Meat & Livestock News

Study Warns of Billion-Dollar Threat from Invasive Weed to New Zealand’s Economy and Environment


  • New research highlights the billion-dollar threat posed by Chilean needle grass, a ‘sleeper weed’, to New Zealand’s economy and environment.
  • The study advocates for a nationally coordinated management strategy to contain its spread, justifying significant annual expenditure on prevention measures.

Recent studies have spotlighted the severe economic and environmental threat that Chilean needle grass (Nassella neesiana) poses to New Zealand, potentially costing the country over a billion dollars if unaddressed.

This invasive species, already rooted in regions like Hawke’s Bay, Canterbury, and Marlborough, is notorious for its sharp seeds that can harm livestock and degrade pasture quality, thereby impacting farm production financially.

Chilean needle grass is among roughly 22,000 introduced plant species in New Zealand, with a critical scientific challenge being the identification of those that present a significant threat before they become widespread. The goal is to prioritise these ‘sleeper weeds’ for management by regional councils and the Department of Conservation to halt their spread.

Dr Graeme Bourdôt, a principal scientist at AgResearch, emphasises the breakthrough in developing models and tools for identifying sleeper weeds, predicting their spread in changing climates, and estimating potential economic and environmental damages.

This initiative is a collaborative effort with Manaaki Whenua – Landcare Research, and aims to support informed decision-making for managing these threats through a web-based tool being developed in partnership with regional councils, the Department of Conservation, and the Ministry of Primary Industries.

The research, published in the science journal PLOS One by Bourdôt and colleague Dr Chris Buddenhagen, employs climate niche modelling and spread models to assess the economic impact of Chilean needle grass under a scenario of inaction.

The findings suggest that, depending on the spread rate, the weed could occupy up to 90% of its potential range within 100 to 201 years, resulting in losses to the pastoral sector ranging from $192 million to $1.16 billion. These figures support the case for annual expenditures of $5.3 million to $34 million on prevention efforts.

Buddenhagen advocates for a nationally coordinated approach to managing Chilean needle grass, including surveillance in susceptible regions and control measures in already infested areas, as the most economically sensible strategy.