environment

A billion trees and a trillion weeds

Planting trees is only part of the battle to scale up native tree regeneration efforts. In order for the trees to thrive, a war must be waged on weeds and wildings.

The issue of weed and wilding conifer control dominated a lecture given by ecologist Willie Shaw at the Auckland Museum on challenges to revegetate New Zealand with indigenous trees.

For the One Billion Trees project to successfully increase the number of native trees in New Zealand over the next 10 years, maintenance will need to be undertaken for several years until the native trees are tall enough to choke the sunlight from the weeds on the ground.

Shaw has worked as an ecologist for decades and is involved in projects where large areas of land are being returned to native bush.

He described weeds and as a monstrous issue when trying to establish native forest.

One project he is involved with in the Bay of Plenty is attempting to return 640 hectares of pine plantation back to indigenous bush.

Ngāti Whare’s settlement with the Crown is seeing this land returned to iwi. Shaw said the iwi’s plan is turn back the clock and establish native forest on the land, so it is “as it was in the time of their tīpuna”.

The land, currently a pine plantation, is being gradually handed back to Ngāti Whare as the pines are harvested but the condition of the land means significant work needs to be done before natives can be planted.

“What Ngāti Whare get back is a sea of weeds,” said Shaw.

Flat sites are infested with blackberry, broom and wildings. Hill sites are covered in wildlings as well as buddleia.

Within 12 months of planting native seedlings Shaw said the broom is back: “You can see the natives scattered through but also a sea of broom. All we are trying to do is get them over the top of the broom and then just leave them to it.”

“They’ve tried everything here. All the wildlings are felled by hand with chainsaws, loppers. The cost of it is enormous."

Another native revegetation project is underway in Hawke’s Bay.

The project, undertaken by the Forest Lifeforce Restoration Trust, involves over 4000 hectares of the Maungataniwha Native Forest to be converted from pine to native after logging.

“The aim is to return it to indigenous cover, but wilding pines are a monstrous issue,” said Shaw.

No plantings are being undertaken here as there are native seeds in the soil, however, these need to compete with seeds from the pines. The fast-growing wildings crowd out any natives and starve them of sunlight and space.

Wildings don’t provide food for native birds or insects and their needles form an acidic carpet on forest floors which stops natives regenerating. Their wood is of no value to the forestry industry as it has not been grown correctly.

“They’ve tried everything here. All the wildings are felled by hand with chainsaws, loppers. The cost of it is enormous. They’ve had to resort to aerial spraying of huge densities of wildlings. It is working,” said Shaw.

The numbers

Part of the Ministry for Primary Industry's (MPI) role in the One Billion Trees project is to look at options to scale up some native regeneration projects.

The head of its forestry services arm, Te Uru Rākau’s Julie Collins, told Newsroom last week she expects two-thirds of a $240 million grant scheme will fund native trees. She said this will result in 125 million natives on top of 10 million native trees per year she said are already being planted.

The remaining 775 million plants are likely to be exotics, which can come with the issue of windblown seeds contributing to the wilding conifer issue New Zealand is currently battling.

A 2017 report by the National Wilding Conifer Control Programme estimates 20 percent of the country could be covered with wilding conifers by 2030. The wildings are spreading by more than 5 percent per year despite private land holders, community groups, and central and local government agencies collectively spending about $11 million each year on control.

New plantation forestry environmental standards require new forests, or existing forests due to be replanted with a different type of conifer, to consider the impact of wilding spread.

A scoring system looks at five indicators of how likely wilding spread will be. These indicators include how tasty the seedlings are to typical wind movement around the area to be planted. A high score requires the forester apply for resource consent in order to plant. Replanting existing forests with the same type of conifer appears to fall outside the need to assess wilding spread.

It’s too early to tell if the new standards will reduce the rate of likely wilding spread driven by the push for more planting for the One Billion Trees project. What is evident is even if it does reduce additional wilding spread, a mammoth task remains.

A workforce of weed destroyers is needed to tackle the issue of wildings and weeds.

It’s something The National Wilding Conifer Control Programme report as an issue. Finding and training staff comes at a cost, and staff are sometimes lost to other industries. It suggested intervention from government and industry would be needed to ensure there’s a workforce to control wildings.

The grants and partnerships fund for the One Billion Trees project will support land preparation and maintenance such as weed and pest control said an MPI spokesperson.

The funds will launch later this year and money may come with maintenance conditions attached. Conditions listed on MPI's website for a current afforestation scheme says: “You have to maintain the forest to a set standard to be eligible for the grant. If you cut down the forest or don't look after it, you may have to replant or, as a last resort, pay the grant back.” 

Willie Shaw sharing considerations for successful native regeneration. Photo: Farah Hancock

At Shaw’s Auckland lecture he spoke on the challenges ahead.

“I’ve been to one workshop in Wellington with MPI talking about the programme and you certainly cannot underestimate the complexity of trying to get this thing off the ground and up and running quickly.”

Shaw shared a slide with the audience showing 16 things to consider to ensure successful large-scale native revegetation projects.

“Large-scale revegetation can be challenging and costly. There are very substantial risks and there are plenty of unsuccessful projects scattered around New Zealand.”

Read more:

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Tōtara project sets sights on sustainable timber

Greens win big native trees concession

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