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Criterion 5 Indicator 28
Rationale
Contribution of Forest Products to the Global Carbon Budget
 
During the process of photosynthesis, woody plants absorb carbon dioxide, store the carbon in wood, and release oxygen, thereby mitigating the increase of carbon dioxide in the atmosphere. Wood harvested from forests continues to store carbon until the wood decomposes. Therefore, management of forests for products, particularly products which continue to store carbon in the long-term, is a factor in the amount of carbon entering the world’s atmosphere. For more information on carbon as a policy issue, see Heath and Joyce (1997).

Can This Indicator Be Quantified
Can This Indicator Be Quantified
 
This indicator can be quantified from harvest estimates combined with a modeling approach. The method used is related to the methods for Indicator 26 and Indicator 27. It is important that the accounting system used for forest products is compatible with the accounting system for Indicator 27, contribution of forest ecosystems to the total carbon budget. Emissions of logging residue left in the forest are counted in Indicator 26; however, emissions from mill residues are counted under forest products. Counting carbon in forest products requires an analysis to be completed, estimating the amount of wood removed from forests is utilized for forest products, and estimating the decay rates of carbon from the forest products. Row and Phelps (1996) present results from such an analysis for regions of the United States. Their procedure was adopted, using their estimated disposition percentages for the Pacific Northwest region.
 
The inventory of carbon in forest products is summarized in four categories: products in-use, landfills, emissions from wood burned from energy, and emissions. The products category includes carbon in wood buildings, pallets, furniture, fixtures, paper and paper products. The amount in all categories sums to 100% of harvest. As time since harvest increases, the amount in products from the harvest declines as products are used and disposed of in landfills, and as wood (and therefore carbon) decays and decomposes. The amount in landfills is a balance between additions of products that are disposed of and their decay. The regional percentages are available by hardwood and softwood, and by pulpwood and sawtimber. Figure 28-1 illustrates the pattern of carbon disposition for softwood sawtimber in the Pacific Northwest. At time of harvest, approximately 50% of the harvested carbon is still stored in products, and 50% is emitted. Ten years after the harvest, only 35% remains stored in products, and about 10% is stored in landfills. Multiplying these percentages by the amount of carbon in harvests will produce the amount of carbon still stored in products or landfills, and the amount emitted.
 
All wood harvested in the state is counted. Wood or wood products imported into the state are assumed to be counted where they are grown. This is known as the production approach (see Heath and others, 1996).
 
Previous harvests affect the current contribution of forest products. The change in carbon per year was calculated by taking the difference between the inventories. The estimated average annual flux of forest products is given in Table 28-1. Preliminary analyses showed that counting harvests beginning in 1978 instead of 1948 reduced emissions by only 0.06 million metric tons per year. Because the difference is small, and the disposition percentages are more applicable in the 1980´s, the final estimates were based on harvests beginning in 1978.
 
 
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Figure 28-1. Carbon disposition curves for softwood sawtimber in the Pacific Northwest region. Source is unpublished report by Clark Row, HARVCARB coefficients for estimating carbon flows from regional timber harvests, dated March 12, 1993.
 
Table 28-1. Average annual carbon flux (million metric tons per year) for forest products. A positive flux indicates carbon is being taken out of the atmosphere; a negative flux indicates that carbon is being taken out of the atmosphere.
 
PeriodProducts in useLandfillsEmissions from wood burned for energyEmissions
1978-19820.60-0.3-0.3
1982-19870.60.1-0.3-0.4
1988-19920.40.1-0.3-0.3
1993-19970.20.1-0.2-0.2
 
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The amount being stored in products in use and landfills is already counted in forest growth in the forest ecosystem (Indicator 27). However, emissions from harvested
Carbon are not included. Thus, for 1999, the contribution of forest products to the global carbon budget using this method is approximately -0.4 million metric tons per year (Sum of emissions categories.)

Trends
 
Harvest trends provide a good indicator of carbon emission changes. Because all forest carbon increases are counted in Indicator 27, only emissions are counted in Indicator 28. Emissions have declined slightly in the mid-90's because harvests have decreased in the last ten years.

Data Source and Availability
   
Harvest data were provided by the Oregon Department of Forestry, reported in Scribner board foot. These were converted to cubic feet and carbon using the conversion factor for board foot to cubic foot in Powell and others (1993) and the conversion factor for Douglas-fir cubic foot volume to carbon in Birdsey (1992). Aggregate data were available annually from 1942-1996. The value for 1997 was estimated as the average of the preceding four years.

Reliability of Data
   
Data are compiled from different sources, and reported in ODF annual reports. The disposition percentages are fairly reliable for the base year 1986, and are less reliable for years increasingly greater or less than 1986.

Recommended Action for Data Collection
 
More specific information would improve these estimates. Knowing the amount of harvests by softwood/hardwood type, and by pulpwood/sawtimber would be of use. In addition, having consistent estimates of logging residue, mill residue, and harvests would improve estimates.

Definitions
   
Logging residue – Biomass left on the ground after trees have been harvested and removed, measured in terms of dry weight.
 
Mill residue – Bark and woody materials that are generated in mills when harvested wood is converted to products. Examples are slabs, edgings, trimmings, sawdust, and shavings.
 

Selected References
 
Birdsey, R.A. 1992. Carbon storage and accumulation in United States forest ecosystems. USDA Forest Service, Washington Office, General Technical Report, WO-59. 51 p.
 
Heath, L.S, R.A. Birdsey, C. Row, and A.J. Plantinga. 1996. Carbon pools and fluxes in U.S. forest products. In: (Apps, M.J., and D.T. Price, eds.) Forest Ecosystems, Forest Management and the Global Carbon Cycle, p. 271-278. NATO ASI Series I: Global Environmental Change, Vol. 40, Springer-Verlag, Berlin. 442 p.
 
Heath, L.S., and L.A. Joyce. 1997. Carbon sequestration in forests as a national policy issue. In: Communicating the role of silviculture in managing the national forests: Proceedings of the National Silviculture Workshop, p. 29-36. US DA Forest Service, Northeastern Forest Experiment Station, General Technical Report NE-GTR-238. 205 p.
 
Powell, D.S., J. L. Faulkner, D.D. Darr [and others]. 1992, rev. Forest resources of the United States, 1992. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, General Technical Report RM-GTR-234. 132 p.
 
Row, C. and R. B. Phelps. 1996. Wood carbon flows and storage after timber harvest. In: (Sampson, R.N, and D. Hair, eds.) Forests and Global Change. Vol. 2: Forest management opportunities for mitigating carbon emissions, p. 27-58. American Forests, Washington, DC. 379 p.