Physical Scientist Michelle Leung and Research Geologist Natalie Kehrwald prepare sediment samples from Santa Fe Lake, New Mexico to analyze records of interactions between past fires and human activity over the last few thousand years.
Did we start the fire? Climate, Fire and Humans Active
By Geosciences and Environmental Change Science Center
July 21, 2022
The past decade encompasses some of the most extensive fire activity in recorded history. An area the size of Vermont (~24,000 km2) burned in a single Siberian fire in the summer of 2019 (Kehrwald et al., 2020 and references therein) while Australia, Indonesia and the Amazon have all experienced their most intense fires in recorded history (van Wees et al, 2021 and references therein). As more people move into the wildland-urban interface, these extensive fires are also becoming some of the most expensive fires in history as homes and businesses are caught in the flames. The 2020 fire season in California alone resulted in billions of dollars of damages. Areas such as California and the southwestern US that used to have fire seasons are now preparing for the possibility of fire activity at any time of the year. The sparks that kindled these fires are due to both natural and human ignitions.
The southwestern US and Alaska are also two of the areas of North America that are the most affected by a changing climate. The trends of a hotter, drier, and more fire-prone southwestern US (MacDonald, 2010) have become even more pronounced over the past decade. Alaska is also experiencing some of the greatest mean increases in temperature in North America, resulting northern shifts in vegetation, where this vegetation provides fuel in areas that previously did not burn (Kehrwald et al., 2020 and references therein). As the tundra is turning into tinder, a warming atmosphere results in increased lightning (Chen et al., 2021), thereby increasing ignitions of the thawing permafrost.
While fire activity is increasing in the southwestern US and Alaska, substantial gaps in our knowledge exist regarding fires and climate change in these regions over the past two thousand years. These gaps include:
- Was climate change or human activity the primary driver of fire activity in regions of the southwestern US? Why are there gaps in the fire record when climate conditions would be expected to lead to increased fire activity? Do such gaps suggest previous fire suppression?
- Substantial areas of the southwestern US do not contain paleorecords of precipitation, fire, and/or human activity. The SW is currently in a megadrought and subject to fires that are outside of the scale and intensity in the historical record. We have identified locations to obtain tree-ring and lake sediment records these areas to increase our knowledge of how past fire activity responded to similar droughts.
- What types of vegetation burned in the past? Do these vegetation types differ from the present? (E.g. do we see parallels in the past with the current browning of the Arctic and carbon release from wildfires? Is there evidence for past ecosystem shifts from forests to grasslands after previous intense fires?)
In order to address these research questions, we developed the following three tasks:
Fire, human activity, and climate records in southwestern US sediments
Fire, human activity, and climate records in southwestern US sediments
Fire, human activity, and climate records in southwestern US sediments
Hydroclimate, fire, and human interactions in southwestern US tree ring records
Hydroclimate, fire, and human interactions in southwestern US tree ring records
Hydroclimate, fire, and human interactions in southwestern US tree ring records
Fire and vegetation changes recorded in Alaskan ice cores
Fire and vegetation changes recorded in Alaskan ice cores
Fire and vegetation changes recorded in Alaskan ice cores
References
Chen, Y., Romps, D.M., Seeley, J.T., Veraverbeke, S., Riley, W.J., Mekonnen, Z.A., Randerson, J.T. (2021) Future increases in Arctic lightning and fire risk for permafrost carbon. Nature Climate Change, doi:10.1038/s41558-021-01011-y
Guiterman, C. H., Margolis, E. Q., Baisan, C. H., Falk, D. A., Allen, C. D., and Swetnam, T. W. (2019) Spatiotemporal variability of human–fire interactions on the Navajo Nation. Ecosphere, 10( 11):e02932. doi:10.1002/ecs2.2932
Kehrwald, N.M. Jasmann, J.R., Dunham, M.E., Ferris, D.G., Osterberg, E.C., Kennedy, J., Havens, J., Barber, L.B., Fortner, K. (2020) Boreal blazes: Biomass burning and vegetation types archived in the Juneau Icefield. Environmental Research Letters, 15, 8, doi:10.1088/1748-9326/ab8fd2
MacDonald, G.M. (2010) Water, climate change, and sustainability in the southwest. PNAS, 107 (50) 21256-21262, doi:10.1073/pnas.0909651107
van Wees, D., van der Werf, G.R., Randerson, J.T., Andela, N., Chen, Y., Morton, D.C. (2021) The role of fire in global forest loss dynamics. Global Change Biology, 00: 1-15, doi:10.1111/gcb.15591
Preparing sediment samples in the lab
Physical Scientist Michelle Leung and Research Geologist Natalie Kehrwald prepare sediment samples from Santa Fe Lake, New Mexico to analyze records of interactions between past fires and human activity over the last few thousand years.
Sangre de Cristo Mountains fieldwork
Physical Scientist Michelle Leung prepares to drill tree cores in the southern Sangre de Cristo Mountains, Colorado. Tree cores provide seasonal to centennial records of past precipitation and provide local to regional reconstructions of hydroclimate.
Physical Scientist Michelle Leung prepares to drill tree cores in the southern Sangre de Cristo Mountains, Colorado. Tree cores provide seasonal to centennial records of past precipitation and provide local to regional reconstructions of hydroclimate.
Sangre de Cristo Mountains fieldwork
Michelle Leung and Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Michelle Leung and Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Sangre de Cristo Mountains fieldwork
Physical Scientist Michelle Leung and Geographer Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Physical Scientist Michelle Leung and Geographer Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Sangre de Cristo Mountains fieldwork
Research Geologist Natalie Kehrwald cuts a “cookie” from a fire-scarred tree in the southern Sangre de Cristo Mountains, New Mexico. Cookies are cross-sections of trees that provide information on the interactions between past droughts and fires.
Research Geologist Natalie Kehrwald cuts a “cookie” from a fire-scarred tree in the southern Sangre de Cristo Mountains, New Mexico. Cookies are cross-sections of trees that provide information on the interactions between past droughts and fires.
Coring in Santa Fe Lake, New Mexico
USGS scientists drilling Santa Fe Lake, New Mexico as part of fieldwork conducted with the Did we start the fire? Climate, Fire and Humans project.
USGS scientists drilling Santa Fe Lake, New Mexico as part of fieldwork conducted with the Did we start the fire? Climate, Fire and Humans project.
Preparing sediment samples in the lab
Physical Scientist Michelle Leung and Research Geologist Natalie Kehrwald prepare sediment samples from Santa Fe Lake, New Mexico to analyze records of interactions between past fires and human activity over the last few thousand years.
Physical Scientist Michelle Leung and Research Geologist Natalie Kehrwald prepare sediment samples from Santa Fe Lake, New Mexico to analyze records of interactions between past fires and human activity over the last few thousand years.
Sangre de Cristo Mountains fieldwork
Physical Scientist Michelle Leung prepares to drill tree cores in the southern Sangre de Cristo Mountains, Colorado. Tree cores provide seasonal to centennial records of past precipitation and provide local to regional reconstructions of hydroclimate.
Physical Scientist Michelle Leung prepares to drill tree cores in the southern Sangre de Cristo Mountains, Colorado. Tree cores provide seasonal to centennial records of past precipitation and provide local to regional reconstructions of hydroclimate.
Sangre de Cristo Mountains fieldwork
Michelle Leung and Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Michelle Leung and Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Sangre de Cristo Mountains fieldwork
Physical Scientist Michelle Leung and Geographer Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Physical Scientist Michelle Leung and Geographer Becky Brice collect samples from fire-scarred trees in the southern Sangre de Cristo Mountains, Colorado. Trees provide records of past droughts, fires, and the response of vegetation to a changing snowpack.
Sangre de Cristo Mountains fieldwork
Research Geologist Natalie Kehrwald cuts a “cookie” from a fire-scarred tree in the southern Sangre de Cristo Mountains, New Mexico. Cookies are cross-sections of trees that provide information on the interactions between past droughts and fires.
Research Geologist Natalie Kehrwald cuts a “cookie” from a fire-scarred tree in the southern Sangre de Cristo Mountains, New Mexico. Cookies are cross-sections of trees that provide information on the interactions between past droughts and fires.
Coring in Santa Fe Lake, New Mexico
USGS scientists drilling Santa Fe Lake, New Mexico as part of fieldwork conducted with the Did we start the fire? Climate, Fire and Humans project.
USGS scientists drilling Santa Fe Lake, New Mexico as part of fieldwork conducted with the Did we start the fire? Climate, Fire and Humans project.