Document: CRA-3-68-45

The relative roles of lightning and aboriginal ignitions in pre-1900 fire regimes, southwestern USA.

ALLEN, C.D.*

U.S. Geological Survey, Los Alamos, NM 87544 USA. ¹

Abstract:
Some scholars assert that human-set fires sustained most prehistoric fire regimes across North America, including the southwestern USA. I review multiple lines of evidence to assess the relative roles of lightning versus human ignitions in pre-1900 fire regimes in the upland Southwest. A regional network of dendrochronological fire and climate reconstructions conclusively demonstrates that prehistoric fire patterns (frequency, extent, seasonality, climate and vegetation relationships) are consistent with modern observations of lightning-ignited fire activity. Prehistoric fire scars document unusual fire patterns that may indicate human enhancement of lightning fire regimes only in a few localities during limited time periods. Eyewitness accounts of Indian burning are rare, and the substantial archaeological and ethnographic data available in the Southwest reveal little indication of landscape-scale aboriginal fire use. Modern claims of extensive Indian burning are shown to be based upon a few historic EuroAmerican writings that discounted lightning as a potential ignition source and reflexively attributed almost all fires to human agency, although modern fire records show ~2400 lightning fires/year in the Southwest (~80% of all ignitions). While aboriginal peoples certainly used fire for many localized purposes, evidence of landscape-scale Indian burning is lacking and lightning ignitions sufficiently explain the record of frequent fire as an intrinsic feature of the Holocene Southwest. Since the ecological history of Southwestern fire involves interactions among both natural and cultural histories, generalizations about "pristine" vs. "humanized" landscape conditions need to consider the particulars of variation in the relative effects of people through time and space.

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This abstract is being presented at: 9:30 AM in session:
Oral Session #22: Multiple Disturbance Effects, Including Fire.