Download Impact of Climate Change on the Boreal Forest in Finland and Sweden

Impact of Climate Change on the Boreal Forest in
Finland and Sweden
Authors: Riikka Kinnunen1, Ilari Lehtonen1, Judith Kas2,1,
Riina Järvelä1, Helinä Poutamo 1, Christian Wenzlaff3,1, and Jessica Latus1
[1] {University of Helsinki, Helsinki, Finland}
[2] {Wageningen University, Wageningen, the Netherlands}
[3] {Georg-August-Universität zu Göttingen, Germany}
University of Helsinki
HENVI Workshop 2013: Interdisciplinary approach to forests and climate change
Abstract
Climate change is foreseen to affect the boreal forests of Finland and Sweden in many ways.
Temperatures are projected to rise and more precipitation is expected, especially in winter. This
may have a substantial impact on many abiotic and biotic factors, which influence the boreal
forests. It is likely that insect pests, fungal diseases and forest fire potential may increase while the
risk for snow induced forest damages are likely to diminish. Simultaneously, the lengthening of the
growing season will increase the growing stock of the boreal forests as well as contribute to the
increase of deciduous trees.
One of the direct impacts of climate change is to the phenology of the boreal forest, with the
obvious effect being earlier onset of ontogenic development. Climate change is also having an
impact on forest insects and pathogens due to the increased frequency of storms, warmer
temperatures, and more frequent windfall events, which enable pest insects, such as bark beetles, to
increase their living ranges. These pests have started producing two generations per year, and
therefore their populations are rapidly increasing, and this poses a serious problem to future forest
management.
Climate change is impacting many soil properties, such as pH, nitrogen and carbon circle as well as
soil organic content and soil bacteria content. No changes are expected on the nitrogen cycle, but
the carbon cycle, however, will increase strongly due to higher concentrations of CO2. It is unclear
if and how soil carbon content will change.
The volume of growing stock in Finnish forests has been increasing and is predicted to increase
even more in the future due to longer growing periods and higher effective temperature sums. Even
though climate change affects mostly in northern Finland, it has not been assessed whether or not
the forest line will react to warmer temperatures. Different tree species react to climate change
differently, but forest management will ultimately decide the tree species distribution in the future.
In both Finland and Sweden, forest management practices need to be altered due to the projected
future impacts resulting from climate change. Wood harvesting is becoming more challenging and
additionally there are challenges for water protection. Furthermore, the changes in species
composition and biodiversity are affecting management practices as well. There are also increased
risks for abiotic and biotic damages in the forests. The choice of tree species will need to be
carefully thought out in the future to try to maintain forest health. The EU forest policy provides a
framework for sustainable forest management, yet the 27 Member States are responsible for the
implementation of it. The Finnish forest policy focuses on increasing wood production in a
sustainable way while securing biodiversity in the forests. Yet, there is still an ongoing discussion
about the best ways to manage the forests.
2
Table of Contents
I.
Introduction
4
II.
Effect of Climate Change on the Forest Fire Potential
6
III.
Impacts of Climate Change on the Snow-Induced and Wind-Induced Forest
Damages
8
IV.
Impacts of Climate Change on Boreal Forest Phenology
9
V.
Climate Change Effects on Insects with Focus on Spruce Bark Beetle (Ips
typographus)
12
VI.
Tree Species Distribution in Finnish Forests Now and In the Future
15
VII.
Climate Change Effects on Soil Contents in Finland and Sweden
18
VIII.
Forests and Management
20
IX.
Predictions that are the Possible Effects of Climate Change in Forest
managements in Finland
21
X.
Forestry Policy
22
XI.
Conclusion
25
XII.
Discussion Questions
26
References
27
3
I. Introduction
The Boreal Forest, also known as the Taiga, spans the northern hemisphere across three continents
and ten different countries. In Finland most of the country is covered by coniferous Boreal Forest,
as is Norway and Sweden. In the mountain areas of all three countries there is similar elevation,
terrain and vegetation. The Taiga, which spans across Finland, Sweden, and Norway, is divided into
oceanus and continental zones.
Hemiboreal is the area within the Taiga where the forest transitions from temperate deciduous forest
to coniferous forest. The southwestern part of Finland is considered to be hemiboreal, and this area
is favorable to growing hardwood, such as oak (Quercus robur), ash (Faxinus excelsior) and Forest
linden (Tilia cordata). The southern boreal zone covers most of southern Finland, the middle boreal
zone covers the areas of Ostrobothnia and Kainuu, and the northern boreal zone covers northern
Lapland.
Boreal forest tree species belong to four conifer genera: spruce (Picea), pine (Pinus), fir (Abies) and
larch (Larix). The boreal zone, in addition, is home to a number of deciduous tree genera such as
birch (Betula), aspens (Populus), alders (Alnus), willow (Salix) and mountain ash (Sorbus).
Additionally, the northern border of Fennoscandia (the Scandinavian Peninsula, Finland, Karelia,
and the Kola Peninsula) is formed by the forest subspecies of downy birch, mountain birch (Betula
pubescens ssp. czerepanovii)
The transition area of the Boreal Forest affects the average temperatures with more infrequent
exceptional temperatures, either cold or hot. Furthermore, the transitional zones also define the
extent of cross-species survival. The northern Boreal Forest border is dynamic and highly sensitive
to the weather conditions. The large annual fluctuations in temperature, as a result of climate
change, are also affecting the forest dynamic.
The projected extent of climate change may have a significant impact on boreal forest ecosystems
in Fennoscandia. Currently, the growth of boreal forests in northern Europe is limited by a
particularly short growing season. However, by 2100, the annual mean temperature in northern
Europe, and Finland, is projected to increase by 2–6 °C (Christensen et al. 2007; Jylhä et al. 2009);
the projected warming is to be greater in winter than in summer. As a result of the projected rise in
summer temperatures this will lead to a prolongation of the growing season in Finland by up to 40–
50 days by the end of the 21st century (Ruosteenoja et al., 2011). Simultaneously, the effective
temperature sum would on average double in northern Finland and increase 1.5-fold in southern
Finland. Thus, conditions currently prevailing in southern Finland would be seen in Lapland.
In addition to the projected increase in temperature as a result of climate change, annual
precipitation is projected to increase in northern Europe as well (e.g. Christensen et al. 2007;
Christensen and Christensen 2007; Jylhä et al. 2009; Nikulin et al. 2011). Similar to the resulting
effect on temperature, the projected increase for precipitation is greatest in the winter, and only
small changes in mean precipitation are expected in summer; in southern Scandinavia it is uncertain
whether mean precipitation in summer will increase or decrease. Additionally, heavy precipitation
4
events are projected to intensify in every season, and dry spells in summer might also become
prolonged; because evaporation is enhanced in a warmer climate, these occasional droughts will
probably become more severe in the future. Lastly, climate projections indicate that interannual
variability of precipitation may increase in the future (Räisänen 2002; Giorgi and Coppola 2009). In
summation, both episodes of heavy precipitation and severe droughts are likely to become more
common in the future as a result of climate change.
These anticipated changes in climatic conditions have many possible impacts on the boreal forests.
For example, forest growth and timber production are likely to increase, tree species composition
may change (Kellomäki et al. 2008), and phenological events will take place earlier (Chmielewski
and Rötzer 2001). Additionally, various abiotic risks to forests and forestry may increase, for
example, forest fire potential is projected to increase (Kilpeläinen et al. 2010a) and risk for wind
and snow induced damages may change. Concurrently, the risks of damages caused by insects may
increase. Ideally, EU and Finnish policy can help to mitigate for some of the damage, and
additionally prevent future damages, yet the future is always uncertain.
Some of the impacts of climate change can also be mitigated by increasing the ability of plants and
animals to disperse through protected areas, or increasing the size of protected areas through habitat
corridors and planned new reserves. Figure 1 shows protected areas in Finland. (Loarie et al. 2009).
Figure 1. National parks and nature parks in Finland 2012 (Statistics Finland 2012).
5
II. Effect of Climate Change on the Forest Fire Potential
Along with wind storms, forest fires are one of the largest natural hazards boreal forests have to
cope with. On the other hand, fire is a natural phenomenon and an important factor in the process of
natural forest regeneration maintaining the biodiversity in forests (e.g. Esseen et al. 1997). The fire
danger is determined by the moisture content of the fuel in forests, and is thus reliant on climatic
factors. In predicting forest fire danger, various weather-based indices describing this moisture
content are used. These include, for example, the widely used Canadian fire weather index system
(Van Wagner 1987) and the Finnish forest fire risk index model (Venäläinen and Heikinheimo
2003).
In the future, temperature is projected to increase in Northern Europe (Christensen et al. 2007;
Jylhä et al. 2009). Concurrently precipitation is projected to increase slightly even in summer, albeit
the greatest increase is projected for winter. As higher temperatures enhance evaporation and thus
forest fire potential and heavier rainfalls have an opposite effect, estimation of the impact of climate
change on the forest fire danger is not a straightforward issue. The magnitude of climate change is
also uncertain and dependent on the amount of greenhouse gas (GHG) emissions. However, several
studies have indicated that the fire risk in the northern high-latitude forests will increase during the
forthcoming decades (e.g. Stocks et al. 1998; Flannigan et al. 2005a, 2005b; Wotton et al. 2010).
Kilpeläinen et al. (2010a) studied the forest fire potential in Finland under high-emission A2 GHG
scenario and found the same conclusion to hold true in Finland. Based on their results, the criteria
for a forest fire warning were fulfilled on an average of 60 to 100 days annually in the late 20th
century in the coastal and southern parts of the country where the forest fire potential in Finland is
highest (Fig. 2). The fire potential decreases inland and towards the north, being less than 20 days
per year at its lowest level in eastern and northern Lapland. Until the end of the current century, the
number of forest fire alarm days is projected to increase up to 30% or more. It is expected that this
will yield an increase of 20% in the actual number of forest fires in Finland. However, there exists
great interannual variability in forest fire risk in Finland. Typically, almost 1000 forest fires occur
annually in Finland but the burnt area is relatively small because of active fire suppression
(Tanskanen and Venäläinen 2008). Nevertheless, the dry and warm summer of 2002 manifested
2522 fires and in the extreme dry summer of 2006 over 6200 wildfires occurred in Finland.
Consequently, the large interannual variability in the forest fire danger may overwhelm the
plausible increase, at least in the near future. For the present, no significant change in the fire
proneness of Finnish forests has been found, although a statistically significant increase in the mean
temperature of the forest fire season has been observed (Mäkelä et al. 2012).
Besides weather, many other issues affect the actual number of fires ignited. These include possible
changes in human behavior as the large majority of forest fires are human-caused, resulting mostly
from careless handling of fire. The only natural source of ignition in boreal conditions, lightning,
causes less than 15% of all forest fires in Finland (Larjavaara et al. 2005). Seasonal fire activity
peaks in the open season for elk (Tanskanen and Venäläinen, 2008) when hunters and berry and
mushroom pickers light numerous campfires in forest, even though it is not a risky time of the year
for forest fires based on typical meteorological conditions. Fire danger also varies substantially
between different forest stands (Tanskanen et al. 2005). According to e.g. Wallenius (2002) and
6
Pitkänen et al. (2003), Norway-spruce-dominated forests have vastly longer natural fire intervals
compared to Scots-pine-dominated forests. On the other hand, Norway-spruce-dominated forests,
though resistant to ignition, are more susceptible to high-intensity crown-fires compared to Scots
pine stands (Lindberg et al. 2011).
Figure 2. Mean annual number of days with forest fire potential in Finland (a) for the past (1961–
1990), (b) present day (1990–2020), (c) near-term (2021‒ 2050) and (d) long-term (2070–2099)
30-year periods (Kilpeläinen et al. 2010a).
7
III. Impacts of Climate Change on the Snow-Induced and Wind-Induced
Forest Damages
Within managed forests in Europe, almost one million cubic meters of wood is damaged annually
on average by snow, accounting 3% of the total damage caused by natural disturbances (Schelhaas
et al. 2003). When the soil is frozen, the most common form of snow damage is stem breakage or
bending while trees can also be uprooted if the soil is unfrozen (Solantie 1994; Nykänen et al.
1997). Optimal conditions for snow damages develop when wet snow accumulates on trees with
near-zero temperatures. In addition, snow-induced damages occur in close interaction with windinduced damages.
In the future, snow season is projected to shorten in Northern Europe (Räisänen and Eklund 2012).
Simultaneously, precipitation in winter is projected to increase and hence snowfall amounts during
the midwinter months are likely to increase as well in the northern parts of Fennoscandia. This
could possibly increase the risk for snow-induced forest damages. Studying the impact of climate
change on snow-induced forest damages is, however, somewhat intricate, because occurrence of
these snow-induced damages is spatially and temporally rather coincidental and limited within
certain weather conditions. Furthermore, climate model outputs usually provide only daily averages
of temperature, precipitation and other variables, which is somewhat unsatisfactory when searching
favorable conditions for snow-induced damages. In spite of these restrictions, there exist some
studies dealing with this issue. Kilpeläinen et al. (2010b) conducted that the risk of snow-induced
forest damage will decrease in the future (Fig. 3). However, Gregow et al. (2011) estimated that
heavy snow loads in southern and central Finland would become more common in the future. In any
case, more research would be needed to obtain broader picture of uncertainties related to different
climate scenarios and alternative methods in estimating the changes in the snow-induced forest
damages.
The current knowledge of expected changes in storms and strong winds is somewhat unsatisfactory
due to large scatter among predictions by various models. Nevertheless, projected changes for wind
speed in northern Europe are in general fairly modest (Gregow et al. 2012). When considering
wind-induced damages to forests, more relevant is thus the fact that the duration of soil frost is
expected to decrease in southern Finland approximately from 4–5 months to 2–3 months
(Kellomäki et al. 2010). Increase in the length of unfrozen soil period decreases tree anchorage
during winter which is the windiest time of the year. Consequently, the risk for wind-induced
damages and particularly for uprooting is expected to increase in the future (Peltola et al. 2010).
8
Figure 3. The number of snow damage risk days per year (a) for the past (1961–1990), (b) present
day (1990–2020), (c) near-term (2021–2050) and (d) long-term (2070–2099) 30-year periods
(Kilpeläinen et al. 2010b).
IV. Impacts of Climate Change on Boreal Forest Phenology
Earlier bud burst and flowering time as a result of climate change, and more specifically global
warming, will have many impacts on the boreal forest. This change in phenology will impact all of
the species inhabiting the boreal forest, which includes the trees, fungi, birds, and pollinators. As a
result of the increased lengthening of the green cover period the forest will uptake more carbon
dioxide and similarly it will increase the emission of biogenic volatile organic compounds
9
(Peñuelas et al. 2009). In other words, as a result of an increased green cover period, the forests
will aid in cooling the environment by sequestering more carbon dioxide than before, unless;
however, droughts and dry periods become more prevalent, hindering the evapotranspiration effects
(Peñuelas et al. 2009). If droughts do become more prevalent, hindering evapotranspiration, then
decomposition might accelerate, and therefore overrule the previously mentioned potential for
greater carbon sequestration. Peñuelas et al. have suggested that the extreme hot and dry summers
that Europe has experienced as of late could be from the increased period of evapotranspiration,
because this reduces soil moisture, which increases surface temperature. The general trend,
therefore, is unclear as to whether or not an increased green cover period will either exacerbate or
mitigate the effects of global warming.
Table 1: Blooming and temperature correlation.
It is suggested that phenological changes as a result of climate change are some of the most
sensitive ecological responses, and this can be displayed in a number of ways (Kauserud et al.
2008). Kauserud et al. state that the growing period has actually increased by a total of 11 days
since the 1960s, and Peñuelas et al. project an increase of 3 to 4 days a decade. As an example, the
fruiting period of mushroom species has expanded substantially over the past 20 years, but
interestingly the period is lengthening at the end of the season, rather than at the beginning
(Kauserud et al. 2008). As a result of this warming, and ―spring‖ being extended, most fruiting
plants are seeing their period of fruiting expanded (Kauserud et al. 2008). Table 1. above shows the
results of a study conducted in eastern Fennoscandia, and what is shocking is the effect that a
10
warmer spring-summer of only 3-4 C0 can already result in budding times being earlier than average
(Adrianova).
Of primary focus is the interaction between phenology fluxes and the presence of pollinators. It is
unknown in many instances whether or not the presence of pollinators is dependent on when a
plant’s nectar starts flowing, or if these are independent events. Regardless of whether or not some
pollinators are dependent on the maturity of the flowering species, the impacts of climate change
will undoubtedly affect the species. What is most uncertain, and worrisome, is whether or not
climate change will impact pollinators and plants differently, potentially resulting in the two falling
out of sync, and in turn posing many problems (Lindsey 2007). This would subsequently result in
the possibility of some species of plants suffering due to the lack of pollinators during peak season
(United States). A NASA scientist has proposed using satellite imaging to map flowering times in
order to ―make predictions about what is happening to nectar flows and the species that depend on
them …‖ (Lindsey 2007). Ideally this mapping would allow interested parties all over the globe to
track the impact of climate change to pollinators and plan accordingly.
The changes in temperature, which are resulting from climate change, are posing dramatic effects to
the Boreal forest, and while the exact impact is uncertain, the predicted impacts to phenology are
grave. The onset of ontogenic development of both plant and animal species could potentially be
thrown completely off balance, resulting in many negative impacts (Linkosalo 2000). There is a
potential for many trees to suffer from frost damage, due to their earlier onset of ontogenic
development, when the potential for late seasonal frosts still exists; however, scientists are not
necessarily agreed on this and some argue the impacts of climate change will not be significant
(Linkosalo 2000). It is possible that this risk of frost damage might only be present to the early
bloomers, but it will be curious to see the ultimate result of the lengthened growing period on all
tree species.
Conservation biologists are said to have a good chance at conserving the Boreal forest from the
impacts of climate change if they act now and act aggressively (Dudley el al. 1996). Due to the
limited species of the Boreal forest, and the current healthy state of the system, there is still time to
implement aggressive mitigation methods; it will be interesting to see if scientists can come
together to save the Taiga from the potential catastrophic damages posed by climate change. How
conservation strategies will affect phenology is unique, because for example, by simply creating
more protected areas this will not be sufficient to maintain currently phenology functioning. What is
more important with regards to phenology is the maintenance of the temperature, and this relies on
a reduction in greenhouse gas emissions. As has been suggested by Dudley et al., there needs to be
a ―decrease of pollution below damage thresholds, as measured by critical loads.‖ Only time will be
able to tell if there will be dramatic fluxes in the phenology of the Boreal forest, but without a
concerted effort to mitigate for climate change it seems rather inevitable.
11
V. Climate Change Effects on Insects with Focus on Spruce Bark Beetle (Ips
typographus)
As insects have short life cycles and are sensitive to temperature variances, even a small change in
climate has the potential to influence their distribution and abundance. An increase in temperature
and precipitation can affect both their reproductive potential and their dispersal (Ayres and
Lombardero, 2000). Some insects utilise dead or damaged trees as breeding grounds and with the
right environmental conditions their numbers can drastically increase causing an epidemic that can
become economically devastating, especially for the forest industry (Jönsson and Barring,
2010).This is the case especially when considering some herbivorous insect species such as bark
beetles (Coleoptera: Curculionidae, Scolytinae), which prefer mature, large diameter host trees.
Bark beetles are also known to act as host to several fungus species, some of which can also be
damaging to the economic value of the trees. Large bark beetle outbreaks generally happen after
storms or strong winds cause lot of windfall, offering the beetles plenty of suitable breeding places
(Jönsson and Barring, 2010). When windfall happens in conjunction with an increase in
temperature, as predicted by climate chance projections, beetle numbers can be expected to rapidly
increase as the insects go on to produce two generations per year instead of current one generation
per year.
The ecology and impacts on forests of bark beetle and other common pests and pathogens
Bark beetles have an important role in the forest ecosystem. In the Eurasia region the spruce bark
beetle (Ips typographus) (See Figure 4. below) is one of the most common and one of the most
widely distributed pests of Norway spruce (Picea abies). It uses the phloem tissue of the inner bark
of dead or weakened trees as breeding material helping in renewing the forest by killing old trees
and helping in the decomposition of dead wood, releasing nutrients back into the ecosystem
(Caccianiga, Payette and Filion, 2007). Caccianiga et al. (2007) showed in their study that bark
beetle attacks are usually only occasional and often concentrated on single tree individuals. One
such individual tree was attacked 31 times from 1745-1951. Ips typographus can however also
become a biotic disturbance factor that has the potential to affect boreal ecosystem in a detrimental
way (Caccianiga, Payette and Filion, 2007).
Bark beetles have an adaptive response called reproductive diapause where unfavourable
environmental factors such as day length and temperature initiate a state of dormancy and delay in
development, helping the insect to avoid unsuccessful reproduction. These day length and
temperature requirements can rapidly adjust to changes in climate making the bark beetle a fast
adaptor for new climatic conditions by dispersal and natural selection (Jönsson and Barring, 2010).
12
Figure 4. Adult, larva, pupa and galleries of the European
spruce bark beetle, Ips typographus. (Source: Bugwood.org/1292025/R. Dzwonkowski)
The activity level of bark beetles has been shown to fluctuate depending on environmental factors,
the availability of suitable trees for reproduction, stand conditions and the abundance of bark beetle
parasites and predators (Jenkins, et al. 2008). Although all of these factors have a role determining
bark beetle outbreak level, especially stand conditions such as drought, have been shown to be
important (Kučerová et al. 2008).
Neodiprion sertifer, the European pine sawfly, is another common pest of Pinus sp. found in
Northern Europe. Studies have shown the expected effects of climate change on the European saw
fly to be similar as on the bark beetle (Virtanen et al.1996). Increases in temperature are expected to
cause range shifts to higher latitudes and elevations and more towards eastern Finland, and the
incidence of cold winters (below the critical level for egg mortality of -36 degrees Celcius) is the
factor that most affects the outbreak numbers of this insect currently or in the future (Virtanen et
al.1996).
Another factor to consider regarding bark beetles is their association with a group of
phytopathogens (Ceratocystis, Ophiostoma, Leptographium) called blue-stain fungi. These fungi
commonly use bark beetles as their carrying vector from one tree to another and colonises galleries
dug by the insect, leaving the sap wood stained with blue markings (Linnakoski ja Niemelä, 2011).
The interaction between bark beetles and the pathogen is very complex and dynamic depending on
the specific species involved and predictions for future are therefore hard to make (Linnakoski ja
Niemelä, 2011).
13
Climate change and its effects on forest insects
Climate change projections predict increasing temperatures, drought, changes in atmospheric
concentration and solar radiation as well as other climatic anomalies that are expected to affect
boreal forests altering tree physiology and possibly weakening the defence mechanisms of the trees
making them increasingly susceptible to insect outbreaks (Ayres and Lombardero 2000; Marini et
al. 2012).
Changes in climate and the accompanying effects on forest insects and pathogens can in turn have
an impact on forest biodiversity, forest industry, the recreational and property value of the affected
area and water quality (Ayres and Lombardero, 2000). The change in mean annual temperature has
been shown to be higher at higher latitudes and has to be taken into an account when considering
Nordic countries (Kantola et al. 2010). The effects of this can be beneficial as decrease in snow
cover can increase winter mortality of certain pests (Ayres and Lombardero, 2000), but on the other
hand warmer winters can also have a positive effect on insects and increase insect survival over
winter (Virtanen et al., 1996). Study conducted by Tran et al. (2007) showed the most relevant
climatic factor to affect bark beetle winter survival to be the minimum temperature on the coldest
night. With right environmental conditions bark beetle numbers can rapidly increase as warmer
temperatures enable them to reproduce faster and produce two generations per year instead of the
current one (Jönsson, 2011; Linnakoski ja Niemelä, 2011).
Climate change can also promote the establishment of exotic species outside their natural living
ranges (Vanhanen 2008). Species generally restricted to southern regions can suddenly invade
northern locations previously out of their reach due to low winter temperatures. Temperatures at
winter time are expected to raise more than summer temperatures in the boreal zone, allowing
species that overwinter as eggs or adults to gain an advantage and increase in numbers (Virtanen
and Neuvonen, 1998). This can concern both native and exotic species.
Climate change projections for Scandinavia also predict a shift in the geographical distribution of
Norway spruce and with this a shift in the distribution of its pests (Williams and Liebhold, 2002).
According to these predictions, the living range of Ips typographus has the potential to move 600
km north of its current range (Lange et al. 2006). A change in forest composition and structure can
in some cases lead to a high percentage of susceptible mature, large host trees and decreased overall
heterogeneity (Jenkins, et al. 2008). And if increased temperatures lead to increased insect activity
in boreal forests, and this in turn leads to increase in forest fires one worrying outcome of this
would be fire induced release of carbon from the ecosystem and thus an aggravation of further
climate warming (Ayres and Lombardero, 2000).To prevent outbreaks caused by native or exotic
pests in Finland, several cautionary measures have been made. These include thorough inspection
of imported wood and other goods; quarantine measures; and risk assessments drafted for any high
risk species (Vanhanen, 2008). Other recommended action would be to focus on forest management
and to avoid planting spruce trees or other trees highly susceptible to insect outbreaks outside of
their natural climatic ranges (Wermelinger 2002), or on unfavourable soil where the trees would
undergo high stress e.g. spruce on dry soil.
14
VI. Tree Species Distribution in Finnish Forests Now and In the Future
Finnish wood stock
According to the first three years of the 11th National Forestry inventory (2009-2011), Finland has
2305 million cubic meters of wood, and the annual growth of the wood is 104,0 million cubic
meters. Half of the forest cover is pine (Pinus sylvestris), about a third is spruce (Picea abies), 12%
is downy birch (Betula pubescens), 4% is silver birch (Betula pendula) and the rest is other species,
such as aspens (Populus), alders (Alnus), willows (Salix) and mountain ashes (Sorbus). Comparing
this and the previous NFI tells us that the volume of the wood stock, as well as the annual growth of
wood have both increased by 5% (from 2004 to 2011). NFIs have been conducted in Finland since
1920’s and show us e.g. the area of forests and the increment and volume of wood stocks (Figures 5
and 6).
Figure 5: Volume of growing stock by tree species groups in 1922–2011 (Metla, 11.9.2012)
Figure 6: Annual increment in different inventories and drain in Finland in 1921–2011 (Metla,
11.9.2012)
15
The northern forest line
The forest line started to develop after the last ice-age receded in about 11 500 B.C. and has been in
its current shape from 1000 B.C. (Kallio et al. 1985).During that time the mean temperature has
varied a lot, the hottest being 2-3 degrees Celsiuswarmer than now (Seppä et al. 2009, Salonen et al.
2011). At the time tree species such as oaks (Quercus), common ashes (Fraxinus) and lindens
(Tilia) grew in far more northern regions than today, and common tree species such as birch and
pine also formed their forest lines in (far) more northern regions than they do today (Kallio et al.
1985).
Figure 7: The northern limits of
Norway Spruce and Scots Pine
forests (Kallio et al. 198).
In northernmost regions the forest line moves by strengthening small tree populations’ size and
vitality, rather than pushing forward as a single, unified frontline (Väliranta et al. 2011). This is why
the forest line is not sharp, but consists of up to 100km wide (north to south) shifting area where
tundra and boreal forest patches create the landscape (Virtanen et al. 2004) (Figure 7).
Fennoscandia’s forest line has a few special features that differ from the forest line in Eurasia: in
Fennoscandia spruce does not reach as far as pine, whereasin Eurasia spruce has spread further than
pine; and whilst larch is completely absent from the Finnish forest line, it abounds in the Eurasian
forest line (Kallio et al. 1985).
Finnish wood stock in the future
Mean temperatures rise because of the increasing amount of greenhouse gases in the atmosphere.
In worst case scenarios, representing the largest GHG emissions, climate in Finnish Lapland will
start to resemble the climate in southern Finland, and the conditions in southern Finland will start to
resemble those of central Europe (Ruosteenoja et al., 2010). According to the previous study, the
effective temperature sum will double in northern Finland and increase 1.5-fold in the south. Thus
most of the changes in the Finnish forests are expected to happen in the northernmost forests.
16
Because of the lengthening of growing seasons, total forest growth may increase up to 44% in
Finland. In northern Finland the growth may increase up to 70-100%, while in southern regions the
growth increase is expected to be only about 10–20% (S. Kellomäki et al., 2008) (Figure 8).
Figure 8: "Integrated growth of all tree species -- a) total current growth (m3ha-1yr-1); percentage
of total growth change for b) 1991-2020, c) 2021-2050 and d) 2070-2099". S. Kellomäki et al. 2008
As the growing stock increases, so does the variance in tree species distribution. In northern Finland
pine will become more dominant, while spruce and birch will diminis, spruce more drastically than
birch. In the south, pine and birch will become more dominant, and the distribution of spruce will
17
continue to decrease (Kellomäki et al., 2008, Peltola et al., 2010) (Table 2). Spruce is thought to
suffer more from climate change than other species because of its requirement for moist land.
However, it is unlikely that forest owners will reduce the planting of spruce as dramatically as
studies predict, due to the increased damage that elks cause to pine saplings and the risen price of
spruce timber.
Table 2: "Tree species composition
in per cent of the total stocking."
Northern Finland is above 63°N and
Southern below 63°N. S. Kellomäki et
al. 2008
Forest line movement in the future
As noted earlier the forest line follows the July isotherm of +10 °C (Köppen, 1931). Later studies
found that this coincided line is very coarse and partly follows isotherms up to +13 °C (Tuhkanen
1999, Virtanen et al. 2004). However, air temperature is not the only factor affecting forest line
movement; soil composition and moisture also have a great influence (Sveinbjörnsson 2000, Skre et
al. 2002).
The trees of the forest line react to warmer climates by producing more seeds. These seeds can fly
north and produce saplings, but it can take decades for the new saplings to reproduce new seeds.
This is why the forest line moves very slowly (Heikki Kauhanen, Outa 2/2010). New saplings
outside forests are more exposed to abiotic stresses like wind or snowloads than saplings in the
cover of older trees, and therefore their mortality rate is high. This is why the northernmost forests
have been noted to get denser and bushier, rather than moving northward (Tape et al. 2006).
VII. Climate Change Effects on Soil Contents in Finland and Sweden
There is a strong relationship between soil, climate and vegetation (Blume a. Brümer, 2010). Both
Finland and Sweden are dominated by boreal forests, of which the Northern border is defined by at
least 30 days of temperatures exceeding 10°C, while the Southern border is defined by less than 120
days with temperatures greater than 10°C. The soils of Finland and Sweden are strongly influenced
by the last ice age. The soils of Sweden mostly consist of unconsolidated glacial deposits, and
Finnish soils also consist of unconsolidated glacial deposits, but in northern Finland glacial deposits
18
are detached by organic soils. Soil textures in both countries are a result of small clay particles, and
over time the soil developed into different textures as a result of climate and vegetation (Blume,
Hans – Peter et al., 2010). Due to the similar climate in the two countries, the soil composition is
also similar. Podzols dominate the soil landscape of Finland. More specifically, Histosols and
Glysols dominate northern Finland, and Cambisols can occasionally be found in southern Finland.
Similarly, Podzols dominate the soil texture of Sweden, and in the south Cambisols can be found,
while in the north the area which borders Finland has an increasing amount of Histosols (-,-, 2013).
Due to the predicted rise in carbon dioxide in the atmosphere, and subsequently the strong
relationship between the climate and vegetation, it is expected that soil properties will be altered by
climate change. The nitrogen cycle of boreal forests is very little; the only amount of nitrogen
which enters the soil of the boreal is from the atmosphere. Normally, 1–2 kg N/a/ha of atmospheric
decomposition enters boreal wood (Lukac a. Godbold, 2011). High nitrogen input increases NOx
production, which is also a greenhouse gas (Blume a. Brümer, 2010). It is shown that increasing
amounts of nitrogen in the soil decreases the organic carbon content (Kuzyakov a.
Schneckenberger, 2004), while a high amount of nitrogen increases the total amount of biomass but
decreases the relative amount of roots resulting in a higher shoot-to-root ratio (Kuzyakov et.al,
2010). It is expected that there will be no human input of nitrogen in the form of nitrogen fertilizers
during the next decades, therefore the amount of nitrogen which circulates in the boreal forests is
expected to remain the same (Hari a. Kulmala, 2008). This will further contribute to the small
amount of nitrogen decomposition.
The total carbon content in the first meter of soil in the boreal forest is around 338 Pg of pure
carbon. Globally, soils store twice as much carbon as the atmosphere, rendering them a very
important carbon sink (Amendolara, 2013). Higher temperatures and higher CO2 concentrations
enable trees to produce more organic matter, such as leaves, but also bigger roots to store carbon
and nutrients; approximately 42% of soil Corg content is stored in in the roots.. For the soil, which
was studied by Karhu et al. (2010), an increasing temperature was shown to decrease the carbon
content by 30 – 45%, given that there are no changes of in the atmospheric CO2 concentrations. The
CO2 content of the atmosphere needs to increase by 100 – 120% if the soil carbon is to remain the
same.
Conifer leaves are richer in cellulose and lignin than deciduous leaves. As aforementioned, most
trees in the boreal forest are conifers and birches. Due to the large amount of conifers, the bacteria
and worms need a lot of time to decompose the needles. The growth of soil bacteria depends on
temperature, moisture, enzyme activity and nutrient availability (Amendolara, -,-, Blume, Hans –
Peter et al., 2010). As a result of climate change the trees produce more leaves, however it is not
certain if the organic horizon of Podzols will stay the same, increase or decrease (Lukac a. Godbold,
2011). Yet, it is certain that the pH value of Podzols will increase as a result of the decomposition
producing organic acids, which reduce the pH value.
Several studies show that with increasing temperatures, the decomposition of soil organic matter
will be faster, but with an increase of atmospheric CO2 concentration, the production of litter in the
form of leaves and conifers would be higher. Furthermore, the production of CO2 by roots and soil
19
organisms could increase (Raich, J.W. a. W.H. Schlesinger, 1992). Increased CO2 amounts could
also shift the amount, structure and activity of microbial communities (Blagodatskaya et al., 2010).
Yet it is possible that bacteria could alter their metabolism, and therefore return to the
decomposition rates seen before.
The Podzols in Finland and Sweden will either experience the organic matter decreasing or
increasing, but it is uncertain which; this is why it is hard to say how the typical organic layer (O
horizon) will change,. Nevertheless, the carbon circle in boreal forests will increase. No changes are
expected in nitrogen content due to there being no human inputs of nitrogen. Additionally, Podzols
are not expected to change their different soil layers because Podzol is a final, developed soil
(Blume a. Brümer, 2010). Cambisols in Sweden and Finland will develop to Podzol during the next
centuries because of typical soil processes, which means that there will be higher production of
NOx.
It is unclear how Histols will develop during the next decades. Locally, Histols could change
depending on water fluxes, aerobic and anaerobic conditions and influxes of organic material.
The only thing that is certain to change during the next decades is a higher formation of biomass
and therefore an increase of the carbon circle. Additionally, changes in the pH, nitrogen cycle and
the amount and composition of soil bacteria are likely to occur (Blume, 2011).
VIII. Forests and Management
Climate change may increase forests stemwood growth in mineral soils in Finland, an average of
10% by 2020, 29% by 2050 and 44% by 2100 compared to current (2012) climate, over the same
examination period, if forest management is done by the current forest management guidelines that
are drawn up the Forestry Development Centre Tapio. Tree growth relative increase is much higher
in northern Finland than in Southern Finland. The other hand, growth is expected to spruce up the
declining southern Finland by the year 2100 with permeable habitat types, where the drought limits
spruce growth (Kellomäki et al. 2008 and Päivinen et al. 2011).
Especially in southern Finland birches displace spruces but also partly pines, if not actively
controlled the species relationships in the desired direction in forest managements. This is due to the
fact that birch benefits most from a warming climate (Kellomäki et al. 2008).
Climate change will improve the potential for more cutting and logging in Finland by about 4% in
2020, 52% by 2050 and 82% by 2100 compared to current climate. Estimates assume that the forest
management are in current level in forest management guidelines of trees reduction and reform.
Climate warming will also improve the natural regeneration of forest trees, especially in northern
Finland. There, in the present climate, low temperature limits the amount of seed greening
(Kellomäki et al. 2008).
Forests future growth and possible changes in forest structure, age and tree species, are affecting
together the impact of climate change and the forest management, e.g. thinning intensity and
frequency of rotation. Tillage, that is made when forest is regenerated, changes the environmental
20
conditions and thus contributes to the success of the various plant species. Also same effects occur
when energy biomass is harvested. Climate change may also have an indirect impact to forests soil
minerals by accelerating the mineralization of nitrogen, which promotes the growth of trees, grass
and hays. Various disturbances are causing the new large open areas in the forests allowing the
spread of new species (Vapaavuori et al. 2012).
Necessary management actions in the forests are: careful choice of tree species depending what
kind is the habitat and soil, forest carbon sequestration increasing, destruction of risks taken into
account in the forest management, the forest hygiene management, the biodiversity protection,
forest biomass utilization in the energy production and wood products, logging development (Jylhä
et al. 2009 ; MMM 2012 ; Päivinen et al. 2011). Use of climate adapted and processed material
makes it possible to respond more quickly to climate change than using seeds collected from stands
(MMM, 1/2005).
Different destruction risks increase due to logging may increase because of the growth has
improved. Various destruction risks is an important factor in forest management, forest planning
and harvesting (Vapaavuori et al. 2012 and MMM 2012). For example, root rot control should be
intensified. The new clear-cutting areas next to stands of mature trees increase the wind destruction
risks. Especially old-grown spruces, but also just thinned stands of trees are susceptible to wind
disasters, regardless of the types of tree species. Strong winds and large snow deposit frequency
risks, the prevailing wind direction, as well as the non-frost taken into account in the design of
forest destruction contribute to the risk management (Peltola et al. 2010 and MMM 2012).
In the future forests can be used more intensively and perhaps to new uses. For example, a new kind
of wood construction and increase the use of renewable energy (e.g., forest biomass), also
completely new forest-based products are expected. Utilization of various ecosystem services would
become more important, such as berry and mushroom reserves, even wild herbs (MMM 2012 and
Metsähallitus, Antti Otsamo).
IX. Predictions that are the Possible Effects of Climate Change in Forest
managements in Finland
This chapters predictions are made by summarizing and synthesizing many articles (Main articles:
IPCC 2007; Nabuurs 2007; Stern 2007; IPCC, 2012; Metsähallitus; MMM). Wood harvesting is
becoming more challenging, and challenges also for water protection are expected. There are
coming changes in species composition and biodiversity when forests are changing, increased risk
for abiotic and biotic damages in the forests, choices of tree species changes.
Wood harvesting is becoming more challenging. This is happening because of soils are not properly
frozen in wintertime; there is less snow and unexpected temperature changes. These problems occur
especially on peatlands. There are coming problems in transportation, in wood storage and timing of
activities. New machinery is needed also to work in different kinds of circumstances and forest
types.
21
Changes in forests are causing challenging water protection requirements. The causes are increased
rains, summertime harvesting is becoming more difficult, soil and nutrients leaching are increasing
to waters. Biggest problems are coming in peatland forestry. There are coming problems also for
restoration activities.
Predictions to changes in tree species composition are: all current tree species probably survive also
in the future, Norway spruce might suffer, if summers become drier, deciduous trees are probably
more successful. Certain threatened species may disappear, and some new species invade forests.
Generalist species take advantage of changed environment easily.
In the future there is an increased risk for abiotic and biotic damages. Increased storms are coming
all year around. More wind damages, both in small and large scale, are expected. There will be
more floods. Abiotic damages easily lead to biotic damages, so new and better pest management is
needed. If some new pests come, there need to be action plans for that and private forest owners
need more knowledge.
Choices of tree species: existing tree species will survive, tree species composition may gradually
change, deciduous species may become more common, and tree improvement may partly answer
challenges, introducing the new tree species are not the only answer in the future forests. If there are
taken new kinds of trees to growing, there need to be long period tests before to going the real
forests.
X. EU Forestry Policy
Chapter 1: EU Forestry policy
The European Union has an extended policy to support and steer agriculture and rural development.
There are less regulations and subsidies for forestry and forest industries. Most of the policy is
focused on sustainable development. In the first part of this chapter, the past and future
development of the EU policy will be described. The second part is about national forest policies in
Finland. The last part discusses the effect these policies might have on the environment.
Creation of forest policy in the European Union.
The Member States of the European Union have a long history of national and regional forestry
laws. Still, forest policies are being implemented by the Member States and not by the European
Union. However, since 1995, the European Union has developed a common forestry policy that
mainly focuses on sustainable forest management. In 1998, the Resolution of a Forestry Strategy
was adopted. It took into account commitments made by the EU and its Member States in
international processes and it underlines the multifunctional roles of forests (European Union,
1999). The aim of the Resolution is not to regulate the market, but to improve coordination,
communication and cooperation. The instruments that are used are national and sub-national forest
programmes, but the EU can contribute by implementing certain common policies and active
participation in forest-related international processes (European Union, 1999).
22
The Resolution provided a framework for forest policies, and in 2005 the European Commission
wrote a follow-up report about the implementation of it (Commission of the European Communities
,2005). They evaluated what had been done until then and they paid attention to the implementation
of the Millennium Development Goals in the Forest Strategy. The Member States have prepared
and implemented the policies and there was a reference framework for monitoring these
developments. At European level, the rural development policy that was created with the reforms of
the Common Agricultural Policy (2003), has been the main instrument for implementation of the
Forestry Strategy on Community level. There is a coordination system based on agreement and not
on enforcement by law (European Commission, 2011). A proposal of the European Commission
stresses more integration of forestry policy in rural development policy. The Member States want to
ensure that the national forest programmes are embedded in national sustainability initiatives
(European Commission, 2011).
Summarized, because the European forests and their uses differ substantially, the European Forestry
Policy is less extended than the Common Agricultural Policy. The European Union provides a
framework for sustainable forest management, but the Member States are responsible for the
implementation and the integration with their environmental goals and the adjustments to their local
economies.
Future
In 2011, the European Commission gathered in Brussels to discuss the European Forestry Strategy.
Their conclusions were that the Strategy should be balanced between complementing and
influencing national policies; areas where common action could add value to the strategy should be
found. Already good knowledge about sustainable forest management should be further improved
(European Commission, 2011).
Finnish Forestry Policy
The Finnish Forestry Policy focuses, like the European Policy, on the multiple uses of forests.
Forests are used both for industrial and recreational goals. The Finnish Forestry Policy exists since
the 19th century. The First Forest Law stresses that the forest shall not be destroyed or used in a way
that prevents renewal. During the 1990s, the forest legislation has been completely reformed, in
order to meet requirements of the EU and to harmonize environmental regulation and forestry
regulation (FAO, 2013). The forest policy now focuses on a broad range of aspects. In addition to
economic and ecological aspects, social and cultural features are included. The aims were to
increase forestry production and export by ensuring competitive conditions for the forest industry.
Ecosystem management in forests should secure ecological sustainability.
The new forest policy started with the Forest and Park Service Act (1994), the Act on Forestry
Centres and Forest Development Centre (1996) and continued with the Forest Act (1997). In this
act, certain habitats that require special attention and guidelines to manage these habitats are
defined (FAO, 2013). In the same year, the Nature Conservation Act to harmonize European and
Finnish forest legislation and the Act on Financing of Sustainable Forestry were adopted. The latter
guarantees state subsidies for forest management that would be unprofitable for private landowners.
23
Originally, the total Forest Program was focused on a period of 10 years (FOA, 2013), but in 2008
the program was extended until 2015. The Forest Program was enlarged with the development of
the Forest Biodiversity Program for Southern Finland (METSO). METSO’s aim is to halt the
decline in forest habitats and species, based on voluntary actions by landowners. What is special
about the programme is that it is a collaboration between the Finnish government, the Finnish
Environment Institute and the Forest Development Centre Tapio (Ministry of the Environment and
Ministry of Agriculture and Forestry, 2013).
Future
At the moment, the Finnish government is revising and clarifying the Forest Act. The new act
proposes to increase the options for silviculture for forest owners. Instead of exact directions about
how to manage the forest, the forest owners have more freedom to adopt the strategy they want,
within certain boundaries. The current policy focuses on small forests stands with trees of the same
age. The habitat that is to be maintained is indicated per area, depending on the ecological structure
(Ministry of the Environments and Ministry of Agriculture and Forestry, 2013). Forest must be
regenerated within a reasonable time, depending on the tree species and geographic area. Dead and
decaying trees are left in the forests, to provide a habitat for certain animal and plan species
(Ministry of Agriculture and Forestry, 2010). In the future,forest owners have more freedom to cut
their forest independent of its age and tree size and they are allowed to apply uneven-aged
management that was banned before. The new act is planned to come into force in the beginnen of
next year.
Environmental effects
Forests can play an important role in climate change, as described in the previous chapters.
Conservation of forests gets attention in national and European Forestry Policies. By cooperating
with its member states, the EU can provide general policies for forestry with stronger environmental
regulations. The member states can decide upon instruments that fit their forests and forest industry
to reach these targets.
The forest policies in Finland take into account both environmental and commercial uses of forests.
Although forest globally is decreasing, the Finnish forest area has increased since the 1950s
(Seppälä. 1998). The new forest policies focus on increasing forestry production and environmental
sustainability. Attention is paid to exchange of knowledge about sustainable forest management.
Increased harvesting may lead to decreased biodiversity, but the METSO programme has a positive
effect on biodiversity and biodiversity rich sites are better taking into account nowadays, with the
help of modern technology. Many researchers have argued that the new Forest Act would decrease
forest biodiversity. The Act is still under process in the parliament and it may still change.
Summarized, the EU forest policy is likely to remain quite general, because the situations in the
different Member States differ a lot. The Finnish policy is in line with the EU regulations, but has a
more direct impact on forestry and the environmental effects of changes in the forest management.
It is hard to predict what would be the best policy for Finland to maintain biodiversity and slow
down climate change, there is an ongoing debate among researchers about the best forest
management methods.
24
XI. Conclusion
The projected climate change is expected to have both positive and negative effects on boreal
forests. These impacts may also differ between different locations, e.g., between northern and
southern Fennoscandia. Forests are expected to benefit from longer growing seasons especially in
Lapland where low summer temperatures and short growing season restrict the forest growth more
than in southern locations. In addition, the increasing risk of summer droughts is most prominent in
southern Scandinavia. Some risks, such as the risk for snow-induced forest damages, will most
likely become less relevant in the future, whereas? there are plenty of abiotic and biotic stress
factors expected to affect boreal forests (more frequently) in the future.
The predicted fluxes in phenology could prove to be catastrophic for some species; however, there
is still hope that with the aggressive conservation and legislation (that) the forest can maintain
normal functioning. If not, the result is likely to be that some species will flourish, while others
possibly perish; this will be a direct result of the increase in seasonal temperatures, as well as the
inappropriate timing of pollinators.
It will be vital for forest management practices to be altered so as to navigate the projected impacts
of climate change. Forest management will need to be advanced to meet future needs. The choice of
tree species and management actions will need to be thought of carefully in an effort to try and
minimize the impact of climate change. Figure 9 shows the interactions between forest, forest
management, climate change and the ecosystem.
Figure 9. Multidimensional picture showing the interactions related to(?)forest and climate
Change. Forest environment, humans, the ecosystem itself andactions and plans made for forests
are affecting climate change and its impacts. All different aspects play their part influencing(?)
climate change (Riina Järvelä).
25
Climate change is expected to have an effect on forest insects by resulting in increased numbers of
harmful pest and pathogens due to an expanded living range, which will likely result in effects on
forest biodiversity, forest industry, the recreational and property value of the affected area and water
quality. To prevent possible large scale outbreaks of native or exotic insect pests in the future,
attention must be given to the impacts of imported wood and other goods, quarantine measures and
risk assessments, and forest management practises.
Higher effective temperature and longer growing season has affected Finnish forests by increasing
the (volume of) growing stock of all main tree species. It is predicted that pine and birch will
benefit more from climate change than spruce, andthat spruce numbers will therefore decline , but
in the end it is the forest owners decision what they want to grow in their forests. In the future the
wood stock continues to increase, with the largest increase happening in northern Finland.
However, the northern forest line is not expected to react to warmer temperatures very fast and
therefore the forest line is not predicted to move northwards within the next few decades.
Soil properties are also expected to changebecause of climate change. Largestchanges are expected
on carbon fluxes because of higher temperatures and higher amount of carbon dioxide in the air
which is used by plants for producing litter? and wooden products then decomposed by bacteria.
The effects of climate change on bacteria are unclear; on the one hand decomposition rates could
increase because of higher temperatures but it is unknown if and how bacterial metabolism changes
over time. Water is also needed for decomposition and it is uncertain whether there will be enough
of it during the months withhighest decomposition rates.
The EU forest policy is and is likely to remain quite general, because the situations in the different
Member States differ a lot. The Finnish policy is in line with the EU regulations, but has a more
direct impact on forestry and the environmental effects of changes in the forest management. It is
hard to predict what will be the best policy for Finland to maintain biodiversity and slow down
climate change and there still is an ongoing debate among researchers about the best forest
management methods.
XII. Discussion Questions
1. How should forest management deal with the fact that different species react to climate change
differently?
2. How can we prepare the public to understand the gravity of climate change and its impacts on
the boreal forest?
3. What do you foresee as being the biggest, most consequential, impact to the boreal forest as a
result of climate change?
26
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