Precolonial farmers thrived in one of North America’s coldest places

A laser eye-in-the-sky has uncovered vast, ancient farm fields in an unlikely place — the frosty forests of Michigan’s Upper Peninsula.

Ancestors of present-day Menominee people, a federally recognized Native American tribe, grew maize and other crops in densely clustered earthen ridges from around 1,000 to 400 years ago, researchers report in the June 5 Science.

After clearing trees from large tracts of land, mobile communities accomplished this agricultural feat in the face of cold temperatures unfriendly to maize cultivation, a short growing season and poor soil conditions, say archaeologist Madeleine McLeester and colleagues.

“What is likely based on this new finding, from an area where we would not expect intensive agriculture, is that much of the eastern U.S. was once covered in Native American agricultural ridges,” says McLeester, of Dartmouth College.

A drone-mounted lidar, or light detection and ranging, device peered through trees and ground cover at Michigan’s Sixty Islands archaeological site to reveal the largest preserved system of agricultural fields in the eastern United States. Precolonial agricultural ridges covered a total of at least 2 square kilometers along a river that now separates Michigan from Wisconsin, McLeester estimates.

Radiocarbon dates of burned wood excavated from the site indicate that farming had occurred over roughly 600 years.

Archaeologists informed only by sparse remnants of ancient farm fields visible on the ground and historical accounts have previously downplayed the extent of precolonial farming in eastern North America. For instance, researchers have assumed that Menominee ancestors mainly gathered wild rice.

Ancient Menominee people instead may have cultivated large amounts of maize and other crops as a hedge against food shortages, as trade items or to feed a growing population, as suspected for precolonial farming communities in South America, McLeester says.

Menominee farmers found ways to enrich their soil. Excavations of agricultural ridges uncovered remains of composted household refuse and wetland soils used as fertilizer. Burial mounds, ritual structures and residences also dotted the farm fields.

McLeester expects drone lidar surveys will unveil more landscapes that precolonial Native Americans sculpted into fields of plenty.