New research shows that Chilean needle grass could spread through most of New Zealand and eventually cost the country more than a billion dollars if nothing is done to stop it.
The newly published research in the science journal PLOS One is by Dr Graeme Bourdȏt and AgResearch colleague Dr Chris Buddenhagen.
It combined climate niche modelling to estimate the potential range of the species in NZ and a spread model (to estimate the future economic losses under a “do nothing” scenario) to determine the benefits of stopping the spread.
Under realistic low and high estimates of the weed’s spread rate, where it takes either 201 or 100 years to reach 90% occupation of its potential climatically suitable range covering 3.96 million hectares, the loss to the pastoral sector is $192 million and $1.16 billion respectively.
These losses would justify annual expenditures to prevent the spread of $5.3m and $34m respectively.
The modelling showed that a nationally co-ordinated approach to managing Chilean needle grass makes the best economic sense, AgResearch senior scientist Buddenhagen said.
“This would include surveillance in susceptible regions and control measures in the infested regions.”
Chilean needle grass (Nassella neesiana) is known to have already taken hold in Hawke’s Bay, Canterbury and Marlborough.
Its sharp, penetrating seeds cause blindness in livestock and pelt and carcase damage, and the loss in pasture quality and grazing access leads to farm production taking a financial hit.
It is one of 22,000 species of introduced plants in NZ.
The scientific challenge is to identify those that pose an economic or environmental threat before they become widespread. These weeds can then be prioritised by authorities such as regional councils and the Department of Conservation for management to prevent their spread.
“The exciting part is that we now have the ability through our research to develop models and tools to identify sleeper weeds, predict how and where they will spread in a changing climate, and estimate the economic and environmental damage that would result,” AgResearch principal scientist Bourdȏt said.
“We’ve worked with Manaaki Whenua – Landcare Research on analysing various management scenarios for sleeper pests in general. We are currently working with regional councils, DOC and the Ministry of Primary Industries to develop a web-based tool that will enable informed decisions about investing in sleeper weed management programmes.”