The New Nature Read online

  The Werribee plant feeds in half of all the nitrogen and two thirds of the phosphorus that pollutes Port Phillip Bay. In 1997 it was asked by the Victorian Environment Protection Agency to reduce its nitrogen discharge by 500 tonnes a year. But bird­watchers fear that cleaner water will mean fewer waders. They worry about all those stints and sandpipers around the outflow pipes. Melbourne Water hopes the waders will feed in shallow sewage ponds instead. Not likely: 55 East Conservation Lagoon is a roost for waders, that’s all. Environment Australia is also concerned for the birds, and wields considerable powers under international bird treaties. Melbourne Water has a challenge on its hands – how to please one environment agency without aggra­vating another. Negotiations are under way.

  All over the world sewage farms attract birds and birdwatchers. The Cape Town pools feed flamingos, while Bali’s pools attract herons and teal. Britain’s birdwatchers are worried by a trend towards smaller treatment plants. Sewage farms should be designed with fauna in mind. The slogan should be ‘Shit matters’. The foetid pools are often hot spots for foreign vagrants. A little grebe – the first ever recorded in Australia – lobbed into Darwin’s sewage works in 1999. Australia’s first ever spotted whistling ducks dropped in on Weipa’s pools in 1995. Birds probably learn that the sets of rectangular ponds, wherever in the world they occur, are productive. Birders have certainly learnt this. On a recent trip Rohan Clarke visited sewage plants at Port Hedland, Broome, Derby, Karratha, Hall’s Creek, Wyndham, Kununurra and Alice Springs. He liked Alice Springs best. ‘The gates are partially open for birdwatchers. There is a path, a gazebo where you can sit in the shade, and there’s a full bird list available in a box.’ It’s one of several sewage plants that’s turning into a tourist destination.

  In an article ‘Great sewage farms of Australia’, birder David Andrew describes the farms as ‘probably the best-kept secret in holiday destinations – no entrance fees, no crowds and great birding’. When I visited Port Hedland recently and asked the way to the sewage ponds there, the woman at the information centre never batted an eyelid – she hears this question often enough. Rohan feels sure that birds target sewage ponds because they furnish more food. ‘There are lots of other wetlands you can go to that just don’t harbour birds, or not as many.’ He came upon 1000 ducks in one settling pond at Hall’s Creek. ‘That’s a lot of birds to jam into a small pool.’ Sewage matters.

  Seagulls were probably the first birds to grasp this truth. Their luck turned when messy Englishmen took over Australia. Today’s silver gulls (the common species) dine in our malls, parks, ports, tips, schools, abattoirs – wherever food is free. Like blowflies in bins, they multiply on our wastes. Our cities and towns are now seagull factories pumping out garbage-guzzling birds. Seagulls flourish on the effluents of affluence.

  Australia’s two biggest seagull nesting colonies, each carrying 80 000–100 000 birds, occupy small islands attached to Sydney and Melbourne. They are bird cities that mirror our own. Before 1770 no gull colony held more than 2000 birds, experts believe. Now there are ten bigger than that. The Sydney colony, at Five Islands off Woollongong, holds up to 70 per cent of all breeding gulls in New South Wales. The gull population in that state is as centralised as the human population.

  Gulls are great travellers. One bird tagged in Rockhampton turned up in Tasmania. The gulls in Adelaide visit Victoria and New South Wales. They are so mobile and so canny they can exploit opportunities in vast numbers. This is proving disastrous for one spectacular bird, the banded stilt.

  A hundred years after the banded stilt’s discovery, its eggs remained unknown, many experts guessing that it went abroad to breed. What this long-legged black and white bird does instead is breed after rare desert rains, flocking inland to nest on islands and spits in vast salt lakes. The chicks fatten quickly on brine shrimps dredged from salty pools. In the eastern two-thirds of Australia only four nesting events have been recorded (although many others obviously take place) – at Lake Callabonna in 1930, Lake Torrens in 1989, and Lake Eyre in 1997 and 2000. All the eastern birds breed in unison after rains that fall years apart.

  When Lake Torrens filled for the first time last century in 1989, Keith Bellchambers and Graham Carpenter went out to see the stilts. They found themselves witnessing slaughter. Silver gulls were raiding stilt nests and feasting on eggs and chicks. The stilts couldn’t repel the marauders, and lost 60 per cent of their broods. The surprised biologists concluded that ‘high levels of gull predation are a new danger to banded stilts, something they have not had to cope with in the past and that they are not evolution­arily equipped to combat’. In 1930 when stilts nested at Lake Callabonna, only a few gulls turned up, although raids by ravens and raptors did take place.

  Lake Eyre filled early in March 2000 and the stilts soon arrived. Birder Clive Minton went out in April to record the event. On a triangle of sand he counted 9000 stilt nests. He also counted 2152 pairs of gulls nesting noisily nearby (as well as thousands of pelican nests). ‘We sat and watched the banded stilt colony for several hours each day from 80 metres away,’ he told me. ‘What we observed was a horrifying thing. Two eggs or chicks per minute were predated by the silver gulls. Seven new gulls were arriving every minute.’ The slaughter carried on into the night; Clive could hear the stilts and gulls crying. He estimates that 1500 eggs or chicks were lost each day. After five days, only a third of the nests remained, and three days later there were none. The stilts left. Only 322 chicks reached the water.

  In late April or early May 2000 floodwaters surged into the lake from Queensland and the stilts tried again. Ten thousand clutches were laid. Six thousand gulls turned up too. After carnage lasting six days and nights the stilts gave up. They took to the skies one night and departed. Clive estimates that 30000 stilt eggs were taken this time. ‘I’ve never known any predation on this scale of any animal or bird on any other animal or bird anywhere in the world.’

  In June 2000 the stilts assembled on a new island to try again. Gulls were assembling too. But this time National Parks were ready. They laid thousands of poison baits, and 3500 gulls met timely deaths. Rangers flew over the island almost every day to ensure that the remaining gulls posed no problems. The 36000 stilts that bred yielded about 40000 chicks, enough to guarantee a next generation. Had National Parks not intervened, the stilt population in south-eastern Australia might have been doomed.

  By August there were big creches of young birds watched over by adults. I then quizzed Peter Alexander of South Australian National Parks about the attacks. ‘I think it has the potential to be a very major problem,’ he said. ‘There’s a real chance the stilts could be pitched into the category of an endangered species fairly quickly. The species is going to be reliant on human intervention to survive.’ A gentle bird is in big trouble because people in cities and towns hundreds of kilometres away behave wastefully. Clive said that silver gulls deserted Port Augusta 300 kilometres away when Lake Eyre filled, and that even Adelaide had fewer gulls at this time. Here is more cause and effect operating over vast distances. Siberia, islands off South America and Madagascar, Lake Eyre – our wastes affect ecosystems all over the world.

  No-one knows how stilts and gulls can tell when desert lakes fill. ‘Now you’re asking the impossible,’ Clive Minton said to me. ‘How can the banded stilts at Altona and Melbourne, where there is no rain, know that there’s been this giant flood?’ Pelicans and Caspian terns know too. ‘We had 2000 pink-eared ducks at Werribee in February,’ he said. ‘Suddenly it rained in northern New South Wales and Queensland and they went off. There’s this theory that birds can hear infrasound and can detect storms thousands of miles away. I find it absolutely perplexing.’ Western Australia has it own banded stilts, breeding around inland lakes that gulls don’t visit – yet. Let’s keep our fingers crossed.

  Seagulls are a blight on many other birds, as chapter 16 explains. They trouble us as well, colliding with planes, spreading weed seeds and soiling our water supplies w
ith their wastes, which can carry salmonella and E. coli. Sydney’s main airport had 158 gull strikes in eight years. Problem gulls are sometimes fed hallucino­gens to persuade them to leave. Gulls all over the world are proving bothersome to people and wildlife. They highlight the major theme of this book: that animals who benefit from us (winners) may go on to trouble other species. Stilts in the desert face no threat at all from humans, but we harm them indirectly by feeding their enemies.

  Not all the news is bad. Melbourne’s gluttonous gulls are guaranteeing a bright future for one rare plant. In the 1970s coast hollyhock (Lavatera plebeia var. tomentosa) – a lanky shrub with white hibiscus blooms – suddenly appeared in Port Phillip Bay on the Mud Islands, where Melbourne’s seagulls breed. Coast holly­hock is an ornithocoprophile – a plant adapted to bird-enriched soil. The gulls moved to the islands in the 1960s after their eviction from Port Melbourne. Ibises came in 1990, probably from the Bellarine Peninsula, which lost its ibis colony (in Reedy Swamp) the same year. Never before have straw-necked and white ibises been known to nest on islands. Botanist Jeff Yugovic watched hollyhocks take over half the main island, forming the largest colony known. The ibises helped the hollyhocks by culling the competition, snapping stems off coast saltbush (Atriplex cinerea), which once dominated the island, to make their nests. Hollyhock stems are too fibrous for birds to break. The ibises feed mainly on mainland farms, the gulls in Melbourne and Geelong, so if I toss a chip to a seagull in Fitzroy Gardens I may be fertilising a rare shrub growing 55 kilometres away.

  Our wastes matter to other birds too – to crows and ravens along highways, ducks and ibises in parks, seabirds over fishing grounds, and kites at country dumps. Black kites are graceful birds that ride Outback thermals for the thrill of finding road-kills, farm carrion, roo-shooter camps and dying fish in turbid pools. They gather in the greatest hosts around country towns, at the meatworks and dumps that sustain them through drought. During the 1958 drought 5000 black kites came to Mt Isa, and a thousand found their way to the Ipswich slaughter yards, which lie well outside their usual range. As many as 2800 kites have been counted at a single piggery. Like seagulls, kites exploit us shamelessly. I’ve watched them soaring low over Mt Isa gardens looking intently for dog bones. The trials of Leichhardt and Sturt suggest that kites were using us thousands of years ago, and they still inspect remote Aboriginal camps today. They even use our wastes as fishing bait. One kite was seen dropping bread into a river to lure fish and prawns to the surface; another was seen using potato chips.

  Scrounging by birds is probably the most widespread association between humans and wild animals on the planet. Birds on the remotest oceans know that ships signify food. Some of the world’s rarest seabirds follow boats. Albatrosses will clamber over nets when fish are hauled in. When birdwatchers charter boats to find rare pelagic (ocean-dwelling) species, they throw out baits as attractants. I’ve seen the wake of a boat busy with petrels, terns and albatrosses lured in from over the horizon by slippery lumps of shark liver, a delicacy. Many seabirds have a remarkable sense of smell.

  Prawn trawlers now play a vital role in the seabird economy. In Moreton Bay the pied cormorant, little pied cormorant and crested tern depend mainly on food from fishery discards. Birds in the Gulf of Carpentaria are booming on trawler waste. Brown boobies – big brown seabirds – on Rocky Island went from 2800 pairs in 1982 to six or eight thousand in 1991. Frigatebird numbers trebled.

  Trawlers kill five to ten tonnes of sea life (mostly fish) for every tonne of prawns they haul in. Fifty to 70 per cent of this bycatch sinks, to be eaten within an hour of striking the sea floor, mainly by crabs and sharks. Moreton Bay’s blue swimmer or sand crabs (Portunus pelagicus) get a third of their sustenance from trawlers. They zigzag across the sandy sea floor snatching up dead fish flung overboard. The crabs are themselves trawled, and some trawler waste thus ends up in the human food chain. The twenty trawlers working the bay over summer together dump about 7000 kilograms of matter a night, some 10 per cent of which is taken by birds, a little by dolphins and sharks, and a lot by crabs on the sea floor. Dolphins that follow trawlers often suffer bites from sharks.

  There are other impacts of trawling I should mention in passing. The nets do incredible damage when they drag along the sea bottom, destroying corals and sponges (‘clear-felling the sea floor’). But prawns somehow benefit from this, returning in greater numbers to the trawled areas. Trawlers thus ‘farm’ the same stretches of seabed. Some fish also benefit. A study in the Gulf of Carpentaria found that eighteen fish species declined but twelve increased. There are certain fish that characterise trawl grounds both in Australia and South-East Asia. But trawling is ultimately so destructive I refuse to eat prawns – despite the benefits to all those birds, crabs and fish.

  People also feed the sea by letting fertilisers escape from farms. When the crown-of-thorns starfish (Acanthaster planci) exploded in numbers on the Great Barrier Reef in the early 1970s, experts argued about whether the plagues were natural or not. They still argue. In the last outbreak about 500 of 2900 reefs were harmed. Tourist operators are forced to kill large numbers of starfish to protect the reefs they rely on. The plagues have been blamed on fertiliser runoff from sugar-cane farms, although towns and cow paddocks contribute nutrients as well. The reasoning goes like this: the starfish are incredibly fecund, producing up to 100 million larvae each, which feed on algae. Algae like nutrients. More sugar cane means more nutrients; means more starfish and less coral. The reef receives up to 77 000 tonnes of nitrogen and 11 000 tonnes of phosphorus each year – enough, perhaps, to enhance the survival of baby starfish. Coral-eating snails (Drupella) also harm reefs, and they too may benefit from nutrients from farms and towns.

  Nutrients may also be helping seaweeds (Sargassum) replace corals on some reefs. In South Australia superphosphate blowing off farms is thought to feed beds of sea-grasses (Posidonia and Amphibolis) that keep expanding. Infestations of fireweed (Lyngbya majuscula), a nasty seaweed (classified strictly as a cyanobacterium) that stings fishermen and now blankets 30 square kilometres of seafloor in southern Queensland, are blamed partly on nutrient enrichment (iron plays a role as well). Nutrients also feed toxic blue-green algae in dams. In 1992 an algal bloom stretched 1000 kilometres along the Murray-Darling. Fireweed and blue-green algae are very poisonous; algae that grow abundantly need to be well armed against predators.

  In cities our wastes feed trees. Mangroves around Sydney and Brisbane are spreading, helped along partly by pollutants. The mangroves downcurrent from Brisbane’s main sewer have nitrogen-enriched leaves. Sydney’s sewers overflow into bushland after heavy storms, and stormwater pipes send in food scraps and soap suds. Plants respond dramatically to this free fertiliser. Sydney has three bushland types based upon reactions to sewage and soap – a sandstone heath community that abhors them, a wet sclerophyll community that likes sewage in moderation, and a disturbed forest type that loves the stuff. Sydney’s sewage-fed forests are weedy, with plenty of camphor laurel and privet, but some native plants thrive too – especially sweet pittosporum (Pittosporum undulatum), yellow pittosporum (P. revolutum) and bleeding heart (Homalanthus nutans). Sweet pittosporum likes pollution so much it’s become a major invader. Tests on bleeding heart leaves around Sydney show that very high levels of phosphorus have been absorbed from the soil.

  According to botanist Annemarie Clements, forest succession around Sydney goes like this. If you add soapsuds to infertile sandstone, the heathlands turn to wet sclerophyll, and lilly pillies, blueberry ash and bracken do well. But if soap gets into shale-derived soils, which are already fertile, the shift is to weeds and pittosporums. Streambanks also change. Polluted waters suit native pondweed (Potamogeton tricarinatus) and phosphorus-fond sedges. Nutrient shifts in cities (in gardens as well as bushland) turn dry forests into facsimiles of rainforest. The ‘weeds’ invading gardens in Sydney and Brisbane include local rainforest trees. The shift to rainforest suits ring-tailed possums, whic
h like interconnecting foliage and lush leaves. It also suits figbirds, currawongs and brush turkeys.

  Human wastes were playing an ecological role many thousands of years ago. Evidence for this comes from recent work on dung beetles and bush flies. Entomologist Ian Faithfull has challenged the raison d’être of some biocontrol work done by the CSIRO who, deciding that our native dung beetles aren’t adapted to cowpats, brought in forty-five foreign species, mainly from Africa, to clean up farms. Seventeen became established and several now make good inroads into dung in paddocks. But Ian found only limited evidence to back up the assumption that native dung beetles prefer the small dry pellets of marsupials. More of our native species are known to use cowpats (eighty-five) than marsupial dung (sixty), although these figures partly reflect search effort.2

  Most remarkable of all is the number of native beetles found at human faeces: 214 in all. This discovery exists because scientists – ever practical – use their own excreta to bait beetle traps. Ian cautions that a beetle may come to dung without exploiting it for food or reproduction. ‘Nevertheless’, he writes, ‘it seems likely to me that adults of most species probably feed on human dung. Human turds are quite variable in size, shape, consistency, composition, moisture content etc., providing a wide range of physical and chemical variation which further increases the possibility of exploitation by a wide range of species.’ When the megafauna perished long ago, their specialised dung beetles weren’t necessarily doomed. Human faeces was available as a substitute. Cowpats then took its place. Ian suspects that some dung beetles in Australia may even have evolved into human specialists. It’s a claim made for certain South American beetles. ‘Dungies’ do seem fond of human waste. When I squat in the bush, a beetle will sometimes land before my work is done.