MILES O'BRIEN: You might call him Lord of the Rings. DAVID STAHLE: The tree ring lab is hands-on and so we encourage everybody to touch these pieces of wood. This is a cross section of a Redwood tree. MILES O'BRIEN: David Stahle is dendrochronologist at the University of Arkansas. DAVID STAHLE: The annual growth rings of trees are a natural archive of environmental history. The time series history of fat rings and skinny rings is telling you about the history of wet years and dry years. So this is a piece of African Bloodwood. This was found in Western Zimbabwe. MILES O'BRIEN: Long before hi-tech weather instruments, nature has kept precise records of rain, drought, even fires. DAVID STAHLE: The climate history encoded in the annual rings of trees is unique. It's like fingerprinting. MILES O'BRIEN: With support from the National Science Foundation, Stahle is helping Mexico prepare for future droughts by looking at how trees responded to severe drought in the past. That will help fine-tune predictions about how future dry spells will impact the ecosystem, and could help the country prepare for future water and energy needs.
DAVID STAHLE: One notion is that this 21st Century drought may be being aggravated by human activity, both at the global scale and at the regional scale due to land surface changes. MILES O'BRIEN: Deciphering tree rings can also help historians solve mysteries, like the fate of the New World's Lost Colony of Roanoke. Could drought have been a factor? DAVID STAHLE: This is a piece of Baldcypress from Blackwater River, Virginia. That is the most severe drought of 800 years in this part of the United States. And thats a significant year because of the disappearance of Virginia Dare and the other colonists, the Roanoke Colony in North Carolina. This is a Swedish increment bore, and with this tool, we can extract a core sample without seriously harming the tree.
MILES O'BRIEN: In the fields, Stahle and his team target old-growth forest with the least imprint of human activity. DAVID STAHLE: Oh, man. These are stupendous trees. They are so precious. MILES O'BRIEN: And that's a ringing endorsement from this Lord of the Rings. For Science Nation, I'm Miles O'Brien..