Long before European explorers arrived in the New World, Native American communities used fire to keep warm and to manage the land.

Christopher Roos is an archaeologist at Southern Methodist University and lead author of a new study that looks into how that use of fire affected the ecosystem.

Interview Highlights

On how the land was managed by Native Americans

One of the primary uses of fire on the landscape was to refresh the prairie. Bison was one of their prime prey and the center point for their economy, in terms of food, clothing, shelter and tools. Bison prefer to graze recently burned patches of prairie — it's tastier, it's more nutritious. And so they manipulated the location of bison herds by selectively burning patches of prairie, and one of the things they did for most of the last millennium is burn patches of prairie to lure bison into these parts of the landscape where they could be driven over cliffs and harvested en masse.

On how this management impacted the land

One of the consequences of this is that the burning by these native hunters ended up amplifying the impacts of climate variability on prairie fire activity. This comes about in part because these prairies require good, wet conditions to produce a lot of grass that can carry spreading fires. And the hunters had a pretty sophisticated system in which they used that knowledge to burn when climate conditions were right. And one of the consequences of that is that you ended up with even more fire during these wet periods than you would have otherwise because of the activities of these native hunters.

On what other communities were doing at the time

This period of bison hunting by building landscape scale features and driving them off cliffs spanned about 900 A.D. through about 1650 or 1700. And during this period of time, (I mostly do my other work in the southwestern United States), we have evidence for the ancestors of Pueblo Indians and later of Apaches using fire to manage agricultural lands, to promote certain types of medicinal and wild plants, but also actually in hunting and similar fashion to kind of lure in game to freshly burned areas that they prefer.

On how these communities drove bison without horses

This is really a communal effort. These drive lines were built with a lot of labor. The "stone cairns" — these piles of stone — were lined up sometimes a kilometer or more in length. They would have scarecrows or real humans on them to kind of funnel the bison towards their cliff and these efforts would be in "aggregated bands." Basically, a band might have 150 people, and in these in aggregated bands you might end up with as many as 2,000 people to get working together to scare the bison and get them started and running over the cliff.

Interview responses have been edited for clarity and length.