Ilmastonmuutoksen vaikutukset Suomessa metsänhoidon näkökulmasta

Abstract

Growing forests sequester carbon from the atmosphere, and hence forests have an important role in mitigating climate change. Forests are also important as recreational areas, and natural forests are needed in maintaining biodiversity. On the other hand, the economic importance of forests is substantial in Finland as the forest industry is a major contributor to wellbeing in the country. Ongoing climate change and the multiple contradictory interests towards forests expressed from different sectors in society make it important to study how forests can be exploited in a sustainable way. Information on the magnitude and impacts of climate change are needed in revising the forest management recommendations. In this report, we present an assessment of climate change in Finland based on current knowledge and describe the expected effects of the change on forests and forestry. Over the last 150 years, the mean temperature in Finland has already risen by about 2 °C. Presently, the temperature continues to increase with a rate of almost 0.5 °C per decade, and by the mid-century, temperatures in Finland are expected to be approximately 1-1.5 °C higher than at present. The rate of warming during the latter half of the 21st century will largely depend on the future evolution of global greenhouse gas emissions. In Finland, the rate of warming is about twice as large as the global average. In addition to warming, precipitation levels, particularly in winter, are expected to increase in the future. On the other hand, drought may occur in summer more frequently than at present. Increasing temperature and rising atmospheric carbon dioxide concentration have already contributed to accelerating forest growth. In the future, our forests are projected to grow even more rapidly. On the other hand, an increasing frequency of forest damages may partly overrule this development. Particularly, spruce forests are vulnerable to many insect pests but in southern Finland also to drought. An example of a pest benefitting from the warming is the European spruce bark beetle. In winter, reduction of soil frost complicates the logistics of forest harvesting and increases the risk of root damage during the harvest. The risk of wind damage also increases as the soil frost decreases. Internationally, the goal is to limit global warming to less than 2 °C compared to pre-industrial era, i.e., the mid-18th century. This would require rapid global mitigation of greenhouse gas emissions. So far, limiting the increase in global greenhouse gas emissions has not been adequately successful so that reaching the target would seem likely. Thus, there is a need to be prepared for a more severe warming. In the worst case, the temperature could rise even by more than 4 °C globally by the end of the 21st century. From the forest owner viewpoint, it is important to take care of the growth and vitality of the forest stands and to identify the risks threatening the stands, taking into account the variability of the stands and the terrain. To support risk management, th...

Climate change impacts to the security of supply

“…Suomessa on viime vuosina tuotettu runsaasti tietoa ilmastonmuutoksen vaikutuksista. Selvityksiä on tehty kaupungeille (Mäkelä et al, 2016;Pilli-Sihvola et al, 2018) ja eri toimialoille kuten sähköverkoille (Lehtonen et al, 2019), vesivoimalle (Veijalainen et al, 2018), metsätaloudelle ja metsäpaloille (Venäläinen et al, 2016;Venäläinen et al, 2019;Lehtonen et al, 2020), terveydelle (Ruuhela, 2018), ja maataloudelle (Peltonen-Sainio et al, 2017). Lisäksi Valtioneuvoston kanslia on teettänyt vastaavia selvityksiä keskeisimmistä Suomen sää-ja ilmastoriskeistä ja niiden vaikutuksista varautumisen näkökulmasta (Tuomenvirta et al, 2018) sekä ilmastonmuutoksen vaikutuksista esimerkiksi Suomen kokonaisturvallisuuteen (Hakala et al, 2021) että turvallisuusriskeihin (Erkamo et al, 2021).…”