As the negotiations regarding the international treaty on ...



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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

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

3.3.3 Pest Management………………………………………………………….………... 9

3.3.4 Additional forestry activities……………………………………………………….. 10

3.4 Total sequestration potential………………………………………………….……………... 11

4. Discussion…………………………………………………………………………….…………. 12

4.1 Cross-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.

In contrast, a number of activities can be performed on intensive rangelands to sequester carbon such as rotational grazing, fertilization, irrigation, and sowing of favorable forage grasses and legumes. Were the best management practices to be engaged on all of Canadian and US intensive rangeland, estimates have placed this potential at an average sequestration rate of approximately 0.6 Mt C/year and 9 Mt C/year, respectively (Bruce et al., 1999). This estimate assumes that an uptake rate of 20 g C/m2/year is achieved over approximately 4.3 Mha and 51 Mha of Canadian and US pastureland, respectively.[5],[6] As with some of the agricultural practices, fertilization and irrigation may incur an energy penalty that negates some or all of the sequestration achieved.

The study by STOP (1999) included a more gradual introduction of improved practices in Canada arriving at a sequestration rate of 0.2 Mt C/year by the first commitment period.

In Russia, a recent study assumed an average uptake rate of 5.5 g/m2/year applied across 78 Mha of intensive rangeland, arriving at a total sequestration rate of 4.3 Mt C/year (GCSI, 1999). This is likely to be an unrealistic adoption rate in the near term. Assuming between 10 and 20% of available Russian pasture were engaged in improved pasture management, the sequestration rate would be 0.4 to 0.8 Mt C/year.

The above estimates for rangeland management in Canada, Russia, and the United States are presented in Table 2.

3.3 Forest Management

Forests can be managed to increase carbon stored in both above and belowground biomass. Like the other strategies outlined in this paper, carbon sequestration techniques in forests have been practiced in the past for reasons such as maximizing yield and biodiversity.

Forest management practices considered for carbon sequestration include the addition of amendments such as nitrogen fertilizer, longer rotations, less invasive selective cutting, soil conservation, safeguarding regeneration (from pests, fire, etc), recycling forest products, genetic engineering, and lengthening the residence time of durable products or forest products in landfills.

Most of the analysis performed on national carbon sequestration in the forest sector has focused on activities covered under Article 3.3; afforestation, deforestation, and reforestation. A far smaller amount of analysis has been performed on the implications of Article 3.4.

3.3.1 Nutrient fertilization

Nitrogen availability limits productivity in many temperate forest ecosystems and the addition of nitrogen fertilizer generally increases forest growth (Peterson and Peterson, 1995; Van Cleve, 1973). The response of forest ecosystems to nitrogen additions are, however, variable and depend upon a wide range of factors including soil type, pre-existing nitrogen levels, plant nitrogen demand and stand characteristics such as age and health. While forest growth is frequently limited by nitrogen availability alone, the addition of nitrogen in combination with phosphorus and potassium can lead to even larger increases in productivity (Peterson and Peterson, 1995; Morrison et al, 1997).

The growth of boreal forests, the dominant type in Canada and Russia, are also constrained by a number of additional factors, not the least of which is a harsh climate. In the United States, approximately 1/6th of the forest area is limited by water and/or temperature and is therefore unlikely to respond significantly to fertilization (Hagenstein, 1992). These additional constraints can limit forest response and may make fertilization more effective in climatically favorable areas (Van Cleve and Zasada, 1976). In addition, fertilization tends to be most effective on lands that are neither exceedingly fertile nor exceedingly poor. The intermediate range of ecosystem fertility is generally the target for commercial fertilization operations (FFH, BC gov, 1995).

In managed forest ecosystems in Canada, fertilization is used to accelerate stand development and is generally applied to young and intermediate age forest stands under active management (FFH, BC Gov, 1995). Publications by the government of British Columbia’s forestry department recommend fertilization of Douglas fir and perhaps western hemlock and Sitka Spruce (FFH, BC Gov, 1995).

Although it is possible to increase the growth of mature stands in forest reserves not managed for timber harvest, these increases are likely to be smaller than in younger forests (e.g.Van Cleve and Zasada, 1976; Morrison et al, 1976), though this is not always the case (Miller and Webster, 1979). Forests characterized as over mature (a considerable fraction of Canadian and Russian forests) are unlikely to respond strongly to nitrogen additions because other factors limit their growth rates. There is substantial variation in the response of different tree species to fertilization and important interaction between site characteristics and fertilization responses (Morrison et al, 1976; Morrison et al, 1977; Nams et al (1993) et al, 1993; Peterson and Peterson, 1995).

There is little information on the response of interior Canadian (or Russian) forests to large-scale fertilization. However, black spruce, white spruce and aspen make up a large portion of the interior and boreal forests of Russia and Canada and all of these species have been shown to respond positively to fertilization (Morrison et al, 1976; Morrison et al, 1977; Nams et al, 1993; Peterson and Peterson, 1995).

It is important to note that there are a variety of uncertainties and limitations in estimating carbon sequestration as a result of nitrogen fertilization in forest systems. A review of existing studies on this topic highlights the fact that different tree species may respond quite differently to nitrogen fertilization. For example, in studies on the same site in Southwestern Yukon, Canada, nitrogen additions increased twig growth in white spruce by 60-160% while having no significant effects on balsam poplar (Nams et al, 1993).

Fertilization may also alter soil carbon storage but these aspects of ecosystem responses to fertilization are poorly understood. There is evidence that nitrogen fertilization increases the decomposition of cellulose and litter in a range of systems including prairie (Hunt et al, 1988) and pine forests, alpine meadows (Arnone et al, 1997), and dwarf shrub pine systems (Paavilainen, 1984). However, there is also evidence to suggest that nitrogen fertilization has no effect on decomposition of litter in jack pine and red cedar forests (Prescott, 1995), peat lands (Aerts et al, 1995), or root decomposition in loblolly pine plantations (King et al, 1997). In some cases, it appears that even the form of nitrogen added to soils can influence the direction of the decomposition response: in an experiment with western hemlock litter, decomposition increased following urea additions, but decreased after nitrate additions (Gill and Lavender, 1983).

These variable responses in soil carbon are significant because of the large stock of soil carbon in boreal ecosystems. In fertilization trials in Sweden, Mäkipää et al, (1998) observed a 14% increase in soil carbon stocks over a 26-30 year period of fertilization, corresponding to an annual increase of 73-85 kg C/ha. Extrapolated to the 120 Mha of managed Canadian forest, these rates of carbon uptake would translate into 8.7 to 10.2 Mt C/year due to soil carbon storage alone. However, even at these large storage rates, these increases would not be detectible on short time scales (less than 2-5 years) using conventional soil carbon measurements that have analytical errors of 1-2%.

For the purposes of this assessment, we have not attempted to evaluate species-specific responses to fertilization nor have we estimated interactions between site quality and fertilization response. To carry out these assessments would push the limits of currently available scientific data. Instead, we constrain this analysis to forested areas that are relatively easy to access, (defined as those already under management) and forests in the immature, young and middle-aged age classes as candidate lands for fertilization induced carbon sequestration in Canada and Russia.

The proportional increases in biomass in selected boreal forest fertilization studies are shown in Table 3. In general, nitrogen fertilization increases carbon sequestration into aboveground biomass by 10 to 100%, for either overall site NPP or volume increment measurements. A recent review suggested that the potential for carbon uptake associated with fertilization in Canada ranges from 0.03 to 0.19 t C/ha/year and 0.08 to 0.48 for the United States (Nabuurs et al, 1999). Higher values may also be possible. For example, Lunnan et al, (1991) report uptake rates of 0.7 to 0.8 t C/ha/year for two boreal pine forests in Norway. For boreal Scotts Pine, Mäkipää et al (1998) use a combination of experimental data and models to estimate an annual fertilization uptake of 0.4 t C /ha/year for a dry forest.

Published estimates of the potential for nitrogen fertilization induced carbon uptake across the exploitable forests in the United States (196 Mha) come to 15.7 to 94.1 Mt C/year (Nabuurs et al, 1999). In contrast to the United States where the timber productive land is dominated by young age classes due to intensive harvesting for the past century, Canada and Russia contain relatively large portions of old growth forest (particularly in the boreal regions) that have not been actively harvested, due to inaccessibility, unfavorable climatic conditions and lower population densities.

The extent of timber productive forest in Canada is roughly 245 million hectares (Lowe et al, 1994). Each year approximately 700,000-900,000 hectares of Canadian forests enter management (less than 1% of the total managed forest area in Canada). While it may be expensive and environmentally disruptive to fertilize vast tracks of forest (see discussion below), there is no question that there are large areas of Canadian forest land that could, in theory, be fertilized to increase carbon sequestration rates. To estimate the potential carbon uptake of widespread fertilization activities in Canada we have excluded mature and overmature forests in the Canadian timber productive forest and all forests that are not managed for timber harvests. The remaining 142 million hectares are made up of young aged stands some small fraction of which have previously received fertilizer applications. Applying the Nabuurs et al (1999) estimated Canadian uptake rates to this area yields an annual sequestration of 4.2 to 27 Mt C/year. Using higher values of uptake such as those reported by Lunnan et al, (1991), yields a sequestration estimate of 107 Mt C/year for Canada.

In Russia, the area of managed forest is 761 million hectares, 19% of which is located in forest tundra, sparse taiga, steppe, semi-dessert and dessert (Shvidenko et al, 1997). These areas will be excluded from the analysis presented here. The remaining 616 million hectares include a mixture of age classes ranging from young to overmature. Excluding the mature and overmature stands, there are approximately 230 million hectares of young to intermediate aged Russian forests under management which could be fertilized to increase carbon sequestration. Application of the Nabuurs et al, (1999) fertilization/carbon uptake rates over this entire zone yields uptake estimates of 7 to 44 Mt C/year and at a higher uptake rate of 0.8 t C/ha/year, Russian forests could sequester up to 184 Mt C/year.

Nitrogen additions to ecosystems have a range of effects besides increasing carbon storage. For example, nitrogen additions generally increase the loss of nitrous oxide (N2O), a potent greenhouse gas, from soils. While absolute emissions rates are considerably lower than carbon fluxes from terrestrial ecosystems, N2O is roughly 200 times more powerful as a greenhouse gas and fertilization increase N2O emissions into the atmosphere many fold (Schimel et al, 1996). Nitrogen additions also frequently reduce rates of methane (CH4) oxidation in soils, thereby either reducing soil sinks for CH4 or increasing CH4 fluxes from soils (Delgado et al, 1996; Neff et al, 1994). Widespread application of nitrogen fertilizer for the purpose of carbon sequestration in northern latitude ecosystems will almost certainly increase the production and loss of N2O and methane from these systems partially offsetting the atmospheric carbon removal. More research is required to understand these tradeoffs.

We have not attempted to subtract a baseline for fertilization activities because it is not currently a widespread activity in forest management, particularly in Canada and Russia. If fertilization is considered as a tool for carbon sequestration in Russian, Canadian, and US forests, a detailed analysis of the costs, and relative benefits of fertilization in multiple forest and soil types will be required. Until such an analysis is completed, it will be difficult to reduce the range of uncertainty in estimates of the potential carbon accumulation possible with increased used of fertilization in forest management.

3.3.2 Fire Management

The global emissions of carbon from fires in boreal forests may approach 1 Pg of carbon per year (Harden et al, in press; Kasischke et al, 1995). Boreal forest fire emissions have been substantially altered by fire suppression over the past century, and may soon increase in response to regional climate warming (Linder et al. 1997; Kronberg, 1998; Harden et al., in press; Solomon et al, 1993; Wotton and Flannigan, 1993). Even small increases in fire suppression activities can have large impacts on carbon emissions because of the large fluxes involved.

Annual burns in Canada and Russia cover millions of hectares of forest. In Canada, 3 million hectares of forests burned in 1996 (increased from 1 million in 1980) however the area burned varies substantially from year to year (Simard, 1997). In Russian forests an average of 1.5 million hectares burned annually from 1986 to 1995 with a range from 0.17 million hectares in 1990 to 4.4 million hectares in 1987 (Shvidenko et al, 1998).

The severity of a fire and the landscape in which it occurs strongly influence the amount of carbon that is lost during combustion and subsequent decomposition of soils and residues. On average, 30 to 100% of above ground biomass is consumed in fires (Dyrness and Norum, 1983; Stocks, 1987). With boreal forest carbon content of 4 to 12 kg C/m2 in living biomass and ground layer vegetation, a year in which 3 million acres burned would lead to a net emissions range of 60 to 180 Mt of C/year in Canadian forests. This assumes a 50% loss of the biomass pools. Using similar carbon contents and biomass loss in Russian forests, annual carbon emissions from a 1.5 Mha fire are likely to be in the range of 30 to 90 Mt per year. These fluxes are due to combustion alone and do not take into account emissions from accelerated soil respiration following fire. The flux of CO2 from soils to the atmosphere resulting from post-fire enhancement of soil respiration can be up to 6 times larger (Levine 1991; Melillo et al. 1988) than losses of carbon due to combustion.

In boreal forests (largely in Canada and Russia), Kurz and Apps (1995) have estimated that a 50% reduction in forest fires each year would result in the storage of 2.3 Gt of carbon by 2050 (46 Mt C/year reduction). Because fire frequency, extent and severity are highly variable, a range of emissions reduction scenarios are shown in Figure 2. The scenarios range from 5% to 20% reductions in fire extent for Canada and Russia. By way of comparison, 51% of the land area of Alaska is designated in a non-suppression category with the remaining 49% subject to varying degrees of fire suppression activities (Alaska Department of Forestry). Additional credit for carbon sequestration associated with fire suppression would presumably require increased levels of suppression activities. All three countries have similar low and high values for the area consumed in annual fires so Figure 2 can be taken to represent the high and low values for incremental increases in fire suppression activities in any of the three countries.

There are a number of problems associated with using fire management as a tool for carbon sequestration. One of the most difficult issues is establishing a baseline value for fire emissions in a given year. Credit for fire suppression might include all activities aimed at combating fires or alternatively could include credit for fires outside previously established zones of active suppression (STOP, 1999). However, even if agreement on which fire suppression activities are allowable could be reached, there are substantial technical hurdles in evaluating the difference between how much carbon would have been lost without suppression vs. how much actually was lost during suppression activities. Imposition of required determination of management impacts on fire losses would add significantly to the difficulty of assessing carbon losses (and avoided losses).

A second issue involving fire suppression revolves around the time scale of emissions reduction. In the short term avoided fire emissions can have a large impact on atmospheric carbon. In the long term (decades to centuries), fire suppression activities are likely to lead to larger and more severe fires and therefore to increased carbon emissions in the future. Decades of fire suppression in Canada are, at least, partially attributed to the increases in fire severity and extent in recent years (Linder et al. 1997; Kronberg, 1998; Harden et al. in press; Solomon and Leemans, 1997; Wotton and Flannigan, 1993). For these reasons, activities taken during the current commitment period will have large impacts on latter commitment periods and the mechanisms for handling these types of delayed effects are not yet established and will be difficult to define.

Given these difficulties, we present a range of fire suppression carbon sequestration potentials in Figure 2. It should be understood that there is not, and will never be, a single number that reflects the potential for fire suppression induced carbon sequestration. The large year to year variability in fire extent and carbon losses, particularly from boreal forests, precludes simple estimations of potential carbon sequestration. To frame the question, we take an average value of 1.5 million hectare burned and a 5 - 20% fire reduction range over land areas with a 3 fold span of carbon content. To narrow this estimate would require unjustified assumptions given the variability in both location and magnitude of fires in Canada, Russia, and the United States.

3.3.3 Pest Management

The area of forest impacted by pest outbreaks in Canada, Russia, and the United States covers millions of hectares per year. In Canada, the loss of wood to pests is 70% of the loss to fire according to STOP (1999). In Russia, large areas of forest are also impacted by pest outbreaks but the estimates are lower than for Canadian forests with an average of approximately 30,000 hectares having been affected annually between 1991-1993 (IIASA report). Estimates of potential reductions in pest outbreaks with the use of large scale spraying of pesticides are similar to forest fire reduction estimates, at least for Canada and the United States. Nabuurs et al (1999) use an estimate of 50% reductions in pest outbreaks to suggest that 2.3 Gt of C per year could be preserved in these countries. More realistic reductions are likely in the range of 5-10% and would yield carbon savings of 5 to 60 Mt per year for Canada and the United States. With little data available, the same is assumed for Russia.

3.3.4 Additional forestry activities

There are a number of additional forestry activities that may affect carbon sequestration rates. These activities include improvements in the genetic stock of newly planted trees, changes in the spacing of young stands (juvenile spacing), thinning of older stands and changes in rotation length. Each of these activities will have differing effects depending on the type of trees and site fertility. Estimates of the potential increases in carbon storage with different management activities have been made for Canadian, Russian, and US forests.

Thinning of forests may or may not increase forest growth. There is evidence showing no growth response to thinning (Shvidenko et al, 1997; Schroeder, 1991) and increased growth response to thinning (CPPA, 1998). For densely packed stands, thinning Douglas fir plantations can increase carbon storage by 11% over 50 years but analysis of other forest types such as loblolly pine indicate that thinning may actually reduce net carbon storage (Schroeder, 1991). These issues make it difficult to estimate the sequestration potential of forest thinning. There are however, several published sequestration estimates associated with thinning which can be used to place bounds on this forest management activity.

For Canada, the Canadian Pulp and Paper Association estimates that thinning could increase carbon storage by 7 Mt C/year (CPPA, 1998). For Russian forests, simulations of large scale forestry activities place the potential carbon sink associated with thinning and selective felling at 0 to 2 Gt over 40 years for a rate of 0 to 50 Mt C/year depending on assumptions about the effect of thinning on carbon growth (Shvidenko et al, 1997).

In the US, it has been estimated that approximately 80 Mt C/year could be sequestered into U.S. timberlands averaged over the next 100 years (Vasievich and Alig, 1996; Row, 1996).[7] This study relies primarily on improved regeneration (rapid and improved planting and seeding) and stand thinning. Included in this value is the sequestration due to increasing carbon mass in durables (furniture, lumber, etc.) and in landfills.

At this stage of research, it is difficult to narrow these estimates because of conflicting information stand thinning impacts and because of the need to carefully account for the fate of carbon removed from forests as well as the time scale considered.

The effect of changes in forest rotation length on carbon storage depend entirely on the period of time considered in the analysis and the fate of products removed from the forest. A change in rotation length also reflects a transient increase in carbon storage as the average carbon content increases from a lower to a higher value. Older forests contain more carbon than younger forests but the rate of carbon gain decreases as forests age (Birdsey, 1992). Increasing the average rotation length of a forest will increase carbon storage only until a new average carbon storage is reached. The only way to sustain carbon sequestration with increasing rotation length is to continually increase rotation ages and this can only be done if the older forest will store more carbon than a younger one. It should also be understood that the marginal gain of increasing forest rotation times decreases as the average forest age approaches maturity. Secondly, increasing rotation lengths will only count as carbon sequestration as long as the products of forest removals remain constant. A younger forest that is harvested to create durable products (e.g. timber for houses) could have greater carbon sequestration potential than an older forest that is harvested for short-lifetime products (e.g. paper).

Given these caveats, there are estimates of the potential for increased carbon sequestration associated with increased rotation length of 0.059 t C/ha/year for Canadian Red Spruce forests over the next 50 years (Woodrising Consulting, 1999). Applied to the younger age classes described in the fertilization section above, this amounts to carbon sequestration of 8 Mt C/year for Canada and 14 Mt C/year for Russia. Another estimate for Canada and the US by Nabuurs et al (1999) assumed a 15% increase in rotation length in exploitable Canadian (112 Mha) and US forests (196 Mha) would increase the average content of carbon in these forests by 5% based on some simulation performed on Dutch tree species. This simulation arrived at a sequestration rate of 2.5 and 7 Mt C/year for Canada and the United States, respectively. These estimates should be viewed with considerable caution for the reasons outlined above and considered temporary measures that cannot be sustained for long periods of time.

Improved rates of paper recycling can also enhance carbon sequestration. A 1995 United States EPA study concluded that were 45% of US paper products to be derived from recycled fiber (a 50% increase over current rates) starting in the year 2000, an average carbon sequestration rate of 15.6 Mt C/year could be achieved by 2010 (US EPA, 1995). Consistent with this estimate, a 1995 study assumed that recycling rates increased 20% over current values resulting in about 8 Mt C/year sequestration in the US (Turner, 1995). Similar studies are not available for Canada or Russia.

An important caveat to the recycling estimates is the likelihood of “demand leakage”. The reduced pressure on forest resources may cause price declines thereby stimulating increased demand from other forest product users. This may result in little net gain from a carbon sequestration standpoint. This raises an important general consideration when estimating carbon sequestration within the forest sector. Unlike agricultural soils and rangeland management, much of the sequestered carbon is contained within a market commodity. Changes in the supply of that commodity due to carbon sequestration activities, for example, could have complicated economic feedbacks within the various markets using forest products. True estimates of carbon sequestration within the forest sector require the use of fully coupled economic/forest resource models. None of the estimates presented here, perform such an exercise.

The above estimates for all forest management activities in Canada, Russia, and the United States are presented in Table 4.

3.4 Total sequestration potential

There are numerous management practices described in this paper that may likely be applied simultaneously to the same piece of forest or agricultural land. This issue complicates interpretation of the potential for carbon sequestration over large areas of land and highlight why analyses of potential C gain in vegetation and soils must be approached with caution. For certain activities in forests such as thinning and fertilization, there are strong interactive effects. For example fertilization in unthinned stands may increase tree mortality due to increased competition for space and light (Schroeder, 1991). In this particular case, it may be that fertilization and thinning, when used alone, have little benefit for increased carbon sequestration but when used jointly can lead to large growth increases (Schroeder, 1991). imilar trade-offs are likely for simultaneous use of fertilization with changes in rotation length or fertilization in combination with no-till agriculture. The total sequestration estimates presented in this report do not attempt to unravel these interactions but report a strict sum of the activities outlined as if they were practices in isolation.

Summing the potential from each of these categories comes to roughly 31 to 211 Mt C/year for Canada, 34 to 337 Mt C/year for Russia and 161 to 277 Mt C/year for the United States. Considering just the lower end of these ranges, this translates into over 250% of the 6% Canadian reduction target negotiated in Kyoto and meets over 50% of the needed reductions were Canada to begin concerted action in 2005. In the case of the United States, the lower end of the range presented here will meet roughly 140% of the 7% reduction target (~115 Mt C/year) and 30% of the reduction from 2005 (~520 Mt C/year).

Since Russia agreed to stabilize their emissions at 1990 levels in the first commitment period and they are expected to arrive at emissions that are 250 Mt C/year below 1990 levels in the first commitment period, the sequestration potential outlined here adds to that expected surplus.

In 1990, carbon emissions from the Annex 1 countries (excluding Russia and Ukraine)[8] totaled 3798 Mt C/year. By 1997, this values had risen to 3889 Mt C/year. With a reduction target of 5.2% below 1990 levels, the Annex 1 countries together would have to reduce their emissions 289 Mt C/year from their 1997 levels in order to comply with the Kyoto Protocol (United Nations 1999b). The lower end of the sequestration potential range for Canada, Russia, and the United States alone would meet 76% of this reduction. The upper end of the potential sequestration ranges presented here could meet all of this needed reduction.

4. Discussion

It is clear from the numbers presented that the potential to sequester carbon in Canada, Russia, and the United States under Article 3.4 of the Kyoto Protocol is certainly not trivial in either a political or physical context. The reduction targets agreed to in 1997 implicitly included estimates of what might be achieved under some reasonable definition of Article 3.3. However, the targets were not predicated upon how much offsetting might result from additional activities now being contemplated within Article 3.4. If these sequestration potentials are used as offsets to emissions reduction in the first commitment period, this could be interpreted as renegotiation of the Kyoto Protocol targets and might allow fossil-fuel emissions to rise beyond that expected at the time negotiations were made. For this and other reasons discussed in the following section, sequestration under article 3.4 may best be utilized in the second or later commitment periods.

Aside from the challenge inherent in estimating the magnitude of these activities, a series of potentially difficult issues may arise were these sequestration activities to be considered within the management regime outlined in the Protocol. Some of these issues can be considered scientific or technical problems in that they push the boundary of what is currently known or technically possible regarding carbon biogeochemistry. Others raise complex methodological issues that will require considerable attention before a meaningful accounting of these proposed sequestration activities can be formed into negotiated text.

4.1 Cross-cutting scientific/technical issues

The missing sink: A simple budget of the global carbon cycle is presented in Table 2. The magnitudes of measured atmospheric storage and emissions due to human activities indicate that roughly one-half of the amount of CO2 emitted into the atmosphere each year must be removed. In order to balance the global budget given these relatively well-known flows of carbon, additional uptake must be occurring.[9] Some of this uptake has been attributed to forest regrowth in the mid-latitudes following the reversion of former agricultural land back to forest. The remaining uptake, approximately 1.3 ( 1.5 Mt of carbon each year, has come to be called "the missing sink".

Work in the late 1980s concluded that this missing sink must be acting in the Northern Hemisphere (Enting and Mansbridge, 1989; Keeling and Heimann, 1986; Tans et al., 1990; Keeling et al., 1989). The most compelling evidence of this is presented in Figure 3. Model simulations of the latitudinal gradient of CO2 concentration due to fossil-fuel emissions are placed alongside the latitudinal gradient of CO2 measurements for the 1980s. Both the oceanic uptake and any mechanism (source or sink) at work in the tropics will not cause a change in the latitudinal gradient because these exchanges affect both hemispheres equally. Therefore, the only way in which the latitudinal gradient can be made to conform to the observational data is by removal of CO2 in the northern hemisphere.[10]

Further work in the 1990s with carbon isotopes, 3D inverse modeling, and atmospheric oxygen all point to the terrestrial biosphere as the location of the missing uptake of carbon (Francey et al., 1995; Ciais et al., 1995; Enting et al., 1995; Keeling et al., 1996; Fan et al., 1998). The longitudinal distribution remains somewhat controversial and the mechanism has yet to be firmly established though many researchers believe that photosynthesis within mid- and high-latitude forests may be exceeding current rates of respiration, causing a net addition of carbon to the biosphere (Houghton et al., 1998).[11]

Unless the language is constructed carefully, Article 3.4 could inadvertently include credit for uptake by the missing sink. In drafting Article 3.3, negotiators attempted to ensure that only carbon sequestering activities that were “human-induced” and had begun “since 1990” could be considered as emission reduction offsets. If the intent is to grant credit for such intentional climate-related activities, this same language must find its way into the construction of Article 3.4. If not, Article 3.4 could provide an avenue through which carbon uptake due to missing sink mechanisms might be used as offsetting credits. For example, current projections for forest biomass accumulation estimate that U.S. forests will be sequestering carbon at a rate of about 200 Mt C/year in the year 2010 (Birdsey and Heath, 1995). This rate of carbon uptake is based on current “business as usual” activities. This sequestration is most likely not directly human-induced and may be due to an, as yet unknown, mechanism underlying the missing sink. Were the U.S. to gain credit for this uptake, the 7% below 1990 reduction agreed to in Kyoto would become, in effect, a license to raise emissions 5% over 1990 levels (Lashof and Hare 1999).

Even if Article 3.4 were drafted such that activities were limited to direct human-induced action since 1990, the missing sink may still confound attempts to give appropriate credit. For example, were forest managers to increase fertilization on forest areas in the U.S., it would be unclear whether the gain in biomass was due to direct action by managers or due to mechanisms driving the missing sink. Careful construction of control plots would be required to ensure appropriate credit.

Exogenous permanence: Once it is agreed that biotic sequestration activities can be used to offset emission reductions, the sequestered carbon must be measured and tracked into the indefinite future. A current hypothesis regarding future carbon biogeochemistry suggests that as the planet warms, significant amounts of biotic carbon may enter the atmosphere due to increased heterotrophic respiration (Melillo et al., 1996; Woodwell et al., 1995). Furthermore, changing climate may lead to a degradation of biotic systems in different locations due to increased fire, pests, or ecosystem shifts. This suggests that carbon sequestered in biotic systems may be relatively unstable and sensitive to forces outside of human control.

This raises some complex questions regarding accounting equity as well. Were a given amount of carbon sequestered by a country to re-enter the atmosphere due to warming, should the loss of soil carbon be counted as an emission?[12] From the vantage point of the atmosphere, net sequestration has not occurred.

Measurement challenges: Many of the activities presented here as potential candidates for carbon sequestration in Article 3.4 are based on moving carbon from the atmosphere to the soil. While individual measurements of soil carbon can be quite accurate, evidence of a statistically significant changes require many years (WBGU, 1998). Furthermore, the soil/vegetation properties of many countries exhibit large amounts of spatial heterogeneity within forests or agricultural areas. Accurately portraying sequestration across such spatial heterogeneity is a particular challenge. Careful selective measurements combined with biogeochemical models will likely be necessary.

An inherent tension exists between the desire to comprehensively account for biotic carbon exchange and the ability to measure and monitor managed biota. Comprehensiveness is appealing in that it represents the true net source or sink from a countries managed biota. Yet, for most industrialized countries this encompasses nearly all of the national terrestrial biosphere. This poses significant measurement challenges both in terms of accuracy and spatial coverage. Furthermore, while the US may be able to mount sophisticated biospheric carbon exchange measurements, this may be less true of other countries. In contrast, confining carbon credit to only certain activities may grossly misrepresent the net managed biotic exchange.

Monitoring and verification: Unlike aboveground biomass, carbon sequestered in the soils cannot, at the present, be monitored remotely. Therefore, monitoring and verification of sequestered carbon may require in situ measurement. Article 3.3 requires the activities defined therein to be “transparent” and “verifiable”. How far countries are willing to take the burden of transparency and verification may be a crucial factor in approving many of the activities proposed for Article 3.4.

Transience: The sequestration activities discussed in this report should be viewed as temporary phenomena. In most cases, the goal is to change a biotic system from one equilibrium state to another. The carbon sequestration benefit typically accrues during the transition phase. For example, initiating no-till agriculture on a particular piece of farmland will sequester carbon until the overall rate of respiration from the growing soil carbon approximates the rate of photosynthesis aboveground. Similarly, increasing the rotation length of a forest stand will accrue carbon only between the change from a shorter to a longer rotation length. After that point, carbon sequestration ceases. Only by continually lengthening a particular forest rotation would sequestration continue, but only then with diminishing results as a forest stand reaches old-growth status.

4.2 Cross-cutting methodological issues

Baseline/additionality: Because the activities proposed for Article 3.4 refer mostly to improved management in currently managed systems, some form of strict additionality may be necessary to avoid unintended carbon credit. As was noted before, much of the terrestrial biota in industrialized countries is considered “managed”. Requiring that activities have begun “since 1990”, as used in Article 3.3, may be an insufficient constraint as it may be operationally difficult to distinguish “new” management activities from those currently practiced.

However, determination of additionality is operationally difficult and a topic of growing concern for negotiators. Many countries will likely have engaged in activities that sequester carbon were climate change not an issue of concern. For example, improved forest management and improved soil quality have been programmatically pursued in the U.S. for years. Determining which of these are truly additional and which are not may require the construction of national sequestration baselines against which additional activities are discerned.

Endogenous permanence: As was mentioned previously, inclusion of biotic sequestration into the calculus of the Kyoto Protocol requires both measuring and tracking biotic carbon into the indefinite future. Like climate change itself, the timescales of such a task are measured in decades to centuries. Building institutions that can function consistently and reliably across such timescales may be unrealistic given the historical permanence of human institutions. Decisions regarding the fate of nuclear waste have been faced with similar concerns (Makhijani and Saleska, 1992).

Perverse incentives: As with Article 3.3, Article 3.4 has the potential to create perverse incentives. The most commonly cited is the incentive to decarbonize biotic systems prior to the first commitment period in order to maximize the carbon uptake when credit is computed. Biotic sequestration also presents a strong argument for contiguous periods in the future for the same reasons.

Keep it simple: The Kyoto Protocol is the product of many years of arduous and complicated negotiating. In the long-term, averting serious climate change will be best served by maintaining a reasonable level of simplicity regarding the management of greenhouse gas emissions. While technically feasible for a few countries, a global carbon management system that includes biospheric exchange may digress into incomplete reporting, conflicting verification, and biased results. The result could be a rising cynicism on the part of the public and negotiators and a general reduction in the political will to ensure sufficient greenhouse gas reductions in the future. Far greater than potential loopholes or commitment delays, a loss of political leadership and focus could send the international negotiations back a decade or more.

4.3 Benefits

Though a number of potential problems have been raised in the preceding paragraphs, there are also some accepted benefits that could accrue from the addition of sequestration activities discussed in this paper. First, Article 3.4 may penalize countries for forest degradation. Current discussions on the interpretation of Article 3.3 suggest that countries that do not engage in deforestation but degrade forests will not have the lost carbon counted as an emission. However, such a carbon loss may be accounted for in Article 3.4, were forest sources as well as forest sinks explicitly included.

Were conservation of old-growth forests considered a carbon sequestering activity, additional impetus may be created for preserving primary forest in the U.S. Similarly, Article 3.4 may stimulate a reversion of some managed systems back to native conditions, because these tend to contain more carbon than when under management. A good example is the restoration of wetlands and peat lands which in their native state contain vast stores of carbon. However, this last measure may not yield the benefits expected as wetlands do emit significant amounts of methane, a powerful greenhouse gas. The balance between carbon sequestration and methane emissions needs further research before the net effect can be conclusively determined.

As mentioned previously, carbon sequestration in agricultural soils enhances soil quality, leading to greater productivity and fewer inputs of fertilizer and other amendments. Many of the individual practices being discussed within agricultural soil carbon sequestration have additional co-benefits such as lower farming costs and reduced pollution.

Finally, carbon sequestration may stimulate more sustainable forest and agricultural practices by rewarding higher levels of carbon in biotic systems. For example, less invasive selective cutting in forests lessens the carbon loss from soils and collateral damage and is also considered more sustainable from a biodiversity perspective (Putz and Pinard, 1993).

5. Conclusions

Article 3.4 of the Kyoto Protocol was constructed to allow biotic carbon sequestration activities to be used to offset national emission reductions. Though specific activities and the details of how they might be included have not been negotiated broad carbon sequestration categories and activities have been proposed. The most commonly cited are: cropland management, rangeland management, and forest management.

A review of the work that has been performed on quantifying the sequestration potential of these categories indicates that they could potentially meet a significant portion of the Canadian commitment under the Kyoto Protocol and could add to the projected Russian carbon surplus. Should the lower end of the sequestration range presented in this report be employed, it is possible for the Canada to meet over 250% of the 6% reduction target negotiated in Kyoto and account for over 50% of the needed reductions in 2005 were their national emission to grow as they are currently projected. Were this level of sequestration applied to the first commitment period, this would change the Canadian target from a 6% emissions reduction to a 17% emissions increase.

Should the lower end of the sequestration range be employed within the United States, it is possible for that country to meet approximately 140% of the 7% reduction target negotiated in Kyoto and meet roughly 30% of the needed reductions in 2005. These levels of sequestration would effectively change the 7% reduction to a 11% emissions increase.

The sum of the lower end of the Canadian, Russian, and US sequestration could meet 76% of the entire Annex 1 country reduction (289 Mt C/year). The upper end of the potential sequestration ranges presented here could meet all of this needed reduction.

With this sizeable sequestration potential comes a number of potential difficulties. Unless care is taken to construct the language of Article 3.4, countries may accrue credit for current carbon uptake attributable to the “missing sink”, seriously undermining the emissions reductions that have been agreed to thus far. Proper experimental controls may be necessary to separate carbon uptake due to intentional human-induced activity and carbon uptake due to processes underlying the missing sink.

Furthermore, current hypotheses concerned with the fate of biotic carbon suggest that as the world warms carbon sequestered now may re-enter the atmosphere at a later time. Compared to avoiding the use of carbon sequestered in fossil fuel form, biotic sequestration may be inherently unstable and require long-term accounting and tracking of biotic resources. The institutional requirements will be significant and could result in a diffusion of the focus needed to avert serious climate change in the future.

These problems must be weighed against a series of co-benefits that may accrue from carbon sequestering activities such as the slowing of forest degradation, protection of old-growth forests, stimulation of sustainable forestry and agriculture, and reversion from managed to native ecosystems.

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7. Units and Abbreviations

Mt C/year: million metric tonnes of carbon per year

ha: hectares

Mha: million hectares

t C/ha/year: metric tonnes of carbon per hectare per year

g C/m2/year grams of carbon per meter squared per year

Gt billion tonnes

[pic]

Figure 1. Simulated total soil carbon for the central U.S. corn belt (Lal et al., 1998).

[pic]

Figure 2. Sensitivity of fire suppression emission reductions to reduction level and area burned.

[pic]

Figure 3. Zonally averaged simulated versus observed CO2 concentration (Keeling et al., 1989).

Table 1. Cropland management sequestration(

|Country/Activity |Available area |Carbon uptake rate |Annual sequestration |

| |(Mha) |(g/m2/year) |(Mt C/year) |

|Canada | | | |

|Land conversion |0.5 | 80 |0.4 |

|Land restoration |3.8 |10 - 100 |1.0 |

|Improved management of cultivated |20 – 40 |15 - 80 |3.0 - 6.5 |

|land | | | |

|Total | | |4.4 - 7.9 |

|Russia | | | |

|Land conversion |NA |NA |NA |

|Land restoration |NA |NA |NA |

|Improved management of cultivated |15 – 30 |10 - 20 |5.7 – 8.4 |

|land | | | |

|Total | | |5.7 – 8.4 |

|United States | | | |

|Land conversion |8.7 |80 |7 |

|Land restoration |49.2 |10 - 100 |17 |

|Improved management of cultivated |20 - 123 |20 - 40 |10 - 50 |

|land | | | |

|Total | | |34 - 74 |

( All values have been rounded.

Table 2. Rangeland management sequestration(

|Country/Activity |Available area |Carbon uptake rate |Annual sequestration |

| |(Mha) |(g/m2/year) |(Mt C/year) |

|Canada | | | |

|Pasture improvement |4.3 |20 |0.2 - 0.6 |

|Russia | | | |

|Pasture improvement |7.8 - 16 |5.5 |0.4 – 0.8 |

|United States | | | |

|Pasture improvement |51 |20 |9 |

( All values have been rounded.

Table 3. Nitrogen fertilization response

|Location |Species & Fertilization Rate |% Growth Increase |Reference |

| |(Kg N/ha/year) | | |

| | |Mesic Site - 37% (stemwood) | |

|Sweden |Scots Pine – 20-28 |Dry site – 36% (stemwood) |Mäkipää al, 1998 |

| | | |Nams et al, 1993 |

|S. Yukon, Canada |White Spruce – 180 |10-50% (growth rate increase) |Turkington et al, 1998 |

| | |50% (NPP for N additional alone) | |

|N. Saskatchewan, Canada |Aspen stand – 100-200 |111% (NPP for N, P, K additions) |Peterson and Peterson, 1995 |

Table 4. Forest management sequestration(

|Country/Activity |Available area |Carbon uptake rate |Annual sequestration |

| |(Mha) |(g/m2/year) |(Mt C/year) |

|Canada | | | |

|Nitrogen fertilization |142 |3.0 - 75 |4.2 - 107 |

|Fire suppression |1.5 |- |2 - 20 |

|Pest control |- |- |5 - 60 |

|Stand thinning |- |- |7 |

|Increase rotation length |112 - 142 |- |2.5 - 8 |

|Total | | |20.7- 202 |

|Russia | | | |

|Nitrogen fertilization |230 |3.0 - 75 |7 - 184 |

|Fire suppression |1.5 |- |2 - 20 |

|Pest control |- |- |5 - 60 |

|Stand thinning |- |- |0 - 50 |

|Increase rotation length |230 |- |14 |

|Total | | |28 - 328 |

|United States | | | |

|Nitrogen fertilization |196 |- |16 - 94 |

|Fire suppression |1.5 |- |2 - 20 |

|Pest control |- |- |5 - 60 |

|Stand thinning (includes improved |- |- |80 |

|regeneration) | | | |

|Increase rotation length |196 |- |7 |

|Increased recycling |- |- |8 - 15.6 |

|Total | | |118 - 277 |

( All values have been rounded.

Table 5. Mean global carbon budget for the 1980s (after Schimel et al., 1996).

|CO2 sources |Gt C/year |

|Emissions from fossil fuel combustion and cement production |5.5 ( 0.5 |

|Net emissions from changes in tropical land-use |1.6 ( 1.0 |

|Total Anthropogenic Emissions |7.1 ( 1.1 |

|Partitioning amongst reservoirs | |

|Storage in the atmosphere | |

|Ocean uptake |2.0 ( 0.8 |

|Uptake by Northern Hemisphere forest regrowth |0.5 ( 0.5 |

|Other sinks |1.3 ( 1.5 |

-----------------------

[1] The commitments are stated as a percent change from the baseyear amount, 1990 gross emissions. Countries for whom net biotic exchange in land-use change and forestry were positive are allowed to include this in their baseyear amount. For all others, these emissions are not included in the baseyear amount.

[2] “Participating” countries refers to the 39 parties listed in Annex B of the Protocol , who have agreed to adopt numerical targets. This collection of parties comprises most the “industrial” world.

[3] The first commitment period spans the years 2008 to 2012. As yet, no future commitment periods have been specified.

[4] Because the commitment period is a five year interval, this is the average reduction within this period.

[5] A slight reduction is made to account for a presumed baseline of “business as usual” activity.

[6] A recent meta-study found an average uptake rate of 49 g C/m2/year for the US and Canada. This would more than double the estimate given here (Rich Conant, personal communication).

[7] This estimate attempts to remove the energy offset sequestration as presented by Row 1996.

[8] Because of the collapse of these economies after 1990, including these countries in the Annex 1 total places the Annex1 total in 1997 very close to the Kyoto target reduction of 5.2%.

[9] Of the inputs and outputs, tropical deforestation is considered the least well known and the subject of ongoing revision.

[10] A source in the Southern Hemisphere could also cause a shift in the latitudinal gradient. However, this scenario appears unlikely due to the limited landmass.

[11] Were CO2 fertilization responsible for this lag between photosynthesis and respiration, net carbon uptake would eventually end.

[12] This raises particularly difficult questions were the country in question a small contributor to CO2 levels in the atmosphere.

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