The proposed "tree offset" program is suggested in a discussion paper published on Wednesday as part of a review of the ACT's tree protection laws.

The paper also flags a potential watering down of the criteria for the removal of regulated trees.

Under one "tree offset" model mentioned in the paper, when a tree is axed on a private property, one or more replacement trees would have to be planted on the same block.

Alternatively, the property owner could be forced to pour money into a special fund, which would be used to plant trees on public land.

The scheme would apply to property developers who want to rip up trees in order to clear their land for redevelopment.

City Services Minister Chris Steel said thousands of trees were being removed on private land and not being replaced under the existing laws.

The government was considering the scheme as it attempted to balance the competing demands of simplifying the ACT's Tree Protection Act while also growing Canberra's tree canopy coverage amid increasing urban infill.

Mr Steel said feedback from the community had suggested the government's existing, 15-year-old tree protection laws were at times "inflexible" and could be improved.

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Two categories of trees on private land are granted protection under the laws - registered trees and regulated trees.

Registered trees have the highest protection and cannot be axed.

A regulated tree can be felled, but only with approval from the ACT's Conservator of Flora and Fauna.

The conservator can approve a tree's removal for a number of reasons, including if it is dying, presents a risk to public safety or is causing "substantial" damage to a building.

The paper argues that the requirement for "substantial" damage is a high threshold, citing one example in which a tree cannot be removed despite its roots causing a trip hazard.

It suggests the criteria could be changed to be more "outcome focused".

But any moves to simplify some tree protection laws would sit alongside measures designed to grow and protect Canberra's overall canopy coverage, such as the offset scheme.

The paper notes that without measures to protect Canberra's tree canopy, up to half of the approximately 770,000 trees on private land could be lost over the next 20 years.

Urban infill and ageing trees would drive the decline, the report noted.

The ACT government's planning strategy, published last year, calls for 70 per cent of new homes to be built in existing suburbs.

The government's new climate action plan includes a target of growing Canberra's tree canopy coverage to 30 per cent by 2045. The city currently has about 21 per cent tree canopy coverage.

Greens sustainable city spokeswoman Caroline Le Couteur welcomed a review of the territory's tree protection laws, which she said was well overdue.

Ms Le Couteur said it was "unacceptable" that tree numbers in Canberra were decreasing at a rate of about 3000 a year.

But she unconvinced that a "tree offset" scheme would be the best way to arrest the decline.

"We are somewhat concerned that a reliance on a tree offsets scheme could see some areas left without adequate tree canopy cover, and unduly impacted by the 'urban heat island effect'," she said.

"The scheme would need to be exceptionally well-managed to ensure that we don't leave some areas of Canberra worse off."

Public consultation on the discussion paper is open until December 8.

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