PART 1: (CONTD)
THE AQUATIC VEGETATION OF THE DURRAS LAKE bed has been described in "Seagrass and Saltmarsh" (p.44)
THE INTERTIDAL ZONE has been described in "Aquatic Fauna" (p. 36)
OLD GROWTH FOREST
Ecologists recognise three major stages of forest development; young, mature and old. Foresters call these stages immature, mature and overmature. The structural diversity of the forests of the"Greater" Murramarang National Park provides a wide range of habitat and resources for the park’s remarkably rich biodiversity.
Around 489 ha. or 5% of the"Greater" Murramarang National Park forests are classified ‘old growth.’ The Interim Assessment Process’ official definition of old growth forest is a complicated appraisal of Aerial Photography Interpretation taking into account the proportional representation in the overstory cover of senescent and regrowth trees, the disturbance history and the site quality of the area. The Harvesting Plan for Compartment 133 for example, states there are "no areas of candidate old growth forest larger than 25 ha" though there are "mature and overmature trees scattered at various densities throughout the regrowth" (State Forests, 1996). To the outside observer using only the official ‘old growth’ definition, the ecological significance of the many ‘old growth’ high quality habitat trees which are found in Compartment 133 and throughout the "Greater" Murramarang National Park, is undermined and ignored.
‘Old growth’ forest will not last forever. Destructive natural events such as wildfire will in all probability convert parts of existing old growth forests into younger-aged forest. Logging has been the destructive agent for the majority of the coastal forests, creating forests dominated by regrowth of selected timber production trees. Few south coast forests have the ‘old growth’ elements and structural diversity found in the "Greater" Murramarang National Park. Not only is it essential that all coastal, ‘old growth’ forest elements be preserved (be they greater than 25 ha or single trees) but that some regrowth be allowed to become ‘old growth’. With a 30 to 50 year harvesting cycle that will never happen. Most Eucalyptus species require at least 200 years to develop hollows, the age at which a tree is considered mature. Allowing forest succession to continue in the "Greater" Murramarang National Park, without the constant manipulation which favours immature regrowth, will maximise these forests’ value to a future ‘old growth’ network (Scotts, 1991).
State Forests (1996) found no exotic weeds in Compartment 133. Craven (1987) found Cassia floribunda, a Brazilian native in Compartment 128. This invasive species thrives on disturbed sites. Lantana, Coral Tree, Canna Lilly, Blackberry, thistle, bamboo and other garden exotics are found in the"Greater" Murramarang National Park, generally in small quantities around villages. Bitou Bush has invaded the coastal region, but in small quantity in limited locations.
Australia has an estimated 777 species of birds; 45% of them are endemic, 20 presumed extinct, 50 are threatened and 32 species have been introduced (ABS, 1996). The"Greater" Murramarang National Park is utilised by 207 species of birds, approximately 40% of the bird species known to occur in New South Wales (Appendix 2). Eighteen species are threatened and three introduced, one of those, the starling, considered a pest (Appendix 4). Forty five species are regarded by the Eurobodalla Natural History Society as ‘regionally rare’ (Appendix 5).
Birds are generally easy to observe and identifiable by many people. Birds add significantly to the aesthetic quality of a landscape and its capacity to satisfy humans. The Friends of Durras and the Eurobodalla Natural History Society have long monitored bird species and populations in the region. More than 1,000 fauna and flora records have been provided to the NSW National Parks and Wildlife Service’s Atlas of Australian Wildlife. The Friends of Durras participated in the Birds Australia national census of birds in the 1980’s and will be part of the follow-up census beginning this year. Our ten years of detailed flora and fauna records are used by students and land managers such as Eurobodalla Shire Council’s Coastal Managers.
The"Greater" Murramarang National Park’s wide variety of ecosystems offer a vast range of niche habitats for birds: upper, middle and low canopy, sparse and dense undergrowth with varying degrees of leaf litter, dry schlerophyll ridges, rainforest, wet gullies with vine thickets, thick barked and ‘clean-skin’ trees, streams and riparian vegetation, ocean and lake shoreline, with gradation through to deep lake and ocean waters and offshore islands.
Sixty one species migrate to and leave the park during the year (Appendix 6). Some are waders arriving from as far afield as Alaska and Russia, others like the Regent Honeyeater come north for the flowering of the ironbarks. Migrant species are reliant on the continued functioning of forest ecosystems and riparian and aquatic systems at the landscape level.
A large number of birds are dependant on the moist forests such as the White breasted and Wonga Pigeon, Brush Bronzewing, Yellow-tailed Black Cockatoo, Superb Lyrebird and Brown Gerygone (NSW National Parks and Wildlife Service, 1998). Others rely on relatively large areas of heterogeneous eucalypt forest for foraging, shelter and breeding. The Peregrine Falcon, Little Penguin, White-faced Storm Petrel, Eastern Reef Egret, Sooty Oystercatcher, Wedge-tailed and Short-tailed Shearwaters prefer the isolation of the offshore islands for shelter, breeding and from which to forage.
Logging and burning does affect the abundance of bird species. For many species these effects disappear over a reasonable time scale. The pattern of harvesting often employed during integrated harvesting (alternate coupe) can increase the likelihood of local extinction of population and prevent or limit the dispersal of animals and gene flow between populations (Norton and May, 1993).
Tree hollows do not usually develop in trees that are less than 200 years old. The logging cycle in the Batemans Bay Management Area is between 30 to 50 years (State Forests, 1996). The removal of stags, over-mature and defective trees for pulp, will produce a large and permanent reduction in the availability of tree hollows (Pyke and O’Connor, 1991). Over 30 bird species found in the"Greater" Murramarang National Park utilise tree hollows (Appendix 7) including the threatened Glossy Black Cockatoo, Turquoise Parrot and Powerful, Masked and Sooty Owl (Gibbons and Lindenmayer, 1997). Birds Australia estimate that forestry operations (altered fire regimes, and the reduction in tree hollows) pose a threat to more than 40 species of birds (Department of the Environment , Sport and Territories, 1995b).
Of particular concern is the long-term impact integrated harvesting may have on the large owl species. The"Greater" Murramarang National Park is home to the Powerful, Masked, Sooty, Southern Boobook and Barn Owl as well as the Tawny Frogmouth. These are the forests principal predators and their intentional or unintentional removal (permanently or temporarily) may affect the trophic flow-down affect and result in a dramatic reduction in species diversity and simplified primary production (NSW Field Ornithologists Club, 1994). This is further detailed in "Hollows and Corridors" (p. 37).
The "Greater"Murramarang National Park native bird fauna is in an enviable position with only three introduced bird species recorded. The Common Starling and Spotted Turtle-Dove have small resident populations confined mainly to the village areas and the European Goldfinch has been seen once in the past 10 years. The Sparrow and Indian Mynah are not present. The Indian Mynah’s spread throughout southern Australia, has been rapid. It has a preference for cleared areas, is especially aggressive, displaces native hollow nesters and is very territorial. Forestry operations have the potential to open up large areas and enable introduced species like the Indian Mynah to become established.
Australia has an estimated 268 species of terrestrial mammals with 84% endemic. Nineteen species are presumed extinct, 43 are threatened and 25 have been introduced (ABS, 1996).Arboreal
The "Greater" Murramarang National Park is home to 8 species of arboreal mammal (Appendix 3). The Yellow-bellied Glider and Squirrel Glider are threatened species (Appendix 4). Australia’s arboreal herbivores are concentrated in habitats on soils relatively rich in nutrients which are linked to arboreal marsupial density through forest floristics and leaf chemistry. The relative richness of the "Greater" Murramarang National Park’s overstory vegetation associations has been examined in "Flora Overstory" (p. 27). Such-nutrient rich habitats are limited in Australia due to Australia’s general aridity and its naturally poor endowment of soils of reasonable quality and the extent to which habitats on the better soils have been cleared to service Australia’s social and economic development.
CSIRO’s Dr Braithwaite (1996), an expert in arboreal marsupial herbivores, sees a dim future for these species which are biologically dependant on resource-rich habitats. He sees no immediate end to the clearing of forests on fertile, productive soils or to the pressure from increasing human population. The conservation of Australia’s arboreal marsupial herbivores therefore, is critically dependant on a relatively small and diminishing portion of the total forest resource. Because forests held under public tenure are generally the only forests that can have any guaranteed security against clearing, it follows that those public forests with soil and floristic characteristics of importance to arboreal marsupial herbivores comprise a critical conservation resource. Braithwaite stresses that the first priority for a conservation policy is to ensure that this portion of the forest resource, and its complement of fauna species is maintained.
State Forests (1996) claim that their management ensures viable populations of all species will be maintained in the long term. "In the short to medium term population numbers of disturbance intolerant species may be reduced by the (harvesting) operation, while other species may benefit." Furthermore they suggest that "following the disturbance of a forest area, by an activity like timber harvesting, the adjacent undisturbed or protected forest areas will provide the source for recolonisation for animals (like the arboreal marsupial herbivores) that rely on the tree species that have fallen. As new trees develop and grow in the disturbed forest area to replace the trees removed, the natural habitat slowly re-establishes and, with time, the animals gradually move back into the regrowth forest area" (State Forests, 1997).
There is no scientific evidence to support this extremely simplistic view of the ecological complexity of individual species and communities.
Studies of the Yellow-bellied Glider have shown that this species lives in small family groups which occupy large and exclusive home ranges of between 30 and 65 ha. There is little evidence of overlap between adjacent groups. When a Yellow-bellied Glider family loses all or part of its home range to logging it cannot simply move into the home range of an adjacent family group. More than likely the entire family group will perish or be reduced in size. Currently it is not known whether glider populations can be maintained indefinitely in areas of intensive logging (Goldingay and Kavanagh, 1991).
Tyndale-Biscoe and Smith (in Goldingay and Kavanagh, 1991) found that adult Greater Gliders will not recolonise new sites if a large proportion of their original home range is rendered inhabitable, and Lunney found that the species did not persist in forests from which two-thirds of the stand basal area was removed. The NSW National Parks and Wildlife Service (1998) doubts that the current Murramarang National Park and its limited resources is large enough to sustain viable populations of species like the Yellow-bellied Glider. They "may need a larger area to sustain viable populations than is available in the (current) park." The protection of sites like the"Greater" Murramarang National Park, which support broad assemblages of arboreal marsupial herbivores is critical to their long-term survival. These areas may represent vital ‘source’ populations of species and help to ensure the persistence and spread of species more widely through the regular dispersal of young (Norton and May, 1993). Ground-dwelling
Thirty species of ground-dwelling mammal have been recorded in the"Greater" Murramarang National Park (Appendix 3). The Brush-tailed Phascogale, Long-nosed Potoroo, Spotted-tailed Quoll and White-footed Dunnart are threatened. The black rat, house mouse, fox, rabbit, feral pig and cat are introduced species. The most easily seen of the ground-dwelling mammals are the many Eastern Grey Kangaroos. They are found in large numbers on the grassy camping areas in all the villages and occasionally venture onto the beach - a very unusual sight. They are the ‘darlings’ of the "Greater" Murramarang National Park and one of its great visitor attractions.
From 1989 to 1992, CSIRO Wildlife and Ecology’s, Catling and Burt (1994) examined the distribution and abundance of ground-dwelling mammals in 13 areas comprising 42 eucalypt communities in south-eastern New South Wales. The northern"Greater" Murramarang National Park was one of the study sites. Important features of the study results were the abundance of the fox and cat, the absence of small wallabies (potoroo size) and low abundance of other medium-sized ground mammals such as bandicoots. The Long-nosed Potoroo and the Long-nosed Bandicoot have been observed in the "Greater" Murramarang National Park although little is known of their distribution or population size.
Catling and Burt concluded that the "ground-dwelling mammals present today in south-eastern New South Wales appear to be the remnants of a more diverse fauna left after clearing for agriculture and grazing, disturbance by forestry activities and predation by introduced species." The diversity and abundance of small mammals was high in Spotted Gum and Bloodwood groups with their understory of Macrozamia communis, common vegetation communities in the "Greater" Murramarang National Park.
Catling and Burt believe that the few remaining populations of potoroos, bandicoots and small wallabies, are in urgent need of protection and management. Whereas arboreal mammals inhabit some eucalypt communities and not others, many ground-dwelling species frequent most vegetation communities. However, management strategies based on knowledge of mammals that are reliant almost exclusively on the forest canopy may not be suitable for ground-dwelling mammals.
The impacts of prescribed burning on native ground-dwelling fauna may have also been underestimated by forest mangers. Prescribed burning removes the dense understory habitat preferred by many species of ground mammals and favours the movement and hunting success of the fox and cat (Catling, 1991).Bats
Bats are possibly the most maligned and poorly understood animal group. Very little is known about the ecological requirements of forest bats. In the"Greater" Murramarang National Park, fourteen species have been recorded, including five threatened (Appendices 3 and 4).
As is the case for birds, the"Greater" Murramarang National Park offers bats a wide range of highly desirable habitats. The majority of species found in the "Greater" Murramarang National Park use hollows as diurnal roost sites, places for torpor and sites to rear young. Many species of hollow dependant bats utilise multiple roost sites, some such as Gould’s long-eared bat changing roost sites almost daily (Goldingay and Kavanagh, 1991).
Bats play an important role in natural ecosystems. Fruit and nectar feeders spread seeds and act as pollinators in the forests, and insectivorous bats consume a large number of insects. Bats have only recently been recognised as vital elements of natural ecosystems serving an important function regulating insect populations, and pollinating the flowers and disseminating the seeds of many plant species. The value of insectivores consuming vast numbers of insects in forest and rural areas can not be underestimated.
The destruction of forests is certain to have detrimental effects on many bat species reliant on them for food and shelter (Australian Nature Conservation Agency, 1994). This is further discussed in "Hollows and Corridors" (p. 37).Invertebrates
There is almost a complete absence of invertebrate data from the"Greater" Murramarang National Park. The only known records appear in Appendix 9, 16 species of butterfly and 2 of moth.
In Australia many insects have co-evolved a large number of trophic interactions with the two large and dominant plant genera Acacia and Eucalyptus. These include sucking insects, such as the lerp-forming insects of the family Psyllidae, gall formers such as some wasps of the family Pteromalidae, pollinators of the bee family Colletidae, and seed eaters including many weevils such as species of Melanterius. In addition, a large range of insects chew foliage including leaf beetles of the subfamily Chrysomelinae with more than 600 species, and the Christmas beetles, Anoplognathus.
Other insects such as the spitfires (Pergidae) and many moths associate intimately with acacias and eucalypts. The Oecophorinae, or mallee moths, which comprise around 20% of Australia’s moth and butterfly fauna, with an estimated 5 500 species known, feed mainly on living and fallen Eucalyptus leaves. This is a highly specialised percentage of the total moth fauna, and species of oecophorids perform a key ecological role by breaking down leaves (Department of Environment, Sport and Territories, 1994).
Arthropods of the Phyla Chelicerata, Crustacea and Uniramai constitute by far the largest and most diverse components of the mesofauna within litter and upper soil horizons of the forest. These small animals, together with earthworms are essential in regulating the decomposition of organic matter, aerating soils, recycling nutrients and serving as prey or acting as predators, parasites or parasatoids in food chains.
The diversity of invertebrates presents some formidable problems in studying and understanding the role of fauna in the soil system, particularly in Australia where the difficulties are accentuated by a lack of taxonomic work (Coy, 1994). In comparison to our understanding of other biodiversity, the role of invertebrate fauna in forest ecology is very basic.Reptiles and amphibians
The reptile fauna of Australia is highly distinct. A remarkable 89% of the more than 750 reptile species found in Australia and its external territories occur nowhere else. Australian frogs are also very diverse with some 93% of about 200 species being endemic(Department of Environment, Sport and Territories, 1994).
From the limited survey work done in the"Greater" Murramarang National Park, 13 species of reptile and 11 amphibian have been recorded (Appendix 8). The Diamond Python is considered threatened. It is a species of dry and wet schlerophyll forests. Consequently, logging in the area is likely to detrimentally affect this species and put its survival at risk. Integrated logging is known to generally affect the abundance of reptiles with a few species becoming abundant while most species decrease greatly in numbers.
Frogs depend on water for breeding and rehydrating. Consequently, logging through its effects on stream levels and sediment loads may adversely affect their populations. Little research on these effects has been undertaken. While not breeding, frogs disperse throughout forest areas, some being terrestrial and others arboreal. Logging is likely to affect frogs at this time because of its effects on habitat parameters such as vegetation structure and humidity. This is another area requiring research (Pyke and O’Connor, 1991).
The high conservation values of Durras Lake to biodiversity, fisheries, tourism and recreation have been examined in "Durras Lake" (p.39). In February and May 1998, the Friends of Durras and the Australia-New Guinea Fishes Association conducted preliminary surveys of the small fish of Durras Lake. Species found during these surveys are added to NSW Fisheries (1998) catch data and appear in Appendix 8.
The Lake plays a critical role as a fish and invertebrate nursery. The 44 km. intertidal zone of the"Greater" Murramarang National Park is a crucial link between the Lake and the open ocean. Exchanges of water and biota are common between offshore and onshore areas of the ocean, along coasts washed by the same seas and across a variety of habitats. There is evidence that the larvae of intertidal or nearshore animals (eg barnacles, crabs and fish) are transported to the continental shelf to recruitment sites. Input from the terrestrial environment, by runoff and through Benandarah, Bridge and Ryan’s Creek via Durras Lake can provide nutrients, energy and matter for coastal habitats. Much research is needed before we will fully understand these linkages and their importance. From a conservation perspective, it is unusual to find, for any shoreline in Australia, a listing of rare species living on it, an estimate of the shoreline’s local biodiversity or the effects of human impacts. The Friends of Durras and the Australia-New Guinea Fishes Association will continue their survey work of the non-commercial small fish of Durras Lake. Much more knowledge than is currently available, is needed for comprehensive conservation planning.
We do know that mudflats and sandy habitats are extremely important as feeding grounds for migratory wading birds (Fairweather and Quinn, 1996). Around 60 species of water dependant birds have been recorded on the shores of Durras Lake or the intertidal zone of the"Greater" Murramarang National Park (Appendix 2). Six of these (Blue-billed Duck, Hooded Plover, Sooty and Pied Oystercatcher, Large Sand-Plover and Australasian Bittern) are threatened (Appendix 4). A further five threatened species; three birds (Black-browed, Wandering and Shy Albatross) and two mammals (Humpback and Sperm Whale) have been recorded in Beagle Bay offshore from Durras Lake. Durras Lake is part of the chain of important wetlands which shorebirds use to rest and feed. During the unusually dry summer of 1998, hundreds of black swan and chestnut teal and unusually high populations of great egrets used Durras Lake as a refuge from drought.
When Benandarah, Bridge and Ryan’s Creek flow, many native fish are adapted to move from saline to fresh water and vice-versa to feed and breed. Durras Lake appears to be a refuge for several species of gobies and gudgeon when the creeks dry.
Durras Lake has the potential to produce biodiversity surprises. During the February 1998 Friends of Durras Biodiversity survey, Pacific Blue-eye (Pseudomugil signifer), a popular species with fish fanciers, were found in one of the few remaining pools of Bridge Creek. Pacific Blue-eye are found along the east coast from Cooktown to Narooma. In breeding condition the fish have a dominant yellow/bluish coloration. The primary colour of the Bridge Creek specimens was however, red. Some examples are being bred to determine whether this is a new species or influenced by the immediate environment. The Australia-New Guinea Fishes Association’s field study team expects Durras Lake to produce a wide range of small, non-commercial fish including one of Australia’s rarest and most vulnerable fish the Southern Grayling (Prototroctes maraena).
The intertidal zone is also home to exceptional marine fossil biodiversity. The Snapper Point Nursery Beds and those at Pebbly Beach, Point Upright and Wasp Head are outstanding records of trace fossils, including the oldest record in the world of decapod fossils.
HOLLOWS AND CORRIDORS
Logging has occurred in the"Greater" Murramarang National Park for over 100 years. Until the 1950’s, for reasons noted in "One Hundred Years of Forest Management" (p.53), harvesting was very selective. Most old, large or defective overstory trees were left standing as they were unsuitable for sawlogs. They continue to serve as prime wildlife habitat. Over in the past 30 years, since the introduction of intensive silviculture practices, many of these trees have been "culled (as) large unmerchantable trees to encourage regeneration and release young healthy trees." They became woodchip.
Craven’s 1985 Environmental Survey of the South Durras District, NSW, noted that unlogged, Crown lands adjacent to Compartment 128 were "a superb example of mature forest with many habitat trees providing food and shelter for a wide diversity of animal life." His 1988 Post Logging Assessment of Compartment 128 provided a different picture. He estimated that the logging exercise over 112 ha of the Compartment severely depleted habitat trees, well below the number which should have been retained. "Very few habitat trees were apparent (left) in the cut-over areas."
As outlined in "Wood and Wood Products Industry" (p.67), woodchip is the end product of 95% of all timber harvested from public forests in the South-east Region. The timber industry in this region is undoubtedly woodchip driven. Woodchip is made not just of sawlog salvage and thinnings but also very old, prime habitat trees and trees unsuitable for sawlogs. The Friends of Durras are totally opposed to this narrow view of forest ecosystem management in our public forests.
In recognition of the importance of tree hollows to biodiversity conservation, State Forests are obligated to conduct pre-logging flora and fauna surveys. State Forests claim that the pre-logging fauna survey for Compartment 133 "provided a picture of fauna species occurring in the local area." The component of the survey for arboreal mammals and birds was a 3.45 hour spotlight survey on a single night, July 10th, 1996. During this brief survey period, 1 Feather-tailed Glider, 3 Greater Gliders, 5 Sugar Gliders, 4 Yellow-bellied Gliders and a Powerful Owl were either seen or heard. State Forests are also obligated to retain a number of hollow-bearing and potential habitat trees during harvesting. For Compartment 133, the Harvesting Plan stated that "an average of 3 hollow bearing trees, and 4 additional best potential habitat trees per hectare" would be left (State Forests, 1996). There is no scientific basis for this prescription. We do know from research by Gibbons that in some forests, up to 16 hollow bearing trees per hectare are routinely used by animals and birds.
There has been a great deal of scientific research investigating the potential long-term effects of integrated harvesting on flora and fauna. Much of the research has focused on the practice of removing old, defective, but prime habitat trees and the impact this has on wildlife which is either dependant on, or utilises the hollows and other resources these trees provide. At least 24 mammal species and 33 bird species found in the"Greater" Murramarang National Park have been recorded utilising tree hollows (Appendix 7). Twelve of these are threatened species (Appendix 4).
Research has raised concerns that integrated harvesting , by its very nature, necessitates a reduction in the number of hollow bearing trees. Since the harvesting cycle is 30 to 50 years and tree hollows do not usually develop in trees less than about 200 years old, the reduction in hollow-bearing trees will be large and permanent. Consequently, for species that require tree hollows for nesting and roosting, integrated harvesting will result in reductions in species abundance, that persist indefinitely. Local species extinction may occur. Other species that require mature forest will also be adversely affected by integrated harvesting. Indeed, the loss of hollow-bearing trees has been listed in Victoria as a process threatening populations of wildlife under the Flora and Fauna Guarantee Act 1988 (Pyke and O’Connor, 1991).
Gibbons and Lindenmayer (1997) from the Australian National University’s Centre for Resource and Environmental Studies, have completed the most in-depth study of the impact of harvesting on hollow-dependant fauna to date. In summary they concluded that:
Gliders and the large forest owls are seen by many forest ecologists as good indicators of the species richness and diversity of a forest. The"Greater" Murramarang National Park is well endowed with richness and diversity with 5 glider and 5 owl species (Appendices 2 and 3). All are to some degree dependant on mature forests containing a plentiful selection of hollows. The Powerful and Sooty Owls are likely to play a functional role in forest communities because of their position as top carnivore. The presence of large carnivores contributes significantly to the maintenance of biological diversity and may indicate the integrity of an important part of the forest ecosystem. The diets of both owl species appear to consist primarily of four species of arboreal marsupials, including the Greater and Yellow-bellied Glider, but many other species are taken. The Powerful Owl has been known to reduce by 90%, the size of populations of its preferred prey such as the Greater Glider. The low reproductive rate of the Greater and Yellow-bellied Gliders (less than one young per adult female per year) inhibits their recovery from habitat disturbance or predation. Hence the continuing presence of the Powerful and Sooty Owl in forests may depend on management practices which maximise populations of possums and gliders (Kavanagh, 1991).
Given that about 20% of the tall open forest and 50% of the open forest in New South Wales has been cleared, populations of Powerful and Sooty Owls may have declined by as much as 50% through habitat loss and the remaining habitat is subject to logging, grazing and burning. The effects of integrated harvesting on glider populations and subsequently on the populations of the large forest owls may take many years to become apparent, may be difficult to detect and quantify and recovery may take a very long time, if ever. Forest managers cannot be content simply that because large forest owls occur in logged forests their continued existence will not be threatened by further logging. They must also consider the long term availability of the Owl’s and therefore the possum and gliders’ resources such as nest sites, prey populations and other resource requirements (Debus, 1994).
The past legacies of forest use have created a highly fragmented and modified eucalypt forest estate. In eastern Australia it is rare to find areas of eucalypt forest larger than a few contiguous catchments that have not been roaded, fragmented and modified to some degree. Integrated harvesting further exacerbates ecosystem fragmentation and destroys or reduces the natural connectivity between and within ecosystems in the landscape (Norton and May, 1995). Retained systems of linear habitat or wildlife corridors are widely used in production forests as a strategy to mitigate the impacts of logging on populations of animals.
Attempts to connect the discontinuous areas of Murramarang National Park with corridors through logged state forest, demands close study. The survival of many species is at risk. The Harvesting Plan for the 302 ha, Compartment 133 for example, set aside 40 ha as ‘non-harvest area.’: an 8 ha. flora and fauna corridor along an un-named creek (50 metres wide on each side of the drainage line), 27 ha of drainage protection and 5 ha of roads (Map 6).
There has been little research into the success of wildlife corridors but there are a number of factors which may potentially influence their use by wildlife. These include: (i) the biology, ecology and life history of species, (ii) habitat suitability and attributes of retained strips such as width and length, (iii) the location of the site in the landscape, (iv) the type of logging operations and their intensity and pattern at landscape scale, (v) the suitability of habitats for fauna in the areas surrounding retained strips and, (vi) the value for fauna of reserves connected by corridors. This diverse array of factors means that, within the constraints which typically apply in timber production forests, it may not be possible to design corridor systems that conserve all those species that are vulnerable to the effects of integrated harvesting. For example, the Greater Glider has rarely been detected in wildlife corridors that supported few nest sites. This species does not favour wet gullies and is rarely detected in corridors with a watercourse. Birds, such as the Gang Gang Cockatoo and the Crested Shrike Tit, which forage over large areas and have specialised habitat requirements, were rare in linear reserves of mature forest. Similarly, the resource requirements of the large forest owls may best be met and the species conserved by the reservation of large areas of mature forest.
Much more research is needed and until studies are completed it is essential there is a conservative approach to forest management (Lindenmayer, 1994). Numerous, hollow-bearing trees of a variety of species and a wide range of ages scattered throughout large undisturbed forest areas are essential to the guaranteed survival of a great many vertebrate forest species.