Since 2016 in the ACT, green spaces - trees, grass, shrubs - have increased 1.3 per cent while grey spaces - roads, paths, car parks, roofs - have increased 1.4 per cent, according to report.

RMIT and The Greener Spaces Better Places, Australia's largest urban greening initiative, this week released the Where Will All The Trees Be? report, a national tree canopy benchmarking document. And it found the ACT was at risk of facing difficulty maintaining or increasing green cover as the population rose and new suburbs were developed.

The report's lead researcher, associate professor Joe Hurley, from RMIT, was heartened that green cover became an issue at last month's ACT election, with both the Liberals and Labor promising to plant more trees if in power, but said the ACT was not out of the woods yet.

Labor promised to plant 450,000 trees over the next 25 years to achieve a 30 per cent tree canopy within that time. The Liberals during the election campaign pledged to plant 1 million trees over the next decade.

"It's great that political leaders are recognising the importance of trees and green cover as a critical piece of infrastructure in cities," Associate Professor Hurley said.

"They're recognising the importance for urban cooling, for urban biodiversity, the health benefits, both physical and mental. Because we can get lulled into a situation where we take it for granted.

"Canberra's a beautiful city but if we take for granted that vegetation, it gets eroded over time - through development, through bushfire and storm events, through natural tree deaths, through the decisions of private land owners to remove trees for various reasons.

"We see a lot of tree loss in cities and that's okay. But we need to have proactive programs to replace those losses, otherwise we will continue to erode this critical infrastructure."

The report found the ACT has:

"Since 2016, there's been a small increase in the green cover in the ACT and that's really good news," Associate Professor Hurley said.

"But when we look at other places with similar characteristics, large LGAs, with lots of urban and non-urban areas, reasonable rainfall, and lower-density urban spaces, they are at the lower end of that group.

"Fundamentally, as our suburbs, towns and cities grow, so should our green cover ".

Associate Professor Hurley said he believed the ACT was on the right track, but its citizens needed to remain vigilant.

"It's a pass mark but the challenges are high and remain," he said.

"It's a wake-up call. Let's treasure what we've got and make sure it's protected and enhanced, not continually eroded."

Professor Hurley said the fact the ACT had an increase in grey cover - those hard surfaces of roads and roofs and car parks - reflected the march of development.

"Just to be clear, that's not a bad thing, what it shows is that it has development pressure. It's more a challenge that some places face," he said.

"Some places [elsewhere in Australia] have increasing green cover but don't have any increase in grey cover or population. They've got an easier wicket [than the ACT].

"The ACT is a growing place in terms of population, in terms of intensification of land use, so we can see the grey cover increasing. What we want to see is green cover increasing alongside that. The ACT is increasing green cover, just not as much as others in their group."

Associate Professor Hurley said one of the real challenges for green cover in cities such as Canberra was new urban development.

"And across the country, we still do a pretty average job of providing green cover along with new suburban development," he said.

"We're getting much better in the public realm, in streets and parks in recent years. But we still have building codes and planning codes and suburb design that, in large part, has designed out the potential for good private contribution to green cover and trees, like we see in our older suburbs."

Associate Professor Hurley said while different local government areas had been placed into groups and analysed against each other, he recognised the ACT was a special case because of its city-territory status.

"From this study, we can see green cover varies wildly by place. For example, Cairns Regional Council has Australia's highest recorded level of green cover, with 82.9 per cent, whereas Wyndham City Council has Australia's lowest recorded level of green cover with 5.4 per cent," he said.

"However, this isn't a full and fair picture of what is going on. Cairns has a higher than average rainfall and contains large areas of native forest. Whereas Wyndham contains large areas of grassland and agricultural land, limiting its opportunities for urban greening. It is important to recognise that place type and context really matters."