Tales in a tree

Nature Conservancy presents a talk by tree ring expert Swetnam

By Ariana Kramer
Posted 9/4/18

The study of tree rings has led to insightful discoveries about the history of people and places. Dr. Tom Swetnam is an expert in using tree rings to learn about environmental and …

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Tales in a tree

Nature Conservancy presents a talk by tree ring expert Swetnam


The study of tree rings has led to insightful discoveries about the history of people and places.

Dr. Tom Swetnam is an expert in using tree rings to learn about environmental and cultural history. He is Regents' Professor Emeritus of Dendrochronology at the University of Arizona and was director of the Laboratory of Tree-Ring Research from 2000-2015. Here in Northern New Mexico, Swetnam has worked with The Nature Conservancy on a project using tree ring research to learn about fire history in the Taos Mountains.

The Nature Conservancy will present a lecture by Swetnam Wednesday (Sept. 5), 5:30 p.m., at the Harwood Museum of Art, 238 Ledoux Street. His talk will focus on tree ring dating and examples of the historical insights from studies in Northern New Mexico. The event is free to the public.

"My talk will be a survey on use of tree rings to study the past history of people, forests and climate in Northern New Mexico," Swetnam said. "Trees have been the main source of information to learn when people moved into the Southwest and when the main pueblo structures were built."

By looking at the tree rings on timbers used to build pueblo structures, historical dating is possible, he explained.

"The general idea is trees grow every year by how much rainfall there is, so a ring is formed every summer," Swetnam explained. "You'll have a pretty narrow ring if you have a drought year and a wide ring if it's a wet year. From these patterns we can tell what years were the drought years and what periods were the worst droughts. We have drought events which coincide with some of the great changes in the Southwest like population changes and changes in forest fire activity."

Swetnam's lecture is part of The Nature Conservancy in Taos Lecture Series, which is supported by the Taos Ski Valley Foundation. Earlier this year, the series brought Dr. Ellis Margolis to Taos to speak about the study being conducted in the Taos mountains to determine the fire history of the area. Margolis was a former doctoral student of Swetnam, and they are current colleagues.

"The Nature Conservancy is hosting these lectures as a way to engage the public and create awareness around the Río Grande Water Fund, the partners involved, why it is needed, how it works and how it benefits nature and the community," said Collin Haffey, conservation coordinator of The Nature Conservancy New Mexico field office based in Santa Fe.

According to its webpage, the Río Grande Water Fund is an initiative started in 2014 and led by The Nature Conservancy to protect the forests of Northern New Mexico and the water that comes from them.

the webpage reads, "With 60 charter signatories, we are working to generate sustainable funding for a 20-year program to restore 600,000 acres north of Albuquerque by thinning overgrown forests, managing fire, restoring wetlands and streams, educating youth, providing research to policy makers, and creating forestry and wood products jobs. Restoring overgrown forests is a proven solution to make forests safer and healthier. And research shows that fighting catastrophic megafires and rehabilitating damaged areas afterward can cost tens of millions of dollars. The bottom line is simple: restoring forests now is a smarter investment."

Amy Rankin, manager of public programs and events for the Harwood Museum of Art, said the museum is supportive of local groups and organizations that are involved with the Northern New Mexico community, the art, and the environment.

Rankin adds, "We depend on organizations, such as The Nature Conservancy, (as well as The Leopold Writing Program, Amigos Bravos, Rivers and Birds, Southern Methodist University in Taos, etc.) to bring in interesting and highly qualified folks to inspire and instigate conversations about relevant cultural and environmental topics."

"This time that person is Tom Swetnam," said Rankin. "I'm really looking forward to hearing what he has to say."

Swetnam operates a small tree ring lab from his home in Jemez Springs and is involved in a number of tree ring dating projects in New Mexico. These include dating historic buildings in Santa Fe, Ranchos de Taos, Abiquiu, Isleta Pueblo and Jemez Springs. Swetnam said the buildings are dated from tree ring samples taken from vigas and door/window lintels to determine when the structures were built or re-roofed.

Swetnam is the principal investigator for a project funded by the National Science Foundation. Titled FHiRE: Fire and Humans in Resilient Ecosystems, the historical case study is designed to determine how human activities at the wildland-urban interface affect the response of fire-adapted pine forests to climate change. It also looks at how people have responded to these changes over many centuries. Archaeology, paleoecology,and computer modeling are all used in the study, which aims to identify sustainability tipping points for the forests and their human communities.

For more information on Swetnam and his research, visit


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