When the ancestral Puebloans lived in the Chaco Canyon area, they chose to locate their great houses in areas with high agricultural productivity, according to a new study in the Journal of Archaeological Science: Reports. 

Lead author Wetherbee Dorshow said these ancient agricultural fields can be hard to identify. And encroaching oil and gas development in the region could threaten the fields.

“There are a lot of areas there that have never been surveyed and we don’t know a ton about,” he said. “There’s also a lot of oil and gas in areas that are highly sensitive.”

He said the fields aren’t lined with stone fences like the masonry walls that have been used in Zuni Pueblo.

Dorshow’s team used GIS—or geospatial imaging—to identify areas that the ancestral Puebloans may have farmed during the time period archaeologists refer to as the Great House period, which stretches from 850 A.D. to 1200 A.D.

Dorshow said there are a variety of different ideas about the role that Chaco Canyon played in the ancestral Puebloan society. He said while some archaeologists believe that most of the food was transported into Chaco Canyon and grown elsewhere, he and his co-author, University of New Mexico Professor Chip Willis, believe that agriculture was abundant in and around Chaco Canyon.

He said the ancestral Puebloan people were adaptive and monitored things like where rain was falling. They would move weirs, or structures intended to control the flow of water, to respond to weather patterns.

Dorshow said archaeology is prone to site bias, meaning that the focus is largely on structures like Pueblo Bonito at Chaco Culture National Historical Park. To reduce site bias, researchers looked at a landscape scale.

The researchers examined hydrological variables as well as soil and vegetation to identify where the agricultural fields may have been.

Dorshow said often when they visit the sites after identifying them they find evidence of past agriculture such as pollen records or artifacts like rock hoes. Based on his research, Dorshow believes the ancestral Puebloans living in and around Chaco Canyon grew large amounts of food.

The researchers also looked at where oil and gas development is occurring and found a lot of it overlaps with where agricultural fields likely were located.

“I would hope that people might look at this study and others like it to broaden the definition of what might be archaeologically sensitive,” he said.

Dorshow said oil and gas extraction is not going to stop in the Chaco area, but, by looking more closely at where the agricultural fields would have been, projects can be moved to avoid impacting the fields. That could mean changing the route a pipeline takes to avoid cutting through an ancient agricultural field.

“It’s an archaeological landscape out there,” Dorshow said, adding that people shouldn’t think about it as cut and dry sites.

Oil and gas development in the Chaco area has come under increasing scrutiny in recent years, leading to the State Land Office placing a moratorium on new leases on state lands within 10 miles of the park in 2019 and the federal government following suit last year by implementing a 20-year moratorium. Both opponents of drilling near Chaco and proponents of extraction in the region say that the 10-mile buffer zone is an arbitrary boundary.

Ancestral Puebloan settlements have been found in southwest Colorado, southeast Utah and northwest New Mexico. These include places like Mesa Verde National Park, Chimney Rock National Monument, Bears Ears National Monument and Aztec Ruins National Monument.

An ancient road system connected Chaco Canyon with various outlying communities.

Environmental and Indigenous advocates say the U.S. Department of the Interior is not doing enough to protect the Greater Chaco region, which also includes sites sacred to the Navajo people. Last week, a coalition of groups sued the U.S. Bureau of Land Management as well as Interior Secretary Deb Haaland, the BLM’s acting New Mexico State Director Melanie Barnes and the New Mexico Deputy State Director for Minerals of the U.S. Bureau of Land Management Sheila Malory. The coalition opposes a decision to reaffirm a lease sale done under former President Donald Trump’s administration that issued leases on 42 parcels within the BLM’s Rio Puerco and Farmington field offices. The BLM also approved about 120 permits to drill on eight of those parcels.

These leases, the coalition argues, will threaten the Sisnaateel Mesa Complex. This 20-mile area is sacred to the Navajo, or Diné, people and is central to their cosmology.