Solar Cycles as Superior Driver of Bark Beetle Forest Calamities in Central Europe: New Robust Evidence

A study published in Forest Ecosystems offers a novel insight into how solar activity, specifically total solar irradiance (TSI), is strongly linked to the cyclical nature of bark beetle-induced forest calamities in Central Europe. “What’s new here is the identification of a consistent 9–12-year cycle in beetle-related salvage logging across Austria, Czechia, and Slovakia—a cycle that aligns with solar minima,” shares lead author Václav Šimůnek.

The researchers found that during periods of low TSI, beetle-induced logging can spike up to 24%, while during high TSI, it drops as low as 3%–5%. “These fluctuations are likely mediated through the North Atlantic Oscillation (NAO), which influences European weather patterns,” adds Šimůnek.

Rising temperatures and reduced precipitation leads to drought, which appear to create ideal conditions for beetle outbreaks the year before they occur. This pattern was confirmed using drought indicators like the Standardized Precipitation Evapotranspiration Index (SPEI). Interestingly, while wind and snow-related salvage logging show shorter, more intense cycles, bark beetle disturbances follow longer, more regular solar-linked patterns. This sheds new light on how climate and solar dynamics converge to affect forest health. Importantly—findings that could improve forest management by offering predictive tools based on these cyclical patterns.

 “This approach opens up possibilities to anticipate calamity peaks and adapt forest policies accordingly, while forest management does not have to be surprised anymore by large forest destructions,” says Šimůnek.

The study’s use of common wavelet spectrum analysis across all countries is also methodologically notable, allowing for the detection of synchronized cycles across different climatic and ecological conditions in the studied countries. “In a time of accelerating climate change, understanding these cycles is crucial not only for reducing economic losses in the timber industry but also for maintaining forest ecosystem stability across Central Europe,” says Šimůnek. On behalf of my co-authors, I call on scientists with access to relevant long-term datasets to join us in a collaborative effort to study these phenomena.”

Contact author details: Ing. Václav Šimůnek, Ph.D., Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, simunekv@fld.czu.cz

Funder: Ministry of Agriculture of the Czech Republic through Project No. QK21010198, Czech University of Life Sciences Prague, Faculty of Forestry and Wood Sciences (Excellent Output 2025). 

Conflict of interest: The authors declare that they have no financial or personal relationships that could have influenced the outcomes of this study. 

See the article: Šimůnek, V., Vacek, Z., Vacek, S., et al., Bark beetle-induced salvage logging cycle is caused by weather patterns linked to the NAO and solar cycle in Central Europe, Forest Ecosystems, Volume 13, 2025, 100328, https://doi.org/10.1016/j.fecs.2025.100328