Loss of Hollow-bearing Trees


*****NOTE: THIS IS A DRAFT STRATEGY***** Tree hollows represent a critical resource for many fauna species, providing shelter and nesting-sites. Their loss from the landscape may therefore have severe impacts on the viability of dependent populations. The density of hollow-bearing trees required to sustain viable populations of vertebrates is a function of the diversity of competing fauna species at a site, population densities of those respective fauna, the number of hollows required by each individual over the long-term, and the hollow formation dynamics of different tree species. There is much circumstantial and some experimental evidence to indicate that hollows are a limiting resource for fauna in many habitats, and that recovery of threatened hollow-dependent fauna is contingent on their increasing availability. The distribution and abundance of hollow-bearing trees in NSW has been reduced and fragmented by extensive clearing of native vegetation during the past two centuries, as well as from the impacts of inappropriate fire regimes (i.e. too frequent or intense). A range of other direct and indirect processes contribute to the ongoing loss of hollow-bearing trees (e.g. forestry activity, grazing inhibiting tree recruitment, firewood collection, pathogens). The relative importance of these processes varies according to past and current land management regimes, but declines in hollow availability are predicted to continue. Owing to the slow process of hollow development, and the disproportionately high habitat and resource values provided by large old trees, adverse effects from the continuing loss of old hollow-bearing trees will take centuries to reverse.

Biodiversity values impacted

In NSW, terrestrial vertebrate species that are reliant on tree hollows for shelter and nests include at least 46 mammals, 81 birds, 31 reptiles and 16 frogs. Of these, more than 40 species are listed as threatened on the Schedules of the Biodiversity Conservation Act 2016. In addition, various invertebrate communities rely on tree hollows for their survival (e.g. Phytotelmata).

Strategy objective

1. To reduce the rate of loss of hollow-bearing trees from the landscape, particularly where tree hollows are relied upon by hollow-dependent threatened species; 2. To promote recruitment of hollow-bearing trees if/where hollow availability has been suppressed or is likely to be suppressed in the future, and; 3. To meet the short-term needs of hollow-dependent fauna when and where hollow availability is deficient and habitat restoration is pending.

Existing policies and programs contributing to the strategy

Information unavailable.

Priority actions for this KTP


Action DescriptionScale
Conduct experimental research to test the assumptions of current best-practice forestry/silviculture prescriptions designed to retain tree hollows in forested landscapes over the long-term.Area
Investigate the efficacy of various methods for augmenting habitat to provide additional hollow resources for hollow-dependent species (e.g. different types of nest-boxes, artificial structures, hollow creation and accelerating hollow formation). Research should target gaps in the existing literature, focus on suitability for and uptake by particular species and cost-effectiveness, as well as informing recommendations for best practice application of such methods.State
Investigate the rate of loss in different species, vegetation communities and habitats and under different disturbance regimes (e.g. fire) to inform land management practices that target the retention and natural succession of hollow-bearing trees for sustaining hollow resources in the landscape.Area


Action DescriptionScale
No critical actions have been identified under a prevention response as the loss of hollow-bearing trees occurs throughout NSW.State


Action DescriptionScale
No critical actions have been identified under a containment response as the loss of hollow-bearing trees is widespread in NSW and cannot be contained to a specific location.State


Action DescriptionScale
Map the distribution and value of hollow resources in NSW to inform and improve the outcomes of land management practices that affect the reproduction and survival of hollow-bearing trees. Mapping should focus on locations for which current data are inadequate and which are likely to represent relatively high risk in terms of the sensitivity of local populations’ viability to changes in hollow availability, for multiple threatened species (prioritisation should be informed by SoS priorities e.g. for landscape species).Area, State
Develop guidelines to inform fire management planning and the implementation of hazard reduction or other planned burns, that aim to minimise the risk and impact of loss of hollow-bearing trees due to fire. These guidelines should incorporate, where appropriate, mapping of high value hollow resources to inform strategic burn planning, and should be fit for application by any fire manager (predominantly National Parks and Wildlife Service (NPWS) and Rural Fire Service). It is also important that the implementation of any such guidelines be linked to a monitoring and evaluation process to ground-truth and test assumptions.State
Develop a decision-support tool (or build on existing tools) that can be used to simulate outcomes from current or proposed activities on hollow resources for threatened hollow-dependent species. The tool should be designed to support land-use planning (e.g. urban development, prescribed burning, timber harvesting or agricultural activities) and regulatory activities (e.g. offsetting).State
Undertake targeted engagement of relevant landholders and land managers responsible for remnant vegetation containing important (live or standing dead) hollow-bearing trees including isolated trees). Engagement should focus on raising awareness of the importance of these trees, both in supporting threatened species and other biodiversity and in terms of their value to primary production (e.g. shelter for stock, soil health) and opportunities for stewardship arrangements, if/where appropriate.Area, State
If/where hollow resources are currently insufficient to support populations of hollow-dependent (particularly threatened) species (i.e. highly modified landscapes), augment habitat with artificial hollow resources (e.g. nest-boxes, dead wood/poles, hollow excavation) in the short term. Any such augmentation should be targeted, both spatially and to species, use methods with empirical evidence supporting their efficacy for the target species, and should be implemented along with a rigorous monitoring and evaluation strategy. In addition, augmentation should be complemented by interventions to establish and maintain sufficient availability of hollows in the long-term (i.e. habitat restoration); augmentation is unlikely to be sustainable of cost-effective beyond the short-term.Site
Undertake targeted engagement with councils and arborist peak groups to raise awareness of the alternative options for reducing safety risks associated with identified ‘dangerous’ trees in urban areas that maximise retention of hollows (e.g. limb removal, landscaping/obstacles to restrict access in high risk areas below trees).Area
Engage with councils, NPWS and other key land managers in urban and peri-urban areas to communicate the importance of maintaining networks of hollow-bearing trees across the landscape. Facilitate cooperation between jurisdictions to ensure that the management of hollow-bearing trees (e.g. removal, weed control, hazard reduction burning) is coordinated at the appropriate scale to ensure strategic retention of networks to support urban hollow-dependent species. This should include preventing illegal disturbance of critical remnant vegetation through targeted measures (e.g. fencing, signage, road closures, cameras).Area

Distribution of the KTP in NSW

Investment prioritisation

Priorities for investment in particular projects under SoS will be determined based on alignment with the critical actions outlined above, as well as their benefit (in terms of meeting SoS objectives) relative to implementation cost, as per the SoS KTP Framework.

Monitoring and evaluation

No monitoring and evaluation information available.

Interaction with other KTPs

Key Threatening ProcessInteraction and impacts
Anthropogenic Climate ChangeClimate change is likely to result in changes in fire frequency and intensity with more severe/catastrophic fire days predicted for many regions, which potentially will lead to accelerated loss of hollow-bearing trees in some areas and/or affect hollow recruitment.
Clearing of native vegetationClearing of native vegetation for development or agriculture is one of the key drivers of loss of hollowing-bearing trees.
Competition from feral honey bees, Apis mellifera L.If and where hollows are a limiting resource for dependent fauna, competition from feral honey bees will further reduce hollow availability and exacerbate the impacts of loss of hollow-bearing trees.
Forest eucalypt dieback associated with over-abundant psyllids and Bell MinersEucalypt species are often the primary source of hollows in the landscape, therefore dieback of these trees can result in significant depletion of the hollow resource.
Aggressive exclusion of birds from woodland and forest habitat by abundant Noisy Miners, Manorina melanocephala (Latham, 1802)Decline in eucalypt canopy health as a result of noisy miners may reduce formation of future hollows
High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and compositionHigh frequency fire is one of the key drivers of loss of hollow-bearing trees; including large living and standing dead trees with available hollows and cohorts of younger trees that could provide hollows in the future.
Infection of native plants by Phytophthora cinnamomiMany hollow-bearing trees are susceptible to Phytophthora, therefore related mortality and collapse in these trees can result in significantly reduced hollow availability across the landscape.
Introduction and establishment of Exotic Rust Fungi of the order Pucciniales pathogenic on plants of the family MyrtaceaeMany Myrtaceae species produce hollows, therefore mortality in these trees due to Myrtle rust can result in significantly reduced hollow availability across the landscape.
Removal of dead wood and dead treesIn many over-cleared rural landscapes, dead standing trees, stumps and hollow logs are often a primary hollow resource, but are taken unsustainably for firewood or burnt to tidy up properties or during stubble burns.

How will this species be managed?

Key management sites for this threatened species are being identified by the Office of Environment and Heritage and other program partners, where feasible, cost-effective and beneficial to the threatened species. Currently, no management sites have been identified for this threatened species.