While recommending more native trees be planted in coming years, the CCC also notes there is limited knowledge on cashflows and carbon absorption rates for natives.
Steve Wakelin and Dr Tim Payn agree in principle with this goal to plant more natives for carbon benefits, but also want to highlight the additional environmental and biodiversity benefits of this focus.
They also note there is a devil in the detail behind the commission’s recommendations.
While acknowledging NZ can grow exotic forests “with one hand tied behind our backs,” native afforestation remains a relatively new and uncertain game.
As appealing as it could be to see the country replanted in lost forests, the scientists caution there could also be some sacrifices in how much carbon is absorbed when opting for natives in the short-term.
“There is a deliberate trade off that will occur between sequestration rates, and increased biodiversity and environmental benefits from having more natives,” Wakelin said.
“This has yet to be analysed in detail.”
The commission has recommended both natural regeneration on farms and native plantations, but it is not always clear which they are referring to within their report.
The scientists caution there can be significant differences in carbon sequestration rates, establishment costs and co-benefits from other ecosystem services.
The rate of carbon absorption (sequestration) by regenerating native forests is known to be considerably slower than exotics. Well-managed native plantations are likely to fall somewhere in between.
The commission’s report adopts the Emissions Trading Scheme (ETS) lookup table assumption a hectare of new native forest of any type will absorb about 6.5 tonnes carbon dioxide every year over 50 years, compared to an average exotic plantation soaking up 34t a hectare every year over 30 years.
However, there is evidence some more intensively managed plantations, including kauri and totara, can absorb carbon dioxide at significantly greater rates than natural regeneration, and for longer than typical exotic plantations.
Other factors pertinent to landowners include the higher establishment costs for planting natives and ensuring their survival, estimated in the report at $6600 a hectare, and access to native seedlings for planting, or nearby seed sources for natural regeneration.
The commission estimates there is about 740,000ha of marginal land unsuitable for commercial forestry that could be allowed to regenerate naturally, providing pests were managed within that estate.
The potential for pines to be used as the nurse crop has been raised, with a managed transition to native forest and retreat of the exotic species.
This approach maximises the carbon sequestration strengths of the exotics and native species, which provide a carbon sink in the short and long-terms respectively.
Wakelin cautions in either case, there is potential for a net loss of carbon at some stages during the transition.
”It would be unwise for a farmer or New Zealand’s Climate Change budget to just count on continuously positive carbon uptake,” he said.
But the scientists also maintain there are other opportunities for landowners who have fenced riparian zones, with about 180,000km of waterways offering opportunities for more than just flaxes and manuka on them.
Payn believes the commission’s target of 25,000ha a year of native forest planted until 2050 is not an unattainable amount.
“If everyone did a small amount across all farmland, you could hit those numbers quite quickly. Even if you think of the corners of paddocks not irrigated, for example, biologically it is quite possible,” he said.
But the scientists agree with farming commentators like Whanganui Federated Farmers president Mike Cranstone, who recently wrote NZ could not “plant its way out of climate change and must decarbonise and reduce emissions at source”.
“Forestry is a key component in the commission’s advice, but trees are not the be all and end all,” Payn said.
“However, they do bring a level of flexibility and buy us some time. As you go through your five-year carbon budgets and review if we are meeting targets or not, there is the flexibility there to increase forestry plantings if necessary.”
Farm offsetting, where trees are planted that absorb that farm’s emissions are also a useful tool for buying some time, but it is one the scientists also see as secondary to the commission’s goal to see emissions reduced at source.
They also caution about the need to make well-informed decisions prior to locking up land for decades, knowing both the economic, environmental and biodiversity benefits they may bring.
“Farmers need to be very clear about what they want to achieve and take a realistic look at the positive and negative impacts of their land-use decisions on their own farms,” he said.
The decision to plant land into carbon forests will be influenced by rising carbon prices, with planted forests on farms capable of generating increasingly healthy carbon earnings as prices surge over $35 a unit, with forward contracts to 2025 offered at $46.
The commission has called for a ceiling of $100 a unit.
“And if you can earn carbon credit income early it helps with your establishment costs, versus waiting 28 years for income from cutting down the forest in the traditional farm forestry model,” he said.
Knowledge needed to spread native story
Work is well underway to improve the level of knowledge and information available to farmers keen to tap into carbon capture opportunities on their properties.
Despite strong farmer interest in field days about forestry and trees on farms, a frequent concern for both farmers and foresters has been the availability of advice to help farmers get the “right tree in the right place”.
Scion’s Dr Tim Payn and Steve Wakelin say there is a lot of information out there, if one knows where to find it, including regional councils and the Farm Forestry Association.
Both He Waka Eke Noa and Te Uru Rakau are focusing on extension approaches, with a knowledge hub being developed by Te Uru Rākau.
New knowledge is being added; for example, Hawke’s Bay Regional Council issuing farm case studies to showcase opportunities to integrate forestry into the landscape.
“There are a number of farm scale evaluations now going ahead, on how to rearrange your farm to increase forestry and carbon capture,” Payn said.
The ground shift from the traditional forest planting-harvest model to carbon income is seeing a variety of options presented to farmers. This has even included establishing high-value ginseng crops below a forest canopy on some iwi land.
Scientists are also keen to work more with farmer-led community catchment groups that have had success with specific native plantings, sharing those success stories more widely.
Local information is the key.
“In the past there have been national-level studies on land-use, but a lot of this does not translate to an individual farm level. With native plantings it comes down to a farm specific level. We are also used to dealing with radiata pine, which to be honest is hard to go wrong with when planting, compared to establishing natives,” he said.
