The place is called Zealandia Te Māra a Tāne, and it was the world's first fully fenced urban ecosanctuary. The idea behind it is counter-intuitive: to bring wildlife back to a city, you first have to build a wall.
01 A closed valley inside the city
The ground was not untouched. It was broadleaf forest until fires in 1850 and 1860 cleared it for grazing, then a small gold rush arrived in 1869 and, from 1873, it became Wellington's water catchment.
The upper reservoir, held by a concrete dam, was completed in 1908. As protected catchment, the valley stayed closed to the public for almost a century and the native forest began regenerating on its own. The upper reservoir was decommissioned around 1991 and the lower one in 1997.
That history explains why it worked: there was a large, contained valley with water and no buildings, right against the suburbs of a capital. The feasibility study came in 1993, public consultation in 1994, and in 1995 the trust that runs it was formed.
02 Fourteen species and a curved cap
The key piece is the fence: 8.6 kilometres of perimeter, completed in late 1999, with a design that was the first in the world able to exclude every land mammal from mouse size upwards.
It has three elements. A very fine mesh, so a mouse cannot pass; an outward-curving cap at the top, so nothing can climb over; and a buried skirt, so nothing can dig under. The list of excluded species includes deer, goat, pig, cat, ferret, weasel, stoat, possum, hedgehog, rabbit, hare, black rat, Norway rat and mouse.
Once the fence was closed, everything inside was eradicated over nine months. The only species that got permanently back in was the mouse, through small defects in mesh damaged during construction. Occasional incursions by weasels or rats, almost always after a storm brings a tree down on the fence, are picked up by tracking tunnels.
03 What came back, and when
Releases started immediately and are documented with exact dates and numbers: twenty little spotted kiwi in July 2000, forty North Island robins in May 2001, three kākā in August 2002, thirty-nine tīeke in June of that same year and twenty-three red-crowned kākāriki in July 2010.
In December 2005, seventy tuatara arrived from Stephens Island. It is not a lizard: it is the sole survivor of an order of reptiles separate from all the others, and it went back to living on the New Zealand mainland inside a city of more than two hundred thousand people.
The forest moves more slowly than the animals. The vegetation is still in an early stage of succession, dominated by pioneer species, and the large podocarps that disappeared from the valley — rimu, matai, miro, kahikatea, tōtara — are being replanted.
04 The spillover
The interesting part did not happen inside the fence but outside it. The protected populations became a source population: the birds come out to feed and breed in the gardens, the parks and the bush of the city's green belt.
Annual counts measure it. Since 2011, the average count of kererū — the New Zealand pigeon — has risen 243 per cent in Wellington's gardens; kākā by 170; tūī by 93; and the small pīwakawaka by 37.
The sanctuary is not the only factor: in parallel, the city has been extending predator control outside the enclosure. But without a permanent source of birds breeding in safety, that control would have nothing to repopulate from.
05 What it reveals
Zealandia works to a five-hundred-year horizon and to an explicit idea: those who run it are not owners but temporary stewards of a process they will not see finished. That is an unusual timescale in public management.
The model was copied fast. Predator-proof fences now protect everything from the 7.7 hectares of a forest remnant in Christchurch to the 3,500 hectares enclosing an entire mountain at Maungatautari.
And it leaves an awkward, useful lesson for any city: the wildlife did not come back when trees were planted or declarations signed, but when someone put up an 8.6-kilometre fence and spent nine months taking out of it everything that did not belong.
