1. Don O’Connor NBB Sustainability Workshop September 27, 2018
CARB’s AEZ Model
Don O’Connor
NBB Sustainability Workshop
September 27, 2018

2. Agenda
AEZ Review
US Forest Service Data
Steps forward

3. ILUC Emissions ILUC emissions are a two stage calculation
What is the land use change?
Magnitude and type?
GTAP results
What is the change in the emissions resulting from the land use change?
GTAP land use change and the AEZ emission factor model.

4. Forest Land
In GTAP, generally more pasture land is converted than forest land.
But emissions per ha for forests are much larger than for pasture.
In general the improvements made to GTAP over the past few years have reduced the proportion of forest land in the converted land and the proportion of land conversions in the developed world.

5. AEZ Model Forest carbon pools in forest land include
Above Ground Biomass
Below Ground Biomass
Understory
Deadwood
Litter
Soil carbon
Foregone sequestration

6. AEZ US Data USA-10 61 15 19 70 USA-11 49 USA-12 43 44 Mg C ha-1 USA-7
Aboveground carbon (in live biomass)
Belowground Carbon
Understory
Deadwood
Litter
Topsoil C (to 30 cm)
Foregone sequestration over assumed time horizon
Mg C ha-1
USA-7 38 10 3 11 26 47 20
USA-8 57 14 89
USA-9 90 22 95
USA-10 61 15 19 70
USA-11 49
USA-12 43 44
USA-13 59 28 72
USA-14 67 16 93
USA-15
105 25
121
USA-16
132 32
148
Typical avg 56 60

7. US Forest Service
The United States is currently in the process of adopting a new approach to forest carbon accounting. The Forest Carbon Accounting Framework (FCAF) will incorporate the most consistently measured annual forest inventories (including all the pools of forest carbon).
Data on the individual pools is available at the state level and overall data is available by year since 1990.

8. USFS Data
State data could be aggregated to the AEZ level for the various carbon pools.
Trend data could be use to confirm lost carbon sequestration potential from land use change.
The online data is not ideal
Area by state is 2010 data
Total carbon pool data is 2014 data.

9. USFS Data Min Max Average Tonnes C per ha Above Ground Biomass1 12.4
95.7
50.9
Below ground Biomass
2.4
20.0
10.1
Deadwood
2.3
28.3
8.7
Litter
3.9
18.0
9.8
Total 21
162
79.5
Soil Carbon
17.1
168
60.4
1 Includes understory

10. Comparison
We are comparing the US average forest data to the average of forest land converted in GTAP.
These may not be exactly equivalent.
Converting the US state data to AEZ data would provide a better comparison.

11. Comparison AEZ USFS Tonnes C per ha Above Ground Biomass1 59 50.9
Below ground Biomass 14
10.1
Deadwood 11
8.7
Litter 20
9.8
Total
104
79.5
Soil Carbon 60
60.4
1 Includes understory

12. Observations
AEZ model is consistently higher than the USFS data for all categories except soil carbon.
The total biomass is 31% higher.

13. Sequestration US forests are gaining carbon.
Through forest area expansion
Through increased carbon stocks in forests remaining forests.
Contribution of each component varies with the region.

14. Net Sequestration

15. Sequestration

16. Foregone Sequestration
An average of 130 million tonnes of carbon have been sequestered since 2010.
Forest area is about 270 million ha.
Net sequestration rate is 0.48 t C/ha/year.
Net sequestration over 30 years is 14.5 t C/ha.
This is also lower than the 20 t C/ha in AEZ.

17. Other Factors
USFS also estimated the carbon in harvested wood products as part of the national inventory. This could be compared to the AEZ model as well.
Other developed regions of the world will also have forest carbon stock data.
Data quality will vary by region.

18. Next Steps
Given that US forest stocks is no longer a large driver of ILUC for most domestic crops is it worthwhile to update the data?
If yes,
Get forest area data for 2014 to replace the 2010 data that has been used here with the 2014 stock data.
Convert state data to AEZ regions.
Publish

19. Next Steps
Investigate the availability of similar high quality forest stock data for other GTAP regions.
If available, convert to AEZ compatible data.

20. Questions?