Removal of dead wood and dead trees - key threatening process listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list Removal of dead wood and dead trees as a KEY THREATENING PROCESS in Schedule 3 of the Act. Listing of key threatening processes is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. The accelerated and ongoing removal of standing dead trees and woody debris on the ground caused by human activity has been recognised as a factor contributing to loss of biological diversity (ANZECC 2001). Examples of the process include illegal or poorly regulated firewood collection from forests and woodlands and unsustainable loss of fallen woody debris, which may be stacked, burnt, mulched or otherwise removed from the site.

2. The removal of deadwood, either standing or fallen, can cause the broadscale change of woodlands into paddocks with isolated standing trees, with little natural understorey and no woody debris on the ground (Landsberg 2000). This may be done to remove obstacles to machinery, increase grazing access and productivity, reduce rabbit harbour and for aesthetic reasons. Local councils and other agencies also "tidy up" by removing dead wood and dead trees from their reserves and from along roadsides.

3. Fire wood collection generally involves removal of relatively undecayed fallen logs, but the repeated loss of this material from woodland sites will over the long term, reduce or eliminate the availability of old fallen logs as habitat. Removal of standing dead wood reduces the availability of hollows over time and the input of material to the litter layer. This process is exacerbated by the failure of regeneration of these plant communities and the resulting reduction in natural accumulation of dead wood.

In New South Wales, firewood includes mainly fallen timber but also comprises standing dead timber with Eucalyptus species including Boxes, Ironbarks and Stringybarks forming the bulk of the wood burned (CSIRO 2000, Wall 2000). Across Australia, over 80% of wood collected for firewood comes from private property.

4. The forests and woodlands of the Western Slopes and Tablelands are the ecological communities most threatened by dead wood removal because they contain popular firewood species. This region of NSW has been extensively cleared for agriculture and remnant patches of woodland are severely impacted by dead wood removal (Wall & Reid 1993). Removal of dead wood may also affect other forest communities, including wet sclerophyll forests and rainforests, particularly in small and easily accessible remnants.

5. In Australia about 290 vertebrate species use tree hollows (Smith & Lindenmayer 1988, Lindenmayer et al. 1991, Gibbons & Lindenmayer 1997), many on an obligate basis. Within NSW about 120 vertebrate species use tree hollows and most can utilise dead trees as nest sites (Gibbons & Lindenmayer 2002). In eucalypts the formation of hollows suitable for wildlife is very slow, taking between 120 and 200 years (Mackowski 1984, Stoneman  et al. 1997). A number of studies have shown that the proportion of trees bearing hollows in eucalypt forests managed for wood production in NSW has substantially declined (Andrews  et al. 1994, Kavanagh & Stanton 1998, Gibbons 1999, Gibbons & Lindenmayer 2002,). Recent studies of forests and woodlands of the western slopes of NSW have found that the number of trees large enough to contain hollows has declined dramatically and the proportion of standing dead trees has also been reduced (Paull 2001, P. Gibbons, pers comm.)

All public land areas managed for wood production in NSW have specific prescriptions and regulations that are intended to protect both standing dead trees and woody debris on the ground. Specifically, these regulations take the form of licences issued by the National Parks and Wildlife Service under the auspices of the Threatened Species Conservation Act 1995 or the National Parks and Wildlife Service Act 1974.

Dead standing trees in paddocks, resulting from clearing efforts or dieback, form a critical resource for threatened and non-threatened fauna (Law et al. 2000). The useful habitat life of these trees is limited by natural factors (decay, windthrow), purposeful destruction by further clearing, and use for firewood (Wall & Reid 1993). There are indications from current studies in NSW (P. Gibbons, pers. comm.) that the decline in the number and quality of dead standing trees is ongoing.

The presence of standing dead trees and woody debris is an important component of the structure of forest and woodland and helps determine the habitat value for a wide range of fauna (Knight & Fox 2000, MacNally et al. 2001).

6. Fallen dead wood provides important habitat for a suite of invertebrate species dependent on decaying wood for their survival. These species play an important role in recycling nutrients in forest and woodland ecosystems. They include a range of species that feed, breed, or shelter in dead wood or may be predators, or parasitoids dependent on species that live on dead wood. Fallen wood, which includes the bark, sapwood and heartwood, comes in a variety of shapes and sizes, permitting habitat specialisation with some species utilising only parts of the fallen wood, or even decaying logs with a particular exposure to sun. Microbial organisms and fungi are also important in the breakdown of timber (Araya 1993) and recycling of nutrients back into the soil. Invertebrates can also feed on, or in wood-decomposing fungi (Grove 2002).

7. Removal of dead old trees (either standing or on the ground) results in the loss of important habitat such as hollows and decaying wood (Gibbons & Lindenmayer 2002) for a wide variety of vertebrates, invertebrates and microbial species and may adversely affect the following threatened species:

8. Removal of dead wood and dead trees and resultant loss of hollows has been identified as a threat that could cause species or populations that are not threatened to become threatened. Examples of species or populations of those species include:

Ground dwelling mammals such as:

Other hollow-dependent species include many of the parrot species (Garnett & Crowley 2000), ground-dwelling mammals (Dickman 1991), possums and gliders (Smith & Lindenmayer 1988) and the forest-dwelling insectivorous bats (Tidemann & Flavel 1987).

9. Removal of dead wood and dead trees may threaten insects which depend on dead wood and forest litter including Isoptera (termites, Whitford et al. 1992), some species of ants (Andrew  et al. 2000), Collembola, Diplura (Heterojapyginae), Blattodea (cockroaches), Dermaptera (earwigs), Gryllacrididae (wood crickets), Diptera (Mycetophilidae, Tipulidae, Asilidae, Stratiomyidae, Dolichopodidae and Myididae), Hemiptera (Aradidae and Lygaeidae), and Lepidoptera (Cossidae and Lycaenidae). Coleoptera (beetles) are particularly vulnerable with many families having representatives that live in rotten wood, including Cerambycidae, Elateridae, Tenebrionidae, Passalidae, Scarabaeidae, Lucanidae, Buprestidae and Curculionidae. Many Carabidae, including endangered species  Nurus brevis and  Nurus atlas, eat saproxylic prey. Amongst non-insect invertebrates, the main group that is affected is the Onychophora (velvet worms), with many endemic species in temperate forests (Scott & Rowell 1991).

10. Removal of dead wood and dead trees may seriously affect the long term availability and viability of habitat. Loss of fallen dead wood from open forests and woodlands will increase impacts of wind on the soil microclimate. Loss of surface moisture resulting from the removal of dead wood will affect soil organisms below fallen logs as well as changing the above ground plant cover and will impact on associated invertebrates (Tongway & Ludwig 1996, Tongway et al. 1989 )

11. In view of the above the Scientific Committee is of the opinion that Removal of dead wood and dead trees adversely affects two or more threatened species, populations or ecological communities or could cause species or populations that are not threatened to become threatened.

Associate Professor Paul Adam
Chairperson
Scientific Committee

Proposed Gazettal date: 12/12/03
Exhibition period: 12/12/03 - 13/02/04

References:

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