Conservationists are concerned an environmental report on the $2.1 billion Coomera Connector lacks detail, with the project marking a "final cut" for koalas living in Gold Coast urban areas.
The state government released the 609-page environment report, which contains 16 long appendices, for community consultation last month.
But Coomera Conservation Group's Katrina Waterman said the report "lacks a lot of specific detail" about how koalas along the route between Nerang and Coomera would be re-located, and whether land bought to offset habitat loss could actually sustain new populations.
The state government purchased two blocks of land to offset habitat loss — the 400-hectare Greenridge site in Pimpama and a 400-hectare site at Tabooba, about 40 kilometres west.
"If local habitat is so sparse that it's difficult to secure local offsets, then you have to really ask should you be clearing habitat in that area?" Ms Waterman said.
"You protect koala habitat and you're protecting habitat for all sorts of things."
A spokesperson for the Department of Transport and Main Roads said "extensive environmental investigations along the stage 1 corridor" have been conducted over the past three years.
"Koala monitoring in the Coomera Connector stage 1 corridor is continuing, with about 35 koalas, who may need to be relocated, identified," the spokesperson said.
"The Pimpama River Conservation Area (PRCA), next to the Greenridge site, has been identified as being suitable for koala relocation.
"The Koala Management Plan sets out five ways koalas will be moved from the corridor before construction starts."
Can offsets sustain koalas?
The environment report notes stage one will impact on four threatened species and clear 68 hectares of koala habitat, with 58 of the marsupials living within the proposed route.
It states this will fragment populations, adversely affect critical habitats and disrupt breeding cycles.
Ms Waterman said it was not clear if there was enough suitable koala habitat in the offsets to sustain their population.
"If there's no immediate plan to plant trees, even that will take five, 10 years to see, but if there's no immediate plans, how far down the road are we looking that they're going to look at restoring that land?" she said.
"Even if you plant a tree, well it's going to be five, 10 years [to grow] but if you're waiting for natural regeneration, you could be waiting 20, 30 years.
"If we want to offset habitat that exists right now, we have to create habitat."
The Department of Transport and Main Roads spokesperson said koalas had already been observed at the offset sites.
"As part of the offset strategy, we will improve both properties through revegetation, regeneration or planting," the spokesperson said.
Congestion pressures
The environment report highlights increasing congestion on the Gold Coast's M1 as an important reason to build the Coomera Connector.
It forecasts minimum speeds during peak hours along the M1 to fall below 19kph on some sections, with the annual cost of congestion to jump from $409 million to more than $3 billion by 2041 without the connector.
But the report also states that "the relatively low public transport mode share in the northern Gold Coast will continue to exacerbate the number of commuter and local and intra-regional car trips on the M1".
Gecko Environment Council campaigner Lois Levy said "we just can't keep building more and more roads with more and more cars".
"I'd really like the government to grasp the nettle and look at how we can possibly get people out of their cars and on to public transport."
Ms Waterman said the Coomera Connector is a "final cut" in a long history of projects that have diminished koala habitat.
"A little bit goes, and little bit more goes, and in the end we're just left with these tiny islands of habitat," she said.
"It was 20 years ago that what we're seeing now was put into action.
"Even if we were to completely stop now, you do wonder what we've set in motion."
The project is subject to federal approval, with consultation ending on November 15.
