Damage to forests caused by abiotic factors last year was the lowest recorded since 2014

Forests, including those in the Czech Republic, have faced increasing exposure to the effects of climate change over the past decade. This has weakened the health and stability of forest stands. A notable example is the bark beetle crisis, which has impacted forests for nearly ten years. However, the situation is gradually improving, as indicated by a significant decrease in damage. This positive change has been aided by more favourable weather conditions in recent years.

Photo: Wind is also damaging beech forests. Author: J. Řezáč

In 2025, the global climate recorded its third warmest year, with an average temperature of 15.0 °C, which is 1.44 °C above the long-term climate average. January 2025 stood out as the warmest January on record worldwide.

In the Czech Republic, temperatures in 2025 were considered (borderline) normal. The average temperature was 8.8 °C, which is 1.5 °C lower than in 2024 and 0.5 °C above the climate normal for the period from 1991 to 2020.

Regarding precipitation, 2025 experienced levels below normal. The total national precipitation measured 571 mm, marking it as the seventh lowest since 1961. In the past decade, only 2015 (531 mm) and 2018 (519 mm) recorded less precipitation than 2025. Precipitation levels in 2025 were at or above the long-term normal only in July, September, and November.

Despite the low levels of precipitation, the weather’s impact on forest stands in 2025 can be viewed as relatively favourable or at least neutral. This is particularly due to the low temperatures in May 2025, which slowed the development of bark beetles, as well as sufficient rainfall in July 2025.

Photo: An individual break of Norway spruce caused by wind. Author: Jan Řezáč

According to records submitted by forest owners and managers to the Forest Protection Service, the total volume of accidental logging in 2025 reached nearly three million cubic meters (2.994 million m³). In 2024, a comparable share of the forest area reported 4.6 million m³ of accidental logging, while in 2023, 5.9 million m³ were reported from two-thirds of the territory of the Czech Republic.

During the years affected by the bark beetle disaster, more than 10 million m³ of accidental logging were reported annually. The highest volumes occurred in 2019 and 2020, with a combined total of 19.8 million m³ and 19.2 million m³, respectively. When comparing 2025 to previous years, there was a noticeable decrease in the volume of accidental logging.

Of the reported volume of 3 million m³ in 2025, abiotic factors accounted for 64% (1.926 million m³), while biotic factors accounted for 36% (1.068 million m³). After the bark beetle calamity subsided in 2024 and 2025, the ratio of abiotic to biotic influences in accidental logging reversed. We have returned to the trend seen before 2016, when the ratio of abiotic to biotic factors typically fluctuated around 60:40.

In 2025, forest owners reported a total volume of 1.93 million cubic meters (m³) of trees felled due to damage from abiotic factors, such as wind, snow, frost, drought, and other causes, including fires and human activities. This represents a decrease from previous years: 2024 had 2.86 million m³, 2023 had 2.54 million m³, 2022 had 4.39 million m³, 2021 had 4.1 million m³, and 2020 had 4.4 million m³.

Photo: Windthrown Scots pine. Author: Jan Řezáč

Wind was the primary abiotic factor responsible for the damage in 2025, with 1.39 million m³ of wood reported as wind-damaged. This amount accounts for 72% of the total attributed to abiotic factors, which is comparable to the previous year; however, there was a year-on-year decrease in the volume of wind-damaged wood. In 2024, forest owners reported 2.12 million m³ of wind-damaged wood, while 2023 had 1.6 million m³, 2022 had 3.2 million m³, 2021 had 2.31 million m³, and 2020 had 2.69 million m³. This marks a significant decrease compared to the previous five-year period, with damage levels consistently below 2 million m³.

On average, for the entire republic, the conditions affecting the state of the forest in terms of stress levels and the impact of abiotic factors have been relatively favourable over the past five to six years. This includes the negative effects of drought; despite experiencing drought conditions every year from 2020 to 2025, significant regional differences were observed in precipitation amounts and distribution throughout the growing season and the entire calendar year.

According to the data provided, in 2025, due to the adverse effects of drought, 454,000 cubic meters of wood were harvested. This represents a decrease of 108,000 cubic meters compared to 2024, and an even more substantial drop from 2023, which saw a harvest of 830,000 cubic meters. In 2025, drought accounted for nearly 24% of abiotic harvesting, compared to approximately 20% in 2024 and nearly 33% in 2023.

Photo: Windthrown Norway spruce on waterlogged soil. Author: Jan Řezáč

Regionally, there was a noticeable increase in frost-related damage, amounting to thousands of cubic meters. The Vysočina and Moravian-Silesian regions were the hardest hit, with frost damage in these areas accounting for three-fifths of the total damage across the Czech Republic. The districts reporting the highest damage volumes were Bruntál (5,871 m³), Jihlava (5,768 m³), Třebíč (3,435 m³), and Opava (3,124 m³).

In terms of calamity harvesting of this type, 2025 proved to be slightly more favourable than previous years in both volume and share of total harvests. This improvement can be attributed to more favourable weather conditions during the year, which included a period of adequate precipitation and fewer heat waves during the summer, both of which significantly reduce water evaporation. Despite 2025 being below average in terms of overall precipitation, the development of bark beetle populations was notably slowed down due to a cooler May and sufficient rainfall in July.

(Note: The data presented here on the volume of harvested wood and the area of stands affected by the evaluated abiotic factors are totals reported by forest owners and managers to the Forest Protection Service. This information covers 70% of the forest area in the Czech Republic and does not represent calculations for the entire territory of the country.)

Prepared by Ing. Jan Řezáč, VÚLHM, v. v. i., e-mail: rezac@vulhm.cz. This document is based on the article titled „Povětrnostní podmínky a abiotická poškození v roce 2025“ (Weather Conditions and Abiotic Damage in 2025) – authors Doc. Ing. Vít Šrámek, PhD, and Ing. Radek Novotný, PhD. The article was published in the Zpravodaj LOS 2026 (LOS 2026 Newsletter), which can be downloaded here.