Australian cities are increasingly becoming concrete jungles as trees and canopy coverage disappear, according to experts who warn this is contributing to an urban "heat island" effect.

Key points: Data shows canopy coverage has declined in almost every state

Data shows canopy coverage has declined in almost every state Urban design experts are calling for a 30 per cent increase in city greenery

Urban design experts are calling for a 30 per cent increase in city greenery Governments are being urged to introduce incentive schemes to prompt residents to plant more

Australia just sweated through its hottest and driest year on record, but researchers and urban planners say the way to make our cities more liveable is as simple as increasing the amount of greenery.

"We know a tried and tested strategy is the introduction of more trees and green roofs in urban spaces, reducing surface temperatures by up to 40 per cent," Griffith University urban and environmental planner Tony Matthews said.

"We need to place a higher social and economic value on trees and green space in our cities.

"It would be great to see residents doing their part to green their properties, and supported by the government via an incentive scheme to do so."

Rooftop gardens could be key to cooler cities. ( Supplied: Frasers Property )

A national initiative — called Greener Spaces Better Places — brings together academic, government and industry groups to promote further greenery in our cities.

Its research says black bitumen and dark roofs compound the already-hot days by creating a so-called heat island effect, absorbing heat and radiating it back like an oven.

It has estimated this can create on-ground temperatures as high as 55 degrees in the sun.

Compounding the issue, a 2017 report by the group, titled Where Should All The Trees Go, found canopy coverage in urban areas had declined in almost every state and territory.

It had dropped by more than 9 per cent in Tasmania in the previous decade, while the Northern Territory was the only place to have seen a modest rise in that time.

The report also measured the vulnerability of each state based on heat, the general health of residents in the area, and whether the area was losing or gaining green space.

Again, Tasmania was found to be worst off, with the ACT leading the country.

The vulnerability of each state rated based on heat, health and greenery. ( Supplied )

The reasons for greenery loss were varied and complex, said RMIT associate professor in international planning, Marco Amati.

In some areas, greenery might be lost because houses were getting bigger and land plots were smaller, so there was less space for plants, he said.

In other cases, it might be that drought or fires had destroyed large swathes of vegetation.

"We're dealing with a natural and human system combined," he said.

Some developers are getting on board with the green trend. ( Supplied: Frasers Property )

And according to Dr Amati, the responsibility didn't just come back to local councils or developers.

"Land in cities is absolutely at a premium … and realistically [councils] don't control very much of their own land," he said.

"There's a lot of area, a lot of residential area, which forms spaces where greenery can be increased and improved.

"So street by street we need a kind of campaign to make people aware of why greenery is important right there in their backyard."

The key to reversing the loss

Trees in suburban streets have been shown to reduce temperatures by as much as 10 degrees, but it's not as simple as just planting more.

Leigh Staas is the project manager of Which Plant Where — a five-year research project investigating how plants cope in extreme environments — and has called to increase urban canopy cover by at least 30 per cent.

But she said it had to be the right kind of greenery.

"While planting trees is increasingly considered a cost-effective method for improving the adaptability and sustainability of cities to projected changes in climate, it won't be if the species planted can't withstand the new normal and die," she said.

"Increasing the diversity of tree species in our cities is crucial in ensuring that our urban landscapes remain resilient to the many challenges of climate change, particularly drought, pest and disease."

The types of trees planted in cities will matter even more as temperatures rise. ( Supplied: Which Plant Where )

And according to Dr Amati, more greenery had to be considered alongside other ideas.

For example, painting all the roofs white might reduce the temperature by two degrees, and increasing canopy coverage could do the same.

"But the two together don't add up to a total reduction of four degrees, because trees will overshadow the white surface area of the roofs," he said.

Researchers say the key to cooling in a mix of approaches. ( Supplied: Binyan Studios )

Similarly, misting sprays won't necessarily cool an area that has a lot of trees because they both do the same thing.

"Trees transpire, so they evaporate water, and that cools the surrounding air," he said.

"Greenery in general provides a relatively cheap and effective way to cool urban environments.

"It's working out what actually benefits in a positive feedback loop.

"That's a really big urban design and urban planning challenge across all the different local government areas that we have in Australia."

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