Calculating how much carbon is in pre-1990 forest land

Preparing to calculate carbon

When you deforest pre-1990 forest land you must submit an emissions return, unless you have an exemption or an approved application to offset your emissions from deforesting. You need to submit an emissions return between 1 January and 31 March of the year after you deforest.

To complete your emissions return you need to know how much carbon was in your forest when it was deforested. You'll need to pay New Zealand Units (NZUs or units) for this amount of carbon. This is known as "surrendering" units. There is a specific way you must calculate this amount. We explain it on this web page.

There are 2 steps you need to have completed before you can calculate your carbon.

Step 1: Identify the forest type, region, and age

You need to know certain things about your forest land, such as the forest type and age of the trees. There are specific rules for how to work these out in the ETS.

Identifying forest type, region, and age for calculating carbon

Step 2: Group similar areas of forest together into sub-areas

If your forest has trees of more than 1 forest type or age, or across multiple regions (if it's radiata pine), you also need to do some work to separate your forest land into "sub-areas". These are areas of forest with the same characteristics. You'll do your carbon calculations for each of these sub-areas separately.

Grouping areas of forest with the same characteristics for calculating carbon

Using carbon tables

When you do your carbon calculations, you need to refer to "carbon tables". These are tables that tell you how much carbon is in your forest land per hectare.

To calculate the carbon in pre-1990 forest land, you need to use the carbon tables provided in the regulations. They're based on average growth rates across New Zealand.

Tables of carbon stock per hectare for pre-1990 forest land – NZ Legislation

There are 2 tables:

• a table for radiata pine forest, split up by region
• a table with columns for the other types of forest.

If the trees are older than the last age on the carbon tables for that forest type, use the value for the last age.

Find out more about using carbon tables for calculating carbon

How to do your carbon calculations for deforesting pre-1990 forest land

To calculate the total carbon stock of your forest land:

1. For each sub-area, find the value for the forest carbon stock from the carbon tables.
2. Multiply this value by the total area in hectares (rounded to 1 decimal place) of the sub-area. This gives you the total carbon stock for the sub-area.
3. Add together the carbon stock from each sub-area.
4. Round the total to the nearest whole number (0.5 and above is rounded up).

The result is the total amount of carbon emissions you need to report on your emissions return.

If the trees are 8 years old or younger on the land you deforest

If you deforest pre-1990 forest land while the trees on the land are 8 years old or younger, an extra rule applies to how you calculate the emissions. This is because previous forest must have been cleared before the young trees could regenerate or be planted, for it to be pre-1990 forest land. The previous forest may have stored a much larger amount of carbon.

If the trees cleared are 8 years old or younger, you need to calculate the amount of carbon based on trees that were on the land previously. For any trees cleared in the previous 9 years (excluding any time when the land was temporarily unstocked), you must work out:

• the main (predominant) species, and
• of that species, the age of the oldest trees when they were cleared.

You must use this species and age when you calculate the emissions from deforesting the land. This means you're reporting on and paying (surrendering) units for the older trees previously on the land instead of the new growth.

If only part of the land you deforest has trees that are 8 years old or younger, this rule only applies to that area. Emissions from the rest of the forest land are calculated normally.