is needed to investigate the interactionsbetween various outbreak factors. A network ofregularly examined forest health assessment plots,management of insect pest outbreaks and the associatedimpacts on tree growth in river red gum forests willassist in quantifying the extent of this problem. In somecases, while the symptoms are obvious, their underlyingcause is unknown. Treating defoliation symptomschemically does not address the underlying cause ofthe outbreak. However, because the underlying cause isoften difficult to determine, alternative, effective moreenvironmentally friendly management is hard to achieve.European honeybees are an important part of theeconomy (see chapter 13), yet there is considerabledebate on their effects on the Australian environment.While they have been present in Australia for about170 years, their abundance and distribution hasincreased dramatically over the last 60 years (Paton1996). Honeybees potentially affect native flora andfauna though (i) competition for tree hollows (Figure5.25), (ii) competition for nectar and pollen, and (iii)disruption of plant-pollinator systems. A distinctionneeds to be made between commercial honeybeeshoused and transported in hives and feral honeybeesoccupying tree hollows. Honeybees can forage at least20 km from their hives or hollows.82 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
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 72 and 73: dependent species including darling
Page 74: Table 5.7 Summary of risk levels to
Page 77: Figure 5.22 Koala in a river red gu
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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