Vol. 130, No. 1 * Pages 1–100 * January - March 2026

This study evaluates the risk of wood decay in cultural heritage sites across the European part of Russia by analyzing climatic influences on timber deterioration. Timber, a critical component of many heritage structures, is particularly vulnerable to fluctuations in air temperature and moisture, which accelerate biological decay processes. Using the Scheffer Climate Index (SCI) – a metric based on average monthly temperature and the number of precipitation days –, the research assesses decay risk over the period 1961–2020 with daily data from the ERA5 reanalysis. The SCI was decomposed into temperature and precipitation components, and trends were quantified using the nonparametric Mann–Kendall test, with analyses performed for both the 1961–1990 and 1991–2020 periods. Results reveal a southwestward increase in SCI values, with the highest risks (SCI > 100) along the Black Sea coast and Caucasus. Notably, northern regions, home to key heritage sites like Kizhi Pogost, exhibited statistically significant upward SCI trends (up to 0.6/year), driven primarily by rising temperatures. Between 1961–1990 and 1991–2020, low-risk areas decreased by 9%, transitioning to moderate risk, while high-risk zones remained stable (~13%). Temperature contributions to SCI increased by 5–20%, whereas precipitation impacts declined, except in northern regions. Sequential analysis highlighted trend onset in the 2000s, particularly in the northwest and Caucasus. These findings underscore a rising climatic threat to wooden architectural heritage and emphasize the need for enhanced conservation strategies to mitigate future decay risks.