Australia’s pine plantations are supposedly biologicaldeserts, inhospitable to native mammals and birds. Butit seems species like the common ringtail possum andthe rufous whistler don’t know it.

Australian National University ecologist ProfessorDavid Lindenmayer says while it is true that pure, large-scale stands of pines are ecological deserts, aroundTumut, in southern NSW, both possum and whistlerspecies are flourishing in a landscape of 10-year oldpines interspersed with strips and islands of remnanteucalypt woodland. They are actually more abundant inthis radically modified landscape than in the naturaleucalypt woodlands outside the plantations.

In fact, Lindenmayer and his small team ofco-workers from of the ANU’s Centre for Resource andEnvironment Studies (CRES) have recorded more than100 native bird species, along with numerous frogs andreptiles inhabiting the pine-eucalypt mosaic landscapes.

A friend and mentor, former CRES director ProfessorHenry Nix, once told Lindenmayer the only certain thingabout the Australian environment was its uncertainty.

Lindenmayer has established the truth of Nix’sobservation during two decades of field research into

the habits and habitats of native animals – mammals,birds, reptiles and frogs – in human-altered and naturalenvironments in south-eastern Australia.

Popular conservation in Australia is centred onpreserving pristine environments like rainforest andold-growth forest, as much for their aesthetic appeal astheir biodiversity. Almost by default, human activity isregarded as incompatible with wildlife conservation.Lindenmayer’s surprising findings challenge thesebeliefs – he has found that some native animals actuallyflourish in disturbed environments, whether the distur-bance is natural or human-induced.

He says the problem with current conservationphilosophy and practice is that the ecosystems that havesuffered most from human disturbance – woodlands,heathlands and grasslands – still harbour much ofAustralia’s biodiversity, including many rare or endan-gered species. But, they’re not accorded high conserva-tion priority because they’re not pristine, or lack thehigh aesthetic appeal of forested landscapes.

Lindenmayer believes such attitudes must change.‘To my mind, some of Australia’s rusted-on conserva-tionists need to mature their thinking and philosophy,

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David Lindenmayer

Left standing,slender mountainash trees retainedas part of a loggingexperiment.

Some nativeanimals actuallyflourish indisturbedenvironments,whether thedisturbance isnatural orhuman-induced.

Unique, simultaneous studies across different Australian landscapes havethrown up some real surprises about biodiversity conservation in disturbedareas – particularly pine plantations.

Graeme O’Neill reports on David Lindenmayer’s long-range work to forge a new understanding of ecological priorities.

A bigger picture of disturbance

to incorporate conservation in areas that are neitherwilderness or reserves.’

He believes it is essential to conserve endangeredspecies wherever they are found, in pristine or degradedenvironments, even if humans must intervene to createfavourable habitat. His own research has shown thathuman preconceptions of what constitutes ‘favourablehabitat’ do not always coincide with animals’ habitatpreferences in the real world.

‘You always get ecological surprises when you alterthe landscape, he said.

‘While you need pristine environments for somespecies, there are many elements to biodiversity, andsome species don’t do well in large, undisturbedwilderness areas.’

In pre-European times, fires sparked by lightning, orset by Indigenous hunters, created a complex mosaic ofmulti-aged woodland and forest that sustained complexcommunities of plants and animals. Since Europeansettlement, fire suppression and the mass-clearing ofwoodland and forest landscapes has led to the decline of species that thrive in ‘patchy’, naturally disturbedenvironments, because few large, continuous areas ofsuitable habitat remain.

Lindenmayer says some ecosystems have been decimated to the point where the future of theirresident species now depends on active, enlightenedhuman intervention. But such remedies are shunned by sections of the conservation movement that believein conserving pristine environments, and minimisinghuman intrusion into nature’s affairs.

His vision goes beyond merely managing the naturalenvironment – he hopes his research will yield formulaefor designing landscapes to create favourable habitat fordeclining or endangered species.

‘The reality is that we have to manage naturalresources,’ he said. ‘The question is: How can we do it insmart ways, so we can conserve species, while pursuingsome components of commercial production.’

As a PhD student in the early 1980s, Lindenmayerconducted a ground-breaking study of the habitatrequirements of Leadbeater’s possum (Gymnobelideusleadbeateri) in the lofty mountain ash (Eucalyptusregnans) forests of Victoria’s Central Highlands.

Missing, believed extinct for six decades,Leadbeater’s possum was rediscovered in 1961 nearMarysville, in young mountain ash forest regeneratingafter the Black Friday bushfires of 1939. The fires razedhuge areas of old-growth forest, leaving many old,unburnt trunk stags with nesting hollows standingamid vigorously regenerating young trees with an acaciaunderstorey – prime habitat for Leadbeater’s possum.

When Lindenmayer began his survey in 1983, thepossum was under threat on two fronts: the rottingstags were collapsing, and loggers were moving in toharvest the Class of ’39. His original brief was to assessthe impact of logging on the possum’s habitat, anddetermine if it could be mitigated to achieve a betterblend of conservation and timber production.

It evolved into much more than just a habitat study.‘I began looking at conservation reserves, wildlife corri-dors, logging experiments and wilderness.

‘Wilderness is irrelevant to Leadbeater’s possum – it thrives in forest that have been disturbed in specificways.’

His research revealed the possum flourishes in these

fire-disturbed landscapes, commuting from nestinghollows high in the trunks of mature mountain ashtrees to feed on sap and insects in surrounding youngregrowth forest with a dense understorey of acacias.

He became convinced that commercial logging andconservation could not only co-exist in the mountainash forest, but that loggers could actually help recreatethe ‘edgy-patchy’ habitat the endangered marsupialprefers by retaining strategic patches of mature treeswith hollows, close to young forest regenerating onclear-felled coupes.

The mountain ash forest study in the Victorian high-lands, which continues today, was the prototype for histrademark, large-scale, long-duration, multi-siteecological studies – he has five such experimentsrunning concurrently in Victoria, NSW and the ACT.

The ecological research literature contains manyreferences to small, scale studies describing how partic-ular species respond to changes within individual habi-tat patches. Lindenmayer is concerned with the biggerpicture: how do animal communities respond to land-scape-scale disturbance and change?

He has two studies running in the pine plantationsnear Tumut, in southern NSW, another in the farm-lands of the Riverina, and a fifth in the coastal heath-lands of Jervis Bay, ACT. He works with just threefull-time field staff and a statistician, shuttling between

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Leadbeater’spossum, oncebelieved extinctafter thedevastating fires of 1939, seems toneed disturbed,‘patchy’ areas onthe fringes ofmountain ashforest.

The mosaics ofnative bushremnantssurrounded bypine plantationforest at Tumut are surprisinglybiodiverse.

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the five sites, with occasional help from volunteers fromthe Earthwatch Institute and the CanberraOrnithologists Group.

Lindenmayer knows of no other research group inthe world that is attempting to meld data from fivelarge-scale ecological studies in very different land-scapes, to draw out generic themes for conservingspecies and ecosystems.

Each project involves multiple, replicated sites, repre-sentative of the diversity of local environments. Some ofthe animals the ANU researchers are monitoring arecommon to multiple study locations.

Near Tumut, a major plantation forestry project onformer grazing land left islands of eucalypt forest andwoodland scattered through 10 000 hectares of youngradiata pines. The ANU team established 166 sites tomonitor changes in the abundance and diversity ofmammals, birds, reptiles and frogs in the woodlandpatches and surrounding pine forests.

Graziers began clearing the Tumut woodlands in themid-1800s, and the first pine plantations were estab-lished in the 1930s, so the original eucalypt-to-pinetransition occurred long before the current study began

But Lindenmayer learned that NSW Forests plannedto establish a 10 000 hectare pine plantation onNanangroe, a former grazing property with large nativewoodland remnants in a valley 15 km south-west ofTumut. His team set up a 132-site study in 1997, threeyears before planting began, and has been monitoringchanges in the diversity and abundance of native verte-brates as exotic conifers begin growing where clearedand grazed paddocks once occurred.

He says while broad-scale, pure pine plantations arethe biological deserts of repute, many native animals areflourishing in the Tumut landscape’s mixture of youngpine forests and woodland patches. Lindenmayer’s teamhas recorded 100 native bird species. To their surprise,they found the remnant eucalypt woodland ‘islands’retained most of their original animal species – albeit in

lower numbers – where ecological theory predicted adrastic loss of biodiversity.

In a parallel to the Leadbeater’s possum story, thecommon ringtail possum (Pseudocheirus peregrinus) isprospering in the radically altered environment aroundTumut. The possum, which occurs in all five ofLindenmayer’s study landscapes, is uncommon inVictoria’s wet montane forests, but thrives in the pineforests because the remnant eucalypt patches create thefragmented, ‘edgy’ environment it prefers.

Around Tumut, the possums nest in both the euca-lypt patches and surrounding pine plantations, usingpine needles to construct dreys – breeding nests –among the branches. But in the remnant eucalyptwoodlands of Nanangroe, they nest in tree hollows. Thewarmer, drier climate at lower elevation makes it is toohot to nest in the open. The possum’s physiology leadsit to adopt different nesting behaviours in differentenvironments – an unexpected and exciting discovery.

Several once-abundant woodland birds including therufous whistler (Pachycephala rufiventris), red-cappedrobin (Petroica goodenovii), and hooded robin(Melanodryas cucullata), are also flourishing in theTumut plantations.

These species have declined markedly since farmersand graziers cleared much of south-eastern Australia’sextensive box-ironbark woodlands in the late 19th and20th centuries.

The young pines form a dense canopy, and theiruntrimmed lower branches provide a vital structuralelement – an understorey – that has almost disappearedfrom Australia’s remnant box-ironbark communitiesbecause of grazing and changed fire regimes.

The woodland islands that are surrounded by youngpines are experiencing major changes in their avifauna:woodland birds are being displaced by forest-dwellingrelatives like the olive whistler, golden whistler andyellow-faced honeyeater.

Meanwhile, eucalypt woodland remnants on farm-

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Mountain ashcoupes such as thisone in Victoria’sCentral Highlands,may provide thesort of necessarydisturbance that is key to thedistributions ofsome nativespecies.

Lindenmayerknows of noother researchgroup in theworld that isattempting tomeld data fromfive large-scaleecologicalstudies in verydifferentlandscapes,to draw outgeneric themesfor conservingspecies andecosystems.

David Lindenmayer

land outside the Tumut plantations, and on propertiesneighbouring Nanangroe, retain a classical assemblageof woodland birds, including crested shrike tits, easternrosellas and brown treecreepers.

‘The structure of the woodland hasn’t changed; thecontext has,’ Lindenmayer said. ‘The context of thewoodland influences what lives there. Forest birds aremoving into the eucalypt woodland islands becausethey perceive the landscape as a forest.’

Overseas researchers have identified similar contex-tual effects, but Lindenmayer believes his team is thefirst to observe the transformation of a woodland into a‘virtual forest’.

Reptile diversity and numbers are changing muchmore slowly, and the frog assemblage is essentiallyunchanged. ‘Some species of frogs are very dependenton riparian areas – they don’t recognise native vegeta-tion as habitat, and are only affected by hydrologicalchanges,’ he said.

The recently established Riverina Restoration Studyhas underscored the importance of understorey vegeta-tion as habitat for woodland birds. Without this struc-tural refuge, noisy miners (Manorina melanocephla)invade and dominate remnant patches of vegetation,driving out other bird species.

The Riverina study, covering 168 sites, is investigat-ing the ecological effects of revegetation projects onfarms and grazing properties in two areas around theMurrumbidgee and Murray rivers.

The ANU researchers have established sites on‘pigeon-paired’ farms, some with large patches ofremnant vegetation, others with virtually none. Somefarmers are undertaking high-intensity revegetationwith eucalypts and casuarinas, with an understorey ofacacias and grevilleas, while others are revegetating on asmaller scale, or not at all.

The complex experimental design, conceived byLindenmayer’s long-time colleague, CRES biostatisti-cian Professor Ross Cunningham, allows the ANUresearchers to study the ecological effects of differentcombinations of remnant vegetation and revegetation.

Lindenmayer credits Cunningham with investingtheir field experiments with a flexibility that makes itpossible to ask post hoc questions not envisaged whenthey began.

While it’s early days, Lindenmayer says it is alreadyclear that the combination of high-intensity revegetationand woodland remnants attracts a greater number anddiversity of birds than remnant vegetation alone. Withthe benefit of an understorey, declining woodland specieslike redcapped and hooded robins are on the increase.

Where mammals are concerned, common ringtailpossums already seem to be responding to changes atthe level of the individual farm, whereas brushtailpossums (Trichosurus vulpecula) are more responsive to landscape-level changes.

Environment Australia recently commissionedLindenmayer’s team to study the ecological effects ofprescribed patch-burning on coastal vegetation at JervisBay with the aim of maintaining its rich biodiversity.They have established a complex of 112 sites in coastalheathland, woodland and remnant rainforest commu-nities.

Each of the five large-scale studies differs in designbecause they address different ecological questions.‘I’d love to say I had a grand vision 10 years ago, but the statistical tools drawing out common themes, haveonly recently become available,’ Lindenmayer said.

‘The really big insights will come from stitchingtogether large-scale studies.

‘In conservation, everyone is looking for easy, quickanswers, or magic-bullet solutions. Unfortunately, thereare few short-cuts. The big problem in natural resourcemanagement has always been a lack of informed scien-tific data to take us forward.

‘Nature is complex, and the devil is in the detail.It makes ecological research very exciting, but also very difficult.

‘Sometimes you get criticism from both sides. TheGreens have criticised our central highlands experimentbecause it involves traditional logging practices likeclearfelling and burning.

‘They shouldn’t be concerned about how it lookstoday, because we’re trying to create a complex- multi-aged forest that will provide optimum habitat forLeadbeater’s possum and other wildlife in 20 years time.We’re trying to do something similar at Nanangroe.’

Last November a panel of Lindenmayer’s peersrecognised him as Australia’s leading thinker in envi-ronmental science, in the ‘Smart 100’ awards schemesponsored by the national news magazine The Bulletin.

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More Information:Lindenmayer, D.B., and Franklin, J.F. (2002) Conserving

forest biodiversity: A comprehensive multiscaledapproach. Island Press, Washington.

Lindenmayer, D.B., H.P. Possingham, R.C. Lacy, M.A.McCarthy and M. L. Pope. (2003) How accurate are popu-lation models? Lessons from landscape-scale populationtests in a fragmented system. Ecology Letters, 6, 41-47.

Woodland patchesin an emergingpine system nearNanangroe, NSW.

‘In conservation,everyone islooking for easy,quick answers,or magic-bulletsolutions.Unfortunately,there are fewshort-cuts.

Left: Burning off a discarded woodpile in a pineplantation.

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