The Koitajoki Area has a diverse specie population. The area's vegetation and animal species in the area reflect the ruggedness of the terrain. The area offers a habitat for numerous threatened species, such as beetles, polyporous mushrooms and flies that live on decaying wood as well as a habitat for birds.

Koivusuo Strict Nature Reserve

Koivusuo Strict Nature Reserve was established in 1982. All of Koivusuo Mire is not within the strict nature reserve as half of it is ditched so that peat can be produced there. Koivusuo Strict Nature Reserve was established as a research area in order to help preserve Eastern Finland's mire and forest landscape in as natural a state as possible. Visitors may only enter the nature reserve and move within it along marked hiking trails.

Koivusuo Strict Nature Reserve. Photo: Maarit Similä


The River Koitajoki, which is 20 km, winds through the area. Smaller rivers Asumajoki, Alajoki, Niemijoki, Sammalpuro and Hanhipuro flow into the River Koitajoki. The river was probably formed 10,000 years ago during the Ice Age.

The River Koitajoki has many twists and turns. Photo: Markku Tano

The River Koitajoki is part of the Vuoksi water way system of which only part is within Finland's borders. The river is scenically enchanting with its low rapids and sandy hilled shoreline. The river bed makes swift twists and turns along its course. The river banks and their vegetation are given variation by the separate and partially paludified little pools which mark the old course of the river bed.

Mires and Backwoods

The Koitajoki Area stands out from its surrounding areas with its old-growth forests and mires which are in their natural state. Though the area's water areas are not large in proportion to the area's overall size the River Koitajoki's significance landscape-wise is indisputable. The area's terrain is considerably level. The highest hill tops rise to 220 metres and the area's mires are about 170 metres above sea-level.

The area's landscape is dominated by mires, which cover almost 2/3 of the area. Most of the mires are in their natural state, which means they have not been drained of water by ditching. The Koitajoki Area is situated in the transition zone where northern aapa bogs and southern raised bogs meet. There are indeed vast examples of both in the area and Koitajoki's mire vegetation is a mix of northern and southern features. The landscape at Koitajoki is rugged because almost half of the protected area's mires are tree-filled, mainly pine bogs. Part of the present day reserve has previously been used for commercial forestry. The forests and mires in these spots are now being restored to their natural state ( Koitajoki is part of the LIFE-Nature project Karelia Mires and Virgin Forests - Pearls in the Chain of Geohistory (

Old-growth Forests and Decaying Wood

One third of the Koitajoki Area is covered by forest. The area differs from its surroundings with its 150 year old trees. Old-growth forests thrive especially along the River Koitajoki at Koitajokivarsi, in Koivusuo Strict Nature Reserve and in forest islets in Ruosmesuo - Hanhisuo. The forests are pine dominated, but there are also some spruce forests here and there.

Usually the older the forest the more dead decaying wood there is. Decaying wood in spruce and pine forests is the ideal habitats for many polyporous fungi and beetles. The species living on decaying wood play their own role in the forest: they return nutrients tied within the dead trees to nature in a form that they can be used by other plants. Polyporous fungi include mushrooms which get their nutrients while causing wood to decay. Only a small portion of the fungi, the fruit body, is visible on the outside surface of the tree, while most of the fungi lives within the tree.

Publications of Koitajoki Area (