28-05-2025
Bold plan to reintroduce wild animals into Australia's major cities
With the world's urban population set to increase by 20 per cent in 25 years, the footprint of our cities is set to densify and expand. That doesn't have to mean a complete loss of habitat for the native birds, insects, lizards, and mammals that live there too, but for them to survive, humans will need to change their behaviour.
Researchers at the University of Sydney have reviewed 2,800 scientific papers and discovered rewilding of urban spaces can help native creatures thrive in cities. Examples include platypus populations growing outside of Sydney, leopard frogs being restored to Las Vegas, and beavers swimming in London for the first time in four centuries.
Lead author Dr Patrick Finnerty told Yahoo News Australia there's a global push towards both planting more trees, but also repairing corridors between reserves, so populations of animals don't become isolated.
'Improving habitat fragmentation in cities is on people's minds, but it still remains a problem,' Finnerty explained.
Well-known examples of fragmentation problems include:
Grassland earless dragon populations being isolated in Canberra due to unsympathetic planning decisions.
Elephants being fenced into a national park by development in Malawi
Koalas having their natural range dissected in southwest NSW by new housing projects.
Some environmental planners also have concerns that a push to create more density in Melbourne will lead to less habitat for wildlife. Both it and Sydney are already lagging behind other international cities when it comes to providing tree canopy cover for residents.
There are clear leaders in improving the situation for wildlife. Both Adelaide and London have been designated as National Park Cities, a program that works to connect people with nature. And reconnecting the two is important, because 20 years ago, a US Government study found kids could recognise around 1,000 corporate logos but few native animals or plants.
Cities are important hubs for native animals because humans like to build in the same temperate coastal areas where they thrive.
Repairing lost green space results in immediate improvements for mobile species like birds, bats and insects. But if we want to see larger mammals and reptiles using these spaces then coordinated reintroduction is needed.
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Finnerty has been impressed by efforts to both rewild and reintroduce animals from depleted populations into Brazil's second biggest city.
'In Rio de Janeiro, there's been a huge push in improving the bordering national parks around the city and the interconnectedness into the city itself. That's probably the strongest example, because it's resulted in the movement of animals through urban spaces,' he said.
'But there are tonnes of examples of greening spaces. The New York Highline is a good example, and there's a conversation to change the Cahill Expressway in Sydney into a green corridor.'
Finnerty recently worked with experts in Sydney to build a list of wild animals that could be reintroduced locally.
'Our initial list was huge. Sydney is missing dingoes, quolls, everything all the way through to little, tiny bushrats in some reserves, he said.
'Obviously the reintroduction of a dingo or spotted quoll into urban areas wouldn't work. But we narrowed down our list to a top four — the bush rat, the brush-tailed phascogale, echidna and feathertail glider — all smaller mammals into urban reserves.'
Native bush rats are set to be reintroduced into urban reserves around Sydney in August as part of a pilot study. But once wild animals are set free in cities, they face threats they haven't evolved to withstand.
They include:
Vehicle strikes on busy roads that dissect green spaces
Attacks from pets
Rat baits sold at hardware stores, with little warning about their toxicity to wildlife.
'Terrestrial animals face huge problems, and it's a hurdle to rewilding itself. For example, when cats are allowed to freely roam in urban reserves, they decimate small mammal populations,' Finnerty said.
But by reintroducing wild animals into cities, Finnerty hopes human residents will start to rethink their behaviour.
'It could be the impetus for people to think maybe we shouldn't let our cats roam at night, maybe we should slow down on the road,' he said.
The research has been published in the journal BioScience.
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