As Table 3-17 shows, afforestation and reforestation potentially could achieve annual carbon sequestration rates in aboveground and below-ground biomass of 0.4-1.2 t ha-1 yr-1 in boreal regions, 1.5-4.5 t ha-1 yr-1 in temperate regions, and 4-8 t ha-1 yr-1 in tropical regions (Dixon et al., 1994; Nabuurs and Mohren, 1995; Nilsson and Schopfhauser, 1995; Brown et al., 1996; Yamagata and Alexandrov, 1999). The latter two values assume that there is 0.3 t C m-3 of wood in boreal and temperate regions and 0.4 t C m-3 wood in tropical regions (Nilsson and Schopfhauser, 1995). The maximum amount of carbon that might be sequestered by global afforestation and reforestation activities for the 55-year period 1995-2050 was estimated at 60-87 Gt C, with about 70 percent in tropical forests, 25 percent in temperate forests, and 5 percent in boreal forests (Brown et al., 1996). Hence, an average maximum potential carbon sequestration rate would be 1.1-1.6 Gt yr-1 above and below ground (Brown et al., 1996). Although these maximum values represent about 2 percent of the annual global carbon uptake by the terrestrial biosphere, they are much higher values than would be expected from ARD activities in all but the most broadly defined ARD lands (e.g., FAO or Land Cover definitional scenarios).
Table 3-17: Estimate of accounted average annual carbon stock change for ARD activities. The IPCC and FAO Definitional Scenarios and three accounting approaches under the FAO Definitional Scenario have been applied to illustrate with the available data the effect of different accounting approaches. Other Definitional Scenarios described in Table 3-4 have not been included in this analysis. It is assumed that recent area conversion rates ["recent" = for Annex I Parties AR late 1980s/early 1990s and for D 1980s (except for Canada and Russian Federation early 1990s); ARD in other regions 1980s] have applied since 1990 and will continue to do so through the first commitment period. It is also assumed that current uptake rates apply during the first commitment period. The figures and ranges of values in the table are illustrative and provide first-order estimates, and may not encompass the full range of uncertainties. Negative numbers indicate carbon emissions and positive numbers carbon removals. | ||||||||
|
||||||||
Estimated Range of Accounted Average Annual Stock Change 2008-2012 (Mt C yr-1)h | ||||||||
AR Average
|
Area Change (Mha yr-1)
|
Includes carbon in aboveground and below-ground biomass, excludes carbon in soils and DOC | ||||||
Region |
Activity
|
Rate of Uptaked
(t C ha-1 yr-1); D Average Stocka,d (t C ha-1) |
Post-Harvest
Regeneration |
Conversion
between Non-Forest and Forest |
FAO Definitional
Scenario Land-Based I Accountingb |
FAO Definitional
Scenario, Land-Based II Accountingb |
FAO Definitional
Scenario, Activity-Based Accountingb |
IPCC
Definitional Scenariob |
Boreal Region |
AR
|
0.4 0.8 1.2
|
3.1e
|
0.1e
|
R: -209 -191 -164
A: 0.2 0.7 1.6 -18 -227 -208 -180 |
R: -56 -38 -10
A: 0.2 0.7 1.6 -18 -74 -55 -26 |
R: 5 21 46
A: 0.2 0.7 1.6 -18 -13 4 30 |
AR: 0.2 0.7 1.6
-18 -18 -17 -16 |
Total (= Annex I)g |
D
Total ARD |
35
|
0.5e
|
|||||
Temperate Region |
AR
|
1.5 3 4.5
|
5.4e
|
0.5e
|
R: -557 -351 -125
A: 7 25 44 -72(j) -622 -398 -153 |
R: -141 49 259
A: 7 25 44 -72j -206 2 231 |
R: 74 265 475
A: 7 25 44 -72j 9 218 447 |
AR: 7 25 44 |
Annex Ig |
D
Total ARD |
60
|
1.2e,i
|
|||||
Annex I Totalg |
AR
|
8.5e
|
0.6e,i
|
R: -766 -542 -289
A: 7 26 46 -90 -849 -606 -333 |
R: -197 11 249
A: 7 26 46 -90 -280 -53 205 |
R: 80 289 527
A: 7 26 46 -90 -3 225 483 |
AR: 7 26 46
-90 -83 -64 -44 |
|
D
Total ARD |
1.7e
|
|||||||
Temperate Region |
AR
|
1.5 3 4.5
|
n/a
|
1.9f,i
|
R: n/a
A: 27 93 167 -126 n/a |
R: n/a
A: 27 93 167 -126 n/a |
R: n/a
A: 27 93 167 -126 n/a |
AR: 27 93 167
-126 -99 -33 41 |
Total |
D
Total ARD |
60
|
2.1c
|
|||||
Tropical Region |
AR
|
4 6 8
|
n/a
|
2.6f
|
R: n/a
A: 170 305 415 -1644 n/a |
R: n/a
A: 170 305 415 -1644 n/a |
R: n/a
A: 170 305 415 -1644 n/a |
AR: 170 305 415
1644 -1474 -1339 -1229 |
Total |
D
Total ARD |
120
|
13.7c
|
|||||
Global Total |
AR
|
n/a
|
4.6
|
R: n/a
A: 197 399 584 -1788 n/a |
R: n/a
A: 197 399 584 -1788 n/a |
R: n/a
A: 197 399 584 -1788 n/a |
AR: 197 399 584
-1788 -1591 -1389 -1204 |
|
(summing regional totals) |
D
Total ARD |
16.3
|
||||||
|
||||||||
n/a = Area of regeneration after harvest not available. In addition, regeneration after selective cutting, as is often used in tropics, is difficult to capture with the FAO Definitional Scenario. a Literature sources do not allow estimation of uncertainty levels of carbon
stocks prior to deforestation or of areas deforested. |
||||||||
|
Note that the annual carbon sequestration value is not constant; it will vary from year to year with annual weather conditions and would change over longer terms. Nilsson and Schopfhauser (1995) calculated a mean annual global carbon increment of 0.4 Gt C yr-1 above ground, with an additional 0.1 Gt C yr-1 below ground, from potential afforestation and deforestation 20 years after initiation of an optimum set of global forest plantations. Neither the value derived from Brown et al. (1996) nor that from Nilsson and Schopfhauser (1995) included carbon losses to deforestation or degradation from tropical fuelwood extraction (Alcamo et al., 1996; Solomon et al., 1996), from deteriorating climate, or from increasing agriculture (Cramer and Solomon, 1993; Alcamo et al., 1996).
The FAO scenario (with the activity-based approach) and the IPCC scenario produce different estimates of potential carbon stock changes. Under the IPCC definitional scenario, if Annex I countries (approximated by the estimates for boreal and temperate region Annex I countries in Table 3-17) maintain recent rates of afforestation and reforestation from 1990 through 2012, the estimated rate of increase in carbon stocks from these activities would be 7-46 Mt C yr-1. Under the same assumptions, this increase would be offset by estimated decreases in carbon stocks from deforestation of 90 Mt C yr-1, producing a net change of -83 to -44 Mt C yr-1. Under the FAO definitional scenario using the activity-based accounting approach (i.e., the stock change accounting does not start before the activity, nor does it include carbon loss from decaying slash), if Annex I countries maintain recent rates of afforestation and reforestation from 1990 through 2012, the estimated rate of increase in carbon stocks from these activities would be from 87-573 Mt C yr-1, with estimated decreases in carbon stocks from deforestation of 90 Mt C yr-1-producing a net change of -3 to 483 Mt C yr-1. Under the FAO scenario using land-based accounting approach I, the estimated stock change from afforestation and reforestation activities continued at recent rates would be -759 to -243 Mt C yr-1 and from deforestation activities -90 Mt C yr-1, resulting in an estimated net stock change of -849 to -333 Mt C yr-1. Under the FAO scenario using land-based accounting approach II, the estimated stock change for afforestation and reforestation activities continued at recent rates would be -190 to 295 MtC yr-1 and from deforestation activities -90 Mt C yr-1, resulting in an estimated net stock change of -280 to 205 Mt C yr-1.
Under the IPCC definitional scenario, if recent rates of afforestation and reforestation are increased by 20 percent and rates of deforestation decreased by 20 percent in Annex I countries from the year 1990, carbon stocks would increase by 7-49 Mt C yr-1 due to afforestation and reforestation activities and decrease by 72 Mt C yr-1 due to deforestation activities, resulting in a net change in carbon stocks from these activities of -83 to -23 Mt C yr-1 in Annex I countries. For comparison purposes, increases in carbon stocks from afforestation and reforestation globally using the IPCC definitions could result in a stock change of about 197-584 Mt C yr-1 and decreases from deforestation of about 1,788 Mt C yr-1 if current rates are maintained.
In the IPCC Definitional Scenario and FAO Definitional Scenario with land-based I accounting approach, the accounted carbon stock changes are broadly consistent with the 2008-2012 actual changes in carbon stocks from land under Article 3.3. The IPCC and FAO Definitional Scenarios bring different amounts of land under Article 3.3, hence the estimated carbon stock changes in Table 3-17 differ. In the FAO Definitional Scenario with land-based II and activity-based accounting approaches, the accounted carbon stock change is not consistent with the 2008-2012 actual changes in carbon stocks on land under Article 3.3, except in the case of short rotation cycles. In neither of the two Definitional Scenarios is the accounted carbon stock change consistent with the 2008-2012 actual carbon stock changes, nor with the net exchanges with the atmosphere, at the national and global levels in part because the land under Article 3.3 is small in comparison with the national and global forest area (see Section 3.5.2.5).
Other reports in this collection |