Mr Windust said the forest was one of the Bay's gems but pests introduced to the area had taken a huge toll.
"Possums have only been here a little over 50 years and there's been no real pest control for over two decades. You can see big totara and kohekohe trees that have died due to possums chomping their way through the leaves. Kiwi and kukupa are in danger of becoming extinct here if we don't keep these pests under control."
Many people thought possums were herbivores but they regularly ate eggs and chicks from birds' nests, he said.
Following negotiations with DoC and iwi representative Hama Apiata, the group set up its trap network with Oromahoe Track as its "backbone".
It has a 10-year goal of trapping 1000ha of forest, and will soon be extending the network of trap lines off Oromahoe Track so volunteers can have their own line of traps to check every few weeks.
Another trustee, Craig Salmon, said there had already been a noticeable increase of tui, which could raise four chicks over a summer.
The group is encouraging Northlanders to help its work by donating a trap via its website, http://baybushaction.org.nz/. Donors receive updates when their trap catches a pest.