Calculating carbon for post-1989 forest land using averaging accounting

Calculating your emissions returns with averaging accounting

From 1 January 2023, if you have post-1989 forest land in the ETS, you may have:

• only carbon accounting areas for which you're using stock change accounting
• only carbon accounting areas for which you're using averaging accounting, or
• some carbon accounting areas for which you're using each accounting method.

Find out more about accounting for carbon and which method applies to your forest land

When you complete emissions returns, you must calculate the change in carbon for each carbon accounting area separately. There are some differences you need to know about when calculating carbon using averaging accounting.

You may want to appoint a representative to help you complete your emissions return.

Appointing a representative to manage your ETS tasks

For forest land under averaging accounting:

• for the forest's first rotation, carbon is calculated as it would be under stock change accounting, until the trees reach the average age or are cleared (if cleared before the average age)
• once the trees reach the average age or are cleared (and the first rotation ends), the forest is treated as if its carbon storage stays the same through the planting and harvesting cycle.

Each forest type has its own average age.

Find out more about average ages

Find out what makes a forest "first rotation" under averaging accounting

This means that under averaging accounting, after a certain point, the age and forest type you use for your calculations may not be the same as those of the trees on the land. For example, if you harvest radiata pine at age 28 and replant with Douglas-fir, you'll calculate carbon as if the trees were 16-year-old radiata pine. (The average age for radiata pine is 16).

The tree age and forest type to use in your calculations

Emissions returns for post-1989 forest land cover a specific period. This period varies depending on the reason for the emissions return. When you complete an emissions return you must calculate the carbon at the beginning and end of the period. You must then find the difference between them.

The rest of this page explains how to work out what age and forest type to use for your calculations. This depends on whether:

• the forest was on its first rotation and younger than the average age for the whole emissions return period
• the forest’s first rotation reached the average age or was cleared during the emissions return period, or
• the forest was on a later rotation, or past the average age, before the emissions return period.

Once you know this, you can follow the steps for calculating carbon.

Learn how to do the calculations for your emissions return

If the first rotation was younger than the average age for the whole emissions return period

This applies if, during the period covered by the emissions return, the first rotation forest:

• did not reach the average age for the forest type
• wasn’t cleared (so remained on the first rotation).

This forest is considered to gain carbon as it grows. When you calculate the amount of carbon at the start and end of the period, you must use the actual age and forest type of the trees.

If the first rotation reached the average age or was cleared during the emissions return period

Once a first-rotation forest reaches the average age for its forest type or is cleared, it’s treated as if its carbon storage pauses. The amount it pauses at is the assumed average amount of carbon over multiple rotations. The date this happens is called the "settled NACS day" in the Climate Change (Forestry) Regulations 2022. "NACS" means "nominal average carbon stock".

As the planting and harvesting cycle continues, the amount of carbon the forest is considered to have doesn't change.

For future carbon calculations, you must use:

• the forest type of the first rotation, and
• the age at which the carbon storage is considered to have paused.

This age depends on whether the trees were cleared before they reached the average age.

The age to use if the first rotation reached the average age without being cleared

For carbon calculations going forward, use the average age for the forest type of its first rotation. If you clear and re-establish the forest after this, it doesn't affect how much carbon it's considered to have.

The age to use if the first rotation was cleared before it reaches its average age

When you clear the forest, the rotation ends (except if you clear young naturally regenerated scrub to plant forest). If you clear the first rotation before the average age, the carbon pauses at the amount it would have at a younger age. The age you must use for carbon calculations going forward depends on the age the trees were cleared.

It doesn't matter if you clear future rotations at an older age. For carbon calculations, the forest will be treated as if it's the age from the early clearing band above.

Calculating the change in the amount of carbon for your emissions return

In this case, when you do your calculations for your emissions return, you must calculate the carbon at the beginning of the period using the age and forest type of the trees on that date.

You must also calculate the carbon at the end of the period using:

• the forest type of the first rotation
• the age at which the carbon is considered to have paused, based on the average age and when it was cleared.

If the first rotation reached the average age or was cleared before the start of the emissions return period

The carbon in the forest land is considered to stay the same if, before the emissions return start date:

• the first rotation ended, or
• the trees passed the average age for the forest type.

In your emissions return, you must report that the change in carbon stock is 0. This is because the forest is treated as the same age and forest type it was when the first rotation reached its average age or was cleared, if cleared before the average age. This is regardless of any planting, growth, and clearing that happened during the period.

You may have instances where some parts of a carbon accounting area are gaining carbon, and others aren’t. This is dealt with by how you divide your carbon accounting areas into smaller areas for calculating carbon. These are called "sub-areas".

Find out more about dividing your land into sub-areas for calculating carbon

Find out more

Learn about using carbon tables for calculating carbon

Identifying forest type, region, and age for calculating carbon

Find out more about emissions returns and when to submit them

Find out why you need to submit an accurate emissions return