Disease and deterioration will see 42 trees cut down along Canberra's Northbourne Avenue from next month, the first removals ahead of construction of the planned tramline.
Transport and Municipal Services Minister Meegan Fitzharris said the trees had been found to be either dead or decaying and all required urgent removal. They include 41 Eucalyptus elata, or River peppermint trees, on the Northbourne median strip. A mature Eucalyptus mannifera, or Brittle Gum, will also be removed from the road verge for health and safety reasons.
Construction of the city to Gungahlin tram will see more than 860 trees removed from the route, including Northbourne Avenue, Hibberson Street, and around a new city terminus and a depot at Mitchell. More than 130 trees will be cut down from Flemington Road between Gungahlin and the intersection with the Federal Highway, while 245 will go from the Federal Highway to Dickson.
About 830 new trees will be planted, an increase of about 200 trees from present numbers.
The inner row of trees along the corridor will be removed from October before the outer row is removed by mid-2017.
Ms Fitzharris will announce the first felling of dying trees on Monday. She said the removals were based on a recent audit of tree condition between Alinga Street and Antill Street south.
"As Northbourne Avenue is one of Canberra's busiest roads, the assessments determine that the trees cannot be retained for safety reasons.
"The trees are either dead or have structural defects that cannot be corrected by pruning," Ms Fitzharris said.
"The 42 trees have been scheduled for removal in April. This work will take place outside peak hours to limit the impact on traffic movement along Northbourne Avenue."
Wood from the tree trunks will be used in the Molonglo Valley to provide new homes for endangered box-gum woodland creatures including invertebrates, reptiles and birds.
The government faces some community opposition to the removal of trees for the light rail project.
The existing River peppermints were planted between 1983 and 1986, and are the third generation of trees planted in the Northbourne median strip. Ms Fitzharris said the species was chosen because it was expected to be tolerant of the irrigation requirements of the grass.
Experts have told the government the trees were a poor choice for the landscape. A 2014 assessment commissioned by the government found of the trees in the light rail corridor, only 59 per cent were healthy.
A similar 2010 study found some of the trees on Northbourne could remain in place for 20 years.
"Planting these trees in an irrigated environment has resulted in poor root growth and fast grown timber that is vulnerable to fungal decay," Ms Fitzharris said.
"These factors, along with long periods of drought, have had a profound effect on the trees meaning only approximately 420 of the 710 trees originally planted remain today."
About 40 trees will be removed from the site of the planned stabling depot at Mitchell. The Eucalyptus elata will be replaced with semi-mature brittle gum saplings, expected to be grown at the Yarralumla nursery.
Last week the government announced $2 million in upgrades to footpaths and verges along Northbourne Avenue. The Liberal opposition were critical of Ms Fitzharris for not disclosing a nearby investment property when announcing the work.
Territory and Municipal Services tree maintenance crews will also undertake pruning on some of the verge and median trees before the end of June, as part of efforts to improve amenity and structure of the remaining trees.
All the trees along Northbourne Avenue will continue to be monitored for defects and signs of decline and further works will be scheduled as required.
"Eucalyptus mannifera has been selected as the preferred species, a decision that is supported by the NCA, and I am confident these new trees will uphold the grand boulevard character of Northbourne Avenue for many years to come," Ms Fitzharris said.