- The issues
- New Zealand's situation
- The dominant carbon stock changes
- Data, analysis and accounting requirements
- Full carbon accounting?
- Summary table: Carbon stocks and their changes for relevant land system classes in biomass and soil (to 30 cm depth).
Executive Summary
The issues
Article 3.3 of the Kyoto Protocol provides New Zealand with a basis for claiming carbon credits associated with expansion of plantation forestry in the next few decades. Article 3.4 introduces a wider range of carbon stocks and management options which could be considered as optional for the first commitment period, and may become mandatory subsequently.
Key questions for New Zealand at this stage are:
- how would implementation of Article 3.4 affect New Zealand's likely carbon credits1 during the first commitment period? ;
- what are the technical measurement and accounting implications of implementing Article 3.4?; and
- would early implementation of Article 3.4 be justified on the basis of environmental integrity as a move towards full carbon accounting?.
New Zealand's situation
The pre-1990 forests that would be included under Article 3.4 have a high proportion of younger trees that will reach maturity by 2008. During the first commitment period, the net change in above-ground carbon stocks in these forests is expected to be negative as harvesting removals will exceed new growth. This situation may continue to a second commitment period. As a result there would be a reduction in the credits that would be available from post-1990 forests under Article 3.3. [3.10, 3.11]2
Much of New Zealand's land has been changed from indigenous forest to pasture land over the last 150 years. This has tended to maintain high soil carbon levels, whereas the transition in Europe from forest to intensive agriculture has already caused soil carbon depletion. The changes now occurring in New Zealand from pasture to cropping, or intensive forms of agriculture, are more likely to decrease our high soil carbon levels than increase them. [4, 5]
In the case of conversion of pasture to plantation forestry, although the accumulation of above ground carbon clearly dominates, there is evidence for some loss of soil carbon over about 20 years. The magnitude of this loss will depend on the site and its land use prior to afforestation. [3.7]
The dominant carbon stock changes
A summary of estimated carbon stocks and their rates of change is shown in the Summary Table below. The key features, in order of probable significance, are as follows:
Above-ground forest stocks: Inclusion of changes in the above-ground carbon stocks in plantation forest under Article 3.4 in the first commitment period is estimated to nearly halve the carbon credits that are likely to be available under Article 3.3 alone, for a mid-range planting rate scenario. This carbon stock reduction is equivalent to3 3.1 TgC y-1 and is probably the dominant near-term effect of Article 3.4 on New Zealand carbon credits. [3.11]
Below-ground forest stocks: Although there is general agreement that soil carbon stocks under forests are probably decreasing, available data differ according to the methodology used, are often limited to near surface changes, and span a wide range of loss rates. Compensating carbon increases may occur through the accumulation of organic litter on forest floors. Further data and process studies are required to resolve this issue and consequently we do not give an estimate for total carbon changes due to recent New Zealand afforestation. [3.7, 3.10]
Soil erosion: Recent work on soil erosion has identified large carbon fluxes of the order of 3 to 11 TgC y-1. This suggests a potential for restoration of eroded soils to remove significant amounts of carbon from the atmosphere. However, establishing credible accounting procedures and identifying the human component of erosion and restoration activities has not been considered by the IPCC or in New Zealand adequately at this stage. [7.4]
Scrub reversion: Reversion to scrub land is acting to increase above-ground carbon stocks although the amount is uncertain due to poor definition of the areas and rates of land-cover changes involved. The scale of this increase in carbon stocks is estimated as between 0.6 and 3.4 TgC y-1. [6.10]
Pests in indigenous forests: Upper estimates for carbon stock losses in indigenous forests due to pests are 2.5 TgC y-1, but this value is still quite uncertain and the estimated range includes the possibility that pests are not significantly affecting terrestrial carbon stocks in indigenous forests. [7.3]
Other activities: that might be included under Article 3.4, such as cropland management and grazing land management are associated with small carbon stock changes which are probably negative but with a total magnitude of less than 0.3 TgC y-1. However, the associated management options, e.g. minimum tillage, no-till, and residue incorporation, can be of local value and have other benefits. [4.10, 5.10]
Data, analysis and accounting requirements
Accounting techniques for above-ground carbon in plantation forests is well established. However, accounting costs may overwhelm the value of any carbon credits over time, as the maximum credit per hectare is limited whereas accounting may need to continue in perpetuity. Inclusion of pre- and post-1990 forest in a common accounting system for both Articles 3.3 and 3.4 would not lead to any reduction in accounting overheads if Article 3.4 credits were discounted and the pre-1990 forested land had to be tracked separately. [3.5]
There are no comprehensive databases that provide geo-referenced information on land cover and land-use history although this information can be approximated from various sources. There are good prospects for better use of satellite data to rectify this situation in the near-term, and retrospective use of satellite imagery may provide assessments of 1990 land cover. Ongoing development of comprehensive soil carbon databases will provide important complementary information. [4.5, 4.9, 5.9]
Although much of New Zealand's soil carbon stocks appear to be close to a steady state, these stocks are very large and small relative changes, e.g. in pasture land carbon density, can be significant in relation to our Kyoto Protocol commitments. Changes in soil carbon need to be based on a better knowledge of steady state conditions for different land-use, land-cover and land management options. Progress is being made through the improvement of process-based models and the development of models that couple land-use / land-cover with below-ground carbon stock changes. [3.7, 4.6, 5.6, 6.10]
Overseas groups have prepared estimates of some carbon stock changes in New Zealand using inappropriate data. This highlights the importance of doing our own assessments using local data that is specific to New Zealand circumstances. We have internationally recognised expertise in all relevant areas and there is no reason why New Zealand should not be able to provide carbon stock assessments for Article 3.4 of comparable or better quality than those of other Annex I countries.
Full carbon accounting?
The implementation of Article 3.4 in addition to Article 3.3 would increase the number of carbon pools considered, and the range of activities that affect them, for the purposes of assessing human effects on greenhouse gas emissions to and removals from the atmosphere. Thus early adoption of Article 3.4 might be promoted on the grounds of environmental integrity as a move towards full carbon accounting.
However, the extent to which Article 3.4 would achieve real progress towards full carbon accounting depends on the extent to which that would actually capture most of the human-induced changes in carbon stocks. Based on the estimates of New Zealand's carbon stock changes available at present, it appears that afforestation under Article 3.3 already captures the dominant changes. Any significant improvement would require incorporation of erosion and restoration of eroded lands, revegetation, and possibly pest effects in indigenous forests. Dealing with those issues is at present constrained by our limited scientific and technical understanding. With the exception of revegetation, these aspects of carbon stock management have not been addressed in detail by the IPCC.
Thus, in the near term, it appears that adoption of Article 3.4 is unlikely to cover the major carbon stock changes in New Zealand that are not already covered in Article 3.3. Progress towards full carbon accounting rather requires further scientific and technical study and improvement of land-cover/ land-use/ land-management databases. This is a necessary prelude to the development of procedures to assess the effects of erosion and other issues raised in this report; seeking international acceptance of such procedures; and obtaining international acceptance that corresponding activities should be included under Article 3.4.
Summary table: Carbon stocks and their changes for relevant land system classes in biomass and soil (to 30 cm depth).
Estimate for 19901 |
Recent Average Changes1 |
|||||||
Land System |
Area (Mha) |
Veg. C Stock (TgC) |
Soil C Stock (TgC) |
Total C Stock (TgC) |
Area (Kha y-1) |
Veg. C Stock (Tg y-1) |
Soil C Stock (Tg y-1) |
Total C Stock (Tg y-1) |
Managed |
1.3 |
113 |
98 |
211 |
+44 |
3.0 to 7.0 |
-0.4 to -1.0 |
see |
Cropland |
0.3 |
2.5 |
25.7 |
28 |
+3 |
+0.025 |
-0.05 ? |
-0.025 ? |
Grazing Land |
13.4 |
187 |
1598 |
1785 |
-40 |
-0.26 |
Probably 0, possibly -2.7 |
? |
Natural |
2.6, 3.7 |
527 |
393 |
920 |
Uncertain |
0.6 to 3.4 |
? |
? |
1 The sources and derivation of the values shown in the four rows is given
in sections 3.10, 4.10, 5.10 and 6.10 respectively. Recent average changes are for the the
1990 - 1999 period. In some cells two estimates are given, based on different
methodologies.
2 Figures for managed forests are for the total of pre- and post-1990 forest,
section 3.11 discusses the effect of Article 3.4 on assessed carbon stock changes.
3 May be covered under Article 3.3
| The two articles of the Kyoto Protocol most relevant to this report
are copied here with the key terms for consideration in this report underlined. Article 3.3 of the Kyoto Protocol.
The net changes in greenhouse gas emissions from sources and removals by sinks resulting from direct human-induced land use change and forestry activities, limited to afforestation, reforestation, and deforestation since 1990, measured as verifiable changes in stocks in each commitment period shall be used to meet the commitments in this Article of each Party included in Annex I. The greenhouse gas emissions from sources and removals by sinks associated with those activities shall be reported in a transparent and verifiable manner and reviewed in accordance with Articles 7 and 8. Article 3.4 of the Kyoto Protocol.
Prior to the first session of the Conference of the Parties serving as the meeting of the Parties to this Protocol, each Party included in Annex I shall provide for consideration by the Subsidiary Body for Scientific and Technological Advice data to establish its level of carbon stocks in 1990 and to enable an estimate to be made of its changes in carbon stocks in subsequent years. The Conference of the Parties serving as the meeting of the Parties to this Protocol shall, at its first session or as soon as practicable thereafter, decide upon modalities, rules and guidelines as to how and which additional human-induced activities related to changes in greenhouse gas emissions and removals in the agricultural soil and land use change and forestry categories, shall be added to, or subtracted from, the assigned amount for Parties included in Annex I, taking into account uncertainties, transparency in reporting, verifiability, the methodological work of the Intergovernmental Panel on Climate Change, the advice provided by the Subsidiary Body for Scientific and Technological Advice in accordance with Article 5 and the decisions of the Conference of the Parties. Such a decision shall apply in the second and subsequent commitment periods. A Party may choose to apply such a decision on these additional human-induced activities for its first commitment period, provided that these activities have taken place since 1990. |
1 the term "carbon credits" is used loosely in
this report to refer to any benefits that may be related to Assigned Amounts as defined
under the Kyoto Protocol through appropriate national and international mechanisms.
2 Square brackets in the executive summary contain references
to the relevant sections in the main body of the report.
3 The unit TgC denoting 1012 g of carbon is used
here for consistency with units used in reporting national greenhouse gas inventories.
Note that 1 TgC = 1 MtC.
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