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NMSU researchers look to ancient cultures to find patterns of climate change

MONTICELLO, N.M. - Dennis and Trudy O'Toole, who share interests in history and historic preservation, retired and moved to New Mexico from New Hampshire in 1998. But, long before they called the Monticello Box Ranch home, prehistoric people lived and worked on that same land, dating back more than 1,000 years. Those populations may be long gone, but the artifacts and other evidence the people left behind are a virtual time capsule that tells a tale of how they lived.

Professor Curtis Monger shows volunteer archaeologists different layers of soil at an archaeological site at Monticello Box Ranch. (NMSU photo by Audry Olmsted)

Now, New Mexico State University researchers are combining forces with the Caņada Alamosa Project, a joint project of the O'Toole's non-profit organization, the Caņada Alamosa Institute; and a Las Cruces non-profit group, Human Systems Research, Inc., to unearth the pieces left behind that will help shed light on the American Indians who lived on the land, and when and why they left.

"Archaeology - and its related studies - gives us the largest record we have of human interaction and reaction to a changing environment," said Karl Laumbach, archaeologist with Human Systems Research, Inc. "There is not another record that will give you that. That is why it is so important."

Researchers have determined that various cultures lived on this land, an area of approximately 728 square miles, about 2,000 years ago. Using bits of ceramics and other evidence found, they are trying to determine if the land was occupied by the same groups of people, or if the land was repeatedly occupied, abandoned and reoccupied over time.

"This was a huge archaeological site for more than 700 years. Then, the people left," said Curtis Monger, a professor in the Department of Plant and Environmental Sciences. "The question is, 'Why did they leave?' Was it something cultural or was it environmental?"

And that is what the researchers aim to find out. While Laumbach and his team of volunteers with Earthwatch Institute slowly unearth cultural remnants of the lives lived by the Northern Pueblo (Anasazi) and Southern Pueblo (Mogollon) inhabitants, Monger and his team slowly chip away at layer upon layer of soil looking for clues to tell them what kind of environment these prehistoric cultures faced.

"If something happened drastically with the climate, is there a sedimentary record of that climate change having occurred?" Monger questioned. "What's really important is knowing when it occurred."

Researchers can look at sediments to track climate change over time. Monger compared the different landscape terraces to "rings in a bathtub" that tell the former level of the floodplain.

The team is using radiocarbon dating to determine when the soil actually eroded and when the landscape was stable. Once they have a chronological record, this information can tell archaeologists when there was significant environmental change.

They also use a technique where they run samples of soil through a mass-spectrometer to get the relative proportions of carbon isotopes in the soil. This information can tell researchers if the land, now dry and arid, used to be grassland or forest. By using these techniques, they can track the natural cycles of climate change.

Researchers have found that over time, the different cultures in the area weathered periods of tremendous drought, as well as periods of water abundance.

Monger said the NMSU team's goals include satisfying their basic human curiosity to see how the different cultures lived and learning how these people were affected by climate change. The evidence they find will also help them compare global warming today to global warming of the past and determine how the New Mexico landscape responded to those changes. He said they have also found large amounts of calcium carbonate "caliche" in the soil and want to determine whether it came from the atmosphere or soil microorganisms.

"To gauge what we are looking at now, we need to understand the past," Monger said. "Are we in a period of warming? Well, perhaps. If we are, how much warming is it compared to what's happened naturally? We need to understand the natural background level of climate change in order to understand current climate change."

Researchers are wrapping up fieldwork this summer. Afterward, they will continue to analyze the data and evidence they retrieved.

"New Mexico is a wonderful place to probe and look back in time and understand climate change," Monger said.