Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Fuel availability not fire weather controls boreal wildfire severity and carbon emissions


Carbon (C) emissions from wildfires are a key terrestrial–atmosphere interaction that influences global atmospheric composition and climate. Positive feedbacks between climate warming and boreal wildfires are predicted based on top-down controls of fire weather and climate, but C emissions from boreal fires may also depend on bottom-up controls of fuel availability related to edaphic controls and overstory tree composition. Here we synthesized data from 417 field sites spanning six ecoregions in the northwestern North American boreal forest and assessed the network of interactions among potential bottom-up and top-down drivers of C emissions. Our results indicate that C emissions are more strongly driven by fuel availability than by fire weather, highlighting the importance of fine-scale drainage conditions, overstory tree species composition and fuel accumulation rates for predicting total C emissions. By implication, climate change-induced modification of fuels needs to be considered for accurately predicting future C emissions from boreal wildfires.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Map of studied ecoregions and field sites.
Fig. 2: Average above- and belowground pre-fire and combusted carbon (C) pools for each ecoregion group.
Fig. 3: SEM results testing a hypothesized network of top-down and bottom-up controls on C combustion.

Data availability

The data used in this manuscript are archived at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC).

Code availability

No custom code or mathematical algorithms were used in the analyses of these data. The R code for our statistical analyses is available from the authors upon request, and each of the R packages used is referenced in the Methods.


  1. Balshi, M. S. et al. Assessing the response of area burned to changing climate in western boreal North America using a multivariate adaptive regression splines (MARS) approach. Glob. Change Biol. 15, 578–600 (2009).

    Article  Google Scholar 

  2. Flannigan, M. D., Krawchuk, M. A., de Groot, W. J., Wotton, B. M. & Gowman, L. M. Implications of changing climate for global wildland fire. Int. J. Wildland Fire 18, 483–507 (2009).

    Article  Google Scholar 

  3. Calef, M. P., Varvak, A., McGuire, A. D., Chapin, F. S. & Reinhold, K. B. Recent changes in annual area burned in interior Alaska: the impact of fire management. Earth Interact. 19, 5 (2015).

    Article  Google Scholar 

  4. Hanes, C. C. et al. Fire-regime changes in Canada over the last half century. Can. J. For. Res. 49, 256–269 (2018).

    Article  Google Scholar 

  5. Flannigan, M. D., Logan, K. A., Amiro, B. D., Skinner, W. R. & Stocks, B. J. Future area burned in canada. Climatic Change 72, 1–16 (2005).

    Article  CAS  Google Scholar 

  6. Amiro, B. D., Cantin, A., Flannigan, M. D. & de Groot, W. J. Future emissions from Canadian boreal forest fires. Can. J. Res. 39, 383–395 (2009).

    Article  CAS  Google Scholar 

  7. Young, A. M., Higuera, P. E., Duffy, P. A. & Hu, F. S. Climatic thresholds shape northern high-latitude fire regimes and imply vulnerability to future climate change. Ecography 40, 606–617 (2017).

    Article  Google Scholar 

  8. Van Wagner, C. E. Development and structure of the Canadian Forest Fire Weather Index System, vol. 35 (Canadian Forest Service, 1987).

  9. de Groot, W. J., Pritchard, J. M. & Lynham, T. J. Forest floor fuel consumption and carbon emissions in Canadian boreal forest fires. Can. J. Res. 39, 367–382 (2009).

    Article  Google Scholar 

  10. Flannigan, M. et al. Global wildland fire season severity in the 21st century. Ecol. Manag. 294, 54–61 (2013).

    Article  Google Scholar 

  11. Field, R. D. et al. Development of a global fire weather database. Nat. Hazards Earth Syst. Sci. 15, 1407–1423 (2015).

    Article  Google Scholar 

  12. Stocks, B. J. et al. Canadian forest fire danger rating system: an overview. For. Chron. 65, 258–265 (1989).

    Article  Google Scholar 

  13. Walker, X. J. et al. Cross-scale controls on carbon emissions from boreal forest megafires. Glob. Change Biol. 24, 4251–4265 (2018).

    Article  Google Scholar 

  14. Parisien, M.-A. et al. Contributions of ignitions, fuels, and weather to the spatial patterns of burn probability of a boreal landscape. Ecosystems 14, 1141–1155 (2011).

    Article  Google Scholar 

  15. Thompson, D. K., Simpson, B. N. & Beaudoin, A. Using forest structure to predict the distribution of treed boreal peatlands in Canada. Ecol. Manag. 372, 19–27 (2016).

    Article  Google Scholar 

  16. Turetsky, M. R. et al. Recent acceleration of biomass burning and carbon losses in Alaskan forests and peatlands. Nat. Geosci. 4, 27–31 (2011).

    Article  CAS  Google Scholar 

  17. Whitman, E. et al. Variability and drivers of burn severity in the northwestern Canadian boreal forest. Ecosphere 9, e02128 (2018).

    Article  Google Scholar 

  18. Boby, L. A., Schuur, E. A., Mack, M. C., Verbyla, D. & Johnstone, J. F. Quantifying fire severity, carbon, and nitrogen emissions in Alaska’s boreal forest. Ecol. Appl. 20, 1633–1647 (2010).

    Article  Google Scholar 

  19. Ott, L. A. V. R. A., Mann, P. C. A. D. & Van Cleve, K. Successional Processes in the Alaskan Boreal Forest (Oxford Univ. Press, 2006).

  20. Johnson, E. A. Fire and Vegetation Dynamics (Cambridge Univ. Press, 1992).

  21. Hély, C., Bergeron, Y. & Flannigan, M. D. Effects of stand composition on fire hazard in mixed-wood Canadian boreal forest. J. Veg. Sci. 11, 813–824 (2000).

    Article  Google Scholar 

  22. Rogers, B. M., Randerson, J. T. & Bonan, G. B. High-latitude cooling associated with landscape changes from North American boreal forest fires. Biogeosciences 10, 699–718 (2013).

    Article  Google Scholar 

  23. Johnstone, J. F. et al. Fire, climate change, and forest resilience in interior alaska. Can. J. Res. 40, 1302–1312 (2010).

    Article  Google Scholar 

  24. Walker, X. J. et al. Soil organic layer combustion in boreal black spruce and jack pine stands of the Northwest Territories, Canada. Int. J. Wildland Fire 27, 125–134 (2018).

    Article  Google Scholar 

  25. Tarnocai, C. et al. Soil organic carbon pools in the northern circumpolar permafrost region. Glob. Biogeochem. Cycles 23, GB2023 (2009).

    Article  Google Scholar 

  26. Flannigan, M. D. et al. Fuel moisture sensitivity to temperature and precipitation: climate change implications. Climatic Change 134, 59–71 (2016).

    Article  CAS  Google Scholar 

  27. Veraverbeke, S., Rogers, B. M. & Randerson, J. T. Daily burned area and carbon emissions from boreal fires in Alaska. Biogeosciences 12, 3579–3601 (2015).

    Article  CAS  Google Scholar 

  28. Bernier, P. Y. et al. Mapping local effects of forest properties on fire risk across Canada. Forests 7, 157 (2016).

    Article  Google Scholar 

  29. Birch, D. S. et al. Vegetation, topography and daily weather influenced burn severity in central Idaho and western Montana forests. Ecosphere 6, art7 (2015).

    Article  Google Scholar 

  30. Dillon, G. K. et al. Both topography and climate affected forest and woodland burn severity in two regions of the western US, 1984 to 2006. Ecosphere 2, art130 (2011).

    Article  Google Scholar 

  31. Parks, S. A. et al. High-severity fire: evaluating its key drivers and mapping its probability across western US forests. Environ. Res. Lett. 13, 044037 (2018).

    Article  Google Scholar 

  32. Johnstone, J. F., Hollingsworth, T. N., Chapin, F. S. & Mack, M. C. Changes in fire regime break the legacy lock on successional trajectories in Alaskan boreal forest. Glob. Change Biol. 16, 1281–1295 (2010).

    Article  Google Scholar 

  33. Walker, X. J. et al. Increasing wildfires threaten historic carbon sink of boreal forest soils. Nature 572, 520–523 (2019).

    Article  CAS  Google Scholar 

  34. Kelly, R. et al. Recent burning of boreal forests exceeds fire regime limits of the past 10,000 years. Proc. Natl Acad. Sci. USA 110, 13055–13060 (2013).

    Article  CAS  Google Scholar 

  35. US EPA. Ecoregions of North America (2015).

  36. Kasischke, E. S., Williams, D. & Barry, D. Analysis of the patterns of large fires in the boreal forest region of Alaska. Int. J. Wildland Fire 11, 131–144 (2002).

    Article  Google Scholar 

  37. Stocks, B. J. et al. Large forest fires in Canada, 1959–1997. J. Geophys. Res. Atmos. 107, FFR 5-1–FFR 5-12 (2002).

    Google Scholar 

  38. Wang, T., Hamann, A., Spittlehouse, D. & Carroll, C. Locally downscaled and spatially customizable climate data for historical and future periods for North America. PLoS ONE 11, e0156720 (2016).

    Article  Google Scholar 

  39. Johnstone, J. F., Hollingsworth, T. N. & Chapin, F. S., III. A key for predicting postfire successional trajectories in black spruce stands of interior Alaska, general technical report (USDA Forest Service, 2008).

  40. R Development Core Team. R: a language and environment for statistical computing (2018).

  41. Pinheiro, J. et al. Package ‘nlme’. Linear nonlinear mixed effects models version 3–1 (2017).

  42. Zuur, A., Ieno, E. N., Walker, N., Saveliev, A. A. & Smith, G. M. Mixed effects models and extensions in ecology with R (Springer Science & Business Media, 2009).

  43. Lenth, R., Singmann, H., Love, J., Buerkner, P. & Herve, M. Package emmeans: estimated marginal means, aka least-squares means (2019).

  44. Oksanen, J. et al. Package vegan: community ecology package (2013).

  45. Lefcheck, J., Byrnes, J. & Grace, J. Package piecewiseSEM: piecewise structural equation modeling (2018).

  46. Shipley, B. Confirmatory path analysis in a generalized multilevel context. Ecology 90, 363–368 (2009).

    Article  Google Scholar 

Download references


This synthesis work for this project was supported by funding from the NASA Arctic Boreal and Vulnerability Experiment (ABoVE) Legacy Carbon grant NNX15AT71A awarded to M.C.M. The original field studies were supported by funding in the United States from NSF DEB RAPID grant no. 1542150 to M.C.M., NASA ABoVE grant NNX15AT83A to L.B.-C., NASA ABoVE grant NNX15AU56A to B.M.R., S.V. and M.T., Joint Fire Science Program grant 05-1-2-06 to J.F.J., NSF grant 0445458 to M.C.M., NSF support to the Bonanza Creek LTER (DEB-0423442); and in Canada from NSERC Discovery Grant funding to J.F.J. and M.R.T.; Government of the Northwest Territories Cumulative Impacts Monitoring Program Funding project #170 to J.L.B.; NSERC PDFs to N.J.D. and C.M.D.; GNWT logistical and financial support through the Laurier-GNWT Partnership Agreement; Polar Knowledge Canada’s Northern Science Training Program funding awarded to Canadian field assistants; S.V. acknowledges Vidi grant support from the Netherlands Organization for Scientific Research (NWO).

Author information

Authors and Affiliations



M.C.M. and X.J.W. conceived the study with help from B.M.R. and S.V. Field data were contributed by L.B.-C., W.J.d.G., C.M.D., E.H., E.S.K., B.M.R., M.C.M., X.J.W. and E.W. Additional data were contributed by B.M.R., E.H., L.K.J., S.P., and S.V. X.J.W. combined the datasets and analysed the data with help from M.C.M., B.M.R. and S.V. X.J.W. led the writing in collaboration with M.C.M., J.F.J., B.M.R. and S.V. All authors read and edited this manuscript.

Corresponding author

Correspondence to X. J. Walker.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Climate Change thanks Gregory Dillon, Matthew Hurteau, Rachel Loehman and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–6, Tables 1–9, discussion and references.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Walker, X.J., Rogers, B.M., Veraverbeke, S. et al. Fuel availability not fire weather controls boreal wildfire severity and carbon emissions. Nat. Clim. Chang. 10, 1130–1136 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing