Head up the road into the hills behind the Wellington suburb of Johnsonville and you’ll soon find the spot. It’s an 11-hectare block on top of the Ohariu ridgeline that is being replanted in native forest.
Shoots of tōtara and mānuka, planted by volunteers in 2021, can already be seen climbing above the grass and gorse covering most of the hillside.
The reforestation project is being run by Te Herenga Waka—Victoria University of Wellington on land leased from the Wellington City Council.
Andrew Wilks, the University’s director of sustainability, says the plan is to establish 20,000 plants on the site by the end of 2023.
“About 2,400 trees are being planted each year by volunteers—University staff, students, and alumni. Where the terrain makes access trickier, we’re using contractors to help with the job,” he says.
The reforested site will form part of Wellington’s outer green belt, a series of reserves running from Porirua to Wellington’s south coast providing an ecological corridor for native birds and other species.
Tall forest trees such as tawa, kohekohe, and tōtara would once have covered the Ohariu hillsides, says Associate Professor Stephen Hartley, head of the University’s Centre for Biodiversity and Restoration Ecology. A glimpse into this past can be seen in a remnant of native forest on neighbouring land.
As well as restoring the site to its former glory, the project is providing a ‘living lab’ for postgraduate research on ecological restoration, Stephen says.
Data are being collected on tree growth, invertebrate counts, and soil pH, nitrogen, and carbon.
Different proportions of mānuka and kānuka are also being used in planting plots to see how well they do as ‘nurse’ species—plants that suppress grass and help other trees establish.
“We’re monitoring the plots to see how other species perform alongside mānuka and kānuka to help us work out the best planting mix,” Stephen says.
Native trees are expected to form a canopy over 80 percent of the land within seven to eight years. Andrew says carbon captured in the trees and soil will help offset the University’s carbon dioxide emissions.
