The Best Australian Science Writing 2014 (5 page)

Dianella cyanea
. A hairy caterpillar on
Lepidosperma
(I gave it to the Kirchners; I do not know whether it is new).

Let me have a little rest on one of the sandstone boulders or on a dry fallen-down eucalypt trunk. All day I have roved through low-growing bush and scrub land, and my eyes have become tired of looking at the pale-green distance and the simple undulating contours of the hills. Here a deep wooded gully descends to the sea. A small creek gives the vegetation greater freshness and vigour. Not only does the
Eucalyptus
rise to a considerable height in order to look, though unsuccessfully, over the walls of the gully, but also the
Banksia
with its thick knobbly bark rises higher. The warbling of the birds becomes more cheerful, the rustling of the leaves more animated. Below the damp rocks ferns, and particularly beautiful
Osmunda barbata
and
Davallia dubia
grow luxuriantly. The trunk of
Xanthorrhoea arborea
(the
grass-tree) attains a height of 3–4'.
Callicoma serratifolia
bows its ever thirsty branches over the little creek, while the sweetleaved
Smilax
stretches over them. Everywhere
Bauera
is pushing forward to the moisture.
Gleichenia flabellata
. The magnificent
Telopea speciosissima
and a host of small plants, which did poorly in the constant heat of the sun further up, thrive vigorously down here. – And what mild air! Though our senses are not delighted by the perfume of flowers, the fresh smell of the vegetation does invigorate us. The white bulky trunks and branches of the eucalypts, and the frequent dry and leafless trunks add a wintry element to this warm but languid nature.

In a small gully, which runs into the main gully further down, I found a new
Logania
.

Planet of the vines

Joseph Jukes' epiphanie
s

Survival in the city

Nicky Phillips

Most mornings a dozen or so sulphur-crested cockatoos flock to a large yellowwood tree outside my inner-Sydney apartment to feed. They flap and frolic in the tree's canopy. The more adventurous ones swing themselves around overhanging wires like gymnasts on a bar. At times, their squawks are so loud they drown out the Darlinghurst traffic.

But venture back to a Sydney before white settlement and the same species would have been a rare sight. In the early 1800s the British naturalist and explorer George Caley wrote of a flock he encountered in a long meadow near the Nepean River. ‘They are shy and not easily approachable,' he wrote. A few pairs were reported closer to the city in the National Park (now the Royal National Park) in 1945, but large numbers only began to frequent the inner suburbs to feed on open grassy areas in the 1960s. Now, ecologists at the Royal Botanic Gardens and the University of Sydney are part-way through the first study to track the bird's movements. It appears they're true city slickers.

The sulphur-crested cockatoo is one of a number of species that have relocated to Sydney. White ibis, noisy miner birds, green ants and golden orb weaver spiders have also taken advantage of their new surrounds. But it hasn't been easy for everyone.
As their bushland home was transformed into human habitat, local but less mobile species of mammal, reptile and plant have been forced to develop strategies to cope in the remaining pockets of remnant bushland, urban parks and backyards.

Ecologists often prefer to study plants and animals in exotic locations, but a growing number have turned their attention to the complex interactions of the wildlife that inhabit concrete jungles. Inner-city Sydney is the laboratory of choice for these urban ecologists.

The research is timely. More than half the world's population reside in cities, and urban development continues to stretch across the Earth. By 2030 the United Nations projects five billion people will call a city home. ‘We need to understand how cities are changing the ecology of the systems they are built on, and how plants and animals are adapting to them,' says Dieter Hochuli, a biologist at the University of Sydney.

For the most part, plants and animals adapt to their urban surroundings using the traits that help them survive in their natural habitat. But some scientists predict there may come a point when the pressure of the city, especially from pollution, becomes so great that evolution will intervene.

‘We've created this whole new habitat that never used to exist here,' Angela Moles, a UNSW plant biologist, says. ‘There will be some species living here that are not doing so well and there will be selection for individuals who can do better in an urban environment.'

If any species has learnt to thrive in an urban environment, it's the native white ibis. Known as the ‘tip turkey', the bird's reputation for ferreting through inner-city bins and scavenging street garbage has not endeared it to the public.

The white ibis began its move to the big smoke in the 1970s when large parts of its natural habitat, inland wetlands, became degraded or drought affected. ‘The species is a wetland forager,'
says wildlife officer John Martin, from the Royal Botanic Gardens. ‘Now it forages in inland parks and landfill.'

During the peak of their spring breeding season, more than 9000 of the birds call Sydney home.

Specimens at the Australian Museum show the city's bird life has changed dramatically over two centuries. Prior to urban development the native shrubs and bushland were populated by large numbers of small insect-eating birds such as the superb fairy-wren and the eastern yellow robin. Today, homeowners prefer to landscape their backyards with tall trees and manicured lawns, an environment that provides little protection for small avian species.

But one bird's trash is another's treasure. Yards filled with flowering plants and fruit trees encourage omnivorous birds such as currawongs, bowerbirds and the city's most despised resident – the noisy miner. ‘They're a real winner in cities,' Australian Museum ornithologist Richard Major says. ‘The predominant driver in the decline of small birds is that we've made a suitable environment for native noisy miners. They're so aggressive they push out smaller birds.'

But their disappearance has thrown a lifeline to the many insects that would have ended up as small bird tucker.

Hochuli says many invertebrates such as the golden orb weaver spider and the blue triangle butterfly relish living in the city. The golden orb spiders in Sydney are fatter and more fit, he says. ‘We're trying to tease out whether it's more food or the urban heat island effect, as it's up to 4° Celsius warmer in the city.'

Hochuli has also found some varieties of ant more at home in the city. The green ant, known for its painful bite, will build a nest where there is space and food, regardless of whether it's your backyard or a sports oval. ‘It's remarkable how many things persist in urban environments,' he says.

But the decline in birds that eat small insects means these
populations grow unchecked, allowing them to chomp their way through the foliage of the city's trees.

‘Throughout the city we see these shifts in interactions between species as some jobs are lost,' he says. And some shifts will be irreversible.

‘We still have functioning ecosystems, they're just different from what they were 200 years ago,' Hochuli says.

* * * * *

While insects can survive in areas no bigger than a nature strip, mammals have been confined to patches of bushland scattered around Sydney and the national parks. But in the northern beaches, the rabbit-sized, long-nosed bandicoot has discovered the advantages of venturing out of Sydney Harbour National Park and into backyards.

‘They forage for invertebrates in the grass and like the surrounding shrubs to nest and escape from predators,' says Catherine Price, a research associate with the University of Sydney. Price is trying to understand what encourages the small mammal into urban environments. ‘We don't know if it's an overflow from the park, or if they've got particular behavioural traits that allow them to evade dogs and cats, and use the urban habitat that benefits them,' she says.

Despite the remarkable ability of some species to fit comfortably into Sydney's sprawling landscape, Martin says the city's wildlife is far less diverse than it used to be. ‘We are talking about a handful of species that have thrived, many more have lost out,' he says.

It's not just native wildlife that has sought comfort in city living; invasive species such as black rats, cockroaches and foxes have developed survival strategies too. But the pests that have gained the most advantage are the weeds.

‘In residential Sydney there would not be a single area of remnant bushland not infested by introduced plants,' says Michelle Leishman, a Macquarie University plant biologist.

Over 20 years Leishman and her colleagues have shown how the city's vast stretches of impermeable concrete coupled with the stormwater system have helped weeds such as lantana and the small- and large-leafed privet infiltrate pockets of bushland.

As rains wash over backyards and roadways they collect chemicals such as nitrogen and phosphorus which enter the stormwater system where they are piped to the edges of bushland. The nutrient-rich water seeps into the soil and creates the perfect environment for the many exotic species that ‘live fast, and die young,' Leishman says.

Native plants prefer low-fertility soil and struggle to cope with the nutrients.

But development has encroached beyond land. The erection of piers, wharves and sea walls in and around Sydney Harbour, the country's largest urbanised estuary, has provided perfect conditions for invasive marine species, according to Emma Johnston from the Sydney Institute of Marine Science at UNSW. Artificial structures that block sunlight and are positioned vertically favour weedy species transported into the harbour by ships, she says.

Laboratory experiments have also shown that some invasive species, such as lace coral, have huge potential to evolve tolerance to pollutants in the ocean better than native varieties.

Over two to three generations many invertebrates will increase their tolerance to contaminants by five to ten times, Johnston says. ‘Rapid evolution is not uncommon, especially to contaminants.'

Johnston has noticed a similar trend in the offspring of native barnacles. Offspring whose parents were collected from Port Kembla or Port Botany showed a greater tolerance to copper than the young of Clyde River barnacles. ‘But we need multiple
generations to express the same traits to show there has been rapid evolution,' she says.

When Charles Darwin wrote
On the Origin of Species
, he thought evolution would be a process that occurred over tens of thousands of years, says Angela Moles. ‘Now there are lots of examples of proven evolution happening within ten generations.'

Moles' student, Joanna Buswell, has shown that 70 per cent of introduced terrestrial plant species in New South Wales have changed their morphology, altering their leaf or stem size to become more suited to Australian conditions.

Now Moles is trying to determine whether these changes are underpinned by genetic mutations that would suggest they were becoming new species. ‘I absolutely think that's where they're going to go,' she says. ‘Whether they are there yet, we don't know.'

A short walk in the Australian bush

Planet of the vines

Planet of the vines

William Laurance

Gaze out over a tropical rainforest and the scene looks idyllic – a kaleidoscope of trees festooned with colourful vines, orchids, ferns and lichens. Don't be fooled. Myriad ecological battles are being fought beneath this tranquil surface. And none is more embittered than that between trees and their ancient enemies, the vines.

Biologists like myself who study these jungle ecosystems are now seeing a shift in this war. Until a decade or so ago the two adversaries were evenly matched, but vines now seem to be on the march. If that continues, the face of our forests – and of our planet – could be changed irrevocably. We are left scrabbling to unearth the root cause.