Earth Notes: Ancient Peoples and Fire

Jan 15, 2014

In modern times human presence has influenced the size and number of wildfires on the Colorado Plateau. We are, in part, responsible for more big fires and fewer small ones. But is there also a connection between ancient peoples and wildfire?

Prater Canyon in Mesa Verde National Park
Credit Library of Congress

To find out, scientists from Northern Arizona University, the University of Oregon, and the National Park Service examined sediments that have collected over millennia in a canyon in Mesa Verde National Park.

They collected seven meters’ worth of sediment. Charcoal samples in it show that fires occurred as often as every 16 years before the arrival of Ancestral Puebloans at Mesa Verde. Later, when this society was well established, fire frequency dropped to once every 50 years — or even less.

This suggests that fire management was practiced by Ancestral Puebloans, though it isn’t certain whether fires were intentionally set or escaped control. But, investigators think that many peoples used fire to improve growing conditions for favored plants, or for better hunting.

By the 1300s the Ancestral Puebloans had left the area, probably in response to drier conditions that made farming too difficult. The landscape recorded their departure, for pollen records show an increase in populations of drought-tolerant plants.

The climate became wetter before too long, and junipers and piñon pines moved in. Many of them are still present today in Mesa Verde’s old-growth forests. But, large fires in the past decade have consumed many of those ancient trees. They’re a sign that the long interaction between people, place and climate continues today.