Introduction

A major weed control operation to aerially spray invasive pest plants in Otago’s largest wetlands is part of the programme the Lake Waihola Waipori Wetlands Society is undertaking for World Wetlands Day next week (February 2).

A major weed control operation to aerially spray invasive pest plants in Otago’s largest wetlands is part of the programme the Lake Waihola Waipori Wetlands Society is undertaking for World Wetlands Day next week (February 2).

Waihola-Waipori Wetlands. Photo: Lake Waihola Waipori Wetlands Society.
Waihola-Waipori Wetlands

Current conservation efforts by society members at the Waihola-Waipori Wetlands include eradication of introduced pest plants, such as alders, grey and crack willows, and reed sweet grass. Advice and assistance is being provided by the Department of Conservation (DOC), Otago Regional Council, Fish and Game, Sinclair Wetlands and the Clutha District Council.
 
DOC freshwater ranger Pete Ravenscroft says weeds threaten long-term management of the wetlands. “These invasive plants are slowly choking the waters, affecting natural water movement and reducing water quality, as well as contributing to increased siltation.”

“The wetland habitat is degrading, which is bad news for inanga (whitebait), birds and people. Our recreational opportunities will be gone forever if the lake fills up with sediment,” Mr Ravenscroft said. 

The society recently received $280,000 to undertake the first two phases of its weed control plan. Chairman David Vollweiler says the first stage involves spraying in the Titri Wetland restoration project, control of weeds in ecologically important areas, and regrowth spraying in previously controlled areas.

Phase 2 is the eradication of alders and control of crack willow and glyceria. “If these weeds aren’t controlled, the lakes will gradually become shallower and smaller, leading to a decline in recreational access and a decline in flora and fauna.”

Future plans include planting along a track being developed in the Titri Reserve and investigating ways to mitigate sedimentation. The society, in conjunction with Otago Regional Council, is holding a weed control workshop for landowners on February 23. A further field day is planned before duck shooting season to demonstrate to hunters ways of building a mai mai without using willow.

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