Image: Dan Griffin, University of Arizona.
Citation: "Forest responses to increasing aridity and warmth in the southwestern United States." By A. Park Williams, Craig D. Allen, Constance I. Millar, Thomas W. Swetnam, Joel Michaelsen, Christopher J. Still, Steven W. Leavitt. Proceedings of the National Academy of Sciences, Vol. 107 No. 50, December 14, 2010.
Backlink: http://www.wired.com/wiredscience/wp-content/gallery/southwest-water/sw_treecore.jpg