Reading between the Lines

Working in close collaboration with a number of archaeologists and other scientists, Douglass went on to found the world's first center for dendrochronological analysis, the Laboratory of Tree-Ring Research (LTRR) at the University of Arizona. Today the lab is still going strong and is just one of dozens of facilities around the world dedicated to the analysis of tree rings not just as a dating tool but as a window into past environments. Since Douglass's day, the construction of thousands of tree-ring chronologies from both the Northern and Southern Hemispheres has provided striking evidence that climatic patterns recorded in the relatively recent past, since the advent and widespread eployment of weather monitoring instruments, are often far from what is "normal" in a broader historical context. Along with other indicators of past climatic and ecological variabilityincluding ice and sediment cores and annual growth bands in corals-treering data now provide vital information for scientists trying to assess the magnitude and significance of global warming and other environmental changes taking place today. More than just indicators of past temperature and rainfall patterns, tree rings provide a historical perspective on some of the fundamental processes that shape biological communities and ecosystems. "Tree-ring data are vitally important because they provide a temporal scale to studies that need to establish what environmental conditions were like in the past," says Henri Grissino-Mayer, a dendrochronologist at Valdosta State University in Georgia (University of Tennessee as of 1 July 2000). "These reference conditions are becoming increasingly important as we try to restore ecosystems disturbed by human activities." Tree rings can provide information on such things as the structure and composition of past forests and the size and frequency of wildfires and other disturbances before human intervention.