After the bark beetle, wind damages forests the most, but the damage has decreased year-on-year
In the Czech Republic, 2023 was the warmest year since 1961, based on available digitized measurement databases. The average annual temperature was 9.7 °C, 1.4 °C higher than the average for 1991–2020.
Despite the higher temperatures, 2023 was favourable for vegetation and forest health due to above-average precipitation of 732 mm, representing 107% of the annual climate norm. Additionally, forests were less affected by wind, drought, snow, and other environmental factors than in previous years.
Photo: Windbreaks (Orlické hory Mts., May 2023), VÚLHM archive
It is challenging to predict future developments. Due to higher than average temperatures, the timing of plant growth stage has shifted by 4-6 weeks in the country. This includes the start of spring growth for ground vegetation, as well as the sprouting and flowering of trees. Additionally, rainfall has been unevenly distributed over time and across different regions of the country.
The provided data on the volume of wood or the area of stands affected by abiotic factors have been compiled from reports submitted by forest owners to the Forest Protection Service. These data encompass approximately two-thirds of the forested area in the Czech Republic.
Photo: Windfalls of Norway spruce (Vysocko, February 2023), VÚLHM archive
In 2023, the Forest Protection Service VÚLHM received reports from forest owners and managers indicating that the total volume of accidental logging reached 5.97 million m3. This marked a significant decrease compared to previous years. In 2022, 10.2 million m3 was reported from a similarly large area (66.8% of the forest area), and in 2021, 13.8 million m3 of random logging was reported (66.6% of the forest area). In 2020 and 2019, 68% and 69% of the forest reported a total of 19.8 million m3 and 19.2 million m3 of random logging, respectively. The decrease in the volume of random logging is noteworthy.
Abiotic influences (wind, snow, frost, drought, etc.) accounted for approximately 43% (2.56 million m3) of the reported volume of random logging, while biotic influences (insects, fungi) accounted for the remaining 57% (3.41 million m3).
The amount of wood damaged by non-living factors decreased over the years: 2023: 2.56 million m3; 2022: 4.39 million m3; 2021: 4.1 million m3; 2020: 4.4 million m3; 2019: 4.42 million m3; 2018: 6.4 million m3.
In 2023, the random logging returned to the 2016 level (2.49 million m3), after higher reported volumes from 2017 to 2022.
Photo: Extensive Scots pine die-off due to extreme temperatures and drought (Příbram region, August 2023), VÚLHM archive
In 2023, the wind was the main abiotic cause of damage, resulting in the destruction of 1.57 million m3 of wood according to the submitted records. This is about half of the volume reported in 2022 (3.2 million m3 of wood). The damage caused by wind in previous years was as follows: 2021 – 2.31 million m3, 2020 – 2.69 million m3, 2019 – 2.57 million m3, and 2018 – 4.62 million m3.
The years 2020 to 2023 were quite favourable for the state of the forest in terms of reducing drought stress. This is the case although there were periods of dryness each year. This period can be seen as positive, especially when compared to the previous dry to very dry period of 2015 to 2019. For the forest stands to fully regenerate and restore their vitality, they would need rainfall evenly distributed throughout the year, or at least throughout the growing season.
Based on the records provided, 0.835 million m3 of wood was damaged due to drought in 2023. This amount represents a decrease compared to the previous years: 1.06 million m3 in 2022, 1.56 million m3 in 2021, 1.54 million m3 in 2020, 1.29 million m3 in 2019, and 1.62 million m3 in 2018. The share of drought in total abiotic damage in 2023 reached 32.6%.
Photo: Consequences of extreme acute drought in oak forests (Dobříš region, July 2023), VÚLHM archive
In 2021, there was observed a decrease in the volume of damage reported by owners as a result of drought. This marks the second consecutive year with a decline in reported drought damage. Since 2011, drought damage has been on the rise, so we can view the data from 2022 and 2023 with cautious optimism.
A more favourable weather pattern throughout the year, including periods of sufficient precipitation, may also help improve the situation.
Based on the records provided, approximately 77,000 cubic meters of wood were damaged by snow in 2023 (69,000 m3 in 2022, 130,000 m3 in 2021, 119,000 m3 in 2020, 507,000 m3 in 2019, and 49,000 m3 in 2018). Following the significant damage reported in 2019-2021, when hundreds of thousands of cubic meters of wood were damaged, the snow damage was lower in 2022 and 2023.
In 2023, the Central Bohemian Region reported the highest volume of accidental abiotic mining in the Czech Republic, with 310 thousand m3. The South Bohemian Region followed with 281 thousand m3, and the Vysočina Region reported 279 thousand m3. Additionally, the volume of abiotic random mining exceeded 200 thousand m3 in 2023 in the South Moravian Region (262 thousand m3), Olomouc Region (238 thousand m3), and Plzeň Region (228 thousand m3), according to reports received.
The reported values have decreased compared to 2022, particularly the volume of wood damaged by wind and drought.
Processed according to data from the publication Forest Protection Bulletin, Supplementum 2024, which can be downloaded here.
Prepared by Ing. Jan Řezáč, VULHM, v. v. i., e-mail: rezac@vulhm.cz