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Potential impact of climate change on forests
(additional indicator)
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| Storm damages in forests occur mainly localy, but may cause
severe losses in wood production by bending and destroying the
logs totally. Storm damages of pine seed trees in natural
regeneration area. |
The mean annual temperature in Finland is projected to increase
by 2 °C to 6 °C by the year 2100 compared with the past
30-year period. The temperature rise is estimated to be greatest
in the winter (3 °C to 9 °C) and slightest in the summer (1 °C
to 5 °C). The region with the greatest variation is expected to
be northeastern Finland.
Rainfall is also projected to increase by 5% to 25% 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.
Climate change will have two kinds of effect on forests. If the
climate gradually becomes warmer or dryer, for instance, trees
will have to adapt to it. The progress of such adaptation and
measures contributing to it can be planned, to a certain extent.
Adaptation of trees may be jeopardised in northern areas because
their growing rhythm will change as the growing season
lengthens, and they may not be able to cope with the shorter
period of rest (winter).
Gradual change is indicated by changes over the past century
in the time when tree growth begins in the spring each year.
The opening of buds on coniferous trees and flowering now
happens 3 to 11 days earlier in Finland than at the beginning
of the last century. Similarly, it has been observed that bilberry
and cowberry flowering in Finnish forests now begins up to 7
days earlier than just 15 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. Extreme
weather phenomena are impossible to predict accurately,
but advance planning helps prepare for them. Among Finland’s
trees the spruce is the most vulnerable to drought, especially
in rocky terrain where the humus layer is thin and low on organic
material.
Research and long-term experiments with the transfer of tree
species proveniences from the north to the south lead to the following
conclusions regarding future impacts of climate change
in the boreal zone:
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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.
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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.
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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. Spreading
of the pine wood nematode (PWN) is also expected to increase
in probability due to improved breeding conditions.
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. Genetic resource protection
and forest tree breeding also provide tools for improving the
adaptation of forest trees to climate change. Most of Finland’s
forests are under continuous management, which is why their
productivity and vitality remain good.
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