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When possums take over

An operation to save approximately 11,400 hectares of pristine old growth forest, including 3000 hectares of plantation forestry, from damage caused by predators in the Akatarawa Forest is being proposed by Greater Wellington. Source: Timberbiz

“Possum numbers in the forest have risen way above acceptable levels. We need to act now to limit the threat they pose to some of the most treasured forests in the region,” Greater Wellington General Manager, Catchment, Wayne O’Donnell said.

“If we leave them unchecked, we will see significant degradation of the forest environment and the habitats it provides for a wide range of regionally and nationally significant native plants, birds and animals.”

The operation will have the additional benefit of simultaneously controlling populations of rats and stoats, which also predate on native plants, birds and animals.

Greater Wellington’s proposal is for an aerial possum control operation in the Akatarawa Forest from early November, using the biodegradable pesticide sodium fluoroacetate (1080).

It would follow previous aerial 1080 possum control operations, which were carried out in the area in 2007 and 2013. Regular control operations are required for optimum predator control.

“The operation will be subject to strict safety, quality-assurance and monitoring requirements, and full information will be given to neighbouring properties and user groups,” Mr O’Donnell said.

Helicopters will be equipped with GPS navigational technology to ensure the bait is accurately placed within agreed operational areas and identified ‘exclusion zones’ are avoided. This would only take place occur during suitable weather, timed for early November.

The use of 1080 requires consent from the Medical Officer of Health. It also must comply with both the Hazardous Substances and New Organisms Act, and the Resource Management Act. Under the proposed approach non-toxic pre-feed cereal pellets would be sown by helicopter across the forest, attracting and familiarising possums to the bait and encouraging them to later consume toxic pellets which will be sown in a follow-up operation.

They will be applied at a rate of 2kg per hectare, less than the equivalent of one small box of laundry powder per rugby-field-sized area. 1080 breaks down when mixed with water into a harmless substance.

In June 2011 the Parliamentary Commissioner for the Environment strongly endorsed its continued use in New Zealand. To make the pellets less attractive to birds they are 20mm in diameter, coloured green and incorporate cinnamon.

If the proposed operation proceeds, the forest will be closed to all recreational users for three to four days so main tracks can be cleared of 1080 pellets. Following this, motorised recreation, mountain biking and walking will be permitted if precautions on the poison warning signs are followed.

Greater Wellington works in partnership with six mana whenua entities of the region to achieve mutually beneficial outcomes for restoring and protecting the flora and fauna of parks and recognises their interests in a healthy and sustainable environment in the Akatarawa Forest.

Greater Wellington will consult separately with iwi in relation to mana whenua values inherent in the forest and the nature of the operation. Full details of the operation will be provided to farmers and neighbouring properties, along with horse riders and known hunters. Local emergency services, medical centres, veterinary practises and schools will also be notified. Information will be posted on Greater Wellington’s website.

Warning signs and information boards will be put up before the operation starts and will remain in position until poison residues are no longer present. This will ensure the general public and dog walkers are informed before they enter the forest.

Dog walkers will be advised to stay clear of the area until all baits have become nontoxic and possum carcases have decomposed, which will take three to four months following the application of 1080.