If a tree could talk, what might it say?
Would it plead for rain in a drought? Fawn over a neighbor’s foliage? Crack jokes about how fast another tree loses its leaves in fall?
It seems unlikely anyone will ever come across a loquacious linden. But for the arbor-curious, a red oak at the Harvard Forest in Petersham has been tweeting as @awitnesstree since July 17. Outfitted with sensors and cameras, and programmed with code that allows it to string together posts with prewritten bits of text, the Harvard Forest Witness Tree has been sharing on-the-ground insights into its own environmental life and that of its forest.
Already renowned in certain circles as the subject of the popular climate-change book “Witness Tree” by Lynda Mapes, the century-old oak’s social-media debut was the brainchild of Harvard Forest postdoctoral fellow Tim Rademacher and is now a team effort with Clarisse Hart, who heads outreach and education for the forest. Its online presence is modeled after similar “twittering” trees that chronicle their life experiences as part of a tree-water and carbon-monitoring network based in Europe called TreeWatch.net.
“We’ve done the work as a team to equip the tree with a voice, which we decided made the most sense in the first person, and even with a personality, in order to make it relatable to a larger audience,” said Rademacher. “But most importantly, our Witness Tree is an objectively data-driven account, which I expect will amplify messages of climate change. But we don’t decide what gets posted, the tree does.”
In 2018, with support from the National Science Foundation, Rademacher installed equipment on and around the tree to help better understand the tree’s physiology and its place within the environment of the Harvard Forest, and the world beyond.
Dendrometers measure the tree’s growth in real time, evaluating daily changes in the radius of its trunk and providing insights into its health, how it stores carbon, and how it helps remove carbon dioxide from the air. Sensors measure sap and water flow within the xylem, the tree’s transport system to move water and nutrients. This information will help the Harvard Forest team understand how climate, particularly extreme events such as heatwaves and drought, affects water use and nutrient transport within a tree.