Snow-Induced Forest Damage in Finland

Kilpelainen et al. (2010) write that "within Europe's forests, snow-induced damage" -- due to "accumulation of snow load on tree branches" -- "has accounted for a mean annual amount of almost one million cubic meters of damaged wood in managed forests over the period 1950-2000," due primarily to "stem breakage or bending when the soil is frozen," although they say that "trees can also be uprooted if the soil is not frozen." In addition, they note that damages "by insects or fungal attacks are also common in trees suffering from snow damage."

To calculate risk of snow-induced damage to Finland's forests, Kilpelainen et al. employed a snow accumulation model in which cumulative precipitation, air temperature and wind speed were derived from the A2 scenario of the FINADAPT project (Ruosteenoja et al., 2005), where the air's CO₂ concentration was estimated to rise to 840 ppm by 2100 and mean air temperatures were projected to increase by almost 4°C in summer and more than 6°C in winter, after first testing and training the model with real-world data obtained by the Finnish Meteorological Institute (Venalainen et al., 2005) for the 30-year baseline period of 1961-1990.

Defining risk of snow-induced forest damage as being proportional to the number of days per year when the accumulated amount of snow exceeds 20 kg m^-2, the six scientists calculated that over the entire country of Finland, the mean annual number of risk days declined by 11%, 23% and 56% relative to that of the 1961-1990 baseline period in the first, second and third 30-day simulation periods for which they made calculations (1991-2020, 2021-2050, and 2070-2099), respectively. In addition, in the most hazardous areas of northwest and northeast Finland, they report that "the number of risk days decreased from the baseline period of over 30 days to about 8 days per year at the end of the century," which represents a warming-induced decrease in risk of snow damage to forests on the order of 75%.

Additional References
Ruosteenoja, K., Jylha, K. and Tuomenvirta, H. 2005. Climate scenarios for FINADAPT studies of climate change adaptation. FINADAPT Working Paper 15, Finnish Environment Institute Mimeographs 345, Helsinki, Finland.

Venalainen, A., Tuomenvirta, H., Pirinen, P. et al. 2005. A basic Finnish climate data set 1961-2000 -- description and illustrations. Finnish Meteorological Institute Reports 2005:5, Helsinki, Finland.