Forest reveals impact of possums
A section of a Coromandel Forest suffering from ‘‘top-down collapse’’ shows the impact possums can have on an ecosystem not regularly pest controlled.
Newly released drone photography, taken by Department of Conservation staff, show sections of forest canopy in the Papakai block of the Coromandel Forest Park, which straddles the spine of the Coromandel ranges.
One image shows the distinctive redbrown colour of the ra¯ ta¯ trees flowering – an indication of a healthy forest – and the other image, several dead ra¯ta¯ stripped of leaves.
It’s a stark contrast between an area where there has been more than 25 years of predator control effort, to an adjacent section of land where predator control has only been undertaken twice in the last decade, Coromandel operations manager Nick Kelly said in a statement.
‘‘The tops of the ra¯ ta¯ trees in the two images are where the difference is really evident,’’ Kelly said. ‘‘In the area where we’ve had long-term predator control, you can see the distinctive redbrown colour of the ra¯ ta¯ trees flowering – they’re good healthy trees, with plenty of leaf coverage and no signs of the damage possums cause.
‘‘But in the other image, several dead ra¯ta¯ are clearly visible – over time, they’ve been stripped of leaves by possums and that’s led 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.’’
Possums damage native forests by browsing on foliage reducing flowering and fruiting. This leads to a collapse in the forest’s ability to regenerate because fewer seeds are produced. As larger trees begin to die off, it compromises wider biodiversity and forest health with birdlife, insects and other native wildlife affected.
The photos of Coromandel’s damaged canopy were collected when DOC carried out seed collection tasks in summer as part of its efforts to stop the spread of the tree disease myrtle rust and safeguard genetic seed stock for the species. DOC is consulting with iwi, landowners and stakeholders for a Tiakina Nga¯ Manu predator control operation later this year.