In a wide-ranging submission to the newly-established parliamentary inquiry into the urban forest, the City of Marion has warned that a “conflict between trees and utilities” is restricting efforts to plant trees on public land.

The council says laws regulating vegetation clearance for electricity and water infrastructure should be reviewed so they “incorporate a more sophisticated understanding of trees as community and ecological assets that act as important mitigator of climate risk”.

“As infrastructure proliferates with urban sprawl and infill, regulations that allow public trees to be removed and limit any replacement plantings, make it impossible for councils to achieve canopy targets on public land,” the council submitted.

“Councils are continuing to work with SAPN (SA Power Networks) to find a way to maintain existing plantings, but overhead power lines and the Allowed and Permitted vegetation lists are a major impediment to councils with ambitious greening and canopy targets consistent with the 30 Year Plan for Greater Adelaide.”

The City of Marion estimates 15 per cent of its land is covered by tree canopy, below the metropolitan Adelaide average of 24 per cent.

The council has a goal to increase its tree canopy 20 per cent by 2040 by planting 3900 street trees every year along with 15,000 native trees, shrubs and grasses in nature reserves.

The council submitted that the state government should remove the power of utility providers to forcibly remove trees on public land unless an “immediate threat” to public safety is identified.

It also said greater investment should be directed towards the Power Line Environment Committee (PLEC), a body that administers around $10m a year to underground power lines in strategic areas.

“One of the simplest initiatives the state government could invest in to improve urban forest extent and performance is undergrounding of power lines, including in common services trenches under roadways which combine electricity, gas, water and communications services in a single trench,” the submission states.

“This approach also increases the stability of the electricity grid due to damage in storms and fires, as well as removing a major bushfire ignition source in fire-vulnerable areas.

“The placement of a common trench in the middle of roadway also increases the amount of above- and below-ground space for planting on the verge, increasing the number and size of trees that can be planted on roadsides.”

Before and after of a power line undergrounding project on Reservoir Road in Modbury. Photo: PLEC

According to the PLEC’s 2020/21 annual report, $10.96m of funding was approved to underground 3.84km of overhead power lines in 2021/22.

Approximately 53 per cent of the projects were in metropolitan Adelaide while 47 per cent were regional.

SA Power Networks, the state’s sole electricity distributor, chipped in $7.31m of funding towards undergrounding while councils contributed $3.65m.

The City of Marion submitted that undergrounding of power lines “remains rare and is generally restricted to high-profile corridors and developments” due to the limited co-funding available to the PLEC.

It argued additional funding for the PLEC would reduce the level of co-funding required by the local government sector and “allow the removal of more overhead powerlines, and thereby improve safety and public amenity, and [increase] opportunity for greening”.

It also said while the cost of undergrounding power lines is “expensive” at approximately $3000 per metre, funding more undergrounding “would possibly… reduce the net cost per meter due to efficiencies of scale”.

“Alternatively, the state government could identify high priority targets for undergrounding (e.g. specific major transport corridors) to target for powerline undergrounding and greening, providing majority funding as a Major Project,” the council said.

“Such projects could effectively transform a barren transport corridor with minimal greening into shaded boulevards with high public amenity and increased appeal for active transport users.”

The state government has previously warned the cost of undergrounding the entirety of the state’s electricity infrastructure would cost billions of dollars.

The issue of energy security was put back on the agenda by a major storm last November which left 163,000 SA Power Networks customers without power.

Energy and Mining Minister Tom Koutsantonis, in response to questions on notice printed in Hansard last week, advised that the November storm brought down 500 electricity wires.

“In terms of hardening South Australia’s electricity infrastructure, capital investment plans by SA Power Networks and by transmission company ElectraNet are regulated by the Australian Energy Regulator,” Koutsantonis said.

“Undergrounding power infrastructure would cost many billions of dollars.

“Capital costs are ultimately borne by consumers and the AER assesses the balance between the gains to be made by capital investment versus the cost to consumers.”

The City of Marion is among a group of suburban councils which have sought to address dwindling tree canopy, particularly on private land, amid concern about the heating effects of urban infill combined with low tree coverage.

According to the council, 43 per cent of its tree canopy falls on private, primarily residential land, however, only 12.5 per cent of its residential land is covered by tree canopy.

The adjacent City of Unley, which says its tree coverage shrank from 34 per cent in 1979 to 22 per cent in 2017, has asked the state government to approve an offset scheme whereby landowners will pay higher council rates if they build a development which does not reach a minimum 15 per cent tree coverage.

Planning Minister Nick Champion has previously indicated he is doubtful about the scheme, citing advice it would be difficult to implement and measure.

The parliamentary inquiry into the urban forest, being conducted by the Environment Resources and Development Committee, comes alongside two other examinations of South Australia’s tree policy.

The State Planning Commission is compiling a broader review of the state’s regulated and significant tree protections and expects to begin consultation this year on potential changes to tree regulations.

Meanwhile, an expert panel led by planning consultant John Stimson is compiling a wide-ranging review of South Australia’s planning system, with tree protections among the major policy areas being examined.

Stimson’s review has received more than 600 public submissions, including 40 from councils, with the planning minister expecting to receive a final report before Easter.

Parliament’s urban forest inquiry is accepting submissions from the public until February 24, 2023.