# LETTERS

**PUBLISHED ONLINE: XX MONTH XXXX | DOI:**  **10.1038/NCLIMATE1264** 

# Regional carbon dioxide implications of forest **bioenergy production**

**Tara W. Hudiburg 1**  

# ***, Beverly E. Law 1**  

# , Christian Wirth **2** 

# and Sebastiaan Luyssaert**3**



### Mitigation strategies for reducing CO2 

### emissions include 1 

### substitution of fossil fuel with bioenergy from forests1 

### , where 2 

### carbon emitted is expected to be recaptured in the growth 3 

### of new biomass to achieve zero net emissions2

### , and forest 4 

### thinning to reduce wildfire emissions3 

### . Here, we use forest 5 

### inventory data to show that fire prevention measures and 6 

### large-scale bioenergy harvest in US West Coast forests 7 

### lead to 2–14% (46–405 Tg C) higher emissions compared 8 

### to current management practices over the next 20 years. 9 

### We studied 80 forest types in 19 ecoregions, and found 10 

### that the current carbon sink in 16 of these ecoregions is 11 

### sufficiently strong that it cannot be matched or exceeded 12 

### through substitution of fossil fuels by forest bioenergy. If 13 

### the sink in these ecoregions weakens below its current level 14 

### by 30–60 g C m

− 2 

### yr−1 

### owing to insect infestations, increased 15 

### fire emissions, or reduced primary production, management 16 

### schemes including bioenergy production may succeed in jointly 17 

### reducing fire risk and carbon emissions. In the remaining three 18 

### ecoregions, immediate implementation of fire prevention and 19 

### biofuel policies may yield net emission savings. Hence, forest 20 

### policy should consider current forest carbon balance, local 21 

### forest conditions and ecosystem sustainability in establishing 22 

### how to decrease emissions. 23 

### Policies are being developed worldwide to increase bioenergy 24 

### production as a substitution for fossil fuel to mitigate fossil fuel25 

### derived carbon dioxide emissions, the main cause of anthropogenic 26 

### global climate change4,5 

### . However, the capacity for forest sector 27 

### bioenergy production to offset carbon dioxide emissions is limited 28 

### by fossil fuel emissions from this activity (harvest, transport, and 29 

### manufacturing of wood products) and the lower energy output 30 

### per unit carbon emitted compared with fossil fuels6 

### . Furthermore, 31 

### forest carbon sequestration can take from decades to centuries to 32 

### return to pre-harvest levels, depending on the initial conditions and 33 

### amount of wood removed7 

### . The effects of changes in management 34 

### on CO2 

### emissions need to be evaluated against this baseline. 35 

### Consequently, energy policy implemented without full carbon 36 

### accounting and an understanding of the underlying processes risks 37 

### increasing rather than decreasing emissions4,8



### . 38 

### In North America, there is increasing interest in partially meeting 39 

### energy demands through large-scale forest thinning5 

### , with the 40 

### added benefit of preventing catastrophic wildfire and concurrent 41 

### carbon loss3 

### . Although forest thinning can be economically feasible, 42 

### sustainable, and an effective strategy for preventing wildfire where 43 

### risk is high9, 10 

### , it remains unresolved whether this type of forest 44 

### treatment can satisfy both the aims of preventing wildfire and 45 

### reducing regional greenhouse gas emissions. 46 

### For both aims to be satisfied, it needs to be shown that: (1) 47 

### reduction in carbon stocks due to thinning and the associated 48

1 

### Department of Forest Ecosystems and Society, 321 Richardson Hall, Oregon State University, Corvallis, Oregon, USA, 2 

### Department of Systematic Botany and Functional Biodiversity, University of Leipzig, Johannisalle 21-23, 04103 Leipzig, Germany, 3 

### Laboratoire des Sciences du Climat en de l’Environnement, CEA CNRS UVSQ, Centre d’Etudes Ormes des Merisiers, 91191 Gif Sur Yvette, France. *e-mail: Tara.hudiburg@oregonstate.edu

. 

### emissions are offset by avoiding fire emissions and substituting 49 

### fossil fuel emissions with forest bioenergy, (2) the change in 50 

### management results in less CO2 

### emissions than the current or 51 

### ‘baseline’ emissions, and (3) short-term emission changes are 52 

### sustained in the long term. Determination of baseline forest 53 

### sector carbon emissions can be accomplished by combining 54 

### forest inventory data and life cycle assessment (LCA) that 55 

### includes full carbon accounting of net biome production (NBP) 56 

### on the land in addition to carbon emissions from bioenergy 57 

### production and storage in wood products (LCA; ref. 6). NBP 58 

### is the annual net change of land-based forest carbon (NEP; 59 

### photosynthesis minus respiration) after accounting for harvest 60 

### removals and fire emissions. 61 

### Our study focused on the US West Coast (Washington, Oregon 62 

### and California), a diverse region due to the strong climatic gradient 63 

### from the coast inland (300–2,500 mm precipitation per year) and 64 

### a total of 80 associated forest types, ranging from temperate 65 

### rainforests to semi-arid woodlands (Supplementary Table S1). The 66 

### region is divided into 19 distinct ecoregions 11 

### on the basis of climate, 67 

### soil, and species characteristics, and includes a broad range of 68 

### productivity, age structures, fire regimes and topography. Mean 69 

### net primary production (NPP) of the forest types range from 70 

### 100–900 g C m

− 2 

### yr− 1 

### (this study), falling within the global range 71 

### of 100 to 1,600 g C m

− 2 

### yr− 1 

### reported for temperate and boreal 72 

### forests 12 

### . Forest land ownership is divided fairly evenly between 73 

### public and private sectors having different management histories 74 

### and objectives that affect forest carbon dynamics 13



### . 75 

### Carbon sequestration rates vary greatly across the region, with 76 

### mean NEP ranging from

− 85 g C m

− 2 

### yr− 1 

### in the dry Northern 77 

### Basin to more than 400 g C m

− 2 

### yr− 1 

### in the mesic Coast Range. After 78 

### accounting for fire emissions and substantial harvest removals, 79 

### regional NBP remains a significant sink of 26 ± 3 Tg C yr

− 1 

### or 80 

### 76 ± 9 g C m2 

### yr− 1 

### , similar to the US average 14 

### and estimates for 81 

### the member states of the European Union 15 

### . Sixteen of the 19 82 

### ecoregions, representing 98% of the forest area in the region 83 

### are estimated to be carbon sinks (Fig. 1 a; exceptions are drier 84 

### ecoregions where annual productivity is low and fire emissions are 85 

### relatively high). Thus, the observed regional sink is not solely due 86 

### to the region’s highly productive rainforests, which occupy 15% of 87 

### the area. Within the region, California’s NBP is higher than that of 88 

### Oregon andWashington (107 versus 53–61 g C m

− 2 

### yr− 1 

### ), primarily 89 

### owing to differences in NEP (Supplementary Table S2) and harvest 90 

### between similar forest types within the same ecoregions that cross 91 

### state boundaries (Supplementary Discussion and Table S3). 92 

### In addition to current management or Business-As-Usual 93 

### (BAU, characterized by current preventive thinning and harvest 94 

### levels), we designed three treatments (Supplementary Fig. S1a) 95 

### to reflect the varying objectives of potential forest management 96

**NATURE CLIMATE CHANGE** | ADVANCE ONLINE PUBLICATION | www.nature.com/natureclimatechange 1

# LETTERS NATURE CLIMATE CHANGE **DOI: 10.1038/NCLIMATE1264** 



### Figure 1 

### | **Maps of US West Coast NBP and uncertainty for current and threshold conditions.** Map a shows current NBP or BAU; positive values (warm colours) indicate forest sinks whereas negative values (cool colours) are carbon sources to the atmosphere. Map b shows the current NBP uncertainty estimates that were calculated using Monte Carlo simulations of mean forest type values for the components of NBP (net ecosystem productivity, fire and harvest) combined with the uncertainty associated with remote sensing land cover estimates. Map c represents the amount NBP would need to decrease to reach a threshold NPB where bioenergy management may result in emission decreases to the atmosphere.


### systems: forest fire prevention by emphasizing removal of fuel 1 

### ladders (‘Fire Prevention’) in fire-prone areas, making fuel 2 

### ladder removal economically feasible by emphasizing removal of 3 

### additional marketable wood in fire-prone areas (‘Economically 4 

### Feasible’), or thinning all forestland regardless of fire risk to 5 

### support energy production while contributing to fire prevention 6 

### (‘Bioenergy Production’). Removals are in addition to current 7 

### harvest levels and are performed over a 20-year period such that 8 

### 5% of the landscape is treated each year. Our reliance on a 9 

### data-driven approach versus model simulations strengthens our 10 

### analysis in the short term, but limits our ability to make long-term 11 

### predictions. Extending our study beyond a 20-year timeframe 12 

### would overstretch data use because current forest growth is unlikely 13 

### to represent future growth due to changes in climate, climate14 

### related disturbance, and land use 16, 17



### . 15 

### In our study region, we found that thinning reduced NBP 16 

### under all three treatment scenarios for 13 of the 19 ecoregions, 17 

### representing 90% of the region’s forest area. The exceptions where 18 

### NBP was not reduced were primarily due to high initial fire 19 

### emissions compared to NEP (for example, Northern Basin and 20 

### North Cascades; Supplementary Fig. S2). The dominant trend at 21 

### the ecoregion level was mirrored at the regional level, with the 22 

### Bioenergy Production scenario (highest thinning level) resulting in 23 

### the region becoming a net carbon source (Supplementary Table S2 24 

### and discussion of state-level estimates). Regionally, forest biomass 25 

### removals exceeded the potential losses from forest fires, reducing 26 

### the in situ forest carbon sink even after accounting for regrowth, 27 

### as found in previous studies with different approaches or areas 28 

### of inference8, 18 

### . Because we have assumed high reductions in fire 29 

### emissions for the areas treated in each scenario, it is unlikely we are 30 

### underestimating the benefit of preventive thinning on NBP. 31 

### It is important to recognize that even if the land-based flux 32 

### is positive (a source) or zero (carbon neutral), decreases in NBP 33 

### from BAU can increase CO2 

### emissions to the atmosphere. LCA was 34 

### used to estimate the net emissions of carbon to the atmosphere 35 

### in each treatment scenario (Supplementary Fig. S1b and Tables S4 36 

### and S5). LCA at the ecoregion level revealed that emissions are 37 

### increased for 10 out of 19 of the ecoregions (Fig. 2 ), representing 38 

### 80% of the forest area in the region. The combination of in situ 39 

### and wood-use carbon sinks and sources emit an additional 46, 40 

### 181 and 405 Tg C to the atmosphere over a 20-year period (2–14% 41 

### increase) above that of the BAU forest management scenarios 42 

### for the Fire Prevention, Economically Feasible, and Bioenergy 43 

### Production treatments, respectively (Fig. 3 ). 44 

### Sensitivity analysis of our results to a range of fire emission 45 

### reductions, energy conversion efficiencies, wood product decom- 46 

### position rates and inclusion of wood substitution showed that 47 

### carbon emissions varied by

− 10 to 28% from the optimum values 48 

### across the scenarios, depending on the combination of assumptions 49 

### (Supplementary Discussion and Table S6). The analysis revealed 50 

### that an increase in estimated current fire emissions (which effec- 51 

### tively reduces the baseline sink) may decrease total atmospheric C 52 

### emissions in the Fire Prevention scenario, but only given optimum 53 

### conditions for all of the other parameters (for example 100% 54 

### energy efficiency). Nevertheless, if fire frequency and intensity 55 

### increase in the future 19 

### , emissions savings through forest bioenergy 56 

### production may become possible, especially in ecoregions where 57 

### the sink is already weak. 58 

### Previous case studies showed that harvesting an old-growth 59 

### forest in the Pacific Northwest20 

### or increasing the thinning removals 60 

### of temperate forests is likely to deteriorate the forest and wood 61 

### product carbon stock21 

### . However, these studies were limited to a 62 

### handful of sites, relied primarily on modelled results3 , 18 

### and did 63 

### not account for the energy requirements of forest management and 64 

### wood processing nor for the potential to substitute fossil fuels with 65 

### bioenergy. We build on these results by including all ecoregions, 66

2 **NATURE CLIMATE CHANGE** | ADVANCE ONLINE PUBLICATION | www.nature.com/natureclimatechange

# NATURE CLIMATE CHANGE **DOI: 10.1038/NCLIMATE1264**  

# LETTERS

Figure 2 

### | **Life Cycle Assessment carbon emission trends by ecoregion under various management scenarios.**  The x axis is the total harvest (BAU + treatment) and the y axis is the total CO 2 

### flux in Tg C yr

− 1 

### for each ecoregion. Coloured circles represent each scenario (Green = BAU, Yellow = Fire Prevention, Orange = Economically Feasible, Red = Bioenergy Production). Grey circles are the values for each sensitivity analysis set of parameters and the error bars represent the estimate uncertainty. The locations of the ecoregions indicated by labels are shown in Fig. 1a. For most ecoregions, the treatments increase emissions to the atmosphere.


### all age classes (not just old-growth), three treatments including 1 

### bioenergy production, and sector-based LCA. We found that even 2 

### though forest sector emissions are compensated for by emission 3 

### savings from bioenergy use, fewer forest fires, and wood product 4 

### substitution, the end result is an increase in regional CO2 

### emissions 5 

### compared to BAU as long as the regional sink persists. 6 

### To determine a threshold NBP for which bioenergy management 7 

### reduces atmospheric CO2 

### emissions compared to BAU, we applied 8 

### the same assumptions as used in the LCA. We found that if the NBP 9 

### drops by 50–60 g C m

− 2 

### yr− 1 

### in currently productive ecoregions 10 

### or 15–30 g C m

− 2 

### yr− 1 

### in currently less productive ecoregions, 11 

### bioenergy management would come with CO2 

### emissions savings 12 

### compared to BAU (Fig 1c). Aggregating the ecoregion thresholds 13 

### translates into a regional mean NBP of 45 g C m

− 2 

### yr− 1 

### or a 14 

### 41% reduction on average. Reductions in NBP may occur 15 

### due to increased mortality and/or decreased growth due to 16 

### climate, fire, or insect outbreaks. However, reductions in NBP 17 

### from increased harvest do not qualify because harvest increases 18 

### emissions; wood carbon enters the products/bioenergy chain, 19 

### where subsequent losses occur. We cannot predict from the 20 

### data when the threshold NBP would occur because a high 21 

### resolution process-based model with the ability to incorporate 22 

### future climate, nitrogen deposition, age dynamics, disturbance and 23 

### management would need to be used, which is beyond the scope of 24 

### this study. 25 

### Ecoregion threshold NBP is dependent on the scenario treatment 26 

### removals and area because the Fire Prevention treatment targets 27 

### only those areas most likely to burn. For example, to reduce 28 

### emissions in the Sierra Nevada, baseline NBP would have to 29 

### decrease by as much as 84 for the Bioenergy Production scenario 30 

### versus only 13 g C m

− 2 

### yr− 1 

### for the Fire Prevention scenario. In 31 

### ecoregions where current sinks are marginal or weakened by 32 

### climate, fire, or insect outbreaks there may be a combination of 33 

### harvest intensity and bioenergy production that reduces forest 34 

### sector emissions. In nine of the ecoregions where forests are 35 

### carbon neutral or a source of CO2 

### to the atmosphere and/or 36 

### fire emissions are high for BAU, total CO2 

### emissions under the 37 

### Fire Prevention scenario could be reduced compared to BAU. 38 

### They provide examples where management strategies for carbon 39 

### emission reduction or sequestration should differ from the majority 40 

### of the region; a one-size-fits-all approach will not work22 

### . Finally, 41 

### large areas in the Northern Rockies (for example, Colorado and 42 

### Wyoming) are at present experiencing increases in forest mortality 43 

### due to beetle-kill, a trend which could continue in a warmer 44 

### climate23 

### . These areas may already be at or below the threshold NBP; 45 

### if so, they could benefit from targeted bioenergy implementation. 46 

### However, simply lowering current regional harvest intensities 47 

### in areas where NBP is not weakened also reduces emissions 48 

### (Supplemental Discussion and Fig. S3). Also, as we have assumed 49 

### large-scale implementation of these strategies in addition to BAU 50 

### harvest, we may be overestimating future harvest even though 51 

### harvest has declined significantly since 1990 because of restrictions 52 

### placed on harvest on federal lands as part of the Northwest Forest 53 

### Plan. If the strategies were used to substitute for BAU harvest, the 54 

### outcome on NBP would be much different (that is, increased for the 55 

### Fire Prevention scenario). 56



### Figure 3 

### | **Total US West Coast forest sector carbon sinks, sources, and added emissions relative to BAU under various management scenarios.** Units are in Tg C yr

− 1 

### . Life cycle assessment estimates account for changes in carbon on land in addition to emissions associated with production, transport and usage of wood, and substitution and displacement of fossil fuel emissions associated with use and extraction. BAU results in the lowest anthropogenic emissions from the forest sector.

**NATURE CLIMATE CHANGE** | ADVANCE ONLINE PUBLICATION | www.nature.com/natureclimatechange 3

# LETTERS NATURE CLIMATE CHANGE **DOI: 10.1038/NCLIMATE1264** 



### Our study is one of the first to provide full carbon accounting, 1 

### including all of the sinks and sources of carbon emissions from the 2 

### forestry sector and the current in situ sink, for such a large area. 3 

### Given the diversity of woody ecosystems in the study region, ranging 4 

### from highly productive temperate rainforests to less productive 5 

### semi-arid woodlands, the trends in response probably apply to 6 

### other temperate regions globally (Supplementary Table S1) where 7 

### forests are at present a strong net carbon-sink (for example, 8 

### Eastern US, China and Europe), although the extent of the effect 9 

### remains to be established. 10 

### Greenhouse gas reduction plans call for up to 10% reductions 11 

### in emissions by 2020 and forest-derived fuels are being proposed 12 

### as a carbon-neutral solution to reducing energy emissions. In all of 13 

### our proposed scenarios, increases in harvest volume on the US West 14 

### Coast will on average result in regional emission increases above 15 

### current levels, although there are a few ecoregions where the tested 16 

### scenarios could result in emission savings. As long as the current in 17 

### situ NBP persists, increasing harvest volumes in support of bioen18 

### ergy production is counterproductive for reducing CO2 

### emissions. 19 

### In this study region, the current in situ NBP in tree biomass, woody 20 

### detritus and soil carbon is more beneficial in contributing to re21 

### duction of anthropogenic carbon dioxide emissions than increasing 22 

### harvest to substitute fossil fuels with bioenergy from forests. 23 

### Although large uncertainty remains for regional forecasts to 24 

### year 2050 or 2100, it is expected that forest carbon sinks will 25 

### diminish over time because of ageing of the forests, saturation 26 

### of the CO2 

### -fertilization and N-deposition effects, and increased 27 

### mortality due to climate or insects24,25 

### . This would require new 28 

### assessments to identify management options appropriate for each 29 

### situation. Carbon-management is not the sole criteria that should 30 

### be considered when planning forest management. Our findings 31 

### should thus also be evaluated against other ecosystem services, such 32 

### as habitat, genetic and species diversity, watershed protection, and 33 

### natural adaptation to climate change. 34


## Methods 35 We quantified forest sequestration rates and test forest thinning scenarios across 36 the region using a data-intensive approach which, for the first time, takes into 37 account the diversity of forest characteristics and management. We combined 38 Landsat remote sensing data with inventories and ancillary data to map current 39 forest NEP, NBP, and changes in NBP with three thinning scenarios. The approach 40 can be applied at multiple scales of analysis in other regions. 41 We combined spatially representative observational data from more than 6000 42 FIA plots (see Supplementary Methods and Table S7) with remote sensing products 43 on forest type, age and fire risk26 , a global data compilation of wood decomposition 44 data and 200 supplementary plots 13 to provide new estimates of US West Coast 45 ( ∼34 million hectares) forest biomass carbon stocks (Supplementary Table S8), 46 NEP (the balance of photosynthesis and respiration) and NBP (the in situ net forest 47 carbon-sink accounting for removals). We included all forestland in our analysis, 48 across all age classes (20–800 years old) and management regimes. Plot values 49 were aggregated by climatic region (ecoregion), age class and forest type, and this 50 look-up table was used to assign a value to each associated 30 m pixel. 51 We use regional combustion coefficients to determine fire emissions. Only 52 3–8% of live tree biomass is actually combusted and emitted in high severity fire in 53 the Pacific Northwest31 , contrary to other studies that report much higher emissions 54 because they assume 30% of all aboveground woody biomass is consumed27

. 55 Although the latter contradicts extensive field observations28,29 and modelling 56 studies30 in the region, we included 30% as the upper-end combustion factor in 57 our sensitivity analysis (Supplementary Table S9). 58 In addition to the spatially explicit estimates of stocks and fluxes under current 59 management or BAU (current forest harvest), three treatments were designed (Fire 60 Prevention, Economically Feasible, and Bioenergy Production; Supplementary Fig. 61 S1a) to reflect the varying objectives of potential future forest management over the 62 next 20 years; within the proposed time period for CO2 reductions in the US Areas 63 were prioritized for treatment by fire risk and frequency. The proposed treatments 64 result in additional harvest removals because we assume the current harvest rate 65 for wood products will continue in the future. We limit our specific analysis to the 66 short term because this is the timeframe suitable for policymakers, effectiveness of 67 fire protection treatments, and an appropriate use of the data-driven approach. 68 However, to investigate conditions (for example, sink saturation) that could 69 invalidate our short-term results in the long term, we also calculated the in situ NBP 70 at which the atmosphere may benefit from bioenergy removals. Last, we studied the net effects of the thinning treatments on atmospheric 71 CO2 by LCA of carbon sources and sinks that includes the post-thinning NBP 72 and wood use (harvest, transport, manufacturing, decomposition, wood product 73 substitution, conversion and use of bioenergy, and displacement of fossil fuel 74 extraction emissions; Supplementary Fig. S1b and Table S4,S5). 75 

### Received 19 July 2011; accepted 30 September 2011; 76 

### published online XX Month XXXX 77 

## References 78 1. Buyx, A. & Tait, J. Ethical framework for biofuels. Science (2011). 79 2. Gustavsson, L., Börjesson, P., Johansson, B. & Svenningsson, P. Reducing 80 CO2 emissions by substituting biomass for fossil fuels. Energy 20, 81 1097–1113 (1995). 82 3. Hurteau, M. D. & North, M. Carbon recovery rates following different wildfire 83 risk mitigation treatments. Forest Ecol. Manag. 260, 930–937 (2010). 84 4. Fargione, J., Hill, J., Tilman, D., Polasky, S. & Hawthorne, P. Land clearing and 85 the biofuel carbon debt. Science 319, 1235–1238 (2008). 86 5. Richter, D. Jr et al. Resource policy: Wood energy in America. Science 323, 87 1432–1433 (2009). 88 6. Law, B. E. & Harmon, M. E. Forest sector carbon management, measurement 89 and verification, and discussion of policy related to climate change. Carbon 90 Manag. 2, 73–84 (2011). 91 7. Harmon, M. E. & Marks, B. Effects of silvicultural practices on carbon stores 92 in Douglas-fir—western hemlock forests in the Pacific Northwest, USA: 93 Results from a simulation model. Can. J. Forest Res./Rev. Can. Rech. Forest 32, 94 863–877 (2002). 95 8. Searchinger, T. D. et al. Fixing a critical climate accounting error. Science 326, 96 527–528 (2009). 97 9. Evans, A. & Finkral, A. From renewable energy to fire risk reduction: A 98 synthesis of biomass harvesting and utilization case studies in US forests. 99 GCB Bioenergy 1, 211–219 (2009). 100 10. Huggett, R. J. Jr, Abt, K. L. & Shepperd, W. Efficacy of mechanical fuel 101 treatments for reducing wildfire hazard. Forest Policy Econ. 10, 408–414 (2008). 102 11. Omernik, J. M. Ecoregions of the conterminous United States. Map (scale 103 1:7,500,000). Ann. Assoc. Am. Geogr. 77, 118–125 (1987). 104 12. Luyssaert, S. et al. Old-growth forests as global carbon sinks. Nature 455, 105 213–215 (2008). 106 13. Hudiburg, T. et al. Carbon dynamics of Oregon and Northern California 107 forests and potential land-based carbon storage. Ecol. Appl. 19, 163–180 (2009). 108 14. Birdsey, R. A. in US Climate Change Science Program and the Subcommittee on 109 Global Change Research (eds King, A. W. et al.) (2007). 110 15. Luyssaert, S. et al. The European carbon balance: part 3: Forests. 111 Glob. Change Biol. 16, 1429–1450 (2009). 112 16. Battles, J. et al. Climate change impacts on forest growth and tree mortality: A 113 data-driven modeling study in the mixed-conifer forest of the Sierra Nevada, 114 California. Clim. Change 87, 193–213 (2008). 115 17. Ryan, M. G. Temperature and tree growth. Tree Physiol. 30, 667–668 (2010). 116 18. Mitchell, S. R., Harmon, M. E. & O’Connel, K. E. B. Forest fuel reduction 117 alters fire severity and long-term carbon storage in three Pacific Northwest 118 ecosystems. Ecol. Appl. 19 (2009). 119 19. Rogers, B. et al. Impacts of climate change on fire regimes and 120 carbon stocks of the US Pacific Northwest. J. Geophys. Res. 121 http://dx.doi.org/10.1029/2011JG001695 (in the press). 122 20. Harmon, M. E., Ferrell, W. K. & Franklin, J. F. Effects on carbon storage of 123 conversion of old-growth forests to young forests. Science 247, 699–702 (1990). 124 21. Nunery, J. S. & Keeton, W. S. Forest carbon storage in the northeastern United 125 States: Net effects of harvesting frequency, post-harvest retention, and wood 126 products. Forest Ecol. Manag. 259, 1363–1375 (2010). 127 22. Marland, G. & Schlamadinger, B. Forests for carbon sequestration or fossil fuel 128 substitution? A sensitivity analysis. Biomass Bioenergy 13, 389–397 (1997). 129 23. Evangelista, P. H., Kumar, S., Stohlgren, T. J. & Young, N. E. Assessing forest 130 vulnerability and the potential distribution of pine beetles under current and 131 future climate scenarios in the Interior West of the US. Forest Ecol. Manag. 262, 132 307–316 (2011). 133 24. van Mantgem, P. J. et al. Widespread increase of tree mortality rates in the 134 Western United States. Science 323, 521–524 (2009). 135 25. Stinson, G. et al. An inventory-based analysis of Canada’s managed forest 136 carbon dynamics, 1990 to 2008. Glob. Change Biol. 17, 2227–2244 (2011). 137 26. LANDFIRE Data Distribution Site, USGS (US Department of Interior, 138 Geological Survey, 2009) http://gisdata.usgs.net/website/landfire/

. 139 27. Wiedinmyer, C. & Hurteau, M. D. Prescribed fire as a means of reducing 140 forest carbon emissions in the western United States. Environ. Sci. Technol. 44, 141 1926–1932 (2010). 142 28. Campbell, J., Donato, D., Azuma, D. & Law, B. Pyrogenic carbon emission 143 from a large wildfire in Oregon, United States. J. Geophys. Res. 112 (2007). 144 29. Meigs, G., Donato, D., Campbell, J., Martin, J. & Law, B. Forest fire impacts on 145 carbon uptake, storage, and emission: The role of burn severity in the Eastern 146 Cascades, Oregon. Ecosystems 12, 1246–1267 (2009). 147

4 **NATURE CLIMATE CHANGE** | ADVANCE ONLINE PUBLICATION | www.nature.com/natureclimatechange

# NATURE CLIMATE CHANGE **DOI: 10.1038/NCLIMATE1264**  

# LETTERS

30. Ottmar, R. D., Pritchard, S. J., Vihnanek, R. E. & Sandberg, D. V. 14 Final 1 Report JFSP Project 98-1-9-06, 2006. 2 

## Acknowledgements 3 This research was supported by the Office of Science (BER), US Department of Energy 4 (DOE, Grant no. DE-FG02-07ER64361), for the North American Carbon Program 5 study, ‘Integrating Remote Sensing, Field Observations, and Models to Understand 6 Disturbance and Climate Effects on the Carbon Balance of the West Coast US’. We 7 further thank M. Harmon for discussions of wood product life-cycle assessment. T.W.H. 8 is funded by a DOE global change education program PhD fellowship (GREF). S.L. is 9 funded by ERC Starting Grant 242564. 

## Author contributions 10 T.W.H. designed and implemented the study with guidance from B.E.L. and S.L. 11 T.W.H., S.L. and B.E.L. co-wrote the paper and S.L. contributed to parts of the 12 analysis. C.W. provided essential data and methods for the analysis and valuable 13 comments on the manuscript. 14 

## Additional information 15 The authors declare no competing financial interests. Supplementary information 16 accompanies this paper on www.nature.com/natureclimatechange

. Reprints and 17 permissions information is available online at http://www.nature.com/reprints

. 18 Correspondence and requests for materials should be addressed to T.W.H. 19

**NATURE CLIMATE CHANGE** | ADVANCE ONLINE PUBLICATION | www.nature.com/natureclimatechange 5

# Page 1

Query 1: Line no. 48 Please note that the e-mail addresses of all authors have been removed, except that of the corresponding author, as per journal style. Query 2: Line no. 48 Please provide postcodes for first affiliation. Query 3: Line no. 58 You define LCA again here, is this necessary? Query 4: Line no. 61 NEP appears in brackets following a description of NBP. Please check. Query 5: Line no. 70 NPP used only once, style guide dictates that the acronym be removed. Ok?
Page 2 Query 6: Line no. 1 Figure 1 caption, should NPB be changed to NBP?
Page 3 Query 7: Line no. 1 Dotted line present in one version of the two supplied figures. Please check the figure now processed is ok. Query 8: Line no. 30 Is there a missing unit or a percentage value after ‘84’?
Page 4 Query 9: Line no. 54 Please check whether the above given ‘ 31 

# ’ is a reference. Only 30 reference are there. Query 10: Line no. 79 Please provide volume and page range for ref. 1. Query 11: Line no. 79 Because of the odd symbols appearing in the authors of Ref. 2, we have checked and corrected the name of the second author. Query 12: Line no. 116 Please provide page range/article id for refs 18, 28. Query 13: Line no. 119 Any update for ref. 19. Query 14: Line no. 147 Please provide publisher for ref. 30.
Page 5 Query 15: Line no. 8 As NPG do not allow unnamed individuals in the acknowledgement we have modified ‘We further thank an anonymous reviewer for discussions of economic analysis of bioenergy production, an LCA specialist for helpful comments on our LCA, and M. Harmon for discussions of wood product life-cycle assessment.’ to ‘We further thank M. Harmon for discussions of wood product life-cycle assessment.’