Potential impact of climate change on forests
The mean annual temperature is projected to increase by 2 °C to
6 °C, and rainfall by 5% to 25%, by the year 2100 compared with
the past 30-year period. It is also assumed that various extreme
weather phenomena such as storms, hot dry spells in summer
and heavy snowfall and rainfall will become more common.
Gradual change may be measured by when trees begin their
growth phase in the spring. The opening of buds on coniferous
trees and flowering now occurs 3 to 11 days earlier in Finland
than it did at the beginning of the last century, 100 years ago.
However, the most serious immediate threats to forest development
are extreme weather phenomena. Drought, forest fires,
storms and snow damage may cause widespread tree destruction,
preventing forest regeneration, in addition to which the
resulting large amounts of deadwood may prompt a massive
proliferation of forest pests in surrounding healthy forests.
Research and long-term experiments with the transfer of tree
species provenancies from the north to the south lead to the following
conclusions regarding future impacts of climate change
in the boreal zone:
- The growing season will lengthen, and forest growth may
actually increase. This increase could be as much as 20%
- to 50%, depending on the tree species. The increase will
be greatest in the north and in mires.
- Wind damage will probably become more common, although
due to Finland’s geographical location the impact
of winds coming in from the Atlantic is not as pronounced
as it is in southern Sweden, Denmark or central Europe.
Wind damage may be widespread in Lapland, and local
and occasional in southern Finland. The spruce is the tree
most susceptible to wind damage.
- As the climate becomes warmer and local forest damage
occurs, the risk of mass proliferation of pests such as the
large European spruce bark beetle (Ips typographus). Insect
pests are expected to migrate north from the temperate
zone, possibly causing massive damage.
- In forests along the timberline, climate change may cause
the timberline to shift up or north, thereby precipitating
the gradual extinction of certain species.
Forest management according to experience-based best practices
is the principal means for helping forests adapt to climate
change. Managing seedling stands in a timely manner, carrying
out first fellings and avoiding excess density in the growth
phase help secure the vitality of forests, along with genetic resource
protection and tree breeding. Most of Finland’s forests
are under continuous management, which is why their productivity
and vitality remain good.