One of these trees just doesn’t fit in here…
...is that an olive tree growing amongst this clump of pohutukawa? The olive tree was uncovered on Rangitoto Island by Auckland Conservancy staff during a recent weed surveillance survey. Unlike most surveillance work this trip required a good seatbelt rather than good boots...
Surveillance was undertaken in a helicopter and flying was done with the doors off to increase visibility. The helicopter allowed staff to cover much larger areas than possible by foot (searching off track on the rough lava of Rangitoto is very slow!).
So what is weed surveillance? Weed surveillance differs from general weed surveying in that the focus is on finding populations of new invasive weed species at a stage when eradication or containment is still possible. This early action also reduces the cost of controlling the weed species.
The main targets for this surveillance trip to Rangitoto were moth plant and tree privet. Moth plant is an invasive vine which smothers existing vegetation, forming huge patches. It produces clusters of creamy-coloured flowers between December and May, followed by choko-like fruits which open to release hundreds of hairy thistle-like seeds in autumn and winter. These wind-dispersed seeds mean it is possible for moth plant to establish anywhere on Rangitoto.
Fortunately no moth plant or tree privet was found on Rangitoto during this survey however other weeds such as the olive, willow-leaved hakea and pine were picked up. Olive trees are emerging as a new weed threat, spreading on nearby Motuihe Island and around Auckland and Northland. They are one of the weeds targeted for eradication on Raoul Island and are a bad weed in South Australia. This find was a new record for Rangitoto. The olive has been removed and the willow-leaved hakea and pines will be treated by the weed team.
The idea for using a helicopter came from Northland and Waikato Conservancies where they've used them with success for weed surveillance and surveying.
Helicopter surveillance was also undertaken on Little Barrier Island this is another island in the Auckland Conservancy with hard to reach areas. Fortunately, no new weeds were detected in the 380ha covered during this survey.