J. R. Marlon et al., PNAS, Wildfire responses to abrupt climate change in North America

Proceedings of the National Academy of Sciences, February 3, 2009; doi: 10.1073/pnas.0808212106

Wildfire responses to abrupt climate change in North America

1. J. R. Marlon^a,*,
2. P. J. Bartlein^a,
3. M. K. Walsh^a,
4. S. P. Harrison^b,
5. K. J. Brown^c,^d,
6. M. E. Edwards^e,^f,
7. P. E. Higuera^g,
8. M. J. Power^h,
9. R. S. Andersonⁱ,
10. C. Briles^g,
11. A. Brunelle^h,
12. C. Carcaillet^j,
13. M. Daniels^k,
14. F. S. Hu^l,
15. M. Lavoie^m,
16. C. Longⁿ,
17. T. Minckley^o,
18. P. J. H. Richard^p,
19. A. C. Scott^q,
20. D. S. Shafer^r,
21. W. Tinner^s,
22. C. E. Umbanhowar, Jr.^t and
23. C. Whitlock^g

+Author Affiliations

1. ^aDepartment of Geography, University of Oregon, Eugene, OR 97403;
2. ^bSchool of Geographical Sciences, University of Bristol, Bristol BS8 1SS, United Kingdom;
3. ^cDepartment of Quaternary Geology, Geological Survey, Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen, Denmark;
4. ^dRoyal British Columbia Museum, Victoria, BC, Canada V8W 9W2;
5. ^eSchool of Geography, University of Southampton, Southampton SO17 1BJ, United Kingdom;
6. ^fAlaska Quaternary Center, University of Alaska, Fairbanks, AK 99775;
7. ^gDepartment of Earth Science, Montana State University, Bozeman, MT 59717;
8. ^hDepartment of Geography, University of Utah, Salt Lake City, UT 84112;
9. ⁱCenter for Sustainable Environments and
10. ^kEcological Restoration Institute, Northern Arizona University, Flagstaff, AZ 86011;
11. ^jCentre for Bio-Archeology and Ecology (Unité Mixte de Recherche 5059, Centre National de la Recherche Scientifique) and Paleoenvironments and Chronoecology, Institut de Botanique, Université Montpellier 2, 163 Rue Broussonet, F-34090 Montpellier, France;
12. ^lDepartments of Plant Biology and Geology, University of Illinois at Urbana–Champaign, Urbana, IL 61801;
13. ^mDépartement de Géographie et Centre d'Études Nordiques, Université Laval, Québec, QC, Canada G1V 0A6;
14. ⁿDepartment of Geography and Urban Planning, University of Wisconsin, Oshkosh, WI 54903;
15. ^oDepartment of Botany, University of Wyoming, Laramie, WY 82071;
16. ^pDépartement de Géographie, Université de Montréal, C. P. 6128 Centre-ville, Montréal, QC, Canada H3C 3J7;
17. ^qDepartment of Earth Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom;
18. ^rDivision of Hydrologic Sciences, Desert Research Institute, Nevada System of Higher Education, 755 East Flamingo Road, Las Vegas, NV 89119;
19. ^sInstitute of Plant Sciences and Oeschger Centre for Climate Change Research, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland; and
20. ^tBiology and Environmental Studies, St. Olaf College, Northfield, MN 55057

1. Edited by Christopher B. Field, Carnegie Institution of Washington, Stanford, CA, and approved December 29, 2008 (received for review August 19, 2008)

Abstract

It is widely accepted, based on data from the last few decades and on model simulations, that anthropogenic climate change will cause increased fire activity. However, less attention has been paid to the relationship between abrupt climate changes and heightened fire activity in the paleorecord. We use 35 charcoal and pollen records to assess how fire regimes in North America changed during the last glacial–interglacial transition (15 to 10 ka), a time of large and rapid climate changes. We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indicated at any time during deglaciation. There are, however, clear links between large climate changes and fire activity. Biomass burning gradually increased from the glacial period to the beginning of the Younger Dryas. Although there are changes in biomass burning during the Younger Dryas, there is no systematic trend. There is a further increase in biomass burning after the Younger Dryas. Intervals of rapid climate change at 13.9, 13.2, and 11.7 ka are marked by large increases in fire activity. The timing of changes in fire is not coincident with changes in human population density or the timing of the extinction of the megafauna. Although these factors could have contributed to fire-regime changes at individual sites or at specific times, the charcoal data indicate an important role for climate, and particularly rapid climate change, in determining broad-scale levels of fire activity.

• *To whom correspondence should be addressed. e-mail: jmarlon@uoregon.edu

• Author contributions: J.R.M. and P.J.B. designed research; J.R.M., P.J.B., M.K.W., S.P.H., K.J.B., M.E.E., P.E.H., M.J.P., R.S.A., C.B., A.B., C.C., M.D., F.S.H., M.L., C.L., T.M., P.J.H.R., D.S.S., W.T., C.E.U., and C.W. performed research; J.R.M., P.J.B., M.K.W., S.P.H., K.J.B., M.E.E., P.E.H., and M.J.P. analyzed data; and J.R.M., P.J.B., M.K.W., S.P.H., K.J.B., M.E.E., P.E.H., M.J.P., R.S.A., C.B., A.B., C.C., M.D., F.S.H., M.L., C.L., T.M., P.J.H.R., A.C.S., D.S.S., W.T., C.E.U., and C.W. wrote the paper.

• The authors declare no conflict of interest.

• This article is a PNAS Direct Submission.

• © 2009 by The National Academy of Sciences of the U.S.A.

Link to abstract: http://www.pnas.org/content/early/2009/02/03/0808212106.abstract

Link to complete article: http://www.pnas.org/content/early/2009/02/03/0808212106.full.pdf+html