Timber harvests are likely to grow, but the risk of damage to forests may increase


It is important to identify the effects of climate change on forest growth and the relative prevalence of species of trees to allow for long-term forestry planning. From the perspective of forestry, increasing forest growth may mean accelerated harvesting cycles and an increase in potential harvests. Even if no considerable changes were to take place in wind conditions, the decrease of ground frost will damage the ability of trees to root themselves into the ground, which in turn increases the likelihood of wind damage. The condition of roads leading to forestry sites may also deteriorate and make forestry work more difficult. Many forest pests benefit from climate change.

Forestry in the changing climate

Forestry in Finland is based on cultivating naturally occurring species of trees. Economic viability is the most important guideline in forestry, but, since the 1990s, conservation of the biodiversity of forest ecosystems has also been another important element of the principles of sustainable forestry and forest management.

Forest ownership in Finland is highly decentralised. Private households own 60 percent of all forests, the Finnish State owns a quarter, and businesses own a tenth. Approximately 95 percent of the area of Finland's commercial forests has been certified under a national forest certification system, which aims to take into consideration the ecological, economic, and social sustainability of forestry. [1]

In the long term, forests are able to naturally adapt to the changes caused by global warming. Due to the societal importance of forests, it is nevertheless important that potential effects on forest ecosystems are identified, because the changes may have implications on forestry and therefore change forest management techniques and forestry potential. The goal is to predict the effects of climate change, because this allows the industry to benefit from the forecasted positive effects of climate change while keeping the risks associated with the phenomenon as small as possible. Impact and vulnerability assessments can be used to develop measures that allow forest development to be steered in the desired direction when planning forestry and forest management in the changing climate in the long term. [2]

In addition to forestry, changes in forests also have implications on many other economies, because the forestry sector has a central role in Finland's national economy, the vitality of the countryside, and balanced regional development. Revenue from the exportation of forest industry products accounts for almost a quarter of our country's total export revenue, which is ten times more than elsewhere in the world on average. [1]

Figure. Timber waiting to be transported for further processing.

© Marja-Leena Nenonen

Global warming is estimated to increase harvests

The combination of rising temperatures and the effect of carbon dioxide emissions on fertilisation may accelerate forest growth and increase the productivity of boreal forests. From the perspective of forestry, increasing forest growth may mean accelerated harvesting cycles and an increase in potential harvests. [3]

On a national level, potential harvests could increase by 56 percent by the end of the current century and by as much as 80 percent in the longer term. Opportunities for forestry in the northernmost parts of Finland are likely to increase, and harvests in Northern Finland will amount to two thirds of those available in Southern Finland [2].

In terms of species of trees, pine and southern species of broadleaf trees will become more common, while spruce growth will decline. The prevalence of birch is likely to increase especially in Southern and Central Finland, where it will fare better than spruce except in hydric habitats. Pine and spruce will continue to win territory from mountain birch in Northern Finland. The prevalence of each species of trees in Finland is also affected by the future use of forests and demand for wood. [4]

Climate change makes forests vulnerable to damage

Although warm summers, ample rainfall, and the long growing season together with high levels of atmospheric carbon dioxide are likely to increase forest growth, the changing climatic conditions can also make trees susceptible to damage. The changes may reduce forest growth by affecting the relative prevalence of forest species on one hand and cause considerable losses to forest owners as wind damage and damage caused by pests increases on the other. [2]

Increasingly mild winters mean shorter periods of snow cover and ground frost

Mean temperatures are forecasted to rise and rainfall to increase especially during the winter as a result of climate change. Increasingly mild winters mean less snow and shorter periods of snow cover. Damage caused to forests by snowfall is estimated to decrease somewhat in Southern Finland. In Northern Finland, however, where snow damages trees even in the current winter conditions, snow damage may actually increase. [4]

Global warming reduces frost formation to such an extent that the frost thickness in Lapland is likely to be equivalent to that currently found in Southern Finland in the future. The likelihood of the ground not freezing at all also increases. For example, projections predict that the ground will still be unfrozen in Southern Finland in December, and even in January frost will only occur approximately half as often as now. The decrease of frost may complicate forestry work and harvesting in the winter and damage the roads leading to forestry sites. Forest machinery damages the roots of trees when the ground is unfrozen and therefore makes especially shallow-rooted spruce stands susceptible to storm damage and fungi. [2]

The risk of wind damage and forest fires increases

According to the A1B emissions scenario, the average wind speed in Finland will increase by between two and four percent from current levels by 2100 as a result of climate change [5]. Storm damage may become more common with global warming if winds become stronger especially in late autumn and early spring, when the lack of snow and ground frost prevents the ability of the surface roots of spruce, in particular, to attach firmly to the ground [6]. Trees felled by violent winds can cause considerable economic losses for forest owners.

The likelihood and force of forest fires is projected to increase slightly especially in Southern Finland, where evaporation and dry spells will increase more than rainfall. The likelihood and risk of forest fires depends on the regional and temporal distribution of rains. Unusually warm spells in the spring and early summer may accelerate the melting of snow on one hand and the drying of the ground in the summer on the other hand, if rainfall does not increase enough during these seasons. The increasing prevalence of flammable vegetation and plant litter in forests may affect the likelihood of fires during dry summers, and stronger winds may help forest fires to spread. [4]

Pests and non-native species may become more common with global warming

Climate change may also have indirect effects on forests by increasing the risk of pests [3]. Pests are organisms that are known to be detrimental to health or to economic or ecological concerns and that must be controlled. Organisms that cause damage to forests may increase considerably as the climate becomes warmer and more humid and as the growing season becomes longer. Global warming is not believed to have a negative effect on the survival of any of the species of forest pests currently found in Finland [4]. In addition to climate, changes in the geographic ranges of pests and non-native species are also affected by ecological factors, such as nutrition and the prevalence of natural enemies.

Increasingly mild winters may help the survival of pests occurring in Finnish forests and their eggs to survive over the winter and even a small change in temperature to lead to a rapid increase in insect populations. Most of the pests found in Finland can only produce one generation of offspring per summer, but the changing climatic conditions could lead to more than one generation being born during each summer [2]. The damage caused by the autumnal moth (Epirrita autumnata) to birch trees in Lapland, for example, may increase somewhat as a result of global warming. [4]

The rising winter mean temperatures may also favour the growth of fungi that are harmful to trees. Drier and increasingly warm growing seasons may also hinder the spread of fungi, but cold and rainy summers create favourable conditions for fungal growth. Increasingly mild winters may favour the fungi that cause Brunchorstia disease in coniferous trees (Gremmeniella abietina), pine needle blight (Lophodermella sulcigena), and annosum root rot (Heterobasidion annosum), for example.

Finland's cool climate and short growing season have helped to prevent the spread of non-native species to Northern European forests, but the geographic range of some previously foreign pests may move gradually northwards with climate change. Summer dryness and the rising winter mean temperatures are especially favourable to the spread of southern arrivals to Northern Europe. Dry and warm summers may allow the pine wood nematode (Bursaphelenchus xylophilus), for example, to spread to Finland. Pine wood nematodes are pests that have caused significant damage once introduced to areas where pine trees have not yet had a chance to develop immunity to the species. [7]

Adaptation options in forestry

The positive effects of climate change on forests can be utilised and damage minimised by means of forest management techniques. For example, species of trees or genetic origins that are better suited to our changing conditions can be introduced in connection with forest regeneration. Thinning and regeneration felling can be carried out earlier to make use of the increased growth enabled by climate change and to reduce the risk of damage [3]. Changing wind conditions also need to be taken into consideration in forest management planning, because forest cultivation and management techniques may affect the risk of wind damage. Forests regenerate slowly, which is why it also takes a long time to modify the properties that improve their ability to adapt [3]. In order to allow for forest management recommendations to be revised, scientific information on the effects of climate change needs to be compiled to support decision-making.

Climate change increases the need to develop harvesting technologies that are suitable for thinning forests when the ground is unfrozen. The sensitivity of spruce trees to dryness potentially caused by climate change and to other damage may become a problem in Southern Finland. One possible way to adapt may be to substitute pine for spruce in xeric habitats and birch for spruce in hydric habitats. [3]