Mission to restore Aotearoa’s largest wetland brings hope

Residents remember fishing at Canterbury’s largest lake with water so clear you could see aquatic plants swaying and schools of trout swimming.

Due to storms, intensive agriculture and unmanaged pest plants, Te Waihora/Lake Ellesmere’s water became murky and native vegetation was almost lost.

However, for the last seven years, a team of dedicated workers have been on a mission to turn this around. The wetland surrounding the lake is the biggest in Aotearoa, which means this team is tackling 2000 hectares of weeds to restore it.

To boost restoration, 350,000 indigenous trees and shrubs have been planted across 80 hectares of lakeshore conservation land that was retired from livestock grazing.

Seven traplines have been established to control animal pests across 350 hectares of key wetland habitats.

As a result, an abundance of native plants such as raupō and harakeke are popping up, restoring the wetland to its former glory and bringing hope for improving the lake’s water quality for future generations.

Collaborating to strike out weeds  

The Weed Strikeforce project, which began in 2018, is a significant partnership between the Canterbury Regional Council (Environment Canterbury) and Department of Conservation (DOC) under the Te Waihora Co-Governance Group.

Environment Canterbury contributed funding to DOC’s full-time team, focused on removing weed pressure threatening the lake’s biodiversity and water quality.

Before that, contractors were working to control pest plants in specific areas, but it wasn’t enough to reverse or halt the rapid weed growth.

Three surveys have been conducted mapping weed growth at Te Waihora. In 1983, 67 hectares of willow were recorded. That increased to 164 hectares in 2007, after grazing stock were removed from nearby paddocks, and then grew again to 303 hectares in 2017, despite hotspot attempts by contractors to control the pest willow that replaced livestock.

Ultimately, the problem was getting worse, until the introduction of the Weed Strikeforce project.

Hard work paying off

In the last year, the Weed Strikeforce completed 700 hectares of ecological weed control. This included follow-up of previously treated areas as well as breaking new ground on the eastern shoreline and the tributaries of Te Waikēkēwai/Waikēkēwai Stream.

DOC’s Weed Strikeforce project manager, Gary Boyd, said it has been rewarding work witnessing the indigenous wetland vegetation flourishing.  

“The wetland already has all the building blocks. Once we removed that weed pressure, and with grazing pressure already removed, nature did all the hard work,” Gary said.

His team had spent winters drilling holes around the bases of hundreds of willow trees and injecting them with weed killer to remove the pest plants quickly and allow native vegetation to grow without threat. In the summer, they’ve focused on spraying the smaller weeds around the lake.

Their work also involved monitoring and regularly surveying to ensure weeds aren’t popping back up.

With most of the lakeshore now free of willows and major woody weeds, work will continue towards the tributaries to prevent reinvasion from seeds travelling downstream.

Other nearby mahi, such as the Tārerekautuke Wetland project and the Whakaora Te Waikēkēwai project led by Rūnanga, add significant value to supporting overall regeneration of Te Waihora.

Initial weed control work is expected to be complete by 2027. After that, the project will progress to ongoing maintenance and monitoring.

Environment Canterbury water and land partnership programme team leader, David Murphy, said the Weed Strikeforce project is hugely significant.

“Not only for what it is doing – restoring the lakeshore wetland on a landscape scale – but also for how it’s doing it – through building strong partnerships and very cost-efficient delivery.”

Building relationships with landowners

As half of the land surrounding the lake is private, an important part of the project has been building relationships with landowners.

“It’s been educational on both sides. We hear stories from them about what the lake was like back in the day, and we can tell them about the work we’re doing to restore biodiversity and, in the long term, improve water quality,” Gary said.

The lake, which was given back to Ngāi Tahu in 1998, is a significant mahinga kai for iwi. Gathering spread onto the wetland fringes for bird eggs and harakeke/flax use. The lake is a taonga and is central to the culture, traditions, and ongoing identity of iwi. 

The lake was once called ‘Te Kete Ilka o Rākaihautū’ which means ‘the Fish Basket of Rākaihautū’.

Te Waihora Co-Governance Group

The Weed Strikeforce project is one of many initiatives under the Te Waihora Co-Governance Group. Established in 2012, the group is working to restore and rejuvenate the mana, mauri, and ecosystem of the lake.

The co-governance group includes Environment Canterbury, Ngāi Tahu, DOC, Christchurch City Council, and Selwyn District Council.

Environment Canterbury regional biodiversity and biosecurity team leader, Shaun Burkett, said restoring Te Waihora is a top priority.

“It’s the largest lake in Waitaha/Canterbury, and an important link in a chain of coastal lagoons and estuaries. It’s also a habitat to many threatened and at-risk species such as black-fronted terns/tarapirohe, wrybill/ngutu pare and Australasian bittern/matuku.

“We are very happy to partner with DOC to remove the threat of weed invasion and ensure that biodiversity flourishes.”

While it may take two generations to achieve the group's vision, as work is intended to sustain the lake to provide for many generations to follow, the partners are committed to making it happen.