Stockmannetal.CarbonBalanceandManagement2012,7:1 http://www.cbmjournal.com/content/7/1/1 RESEARCH Open Access Estimates of carbon stored in harvested wood products from the United States forest service northern region, 1906-2010 Keith D Stockmann1*, Nathaniel M Anderson2, Kenneth E Skog3, Sean P Healey4, Dan R Loeffler5, Greg Jones2 and James F Morrison1 Abstract Background: Global forests capture and store significant amounts of CO through photosynthesis. When carbon is 2 removed from forests through harvest, a portion of the harvested carbon is stored in wood products, often for many decades. The United States Forest Service (USFS) and other agencies are interested in accurately accounting for carbon flux associated with harvested wood products (HWP) to meet greenhouse gas monitoring commitments and climate change adaptation and mitigation objectives. This paper uses the Intergovernmental Panel on Climate Change (IPCC) production accounting approach and the California Forest Project Protocol (CFPP) to estimate HWP carbon storage from 1906 to 2010 for the USFS Northern Region, which includes forests in northern Idaho, Montana, South Dakota, and eastern Washington. Results: Based on the IPCC approach, carbon stocks in the HWP pool were increasing at one million megagrams of carbon (MgC) per year in the mid 1960s, with peak cumulative storage of 28 million MgC occurring in 1995. Net positive flux into the HWP pool over this period is primarily attributable to high harvest levels in the mid twentieth century. Harvest levels declined after 1970, resulting in less carbon entering the HWP pool. Since 1995, emissions from HWP at solid waste disposal sites have exceeded additions from harvesting, resulting in a decline in the total amount of carbon stored in the HWP pool. The CFPP approach shows a similar trend, with 100-year average carbon storage for each annual Northern Region harvest peaking in 1969 at 937,900 MgC, and fluctuating between 84,000 and 150,000 MgC over the last decade. Conclusions: The Northern Region HWP pool is now in a period of negative net annual stock change because the decay of products harvested between 1906 and 2010 exceeds additions of carbon to the HWP pool through harvest. However, total forest carbon includes both HWP and ecosystem carbon, which may have increased over the study period. Though our emphasis is on the Northern Region, we provide a framework by which the IPCC and CFPP methods can be applied broadly at sub-national scales to other regions, land management units, or firms. Background [2], or the equivalent of about 30 years of US fossil fuel Recent estimates of net annual storage, or flux, indicate emissions at the 2008 rate. The US Environmental Pro- that the world’s forests are an important carbon sink, tection Agency (EPA) estimates that in 2010 net addi- removing more carbon from the atmosphere through tions to ecosystem and harvested wood products (HWP) photosynthesis than they emit through combustion and pools were 235 TgC yr-1 [2]. Thus, US forests function decay [1]. The forest sector of the United States (US) as a carbon sink, annually offsetting about 15 percent of stored about 48,437 teragrams of carbon (TgC) in 2010 the country’s carbon emissions from fossil fuel combustion. About 5 percent of total US forest sector carbon *Correspondence:[email protected] stocks and 6 percent of the annual flux is attributable to 1NorthernRegion,USDAForestService,Missoula,MT,USA carbon in HWP [2]. Though the HWP fraction of the Fulllistofauthorinformationisavailableattheendofthearticle ©2012Stockmannetal;licenseeBioMedCentralLtd.ThisisanOpenAccessarticledistributedunderthetermsoftheCreative CommonsAttributionLicense(http://creativecommons.org/licenses/by/2.0),whichpermitsunrestricteduse,distribution,and reproductioninanymedium,providedtheoriginalworkisproperlycited. Stockmannetal.CarbonBalanceandManagement2012,7:1 Page2of16 http://www.cbmjournal.com/content/7/1/1 pool is small compared to ecosystem carbon, it is an level of an individual harvest [9]. Robust inventory- important component of national level carbon account- based methods for estimating carbon stocks and flux in ing and reporting. As defined by the Intergovernmental forest ecosystems are well established in the US, with Panel on Climate Change (IPCC), HWP are products several tools available to forest managers [9-12]. How- made from wood including lumber, panels, paper, ever, many of the tools used to estimate carbon stored paperboard, and wood used for fuel [3]. The HWP car- in forests, such as the Carbon On Line Estimator Ver- bon pool includes both products in use and products sion 2.0 [13] and the U.S. Forest Carbon Calculation that have been discarded to solid waste disposal sites Tool [14], do not provide estimates of HWP carbon and (SWDS). Additions to the HWP pool are made though other tools are restricted to national level HWP harvesting and emissions are from decay and combus- accounting (e.g., WOODCARB II [3]). While these tools tion of wood products. are relevant for public and industrial timber producers Increasing social and managerial interest in mitigating interested in documenting the carbon fluxes associated rising atmospheric CO concentrations and the resulting with harvesting activities [15], at their current scales of 2 impacts on climate has focused attention on the ecosys- analysis they do not serve the needs of these forest man- tem service of forest carbon storage, including storage agers. Managers need similarly accessible and practical in HWP. Forest management can affect the quantity of tools for estimating and monitoring carbon stocks and carbon stored in both ecosystems and forest products flux in HWP at the agency or firm level [16]. over time, and management activities in the US fre- quently include silvicultural treatments that produce Objectives HWP. Credible information on forest ecosystem and There is a clear need for the means to monitor the con- HWP carbon stocks and fluxes can inform forest man- tribution of HWP to carbon pools and greenhouse gas agers and the public of the tradeoffs between carbon mitigation at sub-national scales. Currently, forest man- storage and other forest management objectives, and agers do not have the tools they need to accomplish between short and long-term carbon consequences of monitoring goals that have been established at the alternative forest management strategies [4-6]. national level. Developing these tools is an important As governments contemplate climate change mitiga- step in facilitating carbon assessment and stewardship tion and adaptation options, there is growing interest and in informing management actions on the ground. among forest managers in monitoring and managing Our objectives with this study are to: 1) use established forests for sequestration of carbon as an ecosystem ser- accounting approaches to make estimates of HWP car- vice. For example, during 2010, the US Forest Service bon stocks and fluxes for the USFS Northern Region as (USFS) developed a climate change scorecard that is to a demonstration of sub-national HWP accounting, and be completed annually for each of the 155 national for- 2) provide a framework with clear metrics and estima- ests and national grasslands managed by the agency [7]. tion methods that can be applied to other regions, land The scorecard includes four categories of scored ele- management units, or firms. We also provide guidance ments: organizational capacity; engagement; adaptation; to managers concerning the differences between alterna- and, mitigation and sustainable consumption. Elements tive approaches with regards to data and resource under mitigation and sustainable consumption direct requirements. We do not develop a system for evaluat- individual forests to develop a baseline assessment of ing the future impacts of specific management actions, carbon stocks, as well as an assessment of the influence nor do we advocate any particular course of action to of disturbance and management activities on these improve carbon stewardship. stocks. These assessments are meant to guide adaptation actions and continued monitoring. Managers are expli- Accounting Approaches citly expected to begin integrating carbon stewardship We use the IPCC production accounting approach, with management of their forest for traditional multiple which has been adopted by the US EPA; hereafter uses and other ecosystem services. These requirements referred to as the IPCC/EPA approach), and the Califor- necessitate robust and accessible monitoring systems nia Forest Project Protocol (CFPP; [17]) to estimate that provide quantitative metrics to gauge progress. Poli- annual changes in HWP pools from 1906 to 2010 for cies and guidelines are currently under development the USFS Northern Region (Figure 1). The Northern regarding the appropriate level of accuracy needed for Region contains approximately 10.9 million hectares of completing carbon assessments and for informing forest federally-owned land in the states of Montana, Idaho, management decisions at the individual national forest North Dakota, South Dakota, and eastern Washington. level. Approximately 8.1 million hectares of this land are HWP carbon monitoring systems have been imple- forested. We chose this region because it represents a mented at the national level [2,3,8], as well as at the management unit of the desired sub-national scale and Stockmannetal.CarbonBalanceandManagement2012,7:1 Page3of16 http://www.cbmjournal.com/content/7/1/1 N. Dakota Montana S. Dakota Idaho É 0 200 400 km Region 1 Boundary R1 National Forest Figure1Mapofthestudyarea.TheUSForestServiceNorthernRegion(theNorthernRegion)administersapproximately8.1millionhectares offederally-ownedforestlandinthestatesofMontana,Idaho,SouthDakota,andnortheasternWashington. managers in this region are particularly interested in Region that were exported outside the region (E ). EX R1 developing tools to meet carbon stewardship objectives. Exports (P ) include wood and paper products, as well EX In the IPCC/EPA production accounting approach, the as roundwood, chips, residue, pulp and recovered annual carbon stock change for the total forest sector (recycled) products from wood harvested in the North- (ΔS) is a function of carbon flow among the atmo- ern Region. Under the production accounting approach, sphere, forest ecosystems, and HWP, and is calculated imports from other regions (indicated with dotted lines as: around the right side portions for both boxes showing HWP in use or in SWDS are not included in Northern (cid:2)S= (NEE−H) + ((cid:2)C ) R1 Region accounting because the emphasis is on the loca- tion of harvest (H). Emissions are further categorized as where NEE is the annual net ecosystem exchange emitted with energy capture (e.g. fuelwood) and emitted between the atmosphere and Northern Region forests without energy capture (e.g. decomposition and burning from all ecosystem processes including photosynthesis, for waste disposal). The relevant metric for this account- decay, and natural and anthropogenic fire, H is the ing approach is annual stock change in the HWP carbon annual harvest of wood from Northern Region forests for products, and ΔC is the annual change in carbon pool. R1 The CFPP was designed for application to smaller stored in HWP that were made from wood harvested geographic areas and uses a simpler accounting from Northern Region forests (Table 1, Figure 2). As approach focused on carbon storage for a single harvest discussed previously, the HWP pool is a relatively small year rather than net annual carbon change due to cur- but important fraction of the total forest sector carbon rent year additions to product pools and current year flux in the US, accounting for about 6 percent of the annual carbon stock change of 235 TgC yr-1. emissions from those pools. The relevant metric for the CFPP accounting approach is 100-year average carbon In this approach, the annual change in carbon stored in HWP (ΔC ) is the sum of the net change in carbon stored from the current year’s harvest - “the 100-year stored in proRd1ucts in use (ΔC ) and the net change average.” Like the production approach, the CFPP IU R1 approach is applied to a specified area of land, and in carbon stored in products at solid waste disposal sites (ΔC ). Figure 2 shows that carbon emissions includes carbon stored in both products in use and SWDS R1 SWDS. The approach uses mill efficiency factors and attributed to HWP from the Northern Region (indicated decay curves for individual product classes to estimate with solid boxes) include both emissions to the atmo- the average amount of carbon that is likely to remain sphere from the Northern Region products that were stored in wood products from a given year’s harvest used within the region (E ) and emissions to the atmo- R1 over a 100-year period [9,18]. Specific estimation sphere from wood products harvested in the Northern Stockmannetal.CarbonBalanceandManagement2012,7:1 Page4of16 http://www.cbmjournal.com/content/7/1/1 Table 1Variable definitions for the IPCC/EPA production accounting approach shown in Figure2[3].Units forall variables are MgCyr-1. Variable Definition ΔS Annualcarbonstockchangeforthetotalforestsector,whichiscalculatedasΔS=(NEE-H)+(ΔC )intheproductionaccounting R1 approach. NEE Annualnetecosystemcarbonexchange,theannualnetcarbonthatmovesfromtheatmospheretoforests. H Annualharvestofwoodforproducts,whichincludeswoodandresiduesremovedfromharvestsites,butexcludesresidesleftatharvest sites. HWP Harvestedwoodproductsinuseoratsolidwastedisposalsites. E AnnualemissionofcarbontotheatmosphereintheNorthernRegionfromproductsmadefromwoodharvestedintheNorthernRegion. R1 E AnnualemissionofcarbontotheatmosphereintheNorthernRegionfromproductsmadefromwoodharvestedoutsideofthe IM NorthernRegionandimportedintoTheNorthernRegion. P AnnualexportsofwoodandpaperproductsoutoftheNorthernRegion,includingroundwood,chips,residue,pulpandrecovered EX (recycled)products. P AnnualimportsofwoodandpaperproductsintotheNorthernRegion,includingroundwood,chips,residue,pulpandrecovered IM (recycled)products. E AnnualemissionofcarbontotheatmosphereinareasoutsideoftheNorthernRegionfromproductsmadefromwoodharvestedinthe EXR1 NorthernRegion. E AnnualemissionofcarbontotheatmosphereinareasoutsideoftheNorthernRegionfromproductsmadefromwoodharvested OTHER outsidetheNorthernRegion. C StockofharvestedwoodproductscarboninuseoratsolidwastedisposalsiteswhereproductsusedwoodfromtheNorthernRegion R1 harvests. ΔC AnnualchangeincarbonstoredinharvestedwoodproductsinproductsinusewhereproductsusedwoodfromtheNorthernRegion IUR1 harvests. ΔC AnnualchangeincarbonstoredinharvestedwoodproductsatsolidwastedisposalsiteswhereproductsusedwoodfromtheNorthern SWDS Regionharvests. R1 ΔC Annualchangeincarbonstoredinharvestedwoodproductsinproductsinuseandatsolidwastedisposalsiteswhereproductsused R1 woodfromtheNorthernRegionharvests. ΔC =ΔC +ΔC R1 IUR1 SWDSR1 methods for both approaches are discussed in detail in added to the HWP pool (Figure 2). Figure 4 shows the the Methods section. cumulative carbon in both the products in use and SWDS components of the HWP pool for the Northern Results Region using the production accounting approach. Between 1906 and 1943, the annual timber harvest in Using a format that matches the reporting for selected the Northern Region remained below 400,000 MgC yr-1 inventory years found in the most recent EPA report (328.5 million cubic feet yr-1) and decreased during the [2], Table 2 shows how the disposition of HWP carbon Great Depression in the 1930’s (Figure 3). After World is broken into the four IPCC/EPA categories: emitted War II, annual harvest levels increased steadily, with with energy capture, emitted without energy capture, some volatility, to maximum harvest levels in the late products in use and products at SWDS. For each inven- 1960’s and early 1970’s. Growth in the annual harvest tory year shown in the first column, the second column was particularly rapid between 1950 and 1956, when the shows aggregate carbon emitted with energy capture (i. annual harvest tripled from half a million MgC yr-1 to e. fuelwood), the third column shows aggregate carbon 1.5 million MgC yr-1 by 1956. At its peak in 1969, the emitted through decay or combustion from SWDS, and annual timber harvest in the Northern Region exceeded the fourth and fifth columns show carbon stored in pro- 2.4 million MgC yr-1. Beginning in the mid-1970’s, the ducts in use and products at SWDS, respectively. The annual harvest decreased steadily, with a brief increase final column, the “Total remaining in the HWP pool,” is in harvesting in the late 1970’s followed by a particularly the sum of products in use (column 4) and carbon at steep decrease during the economic recession of 1981- SWDS (column 5). It is important to understand that 82. Between 1982 and 1987 the harvest level rose shar- the estimate for each inventory year includes the portion ply, but then fell nearly every year from 1988 to 2002. of HWP carbon still in product in use and at SWDS for Harvest levels since 2000 have been relatively stable all previous harvest years back to 1906, in addition to between 200,000 to 400,000 MgC yr-1, which is similar carbon harvested in the inventory year. Some of the to the harvest levels of the early twentieth century. cumulative emissions from the burned and decayed All else being equal, higher harvest levels result in HWP (Table 2, second and third columns) are theoreti- more carbon removed from the ecosystem pool and cally taken out of the atmosphere by regrowth on Stockmannetal.CarbonBalanceandManagement2012,7:1 Page5of16 http://www.cbmjournal.com/content/7/1/1 ATMOSPHERE NEE E E E E R1 IM EX(cid:3)R1 OTHER HWPin(cid:3) HWPin(cid:3) H Forest(cid:3) use(cid:3)or(cid:3)in(cid:3) use(cid:3)or(cid:3)in(cid:3) Ecosystem SWDS SWDS P EX P USDA(cid:882)FS(cid:3)REGION(cid:3)1 IM OUTSIDE(cid:3)REGION(cid:3)1 C –Stock(cid:3)of(cid:3)HWP(cid:3)carbon(cid:3)in(cid:3)products(cid:3)in(cid:3)use(cid:3)or(cid:3)in(cid:3) R1 SWDS(cid:3)where(cid:3)wood(cid:3)came(cid:3)from(cid:3)Region(cid:3)1(cid:3)harvest Figure2Carbon flowsandstocksassociatedwithforestecosytems andharvestedwoodproducts(HWP). Carbon flowsandstocks associatedwithforestecosystemsandharvestedwoodproducts(HWP)areusedtoillustratetheIPCC/EPAproductionaccountingapproach (adaptedfrom[3]). harvested sites, but this effect is accounted for in the ecosystem carbon component of the IPCC/EPA approach (NEE), not in the HWP component (H and 3.0 ΔC ). R1 t(cid:3) The cumulative carbon stored in the Northern Region u 2.5 p HWP pool peaked in 1995 at just over 28 million MgC. t duct(cid:3)Oun(cid:3)MgC) 12..50 FtsheoenrgCreeOrfe2vreeehqniuccielve,astl.ehnSistinaiscnenequ1ua9li9ve5am,lecinsastribotonons1f0srto3omcmk2isl0liionmntilhlMieognHCpWOas2P-, oo r(cid:3)Prmilli 1.0 poolfortheNorthernRegionhavebeenindecline(Figure be( 4). The 2010 HWP pool is estimated to be around 25.8 m 0.5 million MgC (Table 2). Figure 5 and Table 3presentthe Ti trend in terms of net annual change in HWP carbon 0.0 stocks.NegativenetannualchangeinHWPcarbonstocks 0 0 0 0 0 0 0 2 4 6 8 0 means the total carbon stored in the HWP pool in the 9 9 9 9 9 0 1 1 1 1 1 2 inventoryyearislowerthaninthepreviousyear.Adecline Harvest(cid:3)Year intheHWPpoolresultsinatransitionfromapositivenet Figure 3 Annual timber product output in the Northern annual change in carbon stocks to a negative net annual Region,1906to2010.Annualtimberproductoutputinthe changeincarbonstocks.Inthemid-1960s,carbonstocks NorthernRegion,1906to2010arebasedondatacollectedfrom in HWP were growing by nearly one million MgC yr-1, USDAForestServiceArchivesandCut/Soldreports. with peak stock growth occurring during 1967 with the Stockmannetal.CarbonBalanceandManagement2012,7:1 Page6of16 http://www.cbmjournal.com/content/7/1/1 30 Products(cid:3)in(cid:3)SWDS s(cid:3) k 25 c Products(cid:3)in(cid:3)use o t n(cid:3)SC) 20 og bM arn(cid:3) 15 Co WP(cid:3)milli 10 H( al(cid:3) 5 t o T 0 1910 1930 1950 1970 1990 2010 Inventory(cid:3)Year Figure4CumulativetotalcarbonstoredinHWPmanufacturedfromNorthernRegiontimberusingtheIPCC/EPAapproach.Cumulative totalcarbonstoredinharvestedwoodproducts(HWP)manufacturedfromtimberharvestedfromNorthernRegionNationalForestsusingthe IPCC/EPAproductionaccountingapproach.CarboninHWPincludesbothproductsthatarestillinuseandcarbonstoredatsolidwastedisposal sites(SWDS),includinglandfillsanddumps. additionof1,042,158MgCyr-1.Inthemid-1990’s,thenet peaked in 1969 at 937,900 MgC (Figure 6). A declining change moves from positive to negative, and the HWP trend in carbon storage in HWP since 1970 is also pool becomes a net source of atmospheric carbon. The reflected by the 100-year averages (Figure 6, Table 4). In year in the dataset with the largest net emissions from recent years, the 100-year average for the Northern NorthernRegionHWPcarbonpoolwas2002,whenanet Region has been between 84,000 and 150,000 MgC. of228,241MgCyr-1wereemitted.Theseestimatesrelate Though the two estimation approaches differ in meth- only to HWP and do not quantify carbon fluxes in the ods and calculations, they both show a clear and ecosystempool. expected connection between timber harvest trends and The 100-year average calculated using the CFPP for carbon stored in the HWP pool. the Northern Region, which is a projected average car- To quantify uncertainty, confidence intervals were bon stock over 100 years for harvest in a particular year, estimated for both the IPCC/EPA HWP stock estimates Table2CumulativedispositionofHWP carbonforselectedyearsusingtheIPCC/EPA productionaccountingapproach. This table showsthe fate ofallcarbon removed fromthe ecosystem by harvesting. Inventory Emittedwithenergy Emittedwithoutenergy Productsin SWDS TOTALremaininginHWP year capture capture use (MgC) Poola (MgC) (MgC) (MgC) (MgC) 1910 154,281 12,332 235,801 23,865 259,666 1920 957,662 196,962 1,271,481 219,922 1,491,403 1930 1,689,268 601,197 1,954,753 422,240 2,376,993 1940 2,125,441 1,118,607 2,116,591 511,967 2,628,558 1950 3,597,873 1,833,130 3,755,737 754,204 4,509,941 1960 7,561,338 3,672,609 7,394,180 1,894,409 9,288,589 1970 15,294,381 8,049,313 14,002,272 3,822,113 17,824,385 1980 22,072,575 13,859,456 17,464,432 5,855,782 23,320,214 1990 27,098,481 19,166,028 19,466,986 7,584,521 27,051,507 1995 29,034,443 21,725,124 19,855,947 8,396,262 28,252,209 2000 29,951,361 23,991,595 18,692,672 8,844,219 27,536,891 2005 30,634,194 25,950,852 17,589,954 9,084,182 26,674,136 2006 30,773,608 26,313,165 17,416,848 9,121,609 26,538,457 2007 30,884,369 26,664,054 17,186,329 9,151,940 26,338,269 2008 30,989,500 27,004,208 16,960,188 9,179,261 26,139,449 2009 31,112,619 27,333,955 16,743,418 9,204,640 25,948,058 2010 31,258,742 27,653,986 16,545,328 9,229,516 25,774,844 aSumofProductsinuseandSWDS. Stockmannetal.CarbonBalanceandManagement2012,7:1 Page7of16 http://www.cbmjournal.com/content/7/1/1 1,200,000 Products(cid:3)in(cid:3)SWDS Products(cid:3)in(cid:3)use 1,000,000 Net(cid:3)change,(cid:3)1990(cid:3)to(cid:3)2010 ) 1 (cid:882)yr 800,000 C(cid:3) g M s(cid:3)( 600,000 k c o t S n(cid:3) 400,000 o b r a C 200,000 n(cid:3) e(cid:3)i g n 0 a h C (cid:882)200,000 (cid:882)400,000 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Inventory(cid:3)Year Figure5ThenetchangeincarbonstocksinHWPfromthepreviousyearusingtheIPCC/EPAproductionaccountingapproach.The netchangeincarbonstocksinHWPfromthepreviousyearusingtheIPCC/EPAproductionaccountingapproach.Thenetstockchangeisthe sumofnetchangeforSWDS(blackbar)andproductsinuse(graybar).Thetotalnetchangetrendlinefrom1990to2010showsatransition fromnetadditionstocarbonstocksinHWPtoaperiodofnetlossincarbonstocksinHWP. Table 3Annual net change in HWP carbonstocks for and the CFPP 100-year average estimates using Monte selected years forharvests beginning in 1906usingthe Carlo simulation, representing 18 and 15 random vari- IPCC/EPA production accounting approach. able distributions, respectively. Variable distributions Inventoryyear Stockchangea were determined from publications and expert opinion. (MgCyr-1) Table 5 shows the resulting confidence intervals for the 1910 104,116 IPCC/EPA estimates for selected years. For 1995, the 1920 97,021 year of peak carbon stocks for the Northern Region, the 1930 75,712 90 percent confidence interval ranges from 20,723,740 1940 16,051 MgC to 37,108,160 MgC, with a mean value of 1950 298,029 28,272,940 MgC. This is equivalent to a -26.7 percent to 1960 591,785 +31.2 percent difference from the mean. Table 6 shows 1970 966,125 the resulting confidence intervals for the 100-year aver- 1980 437,628 age for selected years. For 1970, the year with the high- 1990 481,517 est 100-year average shown, the 90 percent confidence 1995 59,764 interval ranges from 563,303 to 1,336,731 MgC, with a 2000 -184,812 mean value of 898,820 MgC. This is equivalent to a 2005 -151,437 -37.3 percent to a +48.7 percent difference from the 2006 -135,679 mean. 2007 -200,187 2008 -198,821 Discussion 2009 -191,391 HWP Carbon Estimates for the Northern Region 2010 -173,214 Although these results rely on numerous calculations, aNetannualchangeincarboninproductsinuseandSWDS the time series of annual harvest volume (Figure 3) is at Stockmannetal.CarbonBalanceandManagement2012,7:1 Page8of16 http://www.cbmjournal.com/content/7/1/1 1,000,000 Products(cid:3)in(cid:3)SWDS ) C g Products(cid:3)in(cid:3)use M ( 800,000 e(cid:3) g a r o t S n(cid:3) 600,000 o b r a C e(cid:3) 400,000 g a r e v A r(cid:3) 200,000 a e Y 0(cid:3) 0 1 0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Harvest(cid:3)Year Figure6NorthernRegionharvest100-yearaveragecarbonHWPstorageusingtheCaliforniaForestProjectProtocol.The100-year averagecarbonstorageinHWPforeachyearcalculatedfortheNorthernRegionNationalForestharvestusingtheCaliforniaForestProject Protocol.The100-yearaverageiscalculatedindependentlyforeachharvestyearandconsidersonlycarbonharvestedinthatyear. the root of the trends in carbon stocks and flux for the of 25.8 teragrams of carbon (TgC) in HWP by the sum Northern Region HWP pool. Several recent publications of this HWP estimate and Heath et al.’s [19] estimated help put these HWP carbon estimates in the context of 2010 Northern Region ecosystem carbon stock (25.8TgC the total forest carbon, including both ecosystem carbon and HWP carbon. By dividing our 2010 stock estimate Table 5Confidence intervals forcumulative carbon in HWP forselected yearsfor harvests beginning in1906. Means andconfidence intervals werecalculated using Table 4The 100-yearaverage carbon stored in HWP for Monte Carlo simulation. selected years usingthe California ForestProject Protocol. Inventoryyear SimulationMean 90%Confidenceinterval (MgC) Harvestyear Productsinusea Landfillsanddumpsb Total 5% 95% (MgC) (MgC) (MgC) (MgC) (MgC) 1910 41,496 32,052 73,547 1910 258,847 151,997 383,534 1920 52,862 40,832 93,694 1920 1,490,397 859,969 2,254,610 1930 42,777 33,042 75,819 1930 2,380,130 1,348,945 3,726,131 1940 57,768 44,621 102,389 1940 2,623,487 1,559,630 4,011,111 1950 94,131 86,792 180,923 1950 4,508,105 2,756,788 6,754,915 1960 326,709 301,238 627,947 1960 9,289,140 5,897,037 13,271,680 1970 465,096 432,400 897,496 1970 17,825,210 11,508,690 25,465,070 1980 264,336 238,992 503,328 1980 23,305,620 14,966,770 33,457,600 1990 329,250 284,424 613,675 1990 27,036,780 19,354,590 35,924,610 1995 105,200 102,218 207,418 1995 28,272,940 20,723,740 37,108,160 2000 74,469 68,948 143,417 2000 27,510,220 20,779,040 35,696,240 2005 73,794 66,384 140,177 2005 26,645,420 19,809,180 34,370,610 2006 47,100 44,673 91,774 2006 26,538,740 19,630,590 34,125,580 2007 42,728 45,027 87,755 2007 26,341,320 19,707,340 33,850,080 2008 39,187 45,567 84,754 2008 26,128,290 19,561,330 33,672,940 2009 43,541 48,377 91,917 2009 25,924,090 19,690,110 33,639,540 aThe100-yearaveragecarbonstorageinproductsinusefortheharvestyear. 2010 25,753,020 19,546,530 33,052,480 bThe100-yearaveragecarbonstorageinSWDSfortheharvestyear. Stockmannetal.CarbonBalanceandManagement2012,7:1 Page9of16 http://www.cbmjournal.com/content/7/1/1 Table 6Confidence intervals forthe 100-yearaverage component of the forest carbon pool, and may allow the carbon stored in HWP forselected yearsusingthe evaluation of the effect of alternative harvesting intensi- California ForestProject Protocol. Meansand confidence ties on carbon stocks and fluxes. Furthermore, compari- intervals werecalculated usingMonte Carlosimulation. son of the two approaches is useful in evaluating the Inventoryyear SimulationMean 90%Confidenceinterval feasibility, utility, uncertainty, and limitations of alterna- (MgC) tive metrics and estimation methods that could be used 5% 95% to meet carbon monitoring objectives. Because the (MgC) (MgC) CFPP 100-year average is calculated for a discrete har- 1910 73,654 41,230 117,343 vest year, data for previous harvest years is not needed 1920 93,830 52,524 149,486 to make current or future year estimates. This contrasts 1930 75,929 42,504 120,967 with the IPCC/EPA approach, which requires harvest 1940 102,538 57,399 163,360 information for many prior years to make an estimate of 1950 181,181 113,537 270,498 net change to the carbon stocks in the inventory year. 1960 628,840 394,062 938,842 The CFPP emphasis on harvest year calculations rather 1970 898,820 563,303 1,336,731 than annual changes in total carbon stocks makes the 1980 503,370 382,408 653,254 CFPP approach easier to apply when information on 1990 613,729 463,510 803,920 historical harvest and product disposition is lacking. 1995 207,441 159,195 268,110 Similar to what we expect for other regions of the 2000 143,439 108,755 186,617 country, we had access to detailed recent information 2005 140,321 107,692 179,018 about wood harvest in agency “cut and sold” reports 2006 91,865 70,445 116,970 [20]. We were also fortunate to have archived historic 2007 87,791 67,609 112,596 harvest volume records. Although we made assumptions 2008 84,825 66,493 106,480 about the initiation of several primary product classes 2009 91,998 71,596 115,991 based on historical information, and we assumed consis- tent primary product distributions from the inception of in HWP plus 1,530 TgC total in ecosystem carbon), we processing capacity through the inventory year, in gen- estimate that the Northern Region HWP carbon stocks eral we had a strong set of historical data to use in our represent roughly 1.7 percent of total forest carbon sto- calculations. As expected, records of the partitioning of rage associated with national forests in the Northern the harvest to timber and primary product classes Region. At the national level, based on the EPA’s esti- improved markedly as our records approached the mate for 2010 total US HWP stock estimate of 2,449 present. TgC [2], the Northern Region HWP carbon stocks We recommend that all applications of the IPCC/EPA represented 1.1 percent of total US HWP carbon stocks. approach consider the quality of the data and adjust Research efforts are under way to provide additional their uncertainty analysis accordingly - particularly with estimates of forest ecosystem flux in the West regards to the distributions of random variables. How- [13,15,19]. However, long-term data collection require- ever, though carbon of older vintages may be associated ments will delay reporting until the National Forest with higher uncertainty, it is also likely to have a smaller Inventory and Analysis (FIA) program completes its sec- impact on current stocks and fluxes than more recent ond cycle of plot measurements. Although the third harvests. For example, we estimated the importance of cycle has begun in some southern US states, it will be the early harvests by quantifying the portion in the cur- 2020 at the earliest in the Northern Region before sec- rent HWP pool that is attributable to carbon harvested ond measurement data are available. Our calculations of prior to 1950. In 1950 the HWP carbon pool was 4.5 HWP carbon flux will allow the Northern Region to rea- million MgC. By inventory year 2010, only 1.7 million sonably account for carbon that was harvested between MgC of the carbon harvested before 1950 remained in 1906 and 2010. Ideally, when changes in forest ecosys- products in use and SWDS, which accounted for 6.6 tem carbon are quantified in subsequent research they percent of the total stocks of 25.8 million MgC in 2010. can be linked with our HWP data. This small contribution to current stocks is a result of two factors. There was greater harvesting activity for the Applications of these approaches by forest managers period after than before 1950. Also, following the pas- The availability of credible and practical methods for sage of the Resource Conservation and Recovery Act of estimating this important carbon pool will allow 1976 (RCRA) and after a short lag, a much larger por- resource managers and the public to develop a more tion of discarded HWP goes into modern landfills where complete understanding of the dynamics of HWP as a it is subject to lower rates of decay than in aerobic Stockmannetal.CarbonBalanceandManagement2012,7:1 Page10of16 http://www.cbmjournal.com/content/7/1/1 dumps or disposal by open burning, which were the level). The change in uncertainty would, in large part, dominant disposal methods prior to RCRA. depend on assumptions made about the distributions of Obtaining historical information may present a chal- random variables used in the analysis. In some cases, a lenge for some regions and national forests. It may be regional analysis may be sufficient to inform forest-level particularly difficult to reconstruct harvest data prior to land management planning, forest management prac- the mid-1940s, though regression of trends after the tices, and planning of long-term (programmatic) timber period might be appropriate for extrapolation to earlier harvest levels and associated effects on carbon flux. A periods. Alternatively, regions could base their carbon detailed sub-regional analysis may be needed where accounting on national level parameters, making the there are significant within-region differences in ecosys- assumption that national-level numbers are adequate for tems and disturbance processes and harvest levels (e.g., regional and sub-regional analysis. If national level western Washington compared to eastern Washington). values represent the best available data, the IPCC/EPA In our case, Regional HWP carbon stocks can be mean- method requires only harvest volume information from ingfully partitioned among the national forests in the the user. Many regional and forest type-specific default Region based on harvest records. We are currently dynamics and decay functions are supplied by national working to test these accounting methods, including level work [3,9]. The simplicity associated with using uncertainty analysis, at smaller scales. national data in calculations may make the system func- tional and effective in meeting monitoring needs for for- HWP Carbon change estimates versus Life Cycle est managers both within and outside the National Assessment Forest System (NFS), regardless of data quality. There are well-developed methods of life cycle assess- If time series data are not available or are very costly ment (LCA) that account for all carbon emissions asso- to procure, focusing on annual data may be more pro- ciated with manufactured products and that facilitate ductive. The CFPP 100-year average is an example of an the comparison of different levels of consumption and approach that does not require reconstructing the his- substitution of wood products for alternative products torical harvest. In general, the CFPP has ease of use [21]. Neither the IPCC/EPA nor the CFPP approach superior to the IPCC/EPA production approach but does this, which may be frustrating for some people does not provide the same detailed information about interested in more than HWP stocks and stock change. the HWP carbon pool. The CFPP approach does not For example, carbon emissions from fossil fuels used in estimate temporal trends in this pool whereas the IPCC/ transportation and manufacture of HWP are not EPA approach can show both total stock and annual deducted from the HWP pool. Similarly, though HWP stock change. In addition, our results show that the emissions with energy capture are quantified in the effects of uncertainty appear to be higher for the 100- IPCC/EPA approach, they are not assumed to substitute year average than for the IPCC/EPA estimates, for this for an equivalent amount of fossil fuel carbon. Further- case study, as measured as a percentage difference from more, these approaches do not incorporate carbon the expected value. As with the IPCC/EPA calculations, fluxes associated with product substitution, such as the appropriate regional and forest type-specific variables substitution of HWP for metal or concrete (or vice may be found in published sources [3,9,17]. versa) in building applications, and the associated land The choice about which protocol should be applied use changes that may ensue. could focus on the tradeoff between the simplicity of The IPCC/EPA and CFPP approaches instead focus on data collection and ease of calculations compared to a estimating physical stocks and fluxes of carbon in clearly need to address both total stocks and flux. Also, man- defined forest carbon pools. This information can be agers may need to be consistent in all using one proto- used in an LCA, but does not address the same ques- col or another in order to make results comparable tions as an LCA. However, with some caution, these across regions and easily aggregated in analysis done at approaches can be used to estimate the effects of alter- larger scales. The more resource intensive methods of native past or future harvest levels on HWP carbon the IPCC/EPA estimates are worthwhile only if the addi- stocks and fluxes. For example, a hypothetical time ser- tional detail is useful or if this reporting format is ies of harvest volumes can be used to predict what mandated. future product storage and emissions would look like We successfully applied the methods described by under specific alternative forest management and har- Skog [3] to estimate the uncertainty associated with our vest scenarios. But this is not an effective proxy for a HWP carbon stock estimates (Table 6). However, it is consequential LCA, which might include harvesting, unclear how the magnitude of this uncertainty would transportation and processing emissions, as well as pro- change, if at all, if the analysis were done on smaller duct substitutions, and other trade components not management units (e.g. the individual national forest included in the two approaches used here. For sub-