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Dendrochronologists specialize in analyzing tree rings. By examining a tree core sample, they can uncover valuable information, such as historical climate patterns and the tree's age, by carefully studying the growth lines.
However, as reported by the BBC, one climate scientist was puzzled when she found that numerous trees in Kåfjord, Norway, had no rings. While severe weather and invasive pests can harm trees, they don't typically erase the rings completely.
Claudia Hartl, from Johannes Gutenberg University in Germany, knew the trees had grown since 1945, but that alone wasn't enough to explain their condition. Two other key factors—location and history—provided the missing pieces. During World War II, Nazi forces stationed the Tirpitz, the largest battleship in Hitler's navy, in the waters of Kåfjord to block shipments of supplies to the Soviet Union. To hide the ship, the Germans used artificial smoke containing chlorosulphuric acid, which is thought to have caused the trees' lack of rings.
Researchers discovered that the artificial smoke may have harmed the tree needles, disrupting photosynthesis and slowing the trees' growth. Though recovery takes time, it is achievable. One tree showed no growth between 1945 and 1954, but after three decades, it returned to its normal growth rate. Hartl shared these results at the European Geosciences Union General Assembly in Vienna this week [PDF].
"It's fascinating that the impacts of a single event are still visible in the forests of northern Norway over 70 years later," Hartl told BBC News. She believes her concept of "warfare dendrochronology" could uncover similar findings across the globe.
