A PETITION with more than 17,000 signatures calling for upgrades to the Pacific Hwy to be diverted away from a koala population near Ballina has failed to sway the government's plans.

Debate in NSW Parliament on Thursday revealed the Coalition's intentions were unchanged, despite the urges of local residents and environment groups.

Labor MP Jodi McKay said the koala population on the Blackwall Range was already rapidly decreasing, without being dissected by a major highway.

She said in the past seven months the Friends of the Koala had recorded six koalas killed on the roads, two killed by dogs and foxes, seven by chlamydia and two were euthanised.

"In these circumstances the solution is clear - the roads should be re-routed, and 17,000 people across NSW agree," she said.

Nationals MP Andrew Gee said the government opposed the petition's sentiment.

"We are investing millions to protect flora and fauna along this route, and we're implementing specific measures to protect koalas," he said.

"They include fully fencing nearly 16km of both sides of the new highway which will be connected to fauna-crossing structures."

Under the plan, the number of fauna crossings will increase from the current six structures to 25.

A land bridge at least 30m wide north of the Richmond River near Bagotville will also be built, and 130ha of eucalypts will be planted - at least half before construction begins.

International Fund for Animal Welfare policy and campaigns manager Matthew Collis said there was no proof the measures would have any positive impact on the koala population.

"We have no reason to believe that anything in the new study will change from the previous study, which showed dire consequences if the highway does dissect that colony outside Ballina on the Blackwall Range," he said. "It found it would likely go extinct within 20 years or so."

Mr Collis said recent surveys had revealed the Blackwall Range habitat was home to about 170 or 180 koalas - fewer than the original estimate of 200.

"We also now know how significant this population is. It's a source for breeding programs and the dispersal of other populations heading up towards Byron as well," he said.

"This route was chosen before we knew how important and vulnerable the population was.

"Surely it's possible to find a way to avoid that particular part of the Blackwall Range."

Mr Collis urged the government to re-think its position and devise a new route that would not cut a koala habitat down the middle.

"With all the technology we have around road building and the dangerously low number of koalas across the state and the eastern part of the country, it should not be beyond us to find a way to protect this Australian icon," he said.

-APN NEWSDESK