New paper finds wildfires in the western US are at the lowest levels in 3,000 years

A recent paper reconstructs wildfire activity in the western US over the past 3,000 years and finds current fire activity is at the lowest levels of the entire 3,000 year record. According to the authors, 

"there is now a forest “fire deficit” in the western United States attributable to the combined effects of human activities, ecological, and climate changes. Large fires in the late 20th and 21st century fires have begun to address the fire deficit, but it is continuing to grow."

Variations in western US wildfires over the past 3,000 years. Horizontal axis is calendar years before the present. 

Long-term perspective on wildfires in the western USA

1. Jennifer R. Marlon^a,¹, 
2. Patrick J. Bartlein^b, 
3. Daniel G. Gavin^b, 
4. Colin J. Long^c,
5. R. Scott Anderson^d, 
6. Christy E. Briles^e, 
7. Kendrick J. Brown^f, 
8. Daniele Colombaroli^g,
9. Douglas J. Hallett^h, 
10. Mitchell J. Powerⁱ, 
11. Elizabeth A. Scharf^j, and 
12. Megan K. Walsh^k

+Author Affiliations

1. ^aDepartment of Geography, University of Wisconsin, Madison, WI 53706;
2. ^bDepartment of Geography, University of Oregon, Eugene, OR 97403;
3. ^cDepartment of Geography and Urban Planning, University of Wisconsin, Oshkosh, WI 54901;
4. ^dSchool of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011;
5. ^eSchool of Geography and Environmental Science, Monash University, Victoria 3800, Australia;
6. ^fCanadian Forest Service, Victoria, BC, Canada V8Z 1M5;
7. ^gOeschger Centre for Climate Change Research and Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland;
8. ^hBiogeoscience Institute, University of Calgary, Alberta, Canada T2N 1N4;
9. ⁱNatural History Museum of Utah, Department of Geography, University of Utah, Salt Lake City, UT 84112;
10. ^jDepartment of Anthropology, University of North Dakota, Grand Forks, ND 58202; and
11. ^kDepartment of Geography, Central Washington University, Ellensburg, WA 98926

1. Edited by B. L. Turner, Arizona State University, Tempe, AZ, and approved January 10, 2012 (received for review August 13, 2011)

Abstract

Understanding the causes and consequences of wildfires in forests of the western United States requires integrated information about fire, climate changes, and human activity on multiple temporal scales. We use sedimentary charcoal accumulation rates to construct long-term variations in fire during the past 3,000 y in the American West and compare this record to independent fire-history data from historical records and fire scars. There has been a slight decline in burning over the past 3,000 y, with the lowest levels attained during the 20th century and during the Little Ice Age (LIA, ca. 1400–1700 CE [Common Era]). Prominent peaks in forest fires occurred during the Medieval Climate Anomaly (ca. 950–1250 CE) and during the 1800s. Analysis of climate reconstructions beginning from 500 CE and population data show that temperature and drought predict changes in biomass burning up to the late 1800s CE. Since the late 1800s , human activities and the ecological effects of recent high fire activity caused a large, abrupt decline in burning similar to the LIA fire decline. Consequently, there is now a forest “fire deficit” in the western United States attributable to the combined effects of human activities, ecological, and climate changes. Large fires in the late 20th and 21st century fires have begun to address the fire deficit, but it is continuing to grow.


Full paper available here