You can hike in birch forests grown on slash-and-burn sites, walk in meadows or admire the impressive scenery opening from clifftops. The natural diversity in Koli offers something for everybody. The slopes facing Lake Pielinen are covered by old spruce forests and lush herb-rich forests along brooks. In winter, the thick snow covering the spruces turns the hilltops into a fabulous fairytale world. On the hilltops and on the western slopes of Koli, you can hike in rugged pine forests.
The chain of Koli hills lies on the border between two bedrock areas of different ages. The bedrock east of the Koli hills (mostly granite gneiss) is the oldest in Finland: it was formed more than 2.6 billion years ago. The western part of the chain is younger and made of slate, which mostly comprises hard quartzite. Pale quartzite rock is crossed by dark veins of igneous rocks (mainly diabase), the hardened lava outlet channels of ancient volcanoes.
The bedrock in the Koli area went through a drastic upheaval about 1.9 billion years ago when a volcanic archipelago thrust onto a continent, creating the Karelides mountain range. Originally, the mountain range was almost as high as the Himalayas, but weathering has eroded it to its present dimensions and only the quartzite, the hardest rock material, is left. On the top of the Ukko-Koli Hill, you can sit on the white quartzite that is now visible as a result of the weathering process.
Ukko-Koli is the highest point in Southern Finland, rising 347 metres above sea level and 253 metres above Lake Pielinen.
Traces of the Ice Age
The cliffs in Koli are characterised by smooth, rounded shapes, a result of the fierce touch by the Ice Age. Till is the dominant soil type in the Koli area. In the vicinity of the national park, you can also find examples of moraine formations originating in the Ice Age, such as moraine ridges and drumlins.
East of the national park, on Lake Pielinen, there is a 13-kilometre-long chain of eskers visible as islands. It was formed in the melting phase of the last ice age at the bottom of a crevasse near the glacier edge. Characterised by sandy shores, the formation is protected as a nationally important site containing features of esker nature.
Pielinen - Finland’s fourth largest lake
Pielinen is Finland’s fourth largest lake. It is over 93 kilometres long and has an average depth of less than ten metres. The deepest point (61 metres) has been measured at the northern end of the lake. Lake Pielinen gathers its waters from a wide area and there are substantial fluctuations in its water levels: they are at their highest in spring and early summer after the snow has melted.
At the end of the Ice Age, the glacial lake of Pielinen covered a significantly larger area than the present lake. The oldest and highest shoreline in the Koli area is about 30 metres above the current surface level of the lake. You can find several ancient shore landings and rock-filled places in the national park.
Winter wonderland of the south
Climate in Koli is cooler than in the areas around it. Especially in the autumn, Lake Pielinen warms its surroundings and during the summer months, the moisture rising from the lake condenses into fog and rain over the eastern slopes. As you climb up the hills, the temperature drops. Due to the cool climate, northern forest types thrive at the summits and in winter, the trees are transformed into a snow-covered wonderland (en.ilmatieteenlaitos.fi/).
One tree may carry a snow load of hundreds of kilos. Treetops are often broken under the weight and in fact, there are few full-size trees at Koli summits. Fallen treetops are an important part of the decaying wood in the summit forests, providing habitat for rare species, such as polypores and insects living in decaying wood.
How many species live at Koli?
Koli is a nature lover’s paradise: meadows boasting an abundance of flowers and mushrooms, lush herb-rich forests, old-growth spruce forests, barren rocks and crystal-clear lakes. Over the years, at least 4,078 different animal species have been sighted in the Koli National Park. Koli is the only national park in Finland for which such a comprehensive list of species has been compiled.
A total of 2,310 species of invertebrates (insects, spiders and molluscs) have been found in Koli. Insects account for most of the invertebrates sighted in the area (2,211 species). A total of 191 species of vertebrates are listed. Most of them (148) are birds. The number of mammal species found in the area is 26 (including humans). Four species of bats and 11 species of fish have been sighted. List of the animal species (pdf, 745 kt).
The number of mushroom species is also substantial (879). A total 596 species of plants have been found and of them. 385 are vascular plants and 211 different types of bryophytes. A total of 101 species of lichen have been found. All plant and mushroom species found in Koli (pdf, 543 kt).
The information is based on a large number of different sources and mostly originates from the past two decades. Metsähallitus has commissioned a number of species surveys on different organism groups in the Koli area, and the list also includes species observations by nature enthusiasts. The Bioblitz species mapping event organized by Metsähallitus in August 2018 produced new observations of 370 species that had not been previously reported in the area. In the Bioblitz event, 25 experts in different organism groups tried to find as many different species as possible in the national park within 24 hours. A total of 1,113 species were sighted during one day.
Although the number of species in Koli may sound large, many species, especially in poorly known organism groups, are still waiting to be discovered. For this reason, the list of the species is likely to grow longer each year.
Abundance of flowers and rare butterflies
During the summer months, you have a chance to admire the bloom of flowers in the meadows of Koli and learn to know rare meadow plants. This is because there are plenty of clearings in the national park, created during the era of slash-and-burn and meadow agriculture. They provide important habitats for increasingly rare plant and butterfly species and for this reason they are also nationally important as protected sites. For example, in the meadows, you may spot moonwort fens and stiff-strawed matgrass. When the bloom of flowers fades away in late summer, it is replaced by the sight of agarics and other small mushrooms. However, noticing them can be difficult.
Each type of meadow has its own distinctive range of species. Mountain everlasting, maiden pink and mouse-ear hawkweed are some of the flowers thriving in sunny meadows, such as Havukanaho and Mäkränaho. In the more humid Mustanaho clearing, you can find taller plants such as marsh thistle and meadowsweet. Scarce fritillary, the moth Clepsis lindebergi, the butterfly Plebeius nicias, scare cropper butterfly and common blue are a rare and beautiful addition to insect life in the clearings and meadows of the national park. There are also plenty of other insects, from beetles to grasshoppers, inhabiting the clearings.
The clearings must be mowed each year so that the demanding species habiting the sites can survive. Traditional landscapes (www.metsa.fi) are protected and managed so that their typical features can be preserved. Havukanaho, Mäkränaho, Purolanaho, Ikolanaho, Mustanaho and Vaaralanaho are the clearings in Koli kept open through annual mowing. Pastures and grazed woodlands are forested traditional biotopes. They can be found at the farms of Ollila, Mattila, Seppälä and Lakkala.
Life in forests and lakes
The old-growth forests, slash-and-burn sites, clearings and waterways in Koli provide habitats for a wide variety of mammals, fish, birds and insects.
Life in mixed forests
With some luck, you may spot the flying squirrel in the old mixed forests of Koli at dawn or in twilight hours. This big-eyed mammal, which is smaller than the red squirrel, lives in aspens in which woodpeckers have carved nesting holes. Sturdy old aspens are also critically important for many other species. The grey snail Bulgarica cana lives on large aspen trunks. It is an endangered species and in Finland it has only been found in Koli and in Sipoo near Helsinki. Many rare insects, such as the fly Solva interrupta and the beetle Cis fissicornis also need old aspens or polypores growing on them as their habitats.
The hare populations of the national park, which are beyond the reach of hunters, occasionally reach high levels. This benefits the lynx hiding among the boulders, which is why this big cat has made the area its permanent home. Managed clearings help the mole and mouse populations to thrive, which in turn provides good conditions for small carnivores such as marten and stoat. Even-toothed shrew and wood lemming, both eastern species, are two of the rare mammals occurring in Koli.
In early summer, you are greeted by a mixed chorus of small birds, especially in the northern forests of the national park. Red-flanked bluetail, greenish warbler, red-breasted flycatcher, three-toed woodpecker and wren are some of the old-forest species inhabiting the Koli area. In deciduous forests, you may hear the singing of blackcap or the chirping of Arctic warbler. Capercaillie, black grouse and hazel grouse also thrive in forests of different ages.
Waterways teeming with life
Lake Pielinen used to be known for its ample salmon catch, with lake salmon, sea trout and Arctic char populating its depths. However, the lake salmon population of Lake Pielinen died out in the 1960s as a result of the construction of the Lieksanjoki River. Efforts are under way to revive the population by transferring salmon from Lake Saimaa to Lake Pielinen. Brown trout is also in trouble. River construction work, obstacles, ditches and other human activities have nearly destroyed its spawning places in the rivers flowing to Lake Pielinen. Arctic char spawning in Lake Pielinen already became extinct at the beginning of the 20th century.
The lake still has a grayling population but it, too, has declined. Whitefish, vendace and smelt are the other salmon species occurring in Lake Pielinen. Nowadays, the most important fish caught in the lake are vendace, whitefish, pike, perch and zander.
Black-throated diver and lesser black-backed gull are the most common bird species in Lake Pielinen. Osprey has recently made the artificial nest built in the Koli archipelago as its home. A large number of Arctic water birds, such as geese and swans, fly over Lake Pielinen on their migratory journey each year.
Spread to Koli as a result of the transplantations made outside the area, the North American beaver now inhabits the small water bodies in the southern part of the national park. Two related species: the endangered great crested newt and the more common smooth newt also occur in the waters of the Koli area, which lie at the northern edge of their range.
Conservation by mowing
The hills of Koli were permanently settled in the mid-18th century. The inhabitants slashed and burned forests to create agricultural land and with mowing and cattle grazing, farms and tenant farms gradually became surrounded by slash-and-burn clearings, grazing lands and woodland pastures.
Many of the old farms in Koli were abandoned in the 20th century and the open rural landscape gradually became overgrown with trees. The clearings in the national park are important natural habitats. They are managed by annual mowing so that they remain open and provide living space for flowers, butterflies and other insects. This helps to ensure the diversity of species and the diversity of landscapes.
Busy grazers of summer pastures
Animals also contribute to the management of traditional landscapes: during the summer months, Finnish sheep, ‘kyyttö’ cattle and Finnish horses graze the grounds in Lakkala and Seppälä (at the southern end of the national park) and in Ollila and Mattila (at its northern end).
The ‘kyyttö’ is an endangered Eastern Finnish cattle breed. The word originally meant striped and in fact, the breed is identifiable by its light back and dark sides. It is resilient and well-adapted to Finnish conditions.
There are more than ten hectares of long-time grazing grounds in the national park. Between 2017 and 2018, an additional 16 hectares of woodland pastures were fenced and the partner entrepreneur operating in the national park will expand the pastures in the coming years. The entrepreneur will also provide four-legged ecological managers for the areas. The grazing period lasts from June until September and the animals help to keep the landscape open and alive.
The cattle in Ollila is managed by the Koli local heritage association, while the animals in Mattila are the responsibility of the partner entrepreneurs operating at the farm. In Seppälä and Lakkala, the animals are looked after by voluntary shepherds.
Slashing and burning
Many of the commercial forests planted in the Koli area have been slashed and burned after the establishment of the national park. Preparations for slash and burn in a spruce forest are started several years in advance by girdling (removing a strip of bark from around the tree trunks), which interrupts the flow of liquids and causes the tree to die. In fact, there are several girdled spruce forests of less than a quarter hectare near traditional farms in the national park.
The trees are felled and piled in the spring when they are burned. or in the preceding autumn. In Koli, slashing and burning takes place every two years to keep the tradition alive and to preserve the rye and swede varieties grown in this manner. There are many recently created slash-and-burn sites between Ollila and Mattila in the northern part of the national park. Old deciduous slash-and-burn forests are preserved by removing the spruces from them as necessary.
Herb-rich forests dominated by deciduous trees are also maintained by removing the spruces, which block the light and acidify the soil. This allows more light to enter the forest, helping deciduous trees to grow and benefiting plants in the forest floor.
Decaying wood and resored mires
A hiker in the national park may come across a place where trees have been felled or girdled. The aim of this procedure is to create decaying wood in monocultural forests that have been used for commercial purposes and from where dead trees have been removed. Many forests in the Koli area were restored in this manner, especially during the first decade of the 2000s. At the same time, drained mires in Koli were restored to natural state by blocking the ditches dug in them. For example, the National Land Survey of Finland has already removed the symbols for ditches from the map of the restored Pitkäsuo even though their locations are still visible on aerial photographs. Restoration of forests and mires in the Koli area is continuing in a small scale, as required and as possible, by girdling trees and blocking ditches. Restoration burning would be the best way to enhance the structure of old commercial forests and ensure a wider variety of species in them. However, the uneven terrain in Koli is a factor hampering the efforts.