• CarbonCrop Team

Goodbye Stock Change Accounting, Hello Averaging

Updated: May 5

2022 is the last year you can register your forest to earn ETS carbon credits under the Stock Change accounting model.

At the moment, participants in New Zealand's Emissions Trading Scheme (ETS) can opt to register their forest under Stock Change accounting. From 2023 onwards, forests must be registered under Averaging or Permanent accounting instead. While accounting isn’t a hot topic for most regular people, it’s a big deal for landholders who want the option of harvesting their forest while earning carbon credits.

Spoiler alert: If you’re interested in restoring native forest permanently on your land, you don’t need to worry about Stock Change going away. It won’t make any difference to your carbon credits.

In this post we’ll introduce the different carbon accounting models used in the ETS and go through their pros and cons, to help you decide whether it’s worth the rush to register your forest under Stock Change.

We’ll cover:


Introduction to carbon accounting models

When you register a forest under the ETS, your chosen carbon accounting model informs how your carbon credits (NZU’s) are calculated.

Let’s start with basic principles. As trees grow they remove carbon from the atmosphere and this carbon gets stored in the woody biomass of the forest. Once registered in the ETS, changes in the carbon stock of your forest are monitored and credits are awarded accordingly. The carbon accounting model determines how many carbon credits you receive or need to surrender, which can make a substantial difference to your carbon income.

There are three accounting models used in the ETS:

  • Stock Change

  • Averaging

  • Permanent Forest

Stock Change, the original method of carbon accounting in the ETS, will no longer be available to forests registered from 2023 onwards. However, forests already registered under Stock Change will be allowed to remain under that system after 2023. That’s why landholders who wish to take advantage of Stock Change need to act quickly.

Now let’s review the three accounting models and their pros and cons.


What is Stock Change Accounting?

Under Stock Change, your credits directly reflect changes in the carbon stock of your forest.

As long as you don’t cut the trees down, you continue to receive carbon credits until your forest reaches a steady state of growth. If the carbon remains stored in the forest permanently, you keep the credits. Simple.

But what happens if you want to harvest? If you cut your trees down, the carbon stock of your forest will drop instantly, so you will be required to surrender an equivalent number of credits – up to the amount you earned since registering. If you had already sold those carbon credits you would need to get hold of some more, by using credits from another area of your land or buying replacement credits on the market. Once you plant more trees, the cycle starts again and you continue to earn credits as the carbon stock of your forest increases.

About the carbon plateau: To complicate matters, harvesting leaves behind residual carbon in the form of woody biomass (i.e. roots and tree stumps), so your carbon stock doesn’t go down to zero immediately after clearance. It takes around ten years for this biomass to decay so the carbon stock would continue to decrease during this period. However most people choose to replant soon after harvesting, so the growth of the new trees offsets these old decaying roots. This causes your carbon stock to plateau for about ten years after clearance, before going up sharply. For forests registered when they are very young, there is a certain amount of ‘safe-carbon’ that will not have to be surrendered after harvesting, however this only occurs in very select circumstances.

Here’s a simplified chart showing how credits are awarded for a typical production forest:

Stock Change Accounting ETS - Chart

This distinctive ‘saw-tooth’ style chart is why Stock Change is sometimes referred to as Saw-Tooth Accounting.

Pros of Stock Change:

  • Harvesting is permitted.

  • Second and third rotation forests are eligible for carbon credits, provided they meet the other ETS criteria. Some owners choose to harvest their existing forest, then replant with a view to leaving the next rotation in the ground to earn carbon credits.

  • Flexibility. If you don’t know whether to harvest or not, you don’t have to decide immediately. Once registered you can sit back and weigh up your options by comparing the price of carbon credits and the price of logs. Stock Change keeps your options open.

Cons of Stock Change:

  • If you choose to harvest the trees, you must be prepared to surrender the carbon credits you have already earned.

  • Stock change can be hard to get your head around. It might seem like unnecessary admin.

  • Some say carbon credits shouldn’t incentivise exotic forestry plantations at all and should focus exclusively on incentivising permanent native forest.


What is Averaging Accounting?

Under Averaging, forests earn credits as their carbon stock increases, but only up to a point.

The New Zealand Government introduced this model to make it simpler for people to earn carbon credits from production forestry. Under Averaging, the landholder receives an average carbon stock for their forest based on multiple cycles of planting and harvesting. As long as you keep replanting within a reasonable time period, and grow the trees to a normal rotation length, you’re entitled to keep harvesting and won’t have to surrender any credits.

Here's a simplified chart showing a typical production forest under Averaging:

The average ages used in the ETS:

Douglas fir

26 years

Exotic softwoods

22 years

Radiata pine

16 years

Exotic hardwoods

12 years


23 years

Pros of Averaging:

  • Harvesting is permitted, allowing owners to earn credits as well as forestry income.

  • Averaging can feel less risky than Stock Change because you don’t incur carbon credit liability when you harvest.

  • Incentivises people to plant new forest, rather than providing additional income to owners of second or third rotation plantation forests.

  • You can transition from Averaging to Permanent accounting if you decide that harvesting is not for you, and would rather earn carbon credits instead.

Cons of Averaging

  • Only first rotation forests which are younger than the average age will be eligible for credits under Averaging.

  • If your forest is in the second or third rotation, it won’t earn any credits at all. This gives little incentive to register the forest.

  • Owners of mature forest who decide to transition from Averaging to Permanent accounting will be able to claim carbon credits going forward but will miss out on claiming units back to the average age.


What is Permanent Accounting?

If you register a forest as Permanent Forest, you commit to leaving it in the ground for at least fifty years.

When the permanent forest category goes live in 2023, native forest will be eligible for this accounting method but as of May 2022, the decision to allow exotic forest is under review by the government. We’re expecting a decision on this review later in the year.

Carbon credits are awarded as the carbon stock of your forest increases, until the forest reaches a steady state (as defined by ETS policy). It’s very similar to the original Stock Change model, with the big difference being that you’re not permitted to harvest.

Here's a simplified chart showing the basic principle of Permanent Accounting:

Pros of Permanent Accounting

  • Simpler model to understand.

  • Second rotation forest and older forests are eligible, provided they meet the other ETS criteria.

  • Incentivises long-term carbon sequestration.

Cons of Permanent Accounting

  • The commitment can feel restrictive as it affords less flexibility to current and future landholders.

  • Potentially harsh penalties if the forest is accidentally or deliberately harvested or if an adverse event happens and re-establishment does not occur.

  • Compared with native forest, exotic species are less supportive of native wildlife and generally less resilient to adverse events such as high winds and forest. Many ask: Do we really want exotic trees there ‘permanently’? This question prompted the government’s consultation on exotic forest, which may remove exotic forest from the Permanent Forest category.


If you want to register under Stock Change, it's now or never

If you have exotic trees on your property and wish to earn carbon credits, we strongly recommend acting immediately. At CarbonCrop, about 80% of the forest we register is native regeneration, but many farmers have some exotic trees on their property too, and wish to take advantage of the extra carbon income. The minimum area of forest we can register is one hectare.

For forests registered from 2023 onwards, Stock Change will be replaced by Averaging and Permanent accounting. If your forest is above the average age and intended for harvesting, stock change accounting is essentially your only option to earn carbon credits in New Zealand’s ETS.

To recap:

  • Stock change accounting allows first and second rotation forests maximum flexibility, while earning as many credits as any permanent forest.

  • Averaging accounting allows harvesting to occur but stops issuing credits once the forest reaches a certain age. Additionally, there are no credits issued to second or subsequent rotations.

  • Forests registered under Permanent accounting cannot be harvested for 50 years.

If you want to take advantage of Stock Change, it is best to discuss your options with one of our carbon analysts. The first step is to confirm eligibility for ETS carbon credits via our free assessment.

If your forest is eligible and you choose to proceed, CarbonCrop can register your forest as an authorised representative.

Start with our free carbon assessment

CarbonCrop offers a free land assessment to landholders within New Zealand. We analyse whether your forest is eligible for the ETS and calculate how much your credits could be worth if registered. It’s a remote service, so we don’t even need to visit your land.

If you'd like to discuss your options with one of our carbon analysts, the first step is to confirm eligibility. If your forest is eligible and you choose to proceed, CarbonCrop can register your forest as an authorised representative.


P.S. Don’t miss out on carbon credits from 2018 to 2022!

Stock Change isn’t the only thing changing in 2022, the deadline for the current emissions return period has now passed but we’re still fighting for 2018-2022 carbon credits.

Our message to landholders: You still stand a fair chance of being accepted in 2022 and claiming backdated credits for the period 2018-2022. There’s nothing to lose - and lots to gain - by submitting your application as quickly as possible.

873 views0 comments

Recent Posts

See All