This category includes direct human disturbance of fauna. It is a major threat to the Common Bent-wing Bat and Eastern Horseshoe Bat, a moderate threat to the White-bellied Sea-Eagle and a minor threat to a further 10 species. This category is not considered a threat to 16 of the species covered by this review and its effect is unknown for four species (Table 6.4).
Human disturbance of roost sites of the Common Bent-wing Bat and Eastern Horseshoe Bat may cause the bats to abandon the site. Disturbance of bats in torpor causes them to use valuable energy reserves to raise body temperatures to become active. During winter when food supplies are low, energy supplies may not be replenished and mortalities may occur (Lumsden et al. 1991). It is proposed that known colonies of Eastern Horseshoe Bat are to be protected within the Central Highlands region by a 100m buffer (NRE 1996b). The White-bellied Sea-Eagle is vulnerable to human disturbance, particularly at the nest; birds may desert nests if disturbed by humans (Hunt and Mooney 1983). The Action Statement for this species states visitors will be discouraged and nest sites will be kept confidential. There is only one known nest site of this species in the Central Highlands.
This category includes a number of threats that were identified by experts as being relevant to particular species that were not covered by any of the above categories.
This category refers to competition for resources such as food and shelter with other native species. Competition from introduced species is discussed in another section. Interspecific competition has been recognised as a threat to honeyeater species within the Central Highlands. Bell Miners actively exclude Helmeted Honeyeaters from areas of suitable habitat; habitat is quickly reoccupied if Bell Miners are removed (Pearce et al. 1995, B. Quin, pers. comm.). This is considered a major threat to Helmeted Honeyeater and control of Bell Miners is a management action outlined in the Helmeted Honeyeater Recovery Plan and Action Statement (Menkhorst and Middleton 1991, Baker-Gabb 1992). Loss of high quality sites and fragmentation can also lead to increased competition for limited resources between Regent Honeyeaters and other nectivores. The expenditure of energy in aggressive encounters could potentially reduce the available time and energy for feeding (Franklin and Robinson 1989, Ford et al. 1993, Menkhorst 1993). The effect of interspecific aggression on accessibility of nectar, breeding success, use of optimum habitat and the survival of the Regent Honeyeater requires monitoring and research (Menkhorst 1993, Menkhorst in prep.). The Painted Honeyeater is a specialist mistletoe feeder. Displacement by the generalist Mistletoe-bird Dicaeum hirundinaceum and exclusion by Noisy Miners Manorina melanocephala are likely to have contributed to the decline of the species across its range (Robinson 1994). As this species is marginal to the Central Highlands, interspecific competition is classified as a minor threat (D. Robinson pers. comm.).
The Enhanced Greenhouse Effect is the increase of greenhouse gases caused by human activities and the resultant warming of the atmosphere (Bennett et al. 1991). Species particularly at risk from this phenomenon if it occurs include those with small and genetically impoverished populations, those with disjunct or peripheral populations, coastal, montane and alpine species, species with narrow habitat requirements, and restricted habitats, and those that are poor dispersers. A further problem relates to the depletion of the ozone layer resulting in increased amounts of ultraviolet radiation reaching the earth. There is direct evidence that the Alpine Tree Frog is detrimentally affected by ozone layer depletion (G. Gillespie, pers. comm.). Increased ultraviolet radiation may also be a potential threat to the Baw Baw Frog (Hollis 1996).
Greenhouse-related climate change is recognised as a major threat to the Spotted Tree Frog, Alpine Tree Frog, Baw Baw Frog and Alpine Bog Skink, and a moderate threat to the Leadbeater’s Possum, Helmeted Honeyeater, Sooty Owl, Glossy Grass Skink and Swamp Skink. It may well be a long term issue for many threatened species. An examination of the potential effects of Enhanced Greenhouse climate change on a number of representative fauna using BIOCLIM (Bennett et al. 1991, Brereton et al. 1995) indicated that most would undergo reductions in bioclimate range following climate change. Human development has created a large number of barriers which will prevent less mobile species from shifting their ranges in response to climate change. In order to accommodate changes in the distribution of fauna, Brereton et al. (1995) proposes the need for long-term biotic conservation strategies.
Firewood from the Central Highlands’ forests is in demand from domestic and commercial users from both local communities and suburban Melbourne. Firewood collection areas are open to the public during the drier months of the year. Firewood can be supplied from: site clearing prior to reforestation operations, residual material remaining after timber harvesting operations, salvage operations, thinning operations, Timber Stand Improvement works and roadside clearing works (NRE 1996b). Firewood collection is a threat to species whose habitat is limited to small remnants. It is classified as a moderate threat to Regent Honeyeater and a minor threat to three species. Cutting timber for firewood can result in the loss of important habitat components, including older trees. It can also lead to simplification of the ground layer and the reduction of available foraging habitat for species such as the Grey-crowned Babbler. Habitat management on public land for this species must include the retention of large logs within the home ranges of families and minimising disturbance of roadside ground layers. Firewood collection can also remove standing stags and cause loss of remnant tree hollows, especially in rural areas where roadside reserves are important fauna corridors.
Regent Honeyeater has primarily been recorded in three localities in northern Victoria, outside of the Central Highlands. Suitable habitat for Regent Honeyeater in the Central Highlands is scarce, accordingly loss or degradation of existing habitat by firewood collection is a potential moderate threat to this species. The majority of records for Regent Honeyeater in the Central Highlands are in the vicinity of Melbourne. Suitable habitat occurs primarily in the foothill country to the north and east of Melbourne, and the lower slopes and upper terraces of the Goulburn River. The Plenty Gorge Park, Fraser National Park and Lake Eildon National Park also have potentially suitable habitat.
Firewood collection is permitted in most parks in the Central Highland for use in the park by visitors. Park management plans define the areas in which firewood collection may be permitted and which are to be set aside under the Park Regulations for that purpose. The cutting of live timber is not permitted in parks and, where firewood collection is permitted, hollow logs are retained for wildlife habitat. Firewood collection in forests does not permit the public to cut standing timber such as habitat trees. The cutting of timber, which subsequently may be available for firewood collection, is undertaken by licensed operators that are required to comply with the Code of Forest Practices for Timber Production (Code) and relevant timber harvesting operating prescriptions. With respect to flora and fauna conservation the Code specifies that one of the approaches which should be considered is the retention of habitat trees and old-age understorey elements in appropriate numbers and configurations. A permit is required for firewood collection for domestic purposes from public land. The permit system provides for consideration of biodiversity values and sensitive fauna habitats are avoided.
A number of factors including altered drainage patterns, increased salinity, increased foliar nutrients, insect attack and soil compaction, are thought to contribute to eucalypt dieback (Davidson and Robinson 1992). Increased nutrient levels resulting from leaching of fertilisers from surrounding agricultural land in and around Yellingbo reserve, habitat of the Helmeted Honeyeater, is a potential cause of eucalypt dieback. Dieback may result in deterioration of Helmeted Honeyeater habitat through lowered invertebrate prey and deteriorating health of affected trees. Such trees may produce less flowers, manna and honeydew (Menkhorst and Middleton 1991, Baker-Gabb 1992). Research into the causes of eucalypt dieback within this species’ range is an objective of the Helmeted Honeyeater recovery plan (Menkhorst and Middleton 1991). Woodland remnants, particularly those used for grazing, are particularly susceptible to dieback resulting from increased foliar nutrient levels which can lead to an increase in defoliating insects (Landsberg et al. 1990). The defoliation of eucalypts, particularly Eucalyptus sideroxylon, causes the death of the parasitic mistletoe which results in a decrease in Painted Honeyeater numbers (Eddy 1961). Other species, including the Regent Honeyeater, Swift Parrot and Grey-crowned Babbler, may be similarly affected by eucalypt dieback.
Potential stream works including water diversions, impoundments and water storage maintenance activities can have an adverse effect on species such as the Spotted Tree Frog. The disappearance of the Thomson River population is thought to have been caused by inundation from the reservoir. Dams and aqueducts upstream from Spotted Tree Frog sites result in alteration of stream flow regimes and water temperature. A reduction of water in streams or an excess of water from releases, may result in reduced breeding opportunities or reduced survival of eggs and tadpoles (Watson et al. 1991, Gillespie et al. 1995). Water storage maintenance activities including de-silting, may result in changes to the water quality of streams and adversely affect populations of this species (Robertson in prep.).
Mineshaft Collapse/Overgrown Entrances
Mineshaft collapse and mineshaft entrances becoming overgrown are recognised as major threats to the Eastern Horseshoe Bat and the Common Bent-wing Bat, reducing available habitat and inhibiting bat access. These species are dependent on caves and mineshafts for roosting and breeding. The National Estate Values of the Central Highlands (CNR and AHC 1994) recognise all mines used by colonial breeding or roosting bats as key fauna habitat which should be maintained across the project area. Known colonies of Eastern Horseshoe Bat in State forest are to be protected by a 100 m buffer (NRE 1996b).