Dendrochronology is the science of interpreting over 9,000 continuous years' worth of environmental conditions through tree ring samples. That field of study got its start at the University of Arizona in the Laboratory of Tree Ring Research, and it's still finding answers today.

Samples can be taken from dead trees and, by using an increment borer, from live trees as well. Each ring on each sample tells its own story: a fat ring may represent an easy growing year, while a narrow one can indicate scant resources or drought.

The Tree Ring Lab has amassed nearly three million samples since A. E. Douglass established it in 1937.

“Tree rings can tell us about past climate variations, about the history of people and their societies, the rise and fall of civilizations, all kinds of things,” says Tom Swetnam, director of the laboratory. “Forest fires, earthquakes--it’s amazing, actually, the variety of environmental history that we can learn from tree rings.”

Swetnam was honored as a Regent’s Professor in March of 2012.