Protecting our lakes and rivers from invasive plants

Invasive pests are a concern to the New Zealand public and to those responsible for pest management. Pest aquatic plants pose a significant threat to the New Zealand environment and economy. NIWA is working to help protect our freshwater ecosystems from the effects of these plants. 

Of the more than 70 non-native aquatic plant species with established populations in New Zealand, more than 75% have become problem weeds, or are classified as future problem weeds. Problem weeds are those that pose a threat to the native environment. A lot can be done to protect waterways from future weed issues using management interventions to stop weeds from spreading and to manage their impacts.

This video shows the pure waters of Te Waikoropupū Springs on the left versus a lake bed covered with the invasive weed Lagorosiphon on the right. 

The NIWA freshwater biosecurity team have created a guidance framework for Best Management Practice for Aquatic Weeds. The framework aligns with biosecurity and freshwater priority issues set out in local and national government strategies. This best practice guidance informs biosecurity decision-making including the preventative and reactive management of aquatic weeds. 

The framework sheds light on the mechanisms by which aquatic weeds are transported, become established and have adverse effects on the environment. The framework focusses on the management and mitigation of aquatic weeds and the tools required for strategic analysis, incursion detection and control of established populations. 

The strategic analysis tool within the framework informs the rationale for aquatic weed control using an evaluation of desired outcomes from management. This tool explores why aquatic weeds differ from their terrestrial counterparts and the legislation facilitating their management. The incursion detection tool in the framework helps managers target weed species based on their proximity to different areas and their dispersal pathways. The control toolbox includes detailed methods for removing or preventing the spread of different weed species and recommendations for their use. 

This NIWA research will contribute to the prevention, reduction and elimination of the adverse effects of harmful organisms on economic wellbeing, the environment and human health.

Back to Freshwater Update 82, October 2019