Plaintiff v Defendant [2012] VSC 91 | Case summary

Plaintiff v Defendant [2012] VSC 91 | Case summary | Zoe

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A Population Viability Analysis (PVA) has shown that, for a 100-year projection, simulated populations of 200 animals or more remained demographically stable and experienced a decline of less than 10% in predicted genetic variability (Lindenmayer et al. 1993). With a mean density of one animal per 3 ha of old growth forest (Lindenmayer 1989) populations of Leadbeater's Possum could survive in areas of mature forest as small as 600 ha, such as those currently in the Yarra Ranges National Park. However, this approach by itself does not meet the Victorian Government's commitment to conserve Leadbeater's Possum throughout their range. A more recent and detailed PVA undertaken by Lindenmayer and Possingham (1994), which was commissioned by CNR as part of developing strategies for the conservation of the species, simulated the dynamics of metapopulations of Leadbeater's Possum in three forest blocks where timber harvesting is permitted and one closed water catchment. This study combined extensive information on the life history attributes of Leadbeater's Possum, the habitat requirements of the species, the spatial distribution of suitable habitat patches, changes in the temporal suitability of forest habitats, and data on the frequency and impact of disturbances such as logging operations and wildfire.

Spatial data on the distribution of different types of habitat patches were derived from detailed forest inventory information that has been captured in the database of a Geographic Information System being developed by CNR. The analysis predicted the likelihood of Leadbeater's Possum becoming extinct within the next 150 years in two of the three forest blocks studied due to the limited areas of existing old growth montane ash forest. A higher probability of persistence was predicted in the other forest block and the water catchment which were characterised by larger patches of old-growth forest. On the basis of this work, the authors strongly recommended that a key forest wildlife management objective must be to grow areas of existing regrowth forest through to ecological maturity or old-growth status (i.e. 250 years). Wildfires were predicted to have a major negative effect on the persistence of populations of Leadbeater's Possum, particularly in areas supporting limited or single areas of old-growth forest. It is important to note that wildfire has been instrumental in the habitat development process, but the scale and intensity of wildfires since European settlement, most notably the 1939 wildfires, has resulted in approximately 82% of ash type forests in the Central Highlands being regrowth with few live hollow-bearing trees. Consequently, these regrowth forests require >150 years of growth before fire can effectively create the necessary floristics and structural diversity critical for Leadbeater's Possum habitat.[48]

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The major threats to the long-term survival of Leadbeater's Possum are the progression of current favourable habitat to a structurally less-suitable successional stage and the reduction in the number of available nest-trees (Smith et al. 1985). Currently, 50% of nesting hollows are provided by very old trees killed by wildfire in 1939 and earlier (Smith and Lindenmayer 1988). Lindenmayer (1990) found that 18% of 302 measured living and dead hollow-bearing trees had collapsed through natural decay between 1983 and 1988. These figures translate to a loss of 3.6% per annum for that period. Smith et al. (1985) concluded that, unless then current (1985) management prescriptions in the Central Highlands were altered, Leadbeater's Possum would be eliminated from logged areas. The nominal rotation length of 80 years does not allow trees to grow large enough on harvested areas for hollow formation to begin, let alone develop sufficiently for Leadbeater's Possum to use. Smith and Lindenmayer (1988) have described in detail the form of trees selected as nest sites, and their data emphasise the old age of trees selected. It thus appears, that, to properly cater for Leadbeater's Possum, rotation times should be well in excess of 200 years. However, by that age trees would have senesced and be well beyond optimum harvest age, and the forest structure may not be suitable for Leadbeater's Possum feeding and movement requirements. Therefore, strategies are needed to maintain an adequate number and even distribution of nest-trees in selected areas of regrowth forest and to allow for a proportion of regrowth, either as individual trees or complete stands of forest, to grow through to ecological maturity (>250 years).

Under current forest management practices such strategies would necessarily be confined solely to a strategy of longterm reservation. However, a major program commenced under the Timber Industry Strategy continues 'to evaluate the effectiveness of alternative and potentially more environmentally sensitive silvicultural systems, such as the even-aged shelterwood and uneven-aged group selection systems where clearfelling is now used'. Experimental and operational trials of retained overwood systems have shown particular promise from both environmental and economic perspectives and are approaching the stage where their adoption as a viable alternative to clearfelling systems is a reality. Such a system will be instrumental in providing long-term optimal habitat for Leadbeater's Possum.[49]

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Fire is an integral component of montane ash forest ecosystems and has an important influence on the occurrence, extent and viability of habitat for Leadbeater's Possum. This influence can be both positive and negative, and varies greatly depending on the extent, frequency and intensity of fire. Frequent, low-intensity fire (e.g. every 50 years) will have a positive effect by encouraging floristic and structural diversity necessary for foraging habitat and by not killing existing and potential hollow-bearing trees. While very intense fire will also create suitable foraging habitat, it will kill all or most trees and thus reduce the time during which hollows will be available for the species. Despite careful planning and modern technology, wildfire remains highly probable, yet unpredictable in its effects, so conservation strategies require options with regard to both space and time to attempt to counter widespread deleterious effects of fire and to take advantage of the positive effects.

Both fire and timber harvesting operations, or the absence of them, may result in the loss or development of habitat for Leadbeater's Possum. The varying nature of such disturbances (e.g. fire intensity and different silvicultural systems) and the time between them will, through the process of forest succession, determine when and for how long habitat will occur in an area of forest. Consequently, management for the conservation of the species, which must include the provision of adequate habitat through time, needs to incorporate different strategies, applied individually or in combination, for different timeframes into the future.

A common practice undertaken in Victorian forests following wildfire is salvage logging. In the past little recognition has been given to the value of burnt stems and fire-damaged trees in the forest ecosystem, despite their known importance to a wide variety of hollow-dependent fauna, including Leadbeater's Possum. Extensive salvage logging was undertaken in the montane ash forests of the Central Highlands following the 1939 bushfires and this is suspected to have exacerbated the current extensive areas of regrowth forest where there are few hollow-bearing trees.[50]

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5.1.3.1 Management Zoning

To facilitate the various strategies possible for the conservation of Leadbeater's Possum Smith and Lindenmayer (1988) suggested that timber production forests be categorised into three management zones, and the allocation of forests to these management zones be as follows:

Zone 1 Leadbeater's Possum (and other wildlife) conservation as a priority. Consisting of all remaining areas of mature and multi-age structured forest (where the latter is forest with >12 living, emergent potential nest trees per 3 ha).

Zone 2 Leadbeater's Possum conservation and timber production as joint priorities. Consisting of all regrowth forest with >6 living or dead potential nest trees per 3 ha.

Zone 3 Timber production as a priority. Consisting of remaining harvestable forest, with the exception of streamside connections, wildlife corridors, landscape corridors and other reserves.

Smith and Lindenmayer (1988) further suggested that the appropriate management of these areas should be as follows:

Zone 1 Classification as reserves or protection from all types of timber harvesting other than low-intensity selective logging.

Zone 2 Active protection of existing potential nest-trees as well as their future ecological replacement. To maintain an average maximum density of Leadbeater's Possum 10 evenly-scattered potential nest-trees, and at least an equivalent number of surviving younger trees will need to be retained in every 3 ha of clearfelled coupes.

Zone 3 Current management prescriptions, but desirable to cease the felling of any existing living potential nest-trees.

The concepts of zoning, allocation of forest areas to zones and harvesting prescriptions as suggested by Smith and Lindenmayer (1988) are in principle compatible with current management objectives and silvicultural practices, except with the suggested harvesting prescriptions in Zone 2, where a major problem is apparent. To retain 20 trees per 3 ha evenly scattered throughout the logging coupe and to guarantee their continued survival would require the initial retention of many more trees in order to account for losses due to regeneration fires and windthrow. The retention of such large numbers of trees scattered across logging coupes would mean a major departure from the current silvicultural system of clearfelling and may be undesirable because of the loss of timber volume, and adverse effects on coupe regeneration and contractor safety. The feasibility of such an approach will be evaluated under the Silvicultural Systems Project but until those results are available other strategies must be explored. Smith and Lindenmayer (1988) recognised that it may be impractical or uneconomic to leave trees scattered within coupes and suggested the following alternative harvesting techniques:

1. retention and protection of retained trees in unlogged strips between long, narrow coupes (strip retention and logging);

2. retention of unlogged boundaries around small clearfelled coupes;

3. retention of existing and replacement potential nest-trees in the outer half of logged coupes (the side adjoining streamside reserves or wildlife corridors) and maximum utilisation in the centre of coupes.

Alternative 2 is the preferred option as alternatives 1 and 3 would require major departures from current silvicultural practices and their feasibility will not be known until results of the Silvicultural Systems Project are available. Definitions of the three zoning categories to be used and their management objectives are provided in Chapter 6.[57]

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Many Australian birds, bats, arboreal mammals and reptiles are dependent on tree hollows for nesting and roosting. For the majority of eucalypts in the Central Highlands, hollows are thought to form in trees from about 100 to 150 years of age. Trees of mature and senescent growth stage generally contain more hollows than regrowth trees. The loss of hollow-bearing trees from Victorian native forests is listed as a threatening process under the Flora and Fauna Guarantee Act 1988.

The Code of Forest Practices for Timber Production (Code) specifies the need to retain an appropriate number and configuration of habitat trees, to provide for the replacement of old hollow-bearing trees within and around coupes, and to protect these trees during harvesting and subsequent management.

The location and density of hollow-bearing trees varies across the Central Highlands. Many areas of forest have been utilised for timber harvesting since around 1900 and the 1939 wildfires killed large areas of mature and senescent ash-eucalypt (Alpine and Mountain Ash and Shining Gum) forest. The subsequent regrowth forest generally contains only low numbers of mature and senescent trees.

Predictive modelling of the number of hollow-bearing ash eucalypts indicates that a steady decline will occur until about 2065. After this, the number of trees containing hollows will increase. This forecast is based on research into Leadbeater's Possum that indicates that ash-eucalypt trees with hollows are collapsing at a rate of 3.6% of the total population each year (Lindenmayer et al 1990). This decline is largely attributable to the natural deterioration and collapse of the 1939 fire-killed stags. Protection of existing live hollow-bearing trees and recruitment of trees to grow on to maturity is therefore required to ensure the long-term availability of this component of wildlife habitat.

In other areas of the Central Highlands, particularly in the mixed-species forests in the east of the planning area, hollow-bearing trees are more abundant. In these areas, the trees retained on timber harvesting coupes will be a mixture of existing and potential hollow-bearing trees.

This plan provides a precautionary approach to maintaining hollow-dependent wildlife populations on State forest. At the strategic scale, large areas of forest containing mature and senescent trees are protected within the SPZ. In total, about 64% of the forested public land is not available for sawlog harvesting. At the detailed scale, the guideline below provides for hollow-bearing tree retention and recruitment on timber harvesting coupes.

During the implementation phase of this plan, NRE will examine ways of addressing habitat retention and recruitment on a broader level than individual timber harvesting coupes. This approach will involve determining the configuration of retained areas of vegetation and future timber harvesting coupes at a subcatchment level (generally an area of between 500 and 1000 ha). This will ensure that decisions about habitat retention and recruitment and the placement of timber harvesting coupes are made in a broader context. Priority for implementing this approach will be directed towards areas of particular sensitivity.

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Action 18 Continue to protect habitat from the impacts of timber harvesting.

Timber harvesting potentially poses a significant threat to the survival of Leadbeater's Possum through loss of critical habitat such as den trees and food resources, and mechanisms to manage Leadbeater's Possum habitat in State forest have been developed. The newly-established permanent reserve system for Leadbeater s Possum in State forest will be maintained. Zone 1A or Zone 1B habitat will continue to be protected outside the permanent reserve system from timber harvesting and associated road construction. A process to record the location and boundaries of patches of Zone 1 habitat will be established as they are identified through the coupe planning process and other field-based activities. Long-term monitoring sites for Leadbeater's Possum research are identified in relevant spatial information systems to ensure that they are not affected by timber production and associated road construction/maintenance. Salvage timber harvesting prescriptions will address the maintenance or restoration of habitat connectivity for Leadbeater's Possum following severe fire events. This will be considered at both site- and landscape-scales. The latter will involve assessment of the spatial configuration of salvage logging coupes relative to unburnt/lightly burnt that may provide critical refugia for Leadbeater's Possum following severe fire events.

Responsibility DSE, VicForests

Action 19 Provide training for field staff in identification and protection of habitat

Training will be provided on an annual basis in the recognition and interpretation of Zone 1 habitat and the application of prescriptions for its protection. Training will also emphasise the role of hollow bearing trees and stags in providing habitat even when densities fall below the thresholds for Zone 1, and will canvass measures to protect such trees and stags during harvesting and regeneration burning.

Responsibility: VicForests

Action 20 Continue to audit the planning and execution of timber harvesting and associated activities for compliance with the Code of Practice for Timber Harvesting.

Annual independent audits of compliance with the Code of Practice for Timber Harvesting will continue to be undertaken.

Responsibility: DSE

Action 21 Protect habitat from incompatible fire practices

High intensity fires can affect the availability of den-sites in both the short and long-term in three ways, by killing live hollow-bearing trees, by destroying dead hollow-bearing trees and by killing younger trees thereby preventing them from advancing to maturity and associated hollow-development. Prescriptions will be developed and applied that ensure existing den sites are not destroyed or damaged during planned burns. Sites will be identified where it may be feasible to undertake fire suppression activities to protect important Leadbeater's Possum habitat (i.e. relative to access tracks, fuelbreaks etc). This applies to both mixed age, old-growth and regenerating ash forests. Guidelines will be developed that define appropriate fire suppression operations within important Leadbeater's Possum habitat. Strategic fire suppression sites in important Leadbeater's Possum habitat will be mapped and communicated to fire incident management teams via natural values officers. Where opportunities arise, the effectiveness of fire suppression techniques at protecting critical Leadbeater's Possum habitat in montane ash forest will be investigated.

Responsibility: DSE, Parks Victoria

Action 22 Protect habitat from incompatible development activities.

The Native Vegetation Management Framework, including the policy of avoiding, minimising and offsetting vegetation loss, will continue to be applied to development proposals and other activities that may affect Leadbeater's Possum. Activities include road and track construction or maintenance in or adjacent to habitat, and recreational development in parks, Canopy connectivity will be maintained across tracks and ski trails at Lake Mountain. The Lake Mountain and Mt Baw Baw Alpine Resort Management Boards will be provided with information to guide their site maintenance and development activities to avoid impacts on Leadbeater's Possum's habitat. Canopy connectivity will be maintained across tracks and ski trails on the Baw Baw plateau. Land managers/operational teams for the Baw Baw plateau will be provided with information to guide their site maintenance/development activities so that they do not impact on Leadbeater's Possum s conservation.

Responsibility: DSE

Action 23 Protect post-fire refuge habitat.

Within fire affected areas unburnt or lightly burnt Leadbeater's Possum habitat that may provide critical post fire refugia for the species will be identified, mapped and protected within fire affected areas. This may require control of predators and/or introduced browsers, provision of nest boxes and management of salvage timber harvesting operations. The latter will involve assessment of the spatial configuration of salvage logging coupes relative to unburnt patches that may provide critical refugia for Leadbeater's Possum following severe fire events.

Responsibility DSE, Parks Victoria

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Leadbeater's Possum

There is a large amount of existing data on the distribution, ecology and habitat requirements of Leadbeater's Possum (e.g., Smith and Lindenmayer 1988, Lindenmayer et al. 1991, Lindenmayer 2000, Lindenmayer and McCarthy 2006). However, since the 2009 bushfires burnt a considerable proportion of the species geographic range (45% of the Leadbeater's Possum reserve system was burnt; Steve Smith, DSE, pers. comm.), there will need to be extensive reassessments of where suitable habitat now occurs and where it is likely to occur into the future. Preliminary assessments since 2009 indicate that this species has been severely impacted by the fires. This raises the question as to whether the current reserve system and prescriptions are adequate to ensure the long term future of the species, and this issue will be investigated.

There is a good understanding of what constitutes suitable Leadbeater's Possum habitat. Important habitat features include a combination of tree hollows at a suitable density, horizontal connectivity through the canopy or understory, and high densities of both wattles and decorticating bark to provide a food source (Steve Smith, pers. comm.). Translating this understanding of habitat values into measurable habitat attributes that can be consistently assessed both on the ground, and predicatively mapped across the species range from available modelled and remote-sensed spatial data may be possible based on modelling of existing data sets. This project will develop new methods for assessing and documenting suitable habitat for Leadbeater's Possum, and will incorporate forest stand variables and remote-sensing techniques such as LIDAR (Light Detection and Ranging) where possible. The capacity of remote-sensed datasets to accurately predict habitat suitability for Leadbeater's Possum is currently unknown. However this approach will be investigated to determine if it is adequate for identifying habitat quality with sufficient accuracy for decision making.

The amount of new data collection to be carried out is still to be determined, but will require appropriate sampling stratification between state forest and parks and reserves, forest growth stages and disturbance histories, including sites burnt and unburnt during the 2009 bushfires. Attention will be given to integration of data collection with that being carried out independently by David Lindenmayer and colleagues, to ensure that both datasets are collected in a manner that allows maximal integration of all available data sources at the analysis and modelling stage of the project.

The planning will also factor in a study by Dan Harley, Zoos Victoria, assessing the suitability of habitats for Leadbeater's Possum within the Maroondah and O'Shannassy catchments following the 2009 fires. Key criteria used to identify suitable habitat remaining post-fire in this study included: presence of stags, presence of dense mid-storey vegetation and canopy condition (Parks Victoria 2011).

A number of techniques are potentially suitable for determining the presence of Leadbeater's Possum at survey sites, including stag watching, call surveys (Leadbeater's Possum calls and owl calls) and automated remote camera surveys. A combination of methods will probably be used, some of which will also be of value for detecting other priority threatened species at the same sites (see below). Surveys will be undertaken from spring 2011 until autumn 2012.

Approaches to modelling the available distributional data, and data to be collected during the current project will involve a combination of presence-only (e.g. maximum entropy modelling - Maxent) and presence-absence species distribution modelling techniques. Mapped data sets for habitat variables known to be of significance for determining habitat quality for the species will be included in the models, along with variables related to growth stage, forest structure and age, and recent fire history will also be included wherever possible. The known preferences of Leadbeater's Possum for forest of particular growth stage will be incorporated and the modelling will investigate how the species is likely to be influenced in the future as the forest structure changes.

An important question to be addressed for Leadbeater's Possum, particularly in light of the 2009 fires, is how much habitat is required to support a viable population. A similar approach will be taken as in the Long-footed Potoroo first phase project by undertaking a Population Viability Analysis and determining the area require[d] to support such a population under differing scenarios.

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