Weed Management

The Issue

Of the more than 70 aquatic plant species naturalised in New Zealand, more than 75% have become problem weeds or have been assessed as having the potential to become future problem weeds. Most of our lakes, rivers and streams are affected by at least one of these species. A conservative estimate of the current nationwide cost of their management was $27 million per annum in 2010. The threats and impacts of invasive aquatic weeds require management within a complex range of environments with utilisation of a variety of control methods. Management of aquatic pest plants is a core biosecurity function for regional councils and their key biosecurity partners. Additionally, these pests require management by other regional council groups to ensure efficient land drainage to protect agricultural and urban areas, and to protect and enhance aquatic biodiversity.

The Approach

The NIWA Freshwater Biosecurity team have created a Best Management Practice for aquatic weeds (see document below) which fits strategically within both biosecurity and freshwater priority areas of the Regional Council research and development strategy. Aquatic weeds are stressors to water resources, additional to water quality and quantity issues. Weeds severely impact water uses such as drainage, irrigation and power generation, and are likely to proliferate into the future, unless management interventions are taken.

Implementation of this project will accrue benefits from the co-ordinated adoption of best practice for aquatic weed management, also fulfilling the purpose of the National Policy Direction for Pest Management 2015 (NPDPM - New Zealand Government 2015). In addition to better informed decision-making, including preventative and reactive management of aquatic weeds, these guidelines will ensure legal compliance. Failure to meet these requirements could prejudice future aquatic weed management, with loss of some tools within an already limited control toolbox. Financial benefits will accrue from increased efficiency and effectiveness of control (both in direct control costs and reduced costs resulting from poor control outcomes (e.g., increased flood damage, ineffective management of weed spread). A key component of the development of this Best Management Practice is the provision of feedback from regional council practitioners and managers as well as researchers into the framework. This feedback will ensure currency and allow ongoing maintenance of the framework after completion of this project, to enable continued improvement and effectiveness of aquatic weed management.

NIWA Contacts

Principal Scientist - Freshwater Ecology
Page last updated: 
31 July 2019