What Trees Can Tell Us About the Amazon
Weather in the Amazon has been a little crazy lately. Two of the most severe droughts in a century of weather record keeping in the area happened in 2005 and 2010, while western Amazonia had record flooding in 2012. Maybe wild weather swings are a frequent occurrence in the most biodiverse place on earth, maybe not. Right now there’s no way to tell, because the climate records only go back about 100 years.
David Stahle, a distinguished professor in the U of A’s Department of Geosciences, wants to change that by studying trees there. Stahle and co-researcher Song Feng, a climate change specialist in the U of A’s Department of Geosciences, were recently awarded a three-year, $418,000 grant from the National Science Foundation to extend the Amazon’s climate record by centuries.
Stahle has done similar work before in North America, where he and other researchers extended climate records via the science of dendrochronology, or the study of tree rings. It’s proven remarkably accurate. In a study published last year, Stahle was part of a team that reconstructed drought conditions in Mexico during 22 typhus epidemics of the colonial and modern era. Drought caused famine and created refugees who crowded into shelters where body lice flourished. Typhus is spread in humans via body lice.
One reason there are no tree-ring studies in the Amazon is that tropical trees often don’t have rings. When the growing season is year-round, many species of trees don’t develop these telltale growth characteristics. But some do, including the Bertholettia excelsa, commonly known as the Brazil nut.
It’s illegal to cut down a Brazil nut tree in Brazil, so Stahle will study trees felled during the construction of the massive Belo Monte dam on the Rio Xingu. By studying large sections of the downed trees, he hopes to perfect a non-destructive method of researching the trees in other parts of the Amazon Basin.
Stahle’s goal is to lengthen the Amazon’s climate record by as much as 300 years. That should be enough to put the crazy weather of the past years into context. “Were decade long droughts common in the Amazon during pre-history?,” he says. “Probably not, be we don’t know.”