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Biosequestration
CLIMATE TECHBOOK
Quick Facts
•
Plants, soils, and organic matter contain nearly three times the amount of carbon currently stored in
the atmosphere.
•
Biosequestration has the potential to make a significant impact by absorbing annual human-caused
carbon emissions through changes in land management practices.
•
Increasing rates of biosequestration can support other environmental outcomes such as improved
wildlife habitat, water quality, reduced run-off, and better recreational opportunities.
•
Biosequestration may someday be profitable for private landowners who adopt certain land
management practices and participate in a carbon market.
•
Biosequestration decreases atmospheric CO2 until the carbon that is in the plant, soil, or end product
is released back to the atmosphere.
Background
Addressing the risk of dangerous climate change requires the combined efforts of both greenhouse gas
(GHG) emission reductions and sequestration. The purpose of this document is to discuss briefly the
technology of biotic sequestration (or “biosequestration”): the absorption and storage of carbon in organic
matter.
Biosequestration refers to a category of biological processes that absorb carbon dioxide (CO2), the primary
GHG, from the atmosphere and contain it in living organic matter, soil, or aquatic ecosystems. The
opportunities for expanding biosequestration by changing management and land-use practices are
generating debate among landowners, policymakers, and the media. Other avenues of enhancing natural
carbon capturing processes may exist, but more study is needed to determine their potential for climate
change mitigation. 1
Biosequestration occurs naturally in the global carbon cycle (Figure 1). It is estimated that the atmosphere
contains about 2,750 billion metric tons of CO2 (2,750 gigatons of carbon, GtCO2). 2 Terrestrial vegetation,
soils, and organic matter contain the equivalent of up to 8,030 GtCO2 or just under 3 times the amount
contained in the atmosphere. 3 It is estimated that in the 1990s, 5.8 GtCO2 per year were released into the
atmosphere as a result of global land-use change and deforestation, though some forests expanded in
temperate and boreal zones. 4 For comparison, the United States emitted on average about 7 GtCO2 per
year from land-use change between 2003 and 2007, or about 0.25 percent of the entire atmospheric CO2
each year. 5 Enhancing the capacity for carbon storage or the rate that CO2 is biosequestered is an important
strategy for mitigating climate change.
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Figure 1: The Global Carbon Cycle (in GtC)
Technology, Environmental Benefits, and Emission Reduction Potential
Although biosequestration occurs naturally every day, actions preventing the loss of carbon stocks and
increasing the rate of biosequestration can also be intentional. Some biosequestration methods have a
greater carbon impact than others depending on the rate of carbon absorption and storage. For example,
fast-growing tree species can be used in afforestation and reach sequestration rates of 5 metric tons CO2
(tCO2) per acre per year, while planting prairie grass in place of an annual agricultural crop could sequester
an additional 1.5 tCO2 per acre per year depending on local climate and weather variability. 6,7 A range of
carbon sequestration rates from selected land-use practices is presented below (Table 1). 8,9,10
Although carbon stocks in forests, agricultural lands, and wetlands have been reduced over time, and thus
offer opportunities for carbon storage through restoration, they are not pools where unlimited amounts of
CO2 can be stored. All biosequestration practices will reach a saturation point at which a new carbon
equilibrium is reached. 11
Like other GHG mitigation options, different quantities of biosequestration are achievable at different costs.
Under the cap-and-trade program passed by the U.S. House of Representatives in 2009 (H.R.2454),
domestic biosequestration (in the form of cap-and-trade offsets) was projected to provide between 292 and
676 million metric tCO2 of annual abatement in the year 2030. (For comparison, GHG emissions from
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sources covered under the cap were projected to be between 926 and 2586 million metric tCO2 below the
“business-as-usual” projected emissions level in 2030.) 12,13
Table 1: Estimated Sequestration Potential by Practice in the United States (Metric Tons
CO2 per Acre per Year): Selected Land Use and Production Practice Changes
Activity
Estimated
Sequestration Rate
(MT CO2/acre-year)
EPA
USDA
(2005)
(2004)
Primary
Environmental
Co-Benefits
Activity Description
Forestry
Afforestation
2.2 - 9.5
2.7 - 7.7
Wildlife Habitat
Reforestation
1.1 - 7.7
-
Water Quality
Avoided deforestation
83.7 172.1
-
Wildlife Habitat
Changes in forest
management
2.1 - 3.1
-
Biodiversity
Establishing trees in an area
that was historically not
forested
Replanting trees in a forested
area that is not adequately
regenerating after previous
removal
Reduction of the conversion of
forested land to an alternative
use like housing or agriculture
Increased forest stocking, pestcontrol, forest age optimization
Cropland/Land Use Changes
Afforestation of
croplands
-
2.6 - 6.3
Water Quality
Afforestation of
pastureland
-
2.7 - 7.7
Wildlife Habitat
Cropland conversion
to grasslands
0.9 - 1.9
0.9 - 1.9
Water Quality
Restoration of
wetlands
0.4
-
Wildlife Habitat
Riparian or
conservation buffers
(non-forest)
0.4 - 1.0
0.5 - 0.9
Water Quality
Increased carbon sequestration
rates (trees generally sequester
more carbon per acre compared
to grasses and other annual
species)
Perennial crops are able to
sequester carbon for longer
periods compared to annual
crops depending on the use of
the end-product
Restoring ecological functions to
degraded or drained wetlands
Prevention of soil-erosion into
adjacent waterways
Table 2 (continued)
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Activity
Estimated
Sequestration Rate
(MT CO2/acre-year)
EPA
(2005)
USDA
(2004)
Primary
Environmental
Co-Benefits
Activity Description
Production/Grazing Practice Changes
Reduced/conservation 0.6 - 1.1
tillage
-
Erosion control
Improved rotations,
cover crops,
elimination of summer
fallow
Improved fertilizer
management
-
0.2 - 0.4
Erosion control
-
0.1 - 0.2
Reduced run-off
Improved irrigation
management
-
0.2
Water
Availability
Use of
manure/byproducts
on pasture
-
0.7 - 1.8
Reduced run-off
Rangeland
management
-
0.2 - 0.6
Erosion control
Pastureland
management
Grazing management
-
0.4 - 1.8
Erosion control
0.1 - 1.9
1.1 - 4.8
Erosion control
Reducing soil-erosion,
increasing vegetative cover and
carbon sequestration
opportunities, less soil oxidation
and associated GHG emissions
Increasing sequestration in
soils, reducing over-grazing and
soil erosion
Biosequestration is a biogeochemical process, meaning that it occurs at the interface of living organisms
and geological processes. For example, when CO2 from the atmosphere is taken in by a plant, newly formed
molecules (usually sugars and other carbohydrates that contain the carbon) end up in all parts of the plant
including the leaves, stems and roots (Figure 2). The carbon is considered sequestered until the organic
matter decomposes or burns, at which point it returns to the atmosphere as CO2. After plants die and fall to
the ground, some carbon is incorporated into the soil when roots or dead leaves become soil organic carbon
(SOC). Land that has been afforested or planted in perennial crops may have the greatest potential for
accumulating soil organic carbon. 14
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Figure 2: Biosequestration at the Level of an Organism
Source: http://www.biochar.org/joomla/images/stories/steiner-simple-cycle-vegcarbon.jpg
Not only may biosequestration help to mitigate climate change, but certain methods can also contribute
other significant environmental benefits. For example, changes in forest management can provide benefits
beyond storing carbon by reducing soil-erosion and run-off, reducing flooding, protecting fisheries, and
enhancing wildlife habitat and biodiversity. 15 Similar benefits could also accompany changes in the
management of farmlands and rangelands, and the restoration of wetlands. Environmental benefits will not
happen automatically in biosequestration projects but must be planned for if they are preferred.
Cost
The cost of biosequestration varies widely depending on the practice, the land-owner, and the location of the
biosequestration project. Much agricultural and forested land in the United States is privately-owned.
Biosequestration would likely have to be financially favorable compared with current management practices
for land managers to consider a change. 16 Therefore, increasing carbon sequestration on these lands
probably requires some form of payment for the carbon service provided or the practice implemented.
Carbon markets and other pricing policies are discussed in more detail below.
A review of 11 cost analyses focusing on U.S.-based forest sequestration programs that varied broadly in
their estimated costs of carbon sequestration estimated that 300 million metric tons CO2-equivalent (tCO2e)
of annual carbon sequestration could occur in forest ecosystems at a cost of $7.50 to $22.50 per tCO2e. 17 A
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separate study of the costs of sequestering carbon on agricultural land yielded an estimate of up to 77
million tCO2e per year when carbon is priced in a similar range (~$13 per tCO2/acre/year). 18 For
comparison, total U.S. GHG emissions are about 7 billion metric tons of CO2e per year. The estimate of
agricultural carbon sequestration is about 1 percent of the total annual U.S. GHG emissions. The
aforementioned estimate of forest biosequestration projects is equivalent to about 4 percent of annual U.S.
GHG emissions.
Studies of global biosequestration estimate that a carbon price of $23.54 could induce 744 million tCO2e
per year of forest carbon sequestration by the year 2010. 19 Again, total annual biosequestration would vary
considerably depending on the region, ranging from 20 million tCO2e in Oceania to 280 million tCO2e per
year in North America. The difference between the North American estimate and the U.S. estimate above
illustrates that biosequestration estimates vary.
Carbon prices and markets to trade carbon will help considerably in supporting biosequestration practices.
However, reputable markets will require measurement and verification that also add to the cost of these
practices. It is also reasonable to expect that credit aggregators will act as facilitators between
biosequestration project owners and the credit exchanges. This facilitation will also come with a cost. In the
end, transaction costs such as these could be significant. 20
Current Status
A global system of recognized practices and credits for biosequestration does not currently exist. Policies
and programs that are effective in increasing the adoption of biosequestration practices are fragmentary,
especially in the United States.
The Kyoto Protocol – an international agreement governing GHG emissions – comes nearest to establishing
a global system of biosequestration initiatives. 21 Nations that are party to the Kyoto Protocol have agreed to
country-specific GHG emissions reductions by 2012. Articles 3.3 and 3.4 of the protocol outline the ways in
which nations can account for afforestation, reforestation, deforestation, and certain other land-use
activities in their particular emission reduction goals. Countries are also allowed to reach part of their goal
through investments in flexible GHG offsets guided by United Nations programs called the Clean
Development Mechanism and Joint Implementation (CDM/JI). 22 Biosequestration projects in CDM/JI are
mostly afforestation projects sponsored by countries with carbon reduction targets in countries without
reduction targets (typically, countries that are considered non-industrialized).
The European Union Emission Trading Scheme (EU ETS) is currently the largest mandatory carbon market in
the world. However, offsets from biosequestration are not currently allowed in the EU ETS. 23
Current U.S. drivers of biosequestration include voluntary offset programs like the Chicago Climate Exchange
and the Climate Action Reserve, and regional GHG reduction programs like the Regional Greenhouse Gas
Initiative (RGGI). Each of these programs defines how biosequestration projects can be measured in slightly
different ways. 24,25,26
It bears repeating that biosequestration practices depend on living systems that are not easily quantified in
a direct way. This lack of established measurement protocols leads to uncertainties in actual carbon
sequestered compounded by the uncertain storage time. Measurement is made even more challenging by
seasonal variations in weather and precipitation, differences between plant species, and the variation in the
quality of soils and lands where these practices could be used. Land managers know a lot about growing
trees, perennial crops, managing rangeland for carbon, and even restoring wetlands, but those practices
need better measuring techniques for their legitimacy to be widely accepted.
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Obstacles to Further Development or Deployment
A number of challenges have emerged to the further development of biosequestration practices:
27
•
Lack of a price on GHG emissions
Currently, in the United States there is no comprehensive policy that values biosequestration. A
policy, such as cap and trade (see Climate Change 101: Cap and Trade), that puts a price on GHG
emissions and limits total emissions, could create a market for offsets from biosequestration.
•
Carbon storage easily reversed and re-emitted to the atmosphere
Living systems are subject to natural variation including unforeseeable climatic, weather, and
destructive events. If a biosequestration project is destroyed by wildfire or heavy storms, the carbon
stored there will be rapidly released back to the atmosphere. Without clear ownership or contracts,
the liability of restoring this carbon remains uncertain.
•
Establishing “baseline” measurements
The significance of choosing a baseline year against which sequestered emissions will be measured
and compared is often understated or overlooked. A baseline will determine how much carbon is
sequestered or emitted from a particular practice or project compared to a given year, usually in the
past. This often serves as an anchor to measure how well a certain practice is performing relative to
a certain emission reduction effort.
•
Measurement of real carbon sequestered
Measurement, monitoring, and verification have been mentioned above. Biosequestration is difficult
to quantify quickly or cheaply due to the constant flow of CO2 into and out of these living systems.
This makes trading metric tons of biosequestered carbon difficult without accurate tracking and
certification.
•
Transaction costs
Transaction costs are projected to be significant in carbon markets. For example, in the voluntary
Chicago Climate Exchange (CCX), some aggregators already in operation charge 8-10 percent of the
value of the carbon credits in addition to a common listing fee of $0.20 per metric ton. Costs to
implement biosequestration practices will need to be minimized in order to most cost-effectively
utilize biosequestration for GHG abatement.
•
Property rights and decision-making
Land-use decisions are often complicated by government regulation and property-owner preferences
and traditions. Any successful implementation of biosequestration practices will depend on the
legitimate involvement of all stakeholders including landowners, policymakers, community members,
private enterprise, and other affected parties.
Each of these challenges must be addressed appropriately for biosequestration to be implemented at a
climatically significant scale. 28
Policy Options to Help Promote Biosequestration
There are two primary policy strategies that could help promote biosequestration: 29
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•
Practice-based incentives
Practice-based incentive programs are already common for farmers using conservation practices on
their land. Some U.S. farm programs - for example the Conservation Reserve Program - explicitly
recognize carbon sequestration as a benefit. Farmers implementing a land-use change for the
primary purpose of increasing biosequestration on their land could be supported through costsharing of the practice establishment, for example. Supporting a practice but not performance
leaves little room for rewarding actual carbon benefits aside from the shift in management.
•
Performance-based incentives
Performance-based incentives reward actions that have higher rates of carbon sequestration. 30
Performance-based incentive programs are compatible with a carbon market, which would be
created by a cap-and-trade program (see Climate Change 101: Cap and Trade).
Many cap-and-trade proposals allow biosequestration projects to generate offset credits that can be
used by covered entities to comply with the emission limit. Offsets from biosequestration can be
thought of as reducing carbon emissions in place of actions taken by a covered entity to reduce
emissions directly at the source through energy efficiency measures and other activities. For
example, an electric generator faced with a need to reduce its emissions could do so via a
combination of increasing its non-emitting generation (e.g., from nuclear, wind, or solar power),
decreasing its traditional fossil fueled generation, and paying a forest landowner to increase
biosequestration on her land. If biosequestration offsets are adequately verified, then offsets could
be a cost-effective way of reducing net GHG emissions over time.
Other helpful policies that would foster higher biosequestration penetration in performance-based
markets would include risk reduction strategies for uncontrollable events (wildfires and weather),
transaction cost reduction, and increased certainty in carbon measurement.
Related Business Environmental Leadership Council (BELC) Company Activities
•
ABB
•
Alcoa
•
American Electric Power
•
Baxter International Inc.
•
BP
•
CH2M Hill
•
DTE Energy
•
Duke Energy
•
Entergy
•
Exelon
•
Interface Inc.
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•
Ontario Power Generation
•
PG&E
•
SC Johnson
•
Weyerhaeuser
•
Wisconsin Energy Corporation
Related Pew Center Resources
Agricultural & Forestlands: U.S. Carbon Policy Strategies, 2006.
Agriculture's Role in Greenhouse Gas Mitigation, 2006
Biological Sequestration through Greenhouse Gas Offsets: Identifying the Challenges and Evaluating
Potential Solutions, April 2009 Workshop co-sponsored by the Pew Center.
Briefing on Domestic Offsets in a Greenhouse Gas (GHG) Cap-and-Trade System, 6 March 2009.
The Cost of U.S. Forest-Based Carbon Sequestration, 2005.
Greenhouse Gas Offsets in a Domestic Cap-and-Trade Program, Congressional Policy Brief, 2008.
Issue Overview: Role of Offsets in Cap and Trade, U.S. Climate Action Partnership (USCAP), 2009.
Offset Quality Initiative (OQI).
Further Reading / Additional Resources
Baker JM, Ochsner TE, Venter RT, Griffis TJ (2007). Tillage and soil carbon- what do we really know?
Agriculture, Ecosystems and Environment 118: 1–5.
Birdsey R (2004). Data Gaps for Monitoring Forest Carbon in the United States: An Inventory Perspective.
Environmental Management 33. Supplement 1: S1–S8.
United States Department of Energy (2008). Carbon Cycling and Biosequestration Workshop Report:
Publication No. DOE/SC-108. http://genomicsgtl.energy.gov/carboncycle/
European Union Memo (2008). Questions and answers on deforestation and forest degradation. Reference:
MEMO/08/632.
Hansen EA (1993). Soil carbon sequestration beneath hybrid poplar plantations in the north central United
States. Biomass and Bioenergy 5: 431-436.
Johnson R (2009). Climate Change: The Role of the U.S. Agriculture Sector and Congressional Action.
Congressional Research Service. Publication No. RL33898. www.crs.gov
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Johnson R, Gorte RW (2009). Estimates of Carbon Mitigation Potential from Agricultural and Forestry
Activities. Congressional Research Service. Publication No. R40236. www.crs.gov
Johnson KS, Karl DM (2002). Is Ocean Fertilization Credible and Creditable? Science 296: 467-468.
Kopp RJ, Pizer WA et al. (2007). Assessing US Climate Policy Options. Report briefings on climate policy
options including Biosequestration, among many others.
http://www.rff.org/Publications/Pages/CPF_AssessingUSClimatePolicyOptions.aspx
Lal R (2008). Sequestration of atmospheric CO2 in global carbon pools. Energy & Environmental Science 1:
86–100.
Lewandroski J, Peters M, et al. (2004). Economics of Sequestering Carbon in the U.S. Agricultural Sector.
Technical Bulletin No. (TB-1909). http://www.ers.usda.gov/publications/tb1909/
McLauchlan KK, Hobbie SE, Post WM (2006). Conversion of agriculture to grassland builds soil organic
matter on decadal timescales. Ecological Applications 16: 143-153.
Murray BC, Sohngen B, et al. (2005). Greenhouse Gas Mitigation Potential in U.S. Forestry and Agriculture.
Publication No. EPA 430-R-05-006. http://www.epa.gov/sequestration/greenhouse_gas.html
Nabuurs GJ, Masera O, et al. (2007). Chapter 9: Forestry. Climate Change 2007: Mitigation. Assessment
Report 4 of the IPCC. Cambridge University Press.
Parrotta JA (2002). Restoration and management of degraded tropical forest landscapes. In Modern Trends
in Applied Terrestrial Ecology. R.S. Ambasht and N.K. Ambasht (eds.), Kluwer Academic/Plenum Press, New
York, pp. 135-148 (Chapter 7).
Parry IWH, Pizer W (2007). Backgrounder: Emissions Trading versus CO2 Taxes versus Standards.
Resources for the Future. www.rff.org
Schlamadinger B, Johns T et al. (2007). Options for including land use in a climate agreement post-2012:
improving the Kyoto Protocol approach. Environmental Science and Policy 10: 295-305.
Sedjo RA, Amano M (2006). The Role of Forest Sinks in a Post-Kyoto World. Resources for the Future.
www.rff.org/News/Features/Pages/Role-of-Forest-Sinks.aspx
Shrestha R, Lal R (2008). Offsetting carbon dioxide emissions through minesoil reclamation. Encyclopedia of
Earth. http://www.eoearth.org/article/Offsetting_carbon_dioxide_emissions_through_minesoil_reclamation
Smith P, Martino D, et al. (2007). Chapter 8: Agriculture. Climate Change 2007: Mitigation. Assessment
Report 4 of the IPCC. Cambridge University Press.
United States Department of State (2000). United States Submission on Land-Use, Land-Use Change, and
Forestry to the Kyoto Conference of Parties. Accessed August 1, 2009.
http://www.state.gov/www/global/global_issues/climate/000801_unfccc1_subm.pdf
Wise, A (2008). The US Carbon Market. Renewable Energy World News.
http://www.renewableenergyworld.com/rea/news/article/2008/05/the-u-s-carbon-market-52451
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NETL Regional Carbon Sequestration Partnerships
http://www.netl.doe.gov/technologies/carbon_seq/partnerships/partnerships.html
DOE Terrestrial Sequestration Research
http://www.fossil.energy.gov/programs/sequestration/terrestrial/index.html
See, for example, Johnson KS, Karl DM, “Is Ocean Fertilization Credible and Creditable?” Science 296: 467-468,
2002.
1
The difference between tons of carbon (tC) and tons of carbon dioxide (tCO2) is often confused. It is confusing
because CO2 is 3.67 times more massive than C alone due to the added molecular weight of oxygen (O2). Therefore 1 tC
is equivalent to 3.67 tCO2.
2
3 Stavins R, Richards K, The Cost of U.S. Forest-Based Carbon Sequestration, 2005 Prepared for the Pew Center on
Climate Change.
Nabuurs GJ, Masera O, et al., “Chapter 9: Forestry” in Contribution of Working Group III to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change, 2007. .
4
Johnson R. Climate Change: The Role of the U.S. Agriculture Sector and Congressional Action, Congressional
Research Service, 2009. Report RL33898.
5
Hansen EA, “Soil Carbon Sequestration beneath Hybrid Poplar Plantations in the North Central United States,”
Biomass and Bioenergy 5: 431-436, 1993.
6
McLauchlan KK, Hobbie SE, Post WM, “Conversion of Agriculture to Grassland Builds Soil Organic Matter on Decadal
Timescales,” Ecological Applications 16: 143-153, 2006.
7
Johnson R, Gorte RW, Estimates of Carbon Mitigation Potential from Agricultural and Forestry Activities,
Congressional Research Service, 2009. Report R40236.
8
9 Lewandroski J, Peters M, et al.,Economics of Sequestering Carbon in the U.S. Agricultural Sector, U.S. Department of
Agriculture Technical Bulletin Number1909, 2004.
Murray BC, Sohngen B, et al., Greenhouse Gas Mitigation Potential in U.S. Forestry and Agriculture, U.S.
Environmental Protection Agency (EPA) Publication No. 430-R-05-006, 2005.
10
U.S. EPA , “Representative Carbon Sequestration Rates and Saturation Periods for Key Agricultural & Forestry
Practices,” 2006.
11
Energy Information Administration (EIA), Energy Market and Economic Impacts of H.R. 2454, the American Clean
Energy and Security Act of 2009, 2009. See Table ES-1.
12
13 For more information on H.R.2454, the American Climate and Energy Security Act of 2009 (ACESA), see
http://www.pewclimate.org/acesa.
14 Degryze S, Six J et al., “Soil Organic Carbon Pool Changes Following Land-Use Conversions,” Global Change Biology
10: 1120–1132, 2004.
Parrotta JA, “Restoration and Management of Degraded Tropical Forest Landscapes,” in Modern Trends in Applied
Terrestrial Ecology, R.S. Ambasht and N.K. Ambasht (eds.), Kluwer Academic/Plenum Press, New York, 2002.
15
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16 Richards K, Sampson RN, and Brown S, Agricultural & Forestlands: U.S. Carbon Policy Strategies, 2006. Prepared for
the Pew Center on Climate Change.
17
Stavins, 2005.
Paustian K and Antle JM, Agriculture’s Role in Greenhouse Gas Mitigation, 2006. Prepared for the Pew Center on
Climate Change.
18
Sohngen B and Mendelsohn R, Optimal Forest Carbon Sequestration, Department of Agricultural, Environmental, and
Development Economics, Ohio State University. Working Paper AEDE-WP-0009-01, 2001.
19
20
Nabuurs et al., 2007.
Schlamadinger B, Johns T et al., “Options for Including Land Use in a Climate Agreement Post-2012: Improving the
Kyoto Protocol Approach,” Environmental Science and Policy 10: 295-305, 2007.
21
22
Ibid.
23
European Union, “Questions and Answers on Deforestation and Forest Degradation,” MEMO/08/632, 2008.
24
Chicago Climate Exchange, “CCX Exchange Offsets and Exchange Early Action Credits” in CCX Confidential, 2004.
25
California Climate Action Registry, Forest Project Protocol, 2009..
26
Regional Greenhouse Gas Initiative (RGGI), “Offset Project Categories: Afforestation.”
Smith P, Martino D, et al., “Chapter 8: Agriculture,” in Contribution of Working Group III to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change, 2007.
27
28
Ibid.
29
Richards et al., 2006.
30
Ibid.
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