University law professor Mark Henaghan (inset) believes the councils are in breach of the Biosecurity Act.
University law professor Mark Henaghan (inset) believes the councils are in breach of the Biosecurity Act.
A law expert believes two Northland councils are deliberately choosing not to do anything about an outcrop of invasive Taiwan cherry trees around Whangārei’s wastewater treatment plant on Kioreroa Rd.
Whangārei District Council (WDC), which owns the trees, and its regulatory authority Northland Regional Council (NRC) insist therelevant legislation, the Biosecurity Act 1993, does not apply to the trees in question.
People near the facility are alarmed by the rapid spread of the trees and claim WDC is setting a bad example of weed control.
They say birds easily spread the species’ seeds, putting the wider landscape at risk of infestation by a species known to outcompete native flora.
The Northern Advocate previously reported that Auckland University law professor Mark Henaghan advised the trees should be eradicated. However, both councils continue to stand by their interpretation of the law.
They argue the Biosecurity Act does not apply to the natural spread of pest plants, only to “deliberate” actions such as planting, propagating or selling the species – not passive inaction or natural spread from weeds on a person’s property.
Henaghan disagrees.
“The wording of the [Biosecurity Act] text is broad and the purpose is to control pests.
"Section 52 of the act applies to WDC as the owners of the trees, because the pest is on its land, and as per that section, it can be argued that the council are ‘otherwise causing the spread of’ the pest by not removing it.
“Under Section 53, as persons in charge of the pest and by not containing it, the council is acting in a manner which is likely to cause its propagation,” Henaghan said.
Section 42, which outlines the purpose of sections 52 and 53, includes “instituting precautionary actions” to control pests.
“Letting the cherry trees continue to grow is not a precautionary action. The decision not to control them is a deliberate one,” Henaghan said.
WDC’s wastewater manager Simon Charles said while the council appreciated people’s concerns, it would not budge from its legal stance.
“That said, we are investigating the costs involved in unbudgeted clearance work, in case the NRC requires us to remove the trees.”
Taiwan cherry trees, introduced to New Zealand in the 1960s as ornamental plants, have since become a recognised pest.
Listed by the Department of Conservation in 2024 as one of 385 environmental weeds, the trees are spread primarily by birds, which consume their nectar and berries and disperse the seeds in droppings.
While fans of the trees say they are a seasonal food source for native birds like tūī, critics say the benefit is short-lived and potentially harmful. The sugar-rich nectar may disrupt bird health during lean periods and, once established, the trees form dense stands that crowd out native nectar-producers.
Sarah Curtis is a news reporter for the Northern Advocate, focusing on a wide range of issues. She has nearly 20 years’ experience in journalism, most of which she spent court reporting in Gisborne and on the East Coast
