National Capital Authority chief executive Malcolm Snow says his organisation will block the ACT government's $783 million light rail project if it believes Northbourne Avenue will end up looking like two kilometres of "scorched earth".
On Thursday Mr Snow told a parliamentary committee hearing he had written to Capital Metro project director Emma Thomas to ask for the investigation of construction management options so that "overnight we don't get two kilometres of nothing".
"Our concern is about what I'd call the scorched earth look that could eventuate," Mr Snow told the national capital and external territories committee on Thursday.
Mr Snow said Capital Metro had been at pains to understand and work with the NCA about keeping the beauty of Northbourne Avenue – a factor the NCA sees as a non-negotiable.
His answer came in response to a question from ACT Liberal senator Zed Seselja who asked: "Are there any concerns about the fact we could have a main approach that no longer has the visual beauty we have at the moment?"
Earlier this month it was reported Northbourne Avenue would be bare of trees by late 2016 or early 2017 as the light rail line was built.
A total of 700 brittle gum saplings would be grown before being planted to replace the old trees as "semi-mature" at a height of 2.5-metres.
Mr Snow said tree loss was "a very emotive issue".
"We did explore the planting of super advanced eucalypts...the clear horticultural advice is the failure rate of super advanced eucalypts is not good," Mr Snow said.
He said planting less mature trees in well-prepared soil in the right conditions would result in a higher success rate.
Capital Metro was looking at planting more mature trees around intersections, where landscaping was more noticeable, which Mr Snow said was a risk worth taking.
After the hearing Senator Seselja said the ACT community would welcome the NCA's approach.
"I think there's growing concern that the ACT government is not listening to the community," Senator Seselja said.
"I receive feedback about this constantly.
"Early on [in the process] I don't think there was much awareness of how much Northbourne would change."
Capital Metro Minister Simon Corbell said the agency had been working productively with the NCA during the early planning and design phases of light rail and a phased removal of trees was possible.
"One of the benefits of light rail is that it can integrate with the landscape in a way that other forms of transport can't," he said.
"Following the introduction of light rail the Northbourne Avenue corridor will continue to be a tree lined boulevard that is designed and landscaped to be a grand entrance to the national capital."
Mr Corbell said the consortiums bidding to construct and operate the line to Gungahlin had been told to create a grand boulevard with brittle gum trees on the median strip.
The selection of the tree has been endorsed by the NCA, which requires native species.
"The ACT government has asked the Capital Metro Agency to explore the possibility of phasing the removal and replanting of trees along Northbourne Avenue during construction," Mr Corbell said.