We know that trees can help us sequester carbon and get us to our climate change carbon goals. We also know that native forests are spaces that can help native biodiversity.
So why are people lining up to plant large areas with pinus radiata instead of native ngahere?
The AUT Living Laboratories planting sites at Pourewa Photo: RNZ
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The answer is simple – many exotics, like pine, are lower risk, cheaper and faster to grow, sequestering more carbon in the short term.
Under the New Zealand Emissions Trading Scheme businesses have to surrender one emissions unit – one New Zealand unit – to the Government for each tonne of emissions they emit. Foresters who plant trees that absorb carbon earn units from the government that they can sell.
In a policy framework where carbon sequestration is valued in isolation of other benefits, native trees are at a disadvantage.
This is what the Auckland University of Technology (AUT) Living Laboratories project wants to help address.
It’s a set of planting experiments designed to investigate the quickest, cheapest, most risk-free way of restoring native forests in a farmland context, as well as monitoring the ecosystem benefits such forest provides as it grows.
The mārakai at Pourewa Photo: RNZ
Left to its own devices much of the farmland in Aotearoa would, over time, return to native forest.
First, the pioneer plants would appear – for example, kānuka, mānuka, karamū, māhoe. Able to deal with drier, hotter conditions in open areas, eventually they would provide the cover for the next round of trees to move in – maybe pūriri, rimu, rātā, tōtara. Brought by seeds dispersed by wind or bird, maybe from the native bush nearby.
But this takes time. A lot of time.
Across three sites, the AUT Living Laboratory project is investigating different ways of fast-forwarding this natural plant succession to get to the later, bigger trees earlier.
The first site is on Ngāti Whātua Ōrākei land at Pourewa, where they are revegetating 2.2 hectares and comparing kānuka pioneer plants versus a mixed group of māhoe, ngaio, tarata and karamū.
Here they are working in close collaboration with Ngāti Whātua Ōrākei, to whom this land was recently returned. As gardens curator Rob Small explains, the hapū have big plans for this Pourewa site, including a large veggie garden to produce food for local whānau, a plant nursery, and gardens and artworks to explore the culture and history of Ngāti Whātua Ōrākei.
Rob Small, Ngāpuhi, gardens curator with Ngāti Whātua Ōrākei standing in the mārakai that he designed. Photo: RNZ
In the Living Labs experimental planting blocks, on the slope down to Pourewa creek, late successional trees have been planted every six metres amongst the pioneer plants. The team will monitor individual tree size, soil microbe and animal biodiversity and ecosystem functions (such as reducing erosion, soil decomposition, etc.).
The AUT multi-disciplinary team is co-lead by ecologist Professor Hannah Buckley, spatial ecologist Dr Brad Case, and climate change policy researcher Dr David Hall, and is project-managed by Jeff Silby.
Together they hope that they can provide helpful recommendations for landowners on how to best grow native forest, and for policymakers on how to assign value to our ngahere.
The AUT Living Laboratories project is run by Auckland University of Technology with support from partners Ngāti Whātua Ōrākei, Ngāti Manuhiri, Ngāti Pāoa, Te Whangai Trust and Auckland Council. The team would like to thank all the volunteers who have helped with the project.
Listen - Rob Small speaks to Jesse Mulligan about his garden design.
