The New Nature Read online

  When open-cut mines exhaust their seams, the huge pits fill with groundwater and fish move in. Wayne Young has netted thirty-odd pits, and he told me some surprising tales. ‘The mining voids are pretty impressive. It’s a stark landscape yet the number of fish that turn up is amazing. You go down a pit that’s 80 metres deep, about 150 or 200 metres long, and cut straight into the rock. The edges on one side are all just loose rock and there’s a sheer rock face on the other. Generally there’s only a small pool in the bottom. There’s no overland flow into these pools and there’s no water pumped into them. Yet two or three years after they finish mining there’s absolutely hundreds of thousands of fish in them. Mostly they are rainbows (Melanotaenia splendida) and firetail gudgeon (Hypseleotris galii) and glass perchlets (Ambassis agassizi).’ ‘How do the fish get there?’ I asked, recalling the huge, isolated pits I’ve seen from the air over central Queensland. The rainbows were brought by birds, he replied. ‘They have sticky eggs that are laid in strings and wrapped round and round aquatic plants.’ Wayne believes that ducks browsing sago pondweed (Potamogeton pectinatus) in lagoons carry egg strings tangled around their legs when they drop in on mine pits for a look. Rainbowfish eggs can survive drying, but Wayne can’t explain how other fish reach the pits.

  Ducks bring in pondweed seeds as well, kicking off ecological succession. Fish eat this plant, and birds (grebes, cormorants, darters, kingfishers) eat the fish. ‘If there’s sago pondweed in a pit you can guarantee there’ll be fish there,’ Wayne said. Foodwebs change as new fish arrive. At Peak Downs in 1994 Wayne netted four or five kinds of small fish. Three years later the pool was commandeered by much larger spangled perch, all emaciated and listless. They had eaten the smaller fish and were attacking each other. All the fish in a pit can sometimes die, succession beginning again when birds courier in more eggs.

  The rubble heaps around mine pits also attract life. Lindsay Agnew has found barn owls nesting among overburden and hosts of frogs calling from a puddle on a high mound. Pebble mound mice like nesting among mine rubble, and plants use this ground too. In Victoria in 1916 horticulturist Edward Pescott observed that golden wattle (Acacia pycnantha), Australia’s floral emblem, ‘grows wonderfully in the mining districts of the State, especially where the surface has been turned over, time after time, in the search for gold’. A daisy (Millotia myosotidifolia) likes copper, sprouting around old copper mines. And, although I’m scarcely game to say it, the retention ponds at Kakadu’s Ranger uranium mine provide excellent habitat for frogs. Mike Tyler found one species (Litoria dahlii) to be ‘extremely abundant’ around the edges of these ponds.

  Australia wasn’t like this before we speckled it with dams. John Gould in the 1840s noted the ‘immense tracts of sterile unwatered country which characterize Australia’. More than 23000 bores have been sunk since then in the Great Artesian Basin alone. Many have grown into lush wetlands bordered by rushes and reeds. All the brolgas in South Australia rely on bores, as do all the rare yellow chats in western Queensland. Irrigation channels have allowed spotted marsh-frogs (Limnodynastes tasmaniensis) to populate Victoria’s driest realms. Said frogger Gerry Marantelli, ‘You’ve now got these lovely little frog highways carting water hundreds of kilometres into the mallee.’ Yabbies, fish, dragonflies and insect-eating bats also benefit from irrigation channels.

  Botanist Jill Landsbergh took part in a major study investigating Outback dams. ‘From Australian Mapping you can get locations of watering points as digital information,’ she told me. ‘We searched out every locality that had “dam”, “bore” or “tank” in the name and put those on a base map of Australia and then put a 10-kilometre radius around each point.’ A remarkable picture emerged. Over vast tracts of Australia you can’t get 10 kilometres from a dam without bumping into another dam. The maps underestimate dam numbers because only 29 per cent of water points are actually named. Only in true deserts – the Simpson, Tanami, Gibson, Great Sandy and Great Victoria – is water absent. In sheep country you can’t usually travel more than 2 or 3 kilometres from water, and in cattle country 6 kilometres. In New South Wales it’s now almost impossible to be more than 10 kilometres from water. ‘Before European settlement,’ Jill noted, ‘most of the interior of Australia was waterless for much of the time, except for the rare good seasons. There were the big river systems and then there were waterholes, but they were few and far between. Most of the land was dry. What this means is that grazing by kangaroos must have been restricted to places where water was available or just those seasons when water was widespread. Large parts of inland Australia were not grazed by large mammals for a large part of the time. Now almost everywhere is easily within reach of water for livestock, kangaroos and feral animals, goats in particular.’

  Kangaroos are thriving. Explorer Charles Sturt found that the red kangaroo ‘did not extend beyond the neighbourhood and plains of the Murray, where it is not numerous’. Now it can go everywhere. The constant grazing of the land by stock and kangaroos is turning woodlands into deserts. Despite its attractions for birdlife, all that extra water in the Outback is not a good thing.

  Many birds do incredibly well from dams. Some of Australia’s classic Outback images include corellas on windmills and galahs clustered around dams. A hundred thousand budgerigars will gather at one dam, many of them floating on the water to drink. Parrots, pigeons and finches need water because they eat dry grain. Dams allow them to penetrate much deeper into arid realms and exact a heavy toll on woodland seeds. Honeyeaters and crows must also drink, but many insect-eaters don’t, getting their moisture from the grubs and spiders they eat. Some 47 out of 127 Outback birds need regular water, and many of these are thriving. Those doing better than ever include zebra finches, wood ducks, Bourke’s parrots and possibly emus. On the other hand many insect-eaters are doing badly, because grazing stock destroy the plants on which insects breed. Seed-eaters themselves suffer when grasses are grazed too low to set seed. Dams create plenty of losers as well as winners, and that’s something to keep in mind.

  Most plants are hammered by stock near water, but a few species, such as Bogan flea (Calotis hispidula), thrive. ‘Because it’s small and holds its seeds close to the ground it can complete its life history without getting chopped off,’ said Jill. ‘And each burr carries many seeds that sheep carry around.’ I know this plant well from its tiny burrs that grip my socks and toes, biting like fleas. Around dams, plants with toxic leaves and thorns also do well.

  Our inland streams were once graced by waterholes. Charles Barnard, writing from central Queensland in 1925, described a landscape that had already been lost:

  Fifty years ago the creek banks were well protected by a heavy growth of grass and reeds and at every bend in the creek were nice little waterholes, many of them practically permanent, full of fish, yabbies (crayfish), etc., providing food for the different kinds of Herons, etc. Now the stock have trampled away the long grass along the creeks, and the small waterholes have silted up and disappeared.

  Dams have gone some way towards replacing these waterholes. But they rarely carry thick reeds, so skulking birds (such as bitterns and crakes) miss out.

  When Riverina rice farmers flood their fields a very different kind of wetland is made. Rare southern bell-frogs thrive in the paddies, as I mentioned before. Mosquitoes do too, though, and Ross River virus is benefiting. Barking and spotted marsh-frogs (Limnodynastes fletcheri and L. tasmaniensis) like the ditches and drains that border the fields. Ducks paddle in the paddies and also eat the rice, so farmers in New South Wales can get unrestricted licences to cull shelducks, wood ducks, black ducks, pink-eared ducks, whistling ducks, hardheads and teal. That’s a lot of ducks. Rice fields also suit swamp-loving weeds, and nine of the ten worst species in New South Wales are native plants. I love their names: dirty Dora (Cyperus difformis), brown beetle grass (Diplachne fusca), waterwort (Elatine gratioloides) and sneezeweed (Centipeda cunninghamii). Beetle grass can drop 48000 seeds per square metre, more th
an most foreign weeds. It is ‘apparently preadapted to rice cultivation’, say weed experts. More than forty native plants exploit New South Wales rice crops, including pillwort (Pilularia novae-hollandiae) and stalked brooklime (Gratiola pedunculata), two plants so rare in the natural landscapes of the Riverina they could not be found in a survey of eighty-five swamps and ditches, only in damned rice fields. Eleven native plants now grow in the region only among rice; and another eleven only in roadside ditches. These statistics are unusual, crop fields usually attracting more foreign than native weeds.

  Dams and wetlands are most useful for wildlife when water is the only limiting resource. Animals have multiple needs, and our structures work best when they inject a missing ingredient into an otherwise ideal setting – as when bridges and mines are inserted into landscapes lacking cliffs and caves. Much of what people do to land is almost vandalism, but something or other usually benefits (although most things don’t). We complicate landscapes, bringing resources together in useful combinations.

  We do this even through the vegetation structures we create. Natural vegetation can be monotonous, made up of vast grasslands without cover, or forests without clearings. Most macropods (kangaroos and wallabies) prefer a patchwork of openings to feed in and thickets to hide in. By mosaic burning, Aborigines met their needs, creating clearings near thick unburned areas. Farmers mimic this combination when they clear parts of their land, and most macropods now live along the edges connecting farms to forests.

  The endangered bridled nailtail wallaby is called an ‘edge specialist’. For many years it was confined to a single reserve (Taunton, an old cattle station) in central Queensland. The wallabies shelter there by day in thick scrub less than fifty metres from the paddocks where they feed. To help them along, bulldozers were brought in to make eighteen new clearings up to seven hectares in size – this inside a national park! Taunton looks horribly degraded to my eyes but the wallabies seem to like it. The park is also full of black-striped wallabies that favour the edges too.

  In South Australia’s mallee woodland several birds prefer the edge between mallee and pasture. Magpies and ravens like to feed on bare ground and roost in trees. The red wattlebird is the most consistent edge-user in the area. In Victoria endangered barking owls are also edge specialists. Experts expecting to find them in large forest tracts found them on farms instead. ‘Few Barking Owls have been found in the interior of extensive areas of closed forest’ admitted Iain Taylor and Indre Kirsten in 1999, ‘despite many systematic searches through such habitat. Rather, the species seems to prefer the edges of woodland where it adjoins farmland and where there are strips of large old trees along roads and tracks.’ For barking owls edges provide the best menu: rabbits, magpies and starlings in paddocks, and possums and parrots in trees. Rabbit calicivirus, by wiping out rabbits, is now considered a threat to this bird.

  Animals in artificial settings often elicit our pity; we assume they would rather be somewhere else. For barking owls in Victoria that may be true. In northern Australia, where they remain common, they aren’t so tied to edges. And yet, more often than not, the animals we see in odd places are living where they please. Peregrine falcons aren’t forced into cities by habitat loss, and nor are frogs into toilets. They like the structures we create, sometimes choosing them over anything natural.

  ‘These weeds are now part of a “new” Australian ecology.’

  Greg Czechura, Queensland Museum

  Genetic engineering is very much older than it seems. In nineteenth-century Europe a vegetable Frankenstein was created in hothouses by hybridising various Latin American shrubs. The monster so spawned, lantana (Lantana camara), went on to become one of the world’s worst weeds. This rampant, poisonous shrub is an ‘aggregate’ entity, a hybrid with DNA from several plants.

  Lantana in Australia goes back a long way. Merino breeder John Macarthur grew it at Camden in 1843, and twenty years later it was running amok around Sydney and Brisbane. Up and down the humid coast it stole the newly cleared holdings of pioneers. Around Sydney it formed ‘dense thickets which render the shores almost unapproachable’, complained naturalist Reverend Tenison-Woods in 1881. So entrenched is this invented plant in the minds of ecologists today that no-one can really imagine what Australia looked like pre-lantana. It now covers 4 million hectares and poisons to death 1500 cows each year. It takes over from other plants, including endangered native jute (Corchorus cunninghamii), and rates as one of Australia’s twenty worst weeds.

  Biological control hasn’t worked well against lantana, partly because it’s not an authentic species. Over the years more than thirty insects have been trialled, beginning with four species back in 1914, well before cactoblastis quashed prickly pear. The insects can never match lantana perfectly because they feed on one or other of its parent species, such as Lantana urticifolia, not on lantana itself. There is no Lantana camara in Latin America to collect bugs from, and no bugs that have evolved to eat this hothouse product.

  Although biocontrol boffins desperately want lantana defeated, success may be Pyrrhic. It’s a perverse fact that Australian native animals now rely on this horticultural invention. On overcleared farms leafy lantana tangles in gullies furnish much-needed cover for wallabies, bandicoots, fairy wrens, reptiles, and almost everything else. The prickly walls it throws around small bushland remnants keep out trail bikes and dogs. Made to flower continuously and generously, its nectar sates honeyeaters and butterflies, including rare birdwings. Its tiny fruits feed possums, silvereyes, bowerbirds and rosellas, and reed bees nest in the stems.

  Very few native plants furnish food and shelter for so many. Thirty-two bird species use lantana in north Queensland alone. Like the river red gum, it has become a keystone species for wildlife. No other weed so ingratiates itself with animals. If lantana disappeared overnight most whipbirds would be homeless and many wallabies would die from dog attacks. Butterfly numbers would plummet. One bird, the vulnerable black-breasted button-quail, might even become extinct. This Queensland bird has lost most of its dry rainforest habitat to farmland, and lantana is now a major refuge.

  For such reasons, most biologists grudgingly accept lantana. ‘It’s become part of the Australian flora to the extent that no other weed has. It’s now part of the whole successional process of rainforest, providing a useful role as a soil controller’, said Mike Olsen.1 A naturalist I spoke to was blunter: ‘We should just accept lantana as a native plant and forget all about it.’ Lantana is the weed our wildlife needs. It puts shelter back onto land that farmers would rather keep clean.

  Mike Day works – a little whimsically – on lantana biocontrol. National park rangers warn him from time to time that his work may harm rare fauna. Precedents for this exist. In Tasmania a decline in barred bandicoot numbers is blamed partly on a fungus brought in to kill blackberries. In Western Australia biocontrol of a nasty weed, spiny emex (Emex australis), was held up because red-tailed black-cockatoos rely on the seeds. Biocontrol of another weed, Guildford grass (Romulea rosea), never proceeded because rare Muir’s corellas eat it. And across the Outback birds of prey are suffering because rabbit calicivirus has wiped bunnies off the menu. Birds also suffered when myxomatosis struck.

  Foreign plants – weeds and crops – now feed and shelter millions of native animals, and even a few native plants. Exotic animals – especially rats, mice and rabbits – feed millions of natives too. A typical bird of prey, parrot or orchard swallowtail now eats foreign food. Many species now rely largely on alien tucker. If Australia’s foreign contingent vanished overnight, many ecosystems would be kicked into chaos. Exotic pests thus pose complicated dilemmas for Australia. We want our wildlife saved and pests quelled, but the goals often clash.

  Queensland eighty years ago was awash with prickly pear (Opuntia vulgaris), thanks to birds eating the fruits and strewing about the seeds. ‘Almost pathetic was the plea of many settlers,’ the Prickly Pear Land Commission noted in 1926, ‘that either the birds or the
settlers themselves must go. “What is the use of my clearing pear when for every plant destroyed half a dozen more are sown by the Crows and Emus?” was the logic of these struggling men. And, pointing to paddocks that had recently been cleared, they would show under the green trees crops of seedlings from the droppings of birds coming up not unlike a miniature wheat field.’ But the birds that spread prickly pear seeds were also known to cull pests, a scientist in the 1920s finding 2991 ‘injurious caterpillars’ inside one emu. The Prickly Pear Land Commission acknowledged claims that ‘six to ten years without birds would suffice to bring our whole system of animate nature to an inglorious end: a vast hecatomb of insects – devouring and smothering one another’. A scary scenario, but war on birds was declared nonetheless. A bounty was announced, and within five months more than 8000 emus had been slaughtered, along with 10000 crows and ravens and 1000 currawongs. During three years of carnage 317000 emus lost their lives and 1000 of their big black eggs were smashed. The pear was eventually defeated by biocontrol, not by culling birds.

  Birds keep spreading the wrong seeds, including those of five of Australia’s twenty worst weeds (lantana, blackberry, pond apple, bitou bush and bridal creeper). Weeds would not wreak such havoc if birds would only leave them alone. In north Queensland American Pond apple (Annona glabra) is even spread by an endangered bird, the cassowary. (Flying-foxes, feral pigs and water carry it as well.) The pink-fleshed, heart-shaped fruits grow bigger than most other cassowary foods and ripen abundantly. In one cassowary dropping 850 pond apple seeds were found. The irony here is exquisite – an endangered bird helping to spread a major weed. It’s a challenging example of the riddles of the ‘new nature’. Do we shoot cassowaries to fight weeds, or plant weeds to save vanishing birds? What we should do, of course, is replant native cassowary foods on a vast scale.