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Science  24 Mar 2000:
Vol. 287, Issue 5461, pp. 2117b
DOI: 10.1126/science.287.5461.2117b

The focus on the extensive fires at Yellowstone National Park in 1988 may leave the impression that such conflagrations occur fairly often, but a new study suggests that they are relatively rare events, at least in recent times. Millspaugh et al. constructed a 17,000-year record of fires by examining charcoal layers in sediments in Cygnet Lake in the central part of Yellowstone Park. Unlike other areas in this region, this area has been dominated by lodgepole pine for the past 13,000 years; this long record reveals the influence of climate on fire occurrence during a period of low and constant plant diversity.

Fires were rare in Yellowstone during the waning of the glacial period but increased greatly in the early Holocene to a high of about 15 per 1000 years about 10,000 years ago. At this time, summer insolation in the Northern Hemisphere was at a maximum, and the Yellowstone climate was drier during the summer than it is today. The recent rate for recognizable fire layers is much lower—about 2 to 3 per 1000 years—and does not reveal any regular periodicity in fire occurrence, in contrast to recent suggestions.—BH

Geology 28, 211 (2000).

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