Mapping & Carbon Measurement
Accurate mapping and measurement underpin the entire ETS forestry system. Understanding how carbon is calculated helps you maximise your credits and stay compliant.
Carbon Accounting Areas (CAAs)
What They Are
Your registered forest is divided into Carbon Accounting Areas — distinct zones that are the fundamental unit for carbon calculations.
Each CAA should contain forest that’s:
- Similar in species composition
- Similar in age
- In the same region (for lookup table purposes)
- Practically manageable as a unit
Why They Matter
CAAs determine:
- Which lookup table applies
- How carbon is calculated
- When you can claim credits
- How management is tracked
Well-designed CAAs simplify ongoing management. Poorly designed ones create headaches for years.
Practical Boundaries
Good CAA boundaries often follow:
- Natural features (ridges, streams)
- Planting date boundaries
- Species changes
- Management unit boundaries
Avoid arbitrary lines that don’t relate to the forest or landscape.
Mapping Requirements
Digital Format
MPI requires maps as ESRI shapefiles:
.shp— the geometry file.shx— shape index.dbf— attribute data.prj— projection information
Projection: NZTM2000 (New Zealand Transverse Mercator)
If you’re not familiar with GIS, you’ll need professional help to prepare compliant maps.
Accuracy Standards
Maps must:
- Accurately represent forest boundaries
- Align with legal property boundaries
- Be based on current imagery
- Show all CAAs clearly
Inaccurate maps cause:
- Registration delays
- Incorrect carbon calculations
- Compliance problems later
Getting Maps Prepared
Options:
- Forestry consultants
- Survey companies
- GIS specialists
- Carbon registration services (like ours)
Professional mapping costs vary but typically $500-2,000+ depending on complexity.
Carbon Calculation Methods
Standard Lookup Tables
For forests under 100 hectares, MPI provides pre-calculated carbon values.
How they work:
- Identify your forest type (species category)
- Identify your region (for radiata pine)
- Look up carbon stock by age
- Multiply by area
- Difference between years = credits earned
The tables include:
- Radiata pine (by region)
- Douglas fir
- Other exotic softwoods
- Exotic hardwoods
- Indigenous forest (national)
Advantages:
- Simple and predictable
- No field measurement required
- Lower compliance costs
Limitations:
- May underestimate well-performing forests
- May overestimate poor performers
- No credit for above-average growth
Field Measurement Approach (FMA)
For forests over 100 hectares, you must use actual measurements.
How it works:
- Establish permanent sample plots
- Measure tree attributes (diameter, height)
- Apply allometric equations
- Calculate total carbon stock
- Report actual measurements in returns
Components measured:
- Live above-ground biomass
- Dead wood
- Litter
- Below-ground biomass (modelled)
Advantages:
- Credit for actual performance
- Potentially higher earnings if forest performs well
- More accurate representation
Limitations:
- Costly to establish and maintain
- Requires specialist expertise
- Regular remeasurement needed
Choosing Your Approach
| Consideration | Lookup Tables | Field Measurement |
|---|---|---|
| Required for | <100 ha | >100 ha |
| Optional for | Any size | <100 ha (if you choose) |
| Cost | Low | Higher |
| Accuracy | Standard | Site-specific |
| Variability | None | Reflects actual forest |
Some forest owners with <100 ha choose FMA if they believe their forest significantly outperforms the tables.
Lookup Table Details
Radiata Pine by Region
Radiata pine has region-specific tables recognising different growth rates:
Regions:
- Auckland
- Bay of Plenty
- Waikato/Taupo
- Gisborne
- Hawke’s Bay/Southern North Island
- Nelson/Marlborough
- Canterbury/West Coast
- Otago
- Southland
Each region has different carbon accumulation curves based on typical growing conditions.
Carbon Stock Progression
Typical radiata pine carbon accumulation (example):
| Age | Carbon Stock (t/ha) | Annual Increment |
|---|---|---|
| 5 | ~50 | ~10 |
| 10 | ~200 | ~30 |
| 15 | ~450 | ~35 |
| 20 | ~650 | ~30 |
| 25 | ~800 | ~25 |
| 30 | ~900 | ~15 |
Peak sequestration occurs around years 10-20, then slows as the forest matures.
Indigenous Forest
All native species use a single national table:
- Slower accumulation than exotics
- Continuous growth over long periods
- No regional differentiation (yet)
This averages across fast-growing pioneers and slow-growing podocarps.
Emissions Returns
What You Report
Emissions returns report changes in carbon stock for your CAAs:
- Current carbon stock (using tables or FMA)
- Previous carbon stock
- Net change = units earned (or surrendered)
Return Frequency
Options:
- Annual returns — filed each year
- Multi-year returns — less frequent, but covers longer period
More frequent returns mean more regular unit allocations but more compliance effort.
Supporting Documentation
Keep records of:
- Forest age by CAA
- Any events affecting carbon stock
- Planting and harvesting dates
- Management activities
You may be asked to support your returns with evidence.
Reconfiguring Carbon Accounting Areas
After registration, you may need to change your CAA boundaries. MPI allows reconfiguration, but with rules.
Splitting CAAs
You can split an existing CAA into multiple smaller areas:
- Each resulting CAA must be at least 1 hectare
- The total area must equal the original CAA
- Submit application through Tupu-ake
- Multiple splits can be done in one application
Why split?
- Selling part of your land
- Different management for different areas
- Separating for different harvest timing
- Creating cleaner boundaries for administration
Merging CAAs
Merging is more restricted:
- Contact MPI directly (forestryets@mpi.govt.nz)
- Cannot merge CAAs with different accounting methods (e.g., averaging with stock change)
- For permanent forestry: the later 50-year start date applies to the merged area
- MPI will advise on specific requirements
Why merge?
- Simplify administration
- Combine small adjacent areas
- Reduce compliance complexity
What You Cannot Do
- Add new land via reconfiguration — use a separate application to add land to the ETS
- Remove land via reconfiguration — deregistration is a separate process
- Change total area — splits and merges must maintain the same total registered area
Boundary Adjustments
Minor boundary corrections may be possible if:
- The change reflects more accurate mapping
- Total area remains approximately the same
- You can demonstrate the original boundary was imprecise
Contact MPI to discuss boundary correction options.
Common Mapping Issues
Boundary Disputes
Where forest boundaries differ from property boundaries:
- Get clear agreement with neighbours
- Document any shared or disputed areas
- Consider survey if boundaries are unclear
Pre-1989 Inclusions
If pre-1990 forest is mixed with post-1989:
- Map separately
- Clearly distinguish areas
- Only register eligible portions
Changing Forest Boundaries
If your forest expands over time:
- File applications to add new areas
- Update maps
- Create new CAAs as needed
Professional Support
For most landowners, professional mapping and carbon calculation support is worthwhile:
What consultants provide:
- GIS mapping to required standards
- Lookup table calculations
- FMA design and implementation
- Return preparation
- Ongoing support
When to engage:
- Before registration (mapping)
- At registration (applications)
- Annually (returns)
- When circumstances change
Key Takeaways
- CAAs are the building blocks — design them well
- Maps must be precise — in required format and accurate
- <100 ha uses lookup tables — simple but standardised
- >100 ha requires FMA — more accurate but costly
- Returns report changes — net difference = credits
- Professional help recommended — for most landowners