Effects of climate change on forest biodiversity


The forest species found in the northern parts of Finland are, thanks to the warm North Atlantic Current, surprisingly diverse considering the latitude. Climate change is expected to change the relative prevalence of different species of trees and to affect the interdependence of forest species. Some forest species benefit from climate change and the longer growing season. New species may also arrive in Southern Finland. Species living near the tree line are vulnerable and poorly adaptable to climatic changes.

Effect of climate change on forest species

Climate change may damage European forests through the potential increase of storms, heavy rains, fires, and pests. Climate change does not threaten the survival of forests in Finland or elsewhere in Northern Europe, but it is projected to have a major impact on the structure of forest ecosystems by changing the geographic ranges and numbers of species as well as the interdependence of species. The more abundant and diverse forests are, the better able they are to adapt to changing climatic conditions [1].

Different species react differently to changes in climatic conditions. Some forest species will benefit from global warming in the long term, while other species may decline over time.

Climate change is, above all, likely to benefit vascular plants and trees, which are expected to grow better as the climate becomes warmer [2]. The array of species of plants may change especially in Southern Finland, if new species arrive from the south and the southwest.

Increasing forest growth and the accelerated ontogeny of trees may increase the volume of deadwood in the forest, but the accelerated rate of decomposition will counteract this. The volume of deadwood in forests has a great significance to the survival of species that depend on dead organic matter.

Figure. The volume of deadwood is greater in old-growth forests than in young stands.

© Tapio Heikkinen

The decline of individual species may be due to changes in the physiology or geographic range of the species or in the structure of biological communities. The earlier arrival of the spring may also change the rhythm of biological phenomena. Changes in seasonal rhythms and the temporal distribution of biological activity may damage interaction between pollinators and plants, for example. Many of the rare species of insects found in Finland are fully dependent on the prevalence of a specific plant and the timing of blooms.

Climate change affects the prevalence of Finland's most common species of trees

None of the species of trees found in Finland is likely to disappear with climate change, but the relative prevalence of Finland's most common species of trees – pine, spruce, and birch – will probably change [3].

The percentage of broadleaf trees will increase considerably in the southern parts of the country, and the dominance of spruce will decrease especially in Southern Finland. In the long term, spruce will only dominate over birch and other broadleaf trees in hydric and boggy areas. Pine and birch, on the other hand, will become more prevalent in drier regions. Conditions for species more commonly found in Central Europe – oak, maple, ash, elms, hazel, and lime – will improve in Southwest and Southern Finland.

No new species of trees are expected to spread to Finland naturally, but conditions for cultivating more southern species may improve. The prevalence of each species of trees in Finland is also affected by the future use of forests and demand for wood.

The habitats currently occupied by spruce trees may also change as a result of the decline of spruce. Changes in the geographic distribution of spruce may have implications on species typical of boreal forests; for example, southern species that favour broadleaf forests will be more successful in the changing climatic conditions than species typical of coniferous forests.

The Arctic tree line is sensitive to changes

Climate change may result in significant changes in the array of species found in the ecological boundary region between the tree line and tundra, where the diversity of species is unusually high thanks to the combined effect of the two biomes.

Species that are common in Finland and that have a wide geographic range have the best adaptability to climatic changes. The geographic ranges of species found in the north are often narrow and their numbers small, and they are highly specialised for surviving in harsh climatic conditions. Northern species are believed to be more sensitive to climate change, because their ability to adapt is often limited. The vulnerability of these species increases if their already narrow habitats become increasingly fragmented.