Vulnerabilities – More damage to forests

The more humid, warmer weather pattern predicted for the future is expected to increase the wind throw risk of trees through reduced tree anchorage due to a decrease in soil freezing between late autumn and early spring, i.e during the most windy months of the year (1).

Frost simulations in a Scots pine stand growing on a moraine sandy soil (height 20 m, stand density 800 stems ha-1) showed that the duration of soil frost will decrease from 4-5 months to 2-3 months per year in southern Finland and from 5-6 months to 4-5 months in northern Finland given a temperature elevation of 4°C (1). In addition, it could decrease substantially more in the deeper soil layers (40-60 cm) than near the surface (0-20 cm), particularly in southern Finland. Consequently, tree anchorage may lose much of the additional support gained at present from the frozen soil in winter, making Scots pines more liable to wind throw during winter and spring storms.

Critical wind-speed simulations showed mean winds of 11-15 m/s to be enough to uproot Scots pines under unfrozen soil conditions, i.e. especially slender trees with a high height to breast height diameter ratio (taper of 1:120 and 1:100). In the future, as many as 80% of these mean winds of 11-15 m/s would occur during months when the soil is unfrozen in southern Finland, whereas the corresponding proportion at present is about 55%. In northern Finland, the percentage is 40% today and is expected to be 50% in the future. Thus, as the strongest winds usually occur between late autumn and early spring, climate change could increase the loss of standing timber through wind throw, especially in southern Finland (1).

Climate change is likely to increase the damages caused by extreme weather events also in Finland. On average, some 70% of annual compensations in forest insurance are paid for storm damage (2).

Vulnerabilities – The storm Gudrun in 2005

The storm Gudrun hit Scandinavia and the Baltic States on 7-9 January 2005. It was one of the worst storms in this region in the last 40 years. Detailed information on this storm is presented on the page of Estonia.

The storm Gudrun caused floods in Denmark, Estonia, Finland, Lithuania, Poland and Sweden.Although the water level was record high in Helsinki, severe damages were avoided, partly thanks to the warning issued by the Finnish Institute of Marine Research and the preventive work done by the City of Helsinki rescue services. The flood threatened the historical centre however and in many places the water rose to built areas. It also caused potential disaster situations in the ever increasing underground spaces of the city, such as the multi-utility and metro tunnels (3).

All outlet pipes of the sewage system in Helsinki had to be manually blocked in order to keep the sea water from flowing into the system. A water treatment plant in which all waste water handling in Helsinki is concentrated was flooded, forcing the officials to release some 63,000 m3 of sewage water untreated to the sea. In Finland, the cost to both public and private sectors adds up to a total of 1.5 billion EUR, probably closer to 2, according to the Federation of Finnish insurance companies. Damages were mainly related to the seawater flowing to cellars and harm done to summer houses.

A large amount of the damages relates to Turku harbour, where several hundreds of freshly imported cars got destroyed as harbour storage areas flooded. In Loviisa, the rising water level threatened the functioning of the cooling water system in the nuclear power plant. Should the water have risen any higher, the unit would have had to shut down.

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Finland.

1. Peltola et al. (1999)
2. Ministry of the Environment of Finland (2006)
3. Lilja (2005), in: Haanpää et al. (2007)