The outskirts of Melbourne are a maze of newly-paved culs-de-sac. Freestanding homes twist in on each other, filling the footprint of their small street blocks.

On the other side of the road, short wooden stakes have been tied with fluorescent tape to mark out the next development.

It is a seemingly never ending process to house Melbourne’s rapidly expanding population, which grew 2.3% to 4.85 million people in 2016-17.

But environmental scientists say that unless planners change the way they provide for this growth it will come at the cost of biodiversity.

A new study published online in the British Ecological Society journal this week found that development models based on a “land sharing” approach, where native species are provided with habitat in the form of the inter-connected backyards and tree-lined streets of a low-density suburb, performed poorly compared to a model of medium-density housing alongside continuous tracts of environmental reserve, known as a “land sparing” model.

A survey of bird species in 28 parcels of land throughout Melbourne’s northern and eastern suburbs, including four reserves, found that half of the native species observed decreased significantly in proportion to the density of human occupation, and 13 species were only found in reserves.

Some species, such as rainbow lorikeets, magpies and red wattlebirds were abundant throughout the suburbs.

But to maximise the diversity of native bird species, the study concluded, large tracts of native vegetation must be included alongside urban areas.

It noted that even including reserves was not a perfect model, saying “growth in human population density in large urban centres comes at a cost to biodiversity, regardless of how it is achieved”.

Co-author Dale Nimmo, an associate professor with Charles Sturt University’s Institute for Land, Water, and Society, said the study showed that low-density leafy suburbs could not replace the environmental value of development-free areas.

“There’s no substitute for having these large continuous forest blocks around and through our cities,” Nimmo said. “A lot of people see native birds in their gardens and think that they are being catered for by the vegetation that their gardens provide but without the forest alongside those species would not be catered for.”

The health benefits for humans of living in greener suburbs are significant, and there are some conservation benefits, but Nimmo said both could be met in well-designed medium-density housing while retaining a larger area for conservation.

“People need to get away from the idea that we are all going to be able to have a quarter-acre block within reach of the city, because it’s just not possible.”

The dream of a house on a quarter-acre block has already collapsed in most Australian cities, RMIT professor Sarah Bekessy said. What is offered in new developments on the outskirts of state capitals is an hour-plus commute to an eighth of an acre, with a paved backyard for alfresco dining.

“They don’t provide for access to nature,” Bekessy said.

Bekessy is a national leader on the question of promoting biodiversity in the urban fringe and has been advocating for a move to medium-density, European-style developments, comprised of four or five-storey apartments around a central shared space, as a solution to Melbourne’s burgeoning population.

Melbourne has the largest footprint of any Australian city and is the 29th largest for any city in the world, according to the Demographia World Urban Areas survey.

Bekessy says that both land-sharing and land-sparing development models are required to maintain some degree of biodiversity but that the latter does not have to mean large plant-filled backyards.

Green roofs, green walls and well-developed streetscapes could all encourage native species to come back, she said.

“There’s an opportunity to bring back a whole lot of really exciting butterflies to Melbourne if everyone planted a certain type of species on their balcony,” she said.

Bekessy also argues for a shift in development focus away from greenfields sites on the urban fringe to brownfields developments in abandoned industrial developments and unused defence land.

“Sadly the evidence is that the urban fringes of cities around Australia are very important biodiversity hotspots,” she said. “All these places are jam-packed with threatened species.”

Most at risk are the critically endangered Victorian volcanic plain grasslands to the west of Melbourne, of which less than 1% remain.

The Cumberland plain, west of Sydney, and the Swan coastal plain in Perth are also in the uneasy position of being threatened ecosystems in identified growth corridors.

Prof Brendan Gleeson, director of the Melbourne Sustainable Society Institute at Melbourne University, said that planners had been aware of research around sustainable city development for some time but there was no imperative from governments to change decades-old practice.

“We continue to fail to take biodiversity into account in fringe urban development, which means that we fail to value it and make an effort to protect it,” Gleeson said. “It’s a little bit draining because these debates have been going on for decades in Australian cities.”

There are a few exceptions, such as the development at the brownfield site of Fisherman’s Bend in the inner west, but they are isolated cases in a sea of “chronic inaction”, he said.

“If we are sticking with this scenario of very high if not convulsive population growth then we are going to have to embrace medium-density housing,” he said.