5 Removal units from sinks
This report provides an estimate of removals of CO2 via forest sinks. The projection in this report uses the current inventory methodology and best information available at the time of projection.
A most-likely, pessimistic and optimistic scenario are used to quantify uncertainty around the removals via sinks. The scenarios anticipate the results from when the New Zealand Carbon Accounting System is in operation. It is highly unlikely that all pessimistic or all optimistic situations will occur together and the uncertainty around the projected removals is modelled using a Monte-Carlo simulation. The 95% confidence intervals around the mean are used to represent likely bounds to the pessimistic and optimistic scenarios (Table 6). The change to the New Zealand carbon accounting system will affect all values reported in Table 6.
Table 6. Calculation of projected removal units in CP1 (figures have been rounded).
Projected removal units |
Mt CO2e |
||
|---|---|---|---|
Pessimistic |
Most likely |
Optimistic |
|
Total sequestration combined with new planting rates (0, 10k and 30k ha/yr) |
91.9 |
95.3 |
102.0 |
Loss of soil carbon with afforestation |
-8.6 |
-2.2 |
0 |
Natural scrub meeting Kyoto Forest definition |
0 |
0 |
3.75 |
Planted forest not meeting the Kyoto Forest definition |
-19.3 |
-14.7 |
-7.4 |
Burning of scrub for forest planting |
-1.25 |
-1.25 |
-1.25 |
Deforestation emissions |
-21.0 |
-6.3 |
-6.3 |
Total removal units |
41.8 |
70.9 |
90.8 |
Likely total removals from simulations (95% CI around mean) |
48.1 |
67.8 |
85.6 |
The projected removal units are based on a national radiata pine area-weighted carbon yield table. This yield table has been derived from the National Exotic Forest Description wood volume yield tables and does assume that all planted forests are radiata pine of medium wood density. The same standing stem volumes per hectares are assumed for all forests irrespective of when they were planted. Some experts consider that current carbon sink estimates may be underestimated because most forests planted since the early 1990's have been on more fertile soils with the potential for higher growth rates. There is however, no consensus on this point. A contrary view is that due to the large areas of "non-professionally" managed forests planted since 1990 that the biomass in these forests could be lower because of poorer quality forest management. There also down side risk because 10 percent of New Zealand's planted forest estate is in species other than radiata pine. Generally these other species grow more slowly. No suitable model current exists for alternative species. The Carbon Monitoring System plots and revision of yield tables will help clarify this situation.
The best estimate in the previous projection report was based on a planting rate of 20,000/yr. Current planting rates are around 10,000-15,000 ha/yr. The most likely estimate used in this projection is 10,000 ha/yr. The historical average planting rate is around 40,000 ha/yr meaning that the estimate of 10,000 ha/yr is low in the historical context.
A loss of 2.2Mt CO2 is included for a loss of soil carbon converting "grassland" to pasture. This is based on research by Landcare Research and Forest Research scientists. Earlier estimates assumed no loss of soil carbon.
There is no projected removal from "Kyoto scrub" that meets New Zealand's proposed definition of forest under the Kyoto Protocol. This definition requires New Zealand to state the minimum area, length (and thus width) of land areas categorised as forest land. The previous estimate was 3.75Mt CO2.
A loss of 14.7Mt CO2 is included for forests planted into existing kanuka and manuka forest. Field studies have shown that a proportion of existing planted forests, estimated at up to 16% nationally, were planted in scrub that could meet the definition of forest in the Kyoto Protocol, i.e. the planting was not onto "grassland". The true value won't be known until the New Zealand Carbon Accounting System is in operation. The pessimistic and optimistic estimates use estimates of 21% and 8% of forests being planted in existing forest and 10,000 hectares planted from 2005.
Burning of scrub for forest planting was not included in previous calculations of the balance of units, however this source is included in the change of carbon stocks reported in the national inventory of emissions and removals (MfE, 2005). A constant loss of 1.25Mt CO2 is used for all scenarios. Use of a constant value implies differing percentages under the optimistic and pessimistic scenarios.
The expected value of emissions from deforestation remains the historical (2-3%) rate of deforestation. This equals a loss of 6.3 Mt CO2 under the most likely estimate. The minimum amount of deforestation is also set to 6.3 Mt CO2. Use of a constant value implies differing percentages under the optimistic and pessimistic scenarios. The upper limit is the maximum liability under the deforestation cap. The historic rate of deforestation may not necessarily be an accurate guide of future intentions. Anecdotal information indicates that current and future deforestation is higher than historical levels. A project has recently begun to review methodology options to forecast future deforestation levels.
The projections assume Kyoto accounting rules established for the first commitment period of the Protocol would continue for future commitment periods, for example the "fast growing forest fix" which limits liabilities for Kyoto forests to previous credits claimed. Those countries that will harvest Kyoto forests in the first commitment period need only "pay back" the equivalent carbon units earned in the first commitment period.
The impact of rotation age is most relevant after the first commitment period. The projections assume a rotation age of 28 years. An earlier cut will result in higher carbon emissions during the first commitment period and a later cut would defer carbon emissions. Current forest management trends are toward longer rotations.
5.1 Accounting for Article 3.4 Forest Management
Under Article 3.4 of the Kyoto Protocol, New Zealand has until 2007 to elect which additional Article 3.4 land use, land use change and forestry activities, if any it wishes to account for in the first commitment period. The election of these activities is voluntary for Annex 1 parties. Forest management is one such activity and would include accounting for non-Kyoto forests over the first commitment period. The government has agreed in principle not to account for these activities in the first commitment period. However, a final decision will not be made until closer to 2007, when further information is available.
At present, there is considerable uncertainty in the data on carbon stocks and carbon stock changes for forest land. The available data suggest that carbon stocks are likely to be in a steady state or a slight decline. An assessment of the significance to New Zealand of Article 3.4 forest management activities concluded that the balance lay somewhere between -92 Mt CO2e to 11 Mt CO2-equivalent over the first commitment period. New Zealand is also subject to a cap for Article 3.4 forest management activities.
Whether New Zealand will be obliged to account for such activities in subsequent commitment periods is a matter for future international negotiations. If New Zealand is obliged to account for pre-1990 forests and these forests are in fact losing carbon, then this would add to New Zealand's emissions liabilities.
