Carbon Sequestration Potential in Canada, Russia and the United States Under Article 3.4 of the Kyoto Protocol
Kevin Gurney and Jason Neff
Department of Atmospheric Science
Colorado State University,
Natural Resources Ecology Laboratory
Colorado State University
July 2000
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Table of Contents
1.Introduction……………………………………………………………………………………..1
2.Caveats ………………………………………………………………………………………….1
3. Proposed sequestration activities………………………………………………………………2
3.1 Cropland Management……………………………………………………………………….2
3.2 Rangeland Management……………………………………………………….……………..5
3.3 Forest Management……………………………………………………..……..………….….6
3.3.1 Nutrient fertilization…………………………………………………………………6
3.3.2 Fire Management………………………………………………………….………..8
3.3.3Pest Management………………………………………………………….………...9
3.3.4 Additional forestry activities………………………………………………………..10
3.4 Total sequestration potential………………………………………………….……………...11
4. Discussion…………………………………………………………………………….………….12
4.1Cross-cutting scientific/technical issues……………………………………………………...12
4.2 Cross-cutting methodological issues……………………………………….………………...14
4.3 Benefits………………………………………………………………….…….……………...15
5. Conclusions……………………………………………………………………………………… 15
6. References…………………………………………………………………………………….….17
7.Units and Abbreviations……………………………………………………….………….….…22
List of Figures
Figure 1. Simulated total soil carbon for the central U.S. corn belt (Lal et al., 1998)…………………...23
Figure 2. Sensitivity of fire suppression emission reductions to reduction level
and area burned…………………………………………………………………….…………24
Figure 3. Zonally averaged simulated versus observed CO2 concentration
(Keeling et al., 1989)…………………………………………………………………………25
List of Tables
Table 1. Cropland management sequestration……………………………………………….………….26
Table 2. Rangeland management sequestration…………………………………………………………26
Table 3. Nitrogen fertilization response ………………………………………………….……………..27
Table 4. Forest management sequestration……………………………………………………………..27
Table 5. Mean global carbon budget for the 1980s (after Schimel et al., 1996)…………………………28
1. Introduction
As the negotiations regarding the international treaty on climate change, known as the Kyoto Protocol, move forward, the possibility of transferring carbon between the atmosphere and the biosphere as an offset to industrial greenhouse gas emission reduction commitments has taken on increased emphasis. While inclusion of atmospheric/biospheric exchange may penalize some countries that are increasing their net biotic emissions, much of the motivation comes from the interest in substituting fossil fuel emission reductions with carbon sequestration in vegetation and soils.
The inclusion of atmospheric/biospheric exchange stems from two paragraphs within the section of the Protocol in which the agreed-to levels of emission reductions are specified (United Nations, 1997). The first of these paragraphs, Article 3.3, allows participating countries to modify their greenhouse gas (GHG) emission reduction commitments by activities limited to afforestation, reforestation, and deforestation.[1],[2] These activities must have occurred “since 1990” and must be “human-induced”. While the precise meaning of this paragraph has yet to be enumerated, the expectation is that growing trees where none had been before would be interpreted as an emission reduction but clearing of land without some form of reasonable biotic regeneration would be considered as additional emissions (United Nations, 1998).
The second paragraph relating to this issue, Article 3.4, leaves open the option of adding biotic exchange activities, other than those specified in Article 3.3, to further modify the emission reduction commitments agreed-to by participating countries.
Much attention to date has been devoted to the details of Article 3.3 such as defining “afforestation”, “deforestation”, and “reforestation”. However, discussion has recently begun on Article 3.4. Much of this relates to what additional biotic exchange activities should be allowed as further offsets to fossil fuel emission reductions (United Nations, 1999a; Nabuurs, 1999). The most commonly cited categories include carbon sequestration within agricultural, rangeland and forest systems.
Though the details of how such activities might be included in the calculus of the Protocol have yet to be specified, it is instructive to examine the magnitude of these proposed activities to offset greenhouse gas emission reductions and place them within the political context of the Protocol. This has been done for three key countries with large and active biospheric carbon stocks: Canada, Russia, and the United States.
2. Caveats
A few caveats must be made in relation to the carbon sequestration estimates presented here. First, the estimates represent technically feasible sequestration potential given the current status of land-use within Canada, Russia, and the United States. A number of barriers may exist for realizing these technical potentials, not the least of which are constraints such as financial burden or social barriers.
Where possible, these estimates also attempt to limit the sequestration potential to activities considered additional to what might be considered “business as usual”. This is a key political issue within the confines of the Kyoto Protocol often referred to as “additionality”. Article 3.4 of the Protocol includes no explicit provision for additionality. It does, however, indicate that the negotiators must determine "how" activities are to be added to Article 3.4 leaving open the possibility that additionality may be a consideration. Furthermore, Article 12, referring to the enactment of emission offsetting projects in other countries, does certify emission reduction projects that are “additional to any that would occur in the absence of the certified project activity” (United Nations, 1997). As explained later, additionality may prove to be a necessary provision in the further elaboration of Article 3.4.
It is not yet apparent whether or not carbon sequestration credit gained under Article 3.4 will be applied to the first commitment period specified within the Protocol.[3] Though it is possible that these activities will only be applied to future commitment periods, they are cast here in relation to the first commitment period targets.
Finally, it must be understood that all the estimates presented here are prone to considerable amounts of uncertainty. They are gathered from land use datasets and studies that employ different methodologies and assumptions about driving variables. To the extent possible, adjustments have been made to bring them all within the same metric. Some of the sequestration activities discussed in this report have received country-scale analysis by others and, as such, have been incorporated directly. However, some of the activities presented here have had only global or very little country-scale analysis. In these instances, original estimates have been constructed.
The sequestration potentials presented here are cast relative to two different benchmarks. The first benchmark is the magnitude of emissions reduction below 1990 levels agreed to in the construction of the Kyoto Protocol in 1997. Canada agreed to a 6% reduction which amounts to roughly 10 Mt C/year (United Nations, 1999b).[4] Russia agreed to stabilize their emissions at 1990 levels (United Nations, 1999b). Finally, the United States agreed to a 7% reduction which amounts to roughly 115 Mt C/year (US EPA, 1999). Casting the sequestration potential of activities within Article 3.4 relative to this amount highlights the political implications of additional activities.
The other benchmark relates to the reduction that would be necessary in the future if emissions follow current projections. At some point prior to the first commitment period, participating countries would need to engage in some form of reduction program to meet their Kyoto commitment. Were emission reductions begun in 1997 (the last year of reliable emissions data), Canada would need a reduction of approximately 33 Mt C/year in order to meet their target in the first commitment period (United Nations, 1999b). Were emission reductions begun in 2005, the required reduction would be approximately 49 Mt C/year. The same two benchmarks applied to the United States come to 300 and 515 Mt C/year, respectively (US EPA, 1999). It is physically meaningful to place the carbon sequestration potential within this context. This will give an indication of how much of the necessary reduction additional activities within article 3.4 might achieve were they pursued to the maximum technically feasible level.
Russian emissions dropped considerably after 1990 and are not expected to recover to 1990 levels by the first commitment period. Current projections suggest that the Russian Federation will emit at levels roughly 250 Mt C/year below their levels in 1990 (United Nations, 1999b). Therefore, any additional carbon sequestration will likely add to this projected surplus.
With these two values as benchmarks the relative magnitude of the carbon sequestration activities under Article 3.4 can be placed into a meaningful context.
3. Proposed sequestration activities
3.1 Cropland management
Compared to native ecosystems, land that has undergone cultivation generally contains smaller amounts of carbon (Paustian et al., 1997a). Figure 1 shows a simulation of this effect for a substantial portion of the Central United States. This and similar studies indicate that soils typically lose up to 50% of their original carbon content in the first few decades following cultivation (Schlesinger, 1986).
Under non-managed conditions, soils lose carbon primarily through microbial respiration. This loss is typically balanced by input from aboveground litter deposition and root turnover in the soil column. Cultivation of land for agricultural purposes, however, typically increases the rate of soil carbon loss and slows the rate of soil carbon input (Paustian et al. 1997b). The former occurs because plowing increases the availability of soil organic material, affording microbes greater access to the carbon within soil aggregates. Erosion further increases the loss of carbon through wholesale removal of soil. Cultivation slows the input of carbon to the soil by the removal of aboveground biomass at harvest.
Reversing the decline in soil carbon is desirable from a purely agricultural perspective, as greater levels of soil carbon indicate higher soil quality. Many of the practices recommended in the past as aids to increasing soil carbon are now cited by those suggesting agricultural soils as a means to assist in atmospheric CO2 removal.
The sequestration activities commonly considered under cropland management can be classified as land conversion, land restoration, or improved management of cultivated land. Land conversion generally refers to temporary “set-asides” or retirement of cultivated land. An example from the United States is the Conservation Reserve Program (CRP) in which agricultural land is removed from production for ten-year periods, primarily to reverse degradation and control over-production. Removal is often accompanied by reseeding with perennial vegetation which can increase the soil carbon content. Land conversion also includes projects such as the creation of cultivated field borders, wetland restoration, and grassed waterways. It is worth noting that if set-aside lands are returned to cultivation, the carbon gained during the retirement period may be lost to the atmosphere, leading to no net atmospheric carbon removal in the long-term.
Recent estimates suggest that there are currently 0.5 Mha of land in Canadian set-aside programs but that an estimated 0.5 Mha of additional land could be added with directed policy (Bruce et al, 1999). Uptake rates are estimated at 60 g C/m2/year for existing land and 80 g C/m2/year for new lands. Assuming the existing set-aside land constitutes an approximation to a baseline, Canada could achieve approximately 0.4 Mt C/year of sequestration in the 2008 to 2012 period. The same authors estimate that there are 8.7 Mha of potential set-aside land in the United States (12.8 Mha are currently in the Conservation Reserve Program) which, when considered with an uptake rate of 80 g/m2/year, comes to a sequestration rate of 7 Mt C/year.
Estimates for Russia are not available.
It is important to note that uptake rates of 80 g/m2/year will likely only occur in the first decade or two after initial retirement of cultivated land. Other authors have found much lower uptake rates on land that had been retired many decades prior to measurement (Burke et al, 1995). This is a critical factor if this sequestration activity is to be considered in Kyoto Protocol commitment periods beyond the first.
Land restoration refers to the active restoration of eroded and severely degraded land. Eroded lands are those that experience erosion at rates exceeding 11.2 Mg/ha/year (Lal et al., 1998). In Canada and the United States, estimates suggest that approximately 1.5 Mha and 28.6 Mha, respectively are available for restorative measures such as reversion to natural vegetation and fertilization (Bruce et al., 1999). Degraded lands refer to minelands and salt-affected soils of which about 0.1 Mha and 0.6 Mha are suggested as available. Approximately 2.2 Mha and 20 Mha of salt-affected soils are considered available for restoration in Canada and the United States, respectively. Combining these available areas with uptake rates ranging from 10 to 100 g/m2/year (varying with the practice and land-type included) results in an annual potential sequestration rate of 1 Mt C/year for Canada and 17 Mt C/year for the United States (Lal et al, 1998; Bruce et al, 1999).
Estimates for Russia are not available.
Improved management of cultivated land refers to improved tillage, water management, and cropping practices that can increase the levels of soil carbon. Improved tillage practices encompass a variety of tillage systems that reduce the loss of soil and water from cultivated land. Such “conservation tillage” (CT) systems leave more crop residue on the soil surface and lessen the amount of soil aggregate disturbance relative to conventional tillage practices, thereby increasing soil carbon levels. Other improved management techniques such as the expansion of irrigation in dry areas, can increase soil carbon by increasing aboveground and belowground biomass production. However, irrigation is often associated with significant energy use and when practiced in arid regions, may result in net carbon loss due to the precipitation of calcium carbonate from irrigation water with dissolved calcium (Schlesinger, 1999). This could significantly limit the sequestration potential of irrigation.
Finally, improved cropping practices such as increased fertilization, increased rotation and cover crop use, and elimination of summer fallow can lead to greater amounts of soil carbon. Once again, however, increased energy use must be considered in order to arrive at a true net sequestration potential. For example, a recent discussion suggested that the net effect of inorganic fertilizer is fundamentally sensitive to the trade-offs between fertilization levels and marginal productivity (Schlesinger, 1999; Izaurralde et al, 2000). With an economically optimal level of fertilization, net carbon storage can be achieved, though modified by the energy costs associated with manufacture, transport, and application. Exceeding optimal application levels, however, can eliminate carbon sequestration gains.
Much research has been performed on the impact of different agricultural practices on soil carbon. Most of this has focused on soil quality and nutrient dynamics. For example, one recent study used the CENTURY biogeochemistry model to simulate soil carbon sequestration in Canada under summer fallow reduction (Dumanski et al., 1998). Depending upon the choice of crop in the summer fallow reduction (hay versus cereal), approximate annual sequestration rates came to 0.4 Mt C/year and 1.8 Mt C/year for hay and cereal, respectively.
Other studies have considered the impact of tillage reduction on carbon sequestration. A recent study suggests that adopting reduced-till on 50% of Canada's arable land results in an average sequestration of approximately 4 Mt C/year (Nabuurs et al., 1999). Another recent study arrived at a similar estimate of 4.3 Mt C/year (STOP, 1999). This same work estimated Canadian summer fallow reduction at roughly 0.7 Mt C/year.
A study by Bruce et al (1999) combined practices such as reduced tillage, reduced summer fallow, improved nutrition, and improved amendments and irrigation to arrive at a total sequestration of 7.4 Mt C/year for Canada. Many of these practices will be employed in the future irrespective of climate change policy. Though difficult to estimate, the studies cited thus far imply 1 to 2 Mt C/year as a reasonable baseline for Canada.
Estimates of sequestration due to improved land management in the United States vary somewhat due mostly to assumptions regarding the amount of land that might be incorporated into best management practices in the future. A recent study by Donigian et al (1997) indicate that approximately 6 Mt C/year might be sequestered due to the use of cover crops on all US cropland beyond a projected baseline. Another estimate placed the total at 10.2 Mt C/year, though no explicit baseline was included (Lal et al, 1998).
Increased employment of reduced or no-tillage practices have been estimated at anywhere from 5 to 40 Mt C/year depending upon assumptions about uptake rate (18 to 40 g/m2/year) and land area considered (20 to 123 Mha) (Lal et al, 1998; Nabuurs et al 1999; Kern and Johnson, 1993; Donigian et al, 1997).
The Bruce et al (1999) study which combined a variety of management practices including no-till and increased use of cover crops among others, concluded that improved management in the US could average roughly 20 Mt C/year (a baseline has been removed).
Though the estimates for improved cropland management in the US vary quite a bit, we present a range of 10 to 50 Mt C/year as a reasonable estimate of potential US sequestration in this category.
Estimates of cropland sequestration in Russia considered a variety of practices. Assuming conservation tillage is applied to 33 Mha of cropland (133 Mha total) with an uptake rate of 20 g/m2/year, this practice could total 6.7 Mt C/year (GCSI, 1999). An estimate of a baseline for this activity in Russia is 4.2 Mt C/year. The same study estimated the sequestration resulting from an improvement in irrigation of currently irrigated land (which totals 5.4 Mha). With an uptake rate of 10 g C/m2/year, sequestration for this activity totals 0.5 Mt C/year. Finally, improved productivity is considered with an average uptake rate of 20 g/m2/year. It is difficult to estimate to what extent improved productivity might be applied to Russian cropland. Assuming an adoption range of 10 to 20% of current cropland in Russia, the total sequestration rate in this category could come to 2.7 to 5.4 Mt C/year.
The above estimates for cropland management in Canada, Russia, and the United States are presented in Table 1.
3.2 Rangeland Management
Management of rangelands has also been suggested as a means by which carbon can be removed from the atmosphere. Like agricultural sequestration discussed above, this also removes atmospheric carbon by transferring it to vegetation and ultimately into the soil.
Within temperate countries rangeland can be classified into two broad categories. The first, extensive rangeland, refers to grazing areas for which no amendments, such as fertilizer or water, are applied. The other broad classification is referred to as intensive rangeland or pasture; grazing areas which are managed with the addition of amendments to maintain high forage quality.
Research aimed at understanding the relationship between grazing pressure and soil organic matter indicate that the relationship is a complicated one (Milchunas and Lauenroth, 1993; Frank et al., 1995; Burke et al., 1997; Manley et al., 1995). In some cases, increasing pressure leads to increases in soil carbon while in other instances a reduction in grazing pressure leads to a reduction in soil carbon (Milchunas and Lauenroth, 1993). These counterintuitive results point to the fact that the dynamics determining soil organic matter in grazed systems is not a straightforward one and includes factors such as grazing history, soil type, and plant species composition.