Tree Story

The History of the World Written in Rings

Valerie Trouet, Johns Hopkins University Press (APR 21) Hardcover $27 (256pp), 978-1-4214-3777-4 HISTORY

Oh, the things we know by the way trees grow: about the planet’s climate over the past couple thousand years, about population fluctuation from ancient Rome forward, about solar radiation variations, atmospheric pressure systems, volcanic eruptions, wildfires, hurricanes and other extreme weather events, floods, droughts, and greenhouse gas emissions. Trees, we learn, have near perfect memories.

To tap the great trove of tree knowledge, we have dendrochronoglogists, the scientists who study tree rings. Short of what has survived in written form over the centuries, dendrochronologists have filled in numerous gaps to help historians and archaeologists solve vexing questions about war and conquest, epidemics and migrations, human greed and carelessness.

In her delightful Tree Story, dendrochronologist Valerie Trouet obliterates the layman’s notion that tree rings provide little more information than a tree’s age. Examples abound. She cites Mongolian tree ring research into the period between 1211 and 1225, showing that Genghis Khan went on his roll during the wettest decades of the past eleven hundred years, providing his cavalry’s horses expansive grasslands to feed on. She and a colleague sought to explain a dramatic dip in Caribbean shipwrecks between 1645 and 1715 and realized, through tree rings in the Florida Keys, that record low sunspot numbers related to cooler waters and, thus, far fewer hurricanes during that period. What trees can teach seems limited only by science’s ability to extract the information.