What is forest damage?
Forest damage refers to the deterioration of tree health, growth and quality, potentially leading to their death. Forest damage can be complex and caused by the combined effects of several damage agents or weather phenomena and damage agents.
Risk identification and anticipation are a key part of forest management.
Forest damage and related risks can occur in forests of all ages, both in the short and long term. Forest damage agents can also be hidden or difficult to identify before the trees suffer significant decline or die.
Damage to trees hinders their health, growth and economic value added. The average total cost of all forest damage is estimated at approximately EUR 100 million per year. Financially, the most significant damage agents are root rot among fungal diseases, cervids among mammals as well as storm and snow damage caused by weather phenomena.
Climate change-induced temperature rise and the occurrence of extreme natural events are predicted to increase the likelihood of forest damage. Therefore, taking forest damage risks into account in forestry will be increasingly important in the future.
With global warming, new damage agents can find their way to Finnish forests. Under favourable conditions, agents that typically cause only minor tree damage can become more severe threats. Black arches, Asian longhorned beetle and red-band needle blight are examples of non-native and invasive species that have already been found in Finland.
Different damage agents
Damage by insects
In Finnish forests, insect damage usually occurs in trees in declining health. Decline in tree health may be caused by wind damage, drought and fungal diseases. Mass outbreaks of insects usually coincide with extensive storm damage or prolonged and consecutive heat waves, in which case insects can also damage healthy trees. The occurrence of insect damage is particularly influenced by weather fluctuations, extreme weather conditions and the amount of reproductive material available for insects in forest stands.
Further reading: Insect damage in forests (in Finnish)
Fungal diseases
Among fungal diseases, the most economically significant damage to forests is caused by wood-rotting fungi, especially root rot and honey fungus in coniferous forests. Fungal diseases also make trees more susceptible to consequential damage, such as wind damage. In addition, fungal diseases can increase the tree's susceptibility to drought and insect damage.
Further reading: Fungal diseases in forests (in Finnish)
Cervid and other mammal damage
Cervids are the leading cause of economic damage in Finnish commercial forests, resulting in growth and quality losses. Cervids living in Finland include moose, white-tailed deer, roe deer, Finnish forest reindeer and reindeer, of which moose cause the most significant damage to forests.
Among mammals, moles, rabbits and hares can also cause significant damage regionally and locally. The extent of mammal damage is particularly affected by population dynamics in species, regional predator populations and regional variations in weather conditions.
Further reading: Cervid and other mammal damage in forests (in Finnish)
Damage by natural phenomena
Wind, storms, and snow are the primary causes of weather-related damage in commercial forests. Extreme weather events, such as droughts, floods or strong weather fluctuations, can impede tree growth and deteriorate wood quality. Weather conditions have a significant impact on the spread of fungal diseases and insect damage.
Further reading: Damage caused by natural phenomena in forests (in Finnish)
Forest damage preparedness
Forest management measures cannot eliminate the risk of damage, but they can affect the probability and extent of damage.
The risk of forest damage can be significantly reduced by ensuring the health, vitality and diversity of forests through good forest and nature management. The timing and scope of the measures can affect the likelihood of significant damage.
Further reading:
What to do in the event of forest damage
In the event of forest damage, the Forest Damages Prevention Act obliges forest owners and forest professionals to take certain measures: Forest regulation.
If necessary, contact the forestry professionals in your area to assess the risks of forest damage. They can assess whether damaged trees must be removed or whether they can be left as decaying trees.
If you are planning to carry out felling due to forest damage, report it with the forest use notification (in Finnish).