Pukenui Forest is full of mature native trees, waterways and is home to many taonga species. Photo / Andy Avery, Pukenui Trust
A noisy forest is a sign of a healthy forest and the decibels at Whangārei’s almost 2000-hectare semi-central native expanse are, at times, deafening.
And that’s due to the work of a dedicated team who are celebrating a record-breaking year in pest reduction at Pukenui Forest (Ngahere o Pukenui), enabling it to safely home threatened species such as North Island brown kiwi, kākā and long-tailed bats.
Pukenui Trust chair and volunteer Tim Martin said there has been much positive feedback that birdlife has increased and the understory of the forest has been looking a whole lot healthier.
“You can walk in and go, ‘Wow, the bird song’s really deafening today!’ There’s still a lot to do but we are progressively restoring the balance of the forest and increasing its biodiversity. A healthy ecosystem benefits us all.”
Seventeen years ago, before an intense pest-control programme began, the forest fell silent. But, over the years, with increased capacity, skills and funding, that has changed.
Colloquially referred to as “the lungs of the city”, Pukenui Forest borders Whangārei city on the west, covering around 1700ha from the Whau Valley area, north, down to Kara Rd towards Maungatapere, south.
It was logged in the 1920s but has since regenerated and is the largest remaining remnant of native lowland forest in the district.
The forest is a mix of both old growth – huge kauri trees, taraire, totara and up to 800-year-old kahikatea – and regenerating forest with greatly varying terrain, encompassing mountains, valleys and countless streams.
Additionally, there are several important Māori archaeological sites, including defended pā sites and kāinga (villages).
In the past, species such as North Island kōkako, riflemen, kākāriki and kiwi would have thrived there.
However, due to human impacts; the introduction of mammalian predators such as dogs, mustelids, possums, rats and feral cats, many species have become locally extinct within Pukenui.
In 2008, an elaborate 10-year slog began to intensively manage the 1700ha land and reinstate it to a standard safe for the reintroduction of its former inhabitants.
While goats and pigs were brought under control fairly quickly, when it comes to possums, rats, stoats and weasels, you’ve got to keep the pressure on, Martin said.
“Predator control is key to allow for the taonga species to thrive. It has been the first time since the Trust was formed that the forest has received scalable pest control, which has both been in the form of intensifying trap lines, adopting new trapping technologies, and increasing the toxin baiting networks.
Thousands of possums have been removed using a range of tools, with the amount for rodents removed being much higher. Mustelids such as stoats and weasels have seen the highest catch rate in recent years.”
All data of pest removal is recorded on a GIS-like tool, TrapNZ, and analysed by reviewing recorded trap catches and toxin take.
The latter is carried out by monitoring the amount of bait take and estimate catches based on what the lethal dosage is for the target pest species. The Trust has acquired self-setting traps which put out a fresh lure paste at night. Each battery lasts several months with up to 100 kills on a cycle, before it is brought in to recharge and the lure pouch refilled.
The team were able to increase the network through a Department of Conservation (DoC) grant of $107,000 to use over three years, of which they are halfway through, to intensify predator control.
“Across 1020 of the hectares, we’ve increased from one station per hectare to two. That’s the home range of a rat and that will put every rat at risk of coming across a bait station. The rat numbers are declining – they’ve halved over the last 18 months.
This makes a really big difference for bats, tūī, kākāriki … a lot of species will massively benefit and it’s just the latest piece of the puzzle which has been an amazing step forward for the Trust,” Martin said.
The 1020ha was focused on as it’s the ‘grand central station’ to the rat population and data shows this is where a lot of long-tailed bats reside. While bats aren’t of the noisy variety mentioned earlier – their high-frequency sound of around 45kHz can only be picked up through an electronic device – they are slow breeders and one rat can have a large impact on the bat population.
“There are few places in New Zealand where there are urban bats but Whangārei is one of several locations. Bats have always been there, I think they’ve just been holding on, but bat populations are declining. Bats give birth to one puppy a year just before Christmas and there’s a six-week period where the baby can’t fly so, while mum’s out catching food, the rats crawl into the tree holes and eat the baby bats,” Martin explains.
Possums additionally impact the canopy health, targeting particular tree species they find tasty which can cause tree extinction of some species. They also compete for food with species such as tūī.
“We’re maintaining a high level of control for possums and adding additional pieces of the puzzle for a healthy forest,” Martin said, adding that he has witnessed kiwi walk by since a series of translocations over the years to reintroduce them to the forest.
These anecdotes, with camera footage to monitor interaction, are signs the mahi is paying off.
“I’ve seen and heard kākā in there this year. They are a big noisy bird and were formerly all over Northland but now recently breeding populations are on islands. They have a good knack of knowing when pest populations are low. People in Whangārei won’t be used to seeing and hearing kākā in Whangārei but they’re turning up in the forest now. Particularly with the rat control, there’s more food for them and they’re realising it’s a safe place to be and settle down and breed so they turn up off their own accord. That’s the future that I see and what keeps me going as a volunteer.”
Martin says he moved to Whangārei just over four years ago, which is when he first entered the forest. Although he can’t comment from personal experience what it was like 17 years ago, he knows from the pests present then it would have been what he calls a “silent cathedral”.
“I can attest to the audible bounce back of life over just the past four years. The forest is a lot noisier with bird song and a noisy forest is what you want.”
Martin says the enormous amount of work achieved has been largely thanks to the dedicated work of rangers, volunteers and contractors, who have carried out the pest control in the rugged, steep hills of the forest.
“There are a lot of moving parts to pull off this scale of work, all throughout the ngahere.
We’d like to thank the Department of Conservation, Whangārei District Council, Foundation North, Predator Free Whangārei, Tiakina Whangārei, Northland Regional Council, and Kiwi Coast. Moreover, it is not lost on us that this forest has a lot of history and significance to hapū and iwi. We are extremely grateful to have Matua Winiwini on our board to guide us in the mahi that is carried out.
“One of the many other focus has been to re-establish some volunteering trap lines and work on invasive weed control to grow the volunteering network. There is so much more exciting work to come. If anyone is keen to support the Trust’s work by volunteering or donating, please do reach out, as there’s no shortage of work to be done.”
For further information, visit pukenuitrust.org.nz or follow the Pukenui Western Hills Forest Trust Facebook page.