Litter traps installed along the Yarra River are failing to protect it from pollution, according to an ecology expert.
Dr Vincent Pettigrove, a researcher at Melbourne University, says the 17 traps are not an adequate solution to the litter problem.
“The litter traps in the river just collect floatables, while much more litter sinks to the bottom,” Dr Pettigrove says.
“Microplastics, for example, pose a major threat to the health of the Yarra, but they are far too small to see, and can’t be caught by the traps,” he says.
Litter can cause serious harm to birds, as ingesting plastics and other materials can often lead to death.
Dr Rohan Clarke, a senior lecturer in ecology at Monash University, says there is evidence to suggest that some species of birds are declining due to the sheer volume of plastics and litter they are eating and feeding their chicks.
He says these birds are “urban adapters” which find food in the litter traps.
In doing so, they can be caught in the traps. Materials such as plastics and fishing line restrict blood flow, break bones and can damage feathers, says Wildlife Victoria emergency response operator Andrew Hunter.
“One of the hardest things Wildlife Victoria faces with birds that are entangled with fishing line or plastics is that they are often able to fly and can become further entangled, causing them serious harm,” he says.
In the more than two years from January 2015 to May 2017, Wildlife Victoria attended to 1259 entangled birds in the Melbourne area.
“Littering means plastics are constantly making their way into our environment and ultimately decreasing bird survival,” says Dr Clarke.
Litter traps are a common foraging place for bird species such as black ducks and moorhens, which pick through the captured rubbish for food scraps.
Dr Clarke says: “The terms used to describe this are urban winners and urban losers. As you get more concrete and fewer trees you get a shift in the community structure of birdlife.
“It’s a fair assumption that some waterbirds like black ducks and moorhens, who have become urban winners, will become even more prevalent.”
Parks Victoria representative Jarred Parsons says each trap can hold the equivalent of 200 household-size garbage bins worth of litter and organic matter. They collect items such as organic matter, plastic bottles, plastic bags, cigarette lighters.
They also collect more harmful materials such as polystyrene, syringes and babies’ nappies, keeping them from floating along the river.
“Plastics and fishing lures often replicate natural food sources for many animals and naturally they will try to ingest them, which ultimately leads to entanglement,” Mr Hunter says.
Dr Pettigrove says despite the traps, litter is still a significant problem for the Yarra. He believes the key to proper management lies with councils and the local government raising community awareness, not just the traps.
“Councils are the drivers for litter control, but they need to realise that litter traps are not a fix on their own,” he says.
Melbourne councils spend more than $50 million each year removing litter from waterways and urban areas, according to a statement from Parks Victoria.
Most litter collected from the traps will end up in landfill anyway due to the difficulties in separating organics, recyclables and other rubbish, says Mr Parsons.
Dr Pettigrove says Melbourne has become more litter conscious in recent years.
“There’s actually been a reduction in littering, even though the population has grown,” he says. “A lot of it also has to do with our behavior and attitude towards litter and litterers. But it’s also about education – when you throw something on the ground, where does it go?”
Dr Clarke says: “Where once we’d see human-induced natural selection by feral animals accidentally being released on islands or some such, litter and pollution is now the same sort of disturbance mechanism that is causing mortality.
“The worry is there’s most likely more bird species that will become urban winners over the next few decades and start exploiting food sources such as litter as well.”