To assess carbon stock changes on lands in which ARD activities have taken place, it is necessary to either spatially delineate the land over which ARD activities have occurred and assess the stock changes therein or use a system of remeasured sample plots including the same areas.
The language of decision 9/CP.4 (FCCC, 1998b) implies that carbon stocks need to be measured only in 2008 and 2012 for Article 3.3 adjustments in the first commitment period. In Article 3.4, a stock assessment in 1990 is specifically called for. Incorporation of a D-R Rule (see Section 18.104.22.168), however, would require an additional carbon stock assessment at a specific year prior to 2008 to estimate the carbon stock at the specific time a parcel of land becomes part of the ARD land. Without such a rule, incentives exist for deforestation followed by reforestation after 1990; with the rule, a carbon stock assessment is required for a point in time prior to the deforestation (e.g., 1990).
Absent this rule, an assessment for Article 3.3 (under the land-based I approach) would entail accounting for ARD land at 2008 and 2012. If the measurements do not coincide with the endpoints of the commitment period, however, interpolation may be required.
Section 2.4.2 describes the data requirements for assessment of the carbon stock of a forest. The choice of scenario will not change the data necessary for carbon stock assessments. A carbon stock-based definition of forest implies, however, that a carbon stock assessment is required to determine whether an ARD activity has taken place; other scenarios involve carbon stock assessments only after the determination that land has become ARD land.
Existing forest inventory systems may not be adequate to assess stock changes resulting from ARD activities. For example, the U.S. National Forest Inventory uses a two-phase sampling system that determines the forest/non-forest condition of approximately 3 million plots (using aerial photographs) in the first phase and establishes 300,000 permanent field plots in a second phase. Although information collected from forested field plots should be quite adequate to estimate carbon stocks, there are insufficient data from non-forested areas to accurately assess stocks. An example would be a plot that was forested at one field visit, during which adequate carbon stock information was obtained. Subsequent conversion to a non-forest condition might mean the plot is no longer visited in the field, although it might still contain a substantial portion of the pre-conversion carbon stock. This plot could meet the criteria for Article 3.3, yet insufficient information would be available to assess the stock change. Similarly, application of a definitional scenario based solely on a low percentage of forest cover might result in inclusion of urban lands as forest. For example, an area of non-forest land may be developed for urban use and sufficient trees planted to exceed the minimum cover threshold. Because this land would be classified as forest under such a scenario, its carbon stock would be eligible for Kyoto Protocol purposes.
Most current forest inventories were developed to efficiently estimate merchantable wood production, not biomass or carbon content. Forest inventories generally provide estimates of main stem volume in a green condition. The use of conversion/ expansion factors enables estimation of biomass and carbon from stemwood volume. This technique may mask significant gaps in data for some forest conditions, which may be important depending on the scenario. For example, wood volume in small trees and younger stands is rarely included in forest inventories, causing difficulty in reliably estimating forest biomass. This situation applies to any afforestation/reforestation activities involving young stands. In particular, scenarios in which regeneration after harvest constitutes reforestation (the FAO and Land Cover scenarios) will involve large afforestation/ reforestation areas with young stands. For these cases, special regeneration surveys may be required. The lack of information on the dynamics of young stands (including soil carbon pools) is particularly critical in the first commitment period, when the old stands in the ARD lands will be at most 23 years old.
If the forest products pool is included in the carbon stocks to be reported under Article 3.3, a substantial body of additional data will be required, including estimates of carbon in wood products and the fate of this carbon. This type of data is unavailable in many countries, and collection of such data may be costly in relation to the stock change reported.
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