The history of Zealandia Te Māra a Tāne

What used to be the water supply for Wellington city, the Karori Reservoir has been transformed into a 225-hectare predator-free sanctuary with an 8.6km fence surrounding it, providing a place for native species to thrive. This vision came about from founder Jim Lynch and his wife Eve, who wanted to enhance Wellington’s natural assets and ‘bring the birds back to Wellington’.

This on-going work has helped our city become a leader in conservation and restoring biodiversity. Read on to find out more.

The proposal

Jim and Eve started off as committee members for the local branch of the Royal Forest and Bird society. In early 1990, Jim had a vision for Wellington city, and decided to propose a strategic plan to preserve the capital’s natural assets. Jim recognised that the Karori Reservoir would be an ideal place for a sanctuary, however it was still in use as a water supply at the time. Also around this time, the couple had come across fencing being trialled to keep rats out of a small bush area, which sparked an idea of a fence that could keep predators out.

Not long after this, Greater Wellington Regional Council (GWRC) decommissioned the Karori Reservoir. Jim began another proposal for a sanctuary and began selling the idea to conservation NGO’s, Wellington City Council, GWRC and the Department of Conservation (DOC). 

In July 1995, the Karori Sanctuary Trust was officially launched. Established as a non-profit charitable trust that allows the community to participate in the development of the Karori sanctuary, the Trust and its members were responsible for the direction of the project. 

The final plan was approved in January 1998. In 1999 the Trust signed a 30-year renewable lease with the Council.

The fence

A team of conservation managers, scientists and engineers got together in 1993 to design a totally new predator exclusion fence. 

An extensive programme of animal trialling began in 1994 to test the range of animal capabilities such as jumping, climbing, digging and their ability to pass through different size gaps.

These trials resulted in several prototype designs that were then tested against nearly 200 animals, including rats, mice, cats, stoats, possums, weasels, and ferrets.

The chosen final design was the simplest, most robust and easiest to install. 

In 1999, construction of the fence began in April and was completed in August. The fence is on the inside of a 3-metre-wide track (to stop animals jumping across) and is 8.6 kilometres long. There are three parts to the design: a curved top hat, wire mesh wall, and underground skirt.

The curved top hat stops climbing predators, the skirt prevents burrowing mammals, and the mesh is fine enough that most mammals can’t get through (the only exception to this is baby mice).

To stop jumping animals the fence only needed to be 1.8 metres high. However, the fence has been built alongside a popular recreation track so for safety reasons the height has been raised to 2.2 metres.

Restoring the valley

With all the work being done designing the fence, another key component was restoring the valley from introduced mammals so native species could thrive without this threat. The eradication process happened in various stages, before, during, and after the fence was complete. 

The aim was to remove 13 species at once (opposed to the standard one or two species).  In 1999, 50 kilometres of tracks were cut for bait stations, and possum tracking started through GWRC.

Three tonnes of possums were trapped and over 1000 possums killed in eight weeks. It is estimated before the fence was built that possum browsing removed 400 tonnes of vegetation from the sanctuary valley in a year, severely affecting regionally rare plant species such as northern rātā, kōtukutuku/tree fuchsia and kohekohe.

Bait stations and tracking tunnels were also installed for ground control and monitoring of rodents, mustelids, and hedgehogs. 

The last four possums were removed and the last hedgehog was trapped in 1999.

In 2000, the last rabbit was removed. This meant that pest mammal eradication was complete - no rats or mice were detected in follow-up monitoring. Zealandia was officially the world’s first zone in an urban environment free from introduced mammals!

To ensure mammals can’t access the sanctuary, there is a bag check area and a biosecurity gate at the entrance which has two doors that prevents mammals from running inside. The conservation team also carry out regular audits for any presence of mammalian predators, including the use of DOC conservation dogs.

There is ongoing monitoring of the fence and the ground and vegetation surrounding it to ensure the possibility of something getting in is low. 

The future

The first years of Zealandia Te Māra a Tāne were all about restoring the valley and setting up – constructing the fence to keep taonga species safe, removing introduced mammals and bringing back species of all kinds. We are now seeing the direct impacts of this work, with birds spreading across the city and our community getting behind us with important trapping and restoration work. 

This is creating one of the only cities in the world where biodiversity is increasing. Species such as kākā, once extinct from this region, are now nesting in people’s backyards, effectively reversing people’s experience of nature.

Zealandia's vision now extends beyond our predator-exclusion fence to the Kaiwharawhara catchment, where they work alongside mana whenua and the community through Sanctuary to Sea Kia Mouriora te Kaiwharawhara. This project has a 100-year vision to restore the mouri, or lifeforce, to the Kaiwharawhara and has many ambitious initiatives, such as a goal of recognising the legal personhood of the awa. 

Zealandia is also focusing on the whole ecosystem restoration inside and outside of the sanctuary, specifically bringing back species from functional groups that might be missing. An ecosystem with all the various elements will be more resilient, and able to adapt to change over time.

Zealandia is a beacon of hope in the midst of a biodiversity extinction crisis.

Check out some of the other articles in our City Building series, where we highlight some of the capital's buildings and spaces that make Wellington a better place to live, work, and play.