Possums in Coromandel Forest destroy native trees and wildlife

Dead rātā in Papakai (Coromandel Forest) due to being stripped of leaves by possums. Photo / Department of Conservation

Newly released drone photos show the impact of possums in the Papakai block of Coromandel Forest Park in northern Coromandel.

The Department of Conservation (DoC) in Coromandel district took the pictures in summer as part of a project to stop the spread of the tree disease myrtle rust and safeguard genetic seed stock for the species.

DoC's Coromandel operations manager Nick Kelly says the drone images show the stark contrast between an area with more than 25 years of predator control and an adjacent section of land where predator control was only undertaken twice in the last decade.

"The tops of the rātā trees in the two images are where the difference is really evident. That's where we've had long-term predator control, you can see the distinctive red-brown colour of the rātā trees flowering. They're good healthy trees, with plenty of leaf coverage and no signs of the damage possums cause."

In the other image, several dead rātā are clearly visible as over time, they've been stripped of leaves by possums, leading to the trees dying. "Those dead specimens really stick out, and they're a trigger for what we term a 'top-down collapse' of the forest eco-system."

Blooming and healthy rata at an adjacent section of land near Papakai (Coromandel Forest) thanks to pest control. Photo / Department of Conservation

This means larger trees are dying off due to the impact of possums compromising the wider biodiversity and forest health, as well as affecting birdlife, insects and other native wildlife.

Kelly says the damage done by possums isn't always visible to visitors enjoying the forest.

"You can wander through the forest and not necessarily see the impact of the introduced pests. The drone imagery shows us what people do not see when they're out for a walk."

The protected Coromandel forest is home to important native species such as Archey's frogs, Coromandel striped gecko and Coromandel brown kiwi. It's also believed the area has woodrose (pua o te reinga), Dactylanthus taylorii, an extremely rare and threatened parasitic fungi-like plant which is pollinated by long-tailed bats (pekapeka) - but destroyed by rats and possums.

DoC's predator control efforts are essential to protect New Zealand's native species, as introduced pests like possums, stoats and rats eat native plants, insects, birds and eggs.

The predator control operations target both rats and possums and will also decrease stoat numbers to help protect the rare fauna and forest trees. Reduced possum browsing also results in more food for birds.

DoC is currently consulting with iwi, landowners and stakeholders for a Tiakina Ngā Manu predator control operation recommended for later this year.

Residents can help by contributing to local conservation and environment groups involved in community-driven predator control and replanting exercises, as well as following advice about invasive tree diseases such as myrtle rust and kauri dieback.