Land Use, Land-Use Change and Forestry

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3.5. ARD Examples on Stand, Landscape, Country, Regional, and Global Levels

This section uses case studies to demonstrate the implications of applying the seven definitional scenarios (Section 3.2) at the scales of forest stands, landscapes, countries, regions, and the globe. Most of the country studies done to date have used only two of the definitional scenarios: the IPCC and FAO scenarios.

3.5.1. Stand Level

Figure 3-2 shows a hypothetical example of the stand-level carbon dynamics of afforestation and reforestation initiated on non-forest land. The diagram shows the accumulation of carbon in trees, dead organic matter, and soils until year 30, when the stand is harvested. At that time, carbon stocks are increasing in the dead organic matter and soil pool, but the stock of carbon in trees is reset to zero and starts accumulating again as the stand regrows. The carbon stocks in dead organic matter plus soils normally increase when new forests are established on non-forest land. The example also shows that the harvest in year 30 produces a step increase in the dead organic matter and soil pool followed by a period of net emissions of carbon because the release from decomposing slash is greater than the carbon uptake in young trees. If the stand shown has been established in 1980 (time zero in the graph) and is harvested and replanted in 2010, this activity would qualify as reforestation in the FAO scenario.

Figure 3-2: Hypothetical stand-level dynamics to illustrate carbon stock changes during reforestation or afforestation. The heavy line represents overall carbon stock change relative to initial stock at time zero. This example assumes planting of trees in an area in which dead organic matter and soil pools are low because there was no forest for some time. The GORCAM model used here is described in Marland and Schlamadinger (1999).

In land-based approach I (see Section 3.3.2), one would report a carbon loss according to the top black line. The loss would be equal to -64 t C ha-1 yr-1 (carbon in 2010 [year 32] minus carbon in 2008 [year 28] = 36 - 100). In land-based approach II, the stock change would be counted beginning at the time of regeneration (i.e., year 30) and would amount to -3 t C ha-1 yr-1 (36 - 39). Under both accounting options, one would report a net loss of carbon, albeit at different rates. Only the exclusion of the decaying harvest slash from the accounting (activity-based approach) would yield a net gain in carbon (the tree growth between years 30 and 32). In the second and subsequent commitment periods, all three accounting approaches would lead to carbon credits. The time at which the carbon stock change on the land switches from negative to positive (year 32 in this example) depends on the decay rate of dead organic matter left on the site after harvest and the growth rate of the new forest.

Simplified versions of this stand-level graph demonstrate which land-cover transitions or events, combined with different definitional scenarios, will create ARD land. Figure 3-3 shows 10 cases of activities (or combinations of activities) that could qualify as ARD. For ease of calculation and demonstration purposes, stands are assumed to grow at a constant rate of 1 t C ha-1 yr-1, and soil, woody debris, and wood product pools are excluded from the analysis. For each example, the stock changes reported under Article 3.3 are compared to real stock changes on the land.

Figure 3-3: Ten different cases illustrating development of stand-level carbon stocks between 1990 and 2012. See Section 3.5.1 and Table 3-9 for descriptions and implications of the graphs.

In Table 3-9, the seven definitional scenarios are applied to the 10 cases in Figure 3-3. The first two rows illustrate whether the D-R Rule and the A/R Debit Rule come into effect. Definitional scenarios are grouped into two broad categories:

  • The IPCC, Land Use, Flexible, Biome, and Aggradation/ Degradation scenarios, which usually create small amounts of ARD land because ARD activities require a change in land classification (IPCC, Land Use, Flexible, and Biome scenarios) or forest management regime (Aggradation/Degradation scenario).
  • The FAO and Land Cover scenarios, which include harvest-regeneration cycles.

In the FAO scenario, we distinguish three accounting rules (Section 3.3.2): land-based I and II, and activity-based. In the cases in Figure 3-3 and Table 3-9, there is no difference between land-based II and activity-based approaches because soil and dead organic matter pools are excluded. In both approaches, carbon accounting begins with the activity or in 2008, whichever is later.
For stands that are harvested and regenerated in the commitment period (Table 3-9, cases 7 and 9), significant debits accrue in combination with the Land Cover and FAO scenarios (FAO only with land-based approach I or II). This debiting is reflected in Table 3-9 in the FAO (land-based approach I) and Land Cover scenarios. It is not reflected in the FAO scenario with land-based approach II, however, because soil and dead organic matter are excluded from this analysis. In the FAO scenario with activity-based approach, carbon credits can be achieved as seen in Table 3-9, cases 7 and 9. Credits occur even though the stocks have decreased over the commitment period and between 1990 and 2012.

Table 3-9: Characteristics of cases 1 to 10 in Figure 3-3 for each of the seven definitional scenarios. The definitional scenario FAO is split into two variants: 1) land-based I (accounting of stock changes between 2008 and 2012; see Section 3.3.2), and 2) land-based II and activity-based (accounting of stock changes between start of activity and 2012; see Section 3.3.2). For all other scenarios, this distinction makes no difference for the cases discussed here; thus, the accounting approaches are not shown separately. Changes in soil and dead organic matter carbon as well as carbon in wood products are generally not considered in this table.

Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8 Case 9b Case 10

  Actual Change in Aboveground Carbon Stocks (t C ha-1)

D-R Rule in effect No No No Yes No No No n/a No No
A/R Debit Rule in effect No No No No Yes No No No No No

Real DC 1990-2012 18 18 -60 -42 2.5 -57.5 -38 -38 -197 0
Real DC 2008-2012 5 5 -60 5 -10 -10 -55 5 -197 -5

Definitional Scenario Reported C Stock Changes 2008-2012 (t C ha-1) under Different Scenarios

FAO (land-based I) 5 5 -60 5(0) -10(0) -10 -55 5 -197 0
FAO (land-based II and activity-based) 5 5 -60 5(0) -10(0) -10 2.5 5 2.5 0
IPCC 5 5 -60 5(0) -10(0) -10 0 0 0 0
Land Use 5 5 -60 5(0) -10(0) -10 0 0 0 0
Land Cover 5a 5a -60 5a(0) -10a(0) -10a -55 5(0) -197 0
Flexible 5 5 -60 5(0) -10(0) -10 0 0 0 0
Degradation/Aggradation 5 5 -60 5(0) -10(0) -10 0 0 -197 0
Biome 5 5 -60 5(0) -10(0) -10 0 0 0 0

Notes: Values in parentheses indicate that Deforestation-Reforestation Rule (D-R Rule)and Afforestation/Reforestation Debit Rule (A/R Debit Rule) considered; n/a = not applicable.
a In Land Cover scenario, a forest is only created-thus, a piece of land considered forested-if the land cover has reached the threshold. The longer the time between establishment of the stand and a commitment period, the more likely that ARD land would have been created.
b This scenario involves conversion of high carbon-density forest to plantation forest (could be referred to as degradation), with a reduction of biomass at maturity from 200 to 100 t C ha-1.

Table 3-9 shows no difference among the IPCC, Land Use, Flexible, and Biome definitional scenarios. Credits and debits in these scenarios are the same as the real 2008-2012 carbon stock changes on the land, except in cases 7 to 10; in the latter four cases, no ARD land is created in the IPCC, Land Use, Flexible, and Biome scenarios because a harvest/regeneration cycle takes place. Note that in cases 4 and 5, although there is indeed a match of real and reported carbon stock changes, the D-R Rule and A/R Debit Rule would alter the reported carbon stock changes. In case 4, this alteration removes the incentive for deforestation between 1990 and 2007, followed by reforestation to generate credits. In case 5, debits are limited to the amount previously credited (which is zero prior to the first commitment period). Thus, use of the D-R Rule and the A/R Debit Rule can prevent credits where deforestation previously lost carbon or debits where there is a long-term increase in carbon stocks through afforestation and reforestation. We note, however, that the D-R Rule will also remove the incentive for reforestation following a deforestation that occurred since 1990 or will occur in the future for reasons unrelated to the creation of carbon credits. Case 9 is of interest because it is a special situation: conversion of high carbon-density forest to plantation forest. Only the FAO scenario with stock change 2008-2012 (i.e., land-based approach I) and the Land Cover and Aggradation/Degradation scenarios manage to reflect at least some of the carbon loss that occurs at the stand level.

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