The New Nature Read online

  This catastrophe is seldom spoken of today. Most farmers don’t even know it happened. On pasture maps spear grass shows up as Queensland’s largest unit, stretching from Cooktown to northern New South Wales. It is fit only for cows. N.H. Shaw of the CSIRO deduced in the 1950s that this vast vegetation unit was man-made. He saw kangaroo grass still holding sway along railway tracks and in country cemeteries, where fences held back stock. Burning by farmers had seemed clever at first, forcing kangaroo grass to produce more, but it proved a greedy ruse that took too much from the land.

  Over in Western Australia Alan Newsome looked into the collapsing sheep industry in the Pilbara in the 1960s. Graziers blamed their plight on exploding numbers of euros (wallaroos), but Newsome found the graziers had themselves to blame for stocking so high that sheep took out all the softer grasses. ‘Where once men scythed grass to make haystacks, spinifex had encroached to dominate.’ Wallaroos do better on prickly spinifex than do sheep, and they adapted, coming down from rocky ridges – their usual domain – to roost on the plains by day, under trees, and drink at dams by night. On one station with 6500 sheep nearly 13000 euros were killed. Farmers wanting sheep and grass got euros and spinifex instead. Over-grazing usually leads to change, as Alfred Ewart elegantly explained in 1909: ‘Obnoxious, prickly, woody, and poisonous plants are usually left untouched by healthy well-fed stock, and their growth is favoured by the continual grazing down of the good fodder plants. The condition of affairs obtaining in a well-kept garden is thus reversed, the weeds being favoured, and the useful garden plants suppressed.’

  Farmers were grappling with these shifts in Ewart’s day, and national park rangers face them today. Many of our parks were once grazing runs, on which macropods now feed on grasslands created for stock and where the problems Ewart noted are festering. And there is fire to consider. Like war, it plays a determining role, deciding which community wins control. The fires lit in many reserves today are cooler than Aboriginal fires – for safety reasons – allowing large numbers of seedling shrubs to survive. It’s a surefire recipe for change.

  Burgan (Kunzea ericoides) is one plant to fear. It’s a fine-leafed aromatic bush up to 4 metres tall that takes over partially cleared lands in south-eastern Australia when stock are removed. In the Yarra Valley it’s invading in the wake of clearing, grazing and fewer fires. In Tidbinbilla it seized cleared lands when sheep were withdrawn. Beyond the park boundaries, where sheep still graze, it is kept at bay. Once it grew as scattered shrubs in forest gaps, but it now forms vast monocultures on bared slopes. Nothing much grows under burgan beside a few brambles and ferns. When I suggested to Paul Slinger, ranger of Corranderrk Reserve, Healesville, that burgan might claim his whole reserve, he readily agreed. ‘I wouldn’t be surprised if it does at all.’ Prolific swamp wallabies don’t help by eating out competing plants. Paul blames burgan invasion on several factors. ‘Grazing is one, disturbance is another. Burgan is more prevalent on roadsides – that’s where it starts. It gets a hold there and expands out from those patches. Fire is another. If there’s not enough fire it proliferates.’ Loss of the tree canopy is another problem, probably exacerbated in the past by bellbirds. Paul hopes to quell burgan with poisons, but disposing of all the dead wood may prove difficult. (Coranderrk, by the way, conserves several rare habitats and rare plants.)

  In western Victoria coast wattle (Acacia sophorae) is reckoned among the worst of all weeds. Like coast tea-tree, it has ventured inland from beach dunes, its seeds hitching rides on muddy cars. At Minnie Waters in northern New South Wales it has achieved the amazing feat of dividing a community. Botanist Tim Barlow explained this odd state of affairs. ‘It appears that the entire community of about 200 people is either a member of the local dune-care group, who believe coast wattle to be the devil reincarnate, or a member of the landcare group, who consider coast wattle to be the best thing since sliced bread.’ The wattle sprouts in the thousands on dunes where bushcarers remove African bitou bush, a horrid invader. Many residents welcome the wattles, but others fear they are seeing an Aussie weed replace an African one. Coast wattle doesn’t form monocultures on undamaged dunes. Other native plants swamping reserves to some extent include manuka (Leptospermum scoparium), white kunzea (Kunzea ambigua), mallee cypress (Callitris verrucosa), silvertop ash (Eucalyptus sieberi) and bracken (Pteridium esculentum).

  Vegetation change poses conundrums for Australia. It’s very difficult to manage, and it injects some uncertainty into our conservation goals. Do we preserve the landscapes created by Aboriginal fire, or do we help ‘nature’ revert to its ‘original’ state? Do we let coast tea-trees sweep inland, on the assumption that they were forced out by previous firestick farming, or do we imprison them in the landscape they occupied in 1788? Do we even know what Australia looked like in 1788? Are the shifts underway really due to fire and grazing, or are drought cycles and global warming (natural and human-induced) important too?

  It all depends on where you are. Monocultures of sweet pittosporum, burgan, coast wattle and native hops probably represent something new; monocultures aren’t usually natural. The plants in question have invaded quickly in response to sudden change. With enough time the pittosporum stands around Sydney will diversify into proper rainforests (with weeds) and provide more value to wildlife.

  Invasions by whole habitats deserve more serious consideration. In Tasmania rainforest is invading vast monocultures of buttongrass – an ironic situation. If human fire produced these monocultures, shouldn’t we welcome the rainforest back? It is, in effect, regenerating, not invading. But the monocultures have become vital habitat, not only for endangered orange-bellied parrots, but for ground parrots and native broad-toothed rats as well.

  Similar predicaments exist on Cape York Peninsula, where heavy-handed burning is needed to save dwindling birds, and in the Red Centre, where mosaic burning helps mammals and skinks. But sometimes a choice is made to reject fire. At Wattle Hills on Cape York Peninsula alternative lifestylers have bulldozed firebreaks around 20000 hectares of woodland. Community founder Mia Worsefield celebrates the dramatic changes wrought by a decade without fire. Eucalypt and wattle saplings now grow so thickly that large animals can scarcely move through. Mia insists wildlife adapts well to the change. Wattle Hills adjoins Iron Range National Park, where National Parks and Wildlife rangers incur Mia’s scorn for burning the land. ‘We call them National Sparks and Wildfire. They’re trying to hold it at a point in time,’ she said. ‘They’re deciding that the wet sclerophyll forest needs to be kept as it is and not turned into rainforest. We don’t feel that holding the land at one point in time is appropriate.’ She points out that bushfires release copious volumes of greenhouse gases.

  In many parts of Australia, when fires are excluded new rainforests appear – and do so at no loss to anything rare. John Birbeck, Caloundra’s senior environment officer, watches over four adolescent rainforest patches on the Sunshine Coast, each harbouring rare plants. One contains 130 rainforest species, another ninety. Each has sprouted beneath old eucalypts in fertile soil. He showed me one. ‘It’s all even-aged young rainforest,’ he explained. ‘There are no big trees in it. That’s a good indicator to me that it’s new.’ The sites keep accumulating plants. One that comes in late is a rare vine (Pararistolochia praevenosa) that feeds the Richmond birdwing butterfly, itself rare. Birds commuting between jungle patches ferry in new seeds.

  Alice Springs botanist Peter Latz praises the ‘woody weed’ invasion underway in central Australia. ‘Nature is saying, “Thank you for creating less fire, I can heal things up a bit.”’ His research implies that many species suffered from firestick farming. The ‘woody weeds’ he welcomes in are often nitrogen-fixing wattles that fertilise the land. In southern Africa it’s an interesting fact that invading woody weeds are a boon to birds. Forty-nine species do best on overgrazed farms when thornveld invades: cuckoos, mousebirds, barbets and more. ‘This situation in the Kalahari, where the majority of endemic species ben
efit from the most common forms of land transformation by humans, appears to be quite unique,’ wrote zoologist Marc Herremans. But woody weeds in western New South Wales and Queensland don’t attract hosts of birds. Honeyeaters drop in when the poverty bushes bloom, and parrots take seeds, but there’s no suite of birds that likes woody weeds best.

  Pollen records show that she-oaks once clothed vast tracts of Australia before the eucalypts took over. So should we welcome them back? No fires have burned at Ocean Grove Education Reserve near Geelong for a hundred years, and conquest by black she-oaks (Allocasuarina littoralis) is nearly complete. Every swamp gum is dead or dying. Tree densities have jumped from twenty per hectare to 3000 because she-oaks are crowding the reserve. They didn’t grow here at all in 1864. This place went through a wattle invasion before the she-oaks took over. ‘The abundant recruitment of Acacia species in the mid- to late-1900s may have been a rapid response to the curtailment of Aboriginal burning,’ Ian Lunt concluded, ‘and the more recent invasion of A. littoralis a longer-term response to fire exclusion.’ Sweet pittosporum is now invading. Is this some return to an ancient past? I have no idea. But in north Queensland thickening up by forest oaks (Allocasuarina torulosa) is brightening the future for one rare bird. Glossy black-cockatoos have spread 330 kilometres north into mountains near Townsville to avail themselves of a burgeoning supply of she-oak seeds. They eat nothing else. The implication here is that past Aboriginal fires forced them out of the north by burning back their food trees.

  Vegetation change is like Bible scripture: you can read into it anything you like. A few years ago a booklet came out plying the comforting message that ringbarking by pioneers had restored the bush to the state that prevailed when Aborigines burned. This idea, from the Murrumbidgee Catchment Management Committee of Wagga Wagga, relied on the neat assumption that settlers had cleared only trees that appeared after the Aborigines stopped burning. That booklet, The Australian Landscape: Observations of Explorers and Early Settlers (1995) by D.J. Ryan, J. Ryan and B. Starr, incurred the wrath of botanists John Benson and Phil Redpath, whose damning critique, replete with explorers’ quotes, filled forty-three pages of the learned plant journal Cunninghamia. Also attacked were Tim Flannery and Eric Rolls (author of A Thousand Wild Acres) for making exaggerated claims about landscape change that Ryan and co. could exploit. John and Phil’s critique inspired a flurry of responses, and John is now weary of the whole debate. It’s very reminiscent of the never-ending controversy over crown-of-thorns starfish plagues – are they natural or not?

  Habitat change is a hot topic that deserves more attention. We need more workers like botanist Rod Fensham, whose thoughtful papers are illuminating. He mapped remnant woodlands on the Darling Downs, then pored over old survey maps from a century before, and could find no evidence of vegetation change. In another study he tallied massive tree deaths from drought and concluded that some of today’s regrowth represents recovery from drought, not fire. But after studying grassy clearings (‘balds’) on the Bunya Mountains which are fast disappearing under trees, Rod decided that these were probably kept open by Aboriginal fires. In a fourth study he went through the journal of every Queensland explorer looking for every mention of Aboriginal fire. Fires were often lit to repel explorers, he noted, or to signal their presence. He nonetheless concluded that most habitats near the coast were ‘relatively frequently burnt by aborigines’ for management, whereas inland areas (in Queensland at least) seldom were.

  Rod offers a less extreme picture than Tim Flannery, who argues for massive rainforest destruction, and David Horton, who insisted in the improbably titled The Pure State of Nature (2000) that firestick farming was a myth. ‘It is surprising,’ wrote Horton, ‘given the firestick farming theory, to find how little emphasis there is on fire around Sydney Cove in the observations of the first three years.’ But Horton overlooked the journal of Captain Watkin Tench, who had this to say: ‘The country, I am of opinion, would abound with birds, did not the natives, by perpetually setting fire to the grass and bushes, destroy the greater part of the nests.’ Captain Phillip, surgeon Worgan and Lieutenant Ball also noted Aboriginal fires. I walked once with Aboriginal women as they torched a woodland near Darwin, and I cannot accept firestick farming as a myth. People make a big difference to the land. ‘Pure nature’, not firestick farming, is the myth.

  To burn or not to burn, and when to burn and how to burn, will remain knotty questions. I am sure that in national parks today there are plenty of rangers burning inappropriately (see chapter 22), or acting irresponsibly by not burning. Decisions about fire depend on perceived needs. Here are two examples.

  An endangered plant can be found sprouting in the rainforest gloom along a few streams in south-west Tasmania. Kings holly (Lomatia tasmanica) is a spindly shrub whose reddish blooms never proceed into seed. Genetic work suggests that the three stands, found close together, grew from a single sterile founder. This holly is effectively a single plant, a clone that has spread slowly through the rainforest by sprouting hundreds of woody stems. Some of its fossilised leaves date back 43600 years. Given that Kings holly is evidently a non-reproducing triploid, the fossils imply great antiquity for this plant. Indeed, botanist A. Lynch has suggested to the scientific community that Kings holly may be the world’s oldest plant. Buttongrass plains have divided the clone into three separate stands. Past Aboriginal fires have destroyed perhaps half the colony. Fire suppression will help this plant survive.

  But another endangered plant, the Neilson Park she-oak (Allocasuarina portuensis), desperately needs fire. At Neilson Park, Vaucluse, only one aged tree remains, along with some planted seedlings. For an endangered plant inner-city Sydney is not a safe place to be. I was there in early 2000 when two she-oaks still survived, both crowded in by cheese trees and pittosporum. I could see where rangers had poisoned and hacked back a cheese tree clump, but it wasn’t enough. The she-oaks looked unhappy in the gloom; this slope was obviously more open in the past. Senior ranger Craig Shepherd suspects it was a low to medium heathland, but fifty years without fires have made all the difference. ‘It’s now semi-rainforest, really,’ he admitted. ‘If you left it another hundred years you could get rainforest growing here.’ Craig assured me the rangers had recently cut back all the mesic trees, allowing the last she-oak to burst into bloom for the first time in years. But she-oak seeds can’t sprout in the thick mulch now carpeting the ground. National parks rangers want to burn Neilson Park to allow regeneration, but influential locals have blocked them. Fire management is easier in less affluent suburbs, Craig admitted. The she-oak is now more or less domesticated, its seedlings germinating only in seed trays.

  Vegetation shift intrigues me. I can see it going on out my window. The lush shrubs and trees growing in city gardens turn them into rainforest glades. Ringtails and rainforest butterflies feel at home. Added nutrients and freedom from fire allow wild rainforest plants to sprout. Birds in my garden keep dropping seeds of figs and white cedars, and gardens are now prime habitat for these enterprising trees. A brush-turkey comes by to scratch through my beds, never guessing that this slope once carried grassy woodland where bushfires crackled and kangaroos grazed. For urban turkeys vegetation shift is a boon, but for managers of reserves it’s a conundrum. It impresses me as one of the trickiest issues thrown up by the new nature.

  ‘Unnatural deeds Do breed unnatural troubles’

  William Shakespeare, Macbeth

  Now for a tale of two birds. One, the black-eared miner lived deep inside the mallee, a vast sea of low eucalyptus that flowed from north-west Victoria into South Australia and New South Wales. The other, the yellow-throated miner, was a wide-ranging Outback bird that skirted the mallee, dwelling only on its edges. They seldom met until farmers began clearing the mallee, drawing the two together. Yellow-throats, offered more edges, moved into clearings where dams supplied water and shrubs were trimmed by stock and kangaroos.

  Both miners live communally and look similar. They
are greyish honeyeaters much like the noisy miner. When they fledge, young males stay with the group while young females disperse. But the mallee is now so fractured that many females end up in the wrong places. This is proving calamitous for the black-eared miner, reduced by mallee loss to one of Australia’s most endangered birds.

  Rohan Clarke has studied these birds: ‘The female black-eared miners are dispersing out of their mallee fragments into wheatfields – and vanishing. Perhaps they get eaten by birds of prey. Female yellow-throated miners disperse into their colonies. You get colonies where all the males are black-eared miners but the females are yellow-throated. They hybridise.’ An exchange system that promoted genetic mixing within each species now taints them both. Yellow-throats are winning, their genes prevailing. ‘I know of a site where four or five years ago the birds were mainly hybrids,’ Rohan said. ‘That colony has now changed over to yellow-throated miners. It was really rapid. In two or three breeding seasons the new birds won. And that seems to be what was going on all over the mallee.’