Bysjöholmarna, Naturreservat

The Bysjöholmarnas Nature Reserve comprises six islands in the Dalälven River. Oak trees, rare wood-decay fungi, and lichens thrive here. The abundance of deciduous trees makes this a perfect habitat for woodpeckers. The islands are accessible only by boat or canoe. Expect the islands to be uncrowded. Photo: Anders Heurlin, Dalarna County Administrative Board

Several islands are part of the reserve

Bysjöholmarna is located in Lake Bysjön, part of the Dalälven River. The western islands, Lammön and Långholmen, are part of the Möklinta Ridge, which continues northward to form Byåsen. To the east lie Arnön, Vidön, Lillön, and Drällsholmen.

Oak, linden, and rosebay willowherb

This section of the Dalälven River lies along the biological boundary of Norrland. Here, oak and linden can regenerate naturally, which they cannot do further north. The islands boast a rich flora. In the extensive stands of common reed and common bulrush or Norrland sedge, the rare marsh marigold clings to the ground. Along the water’s edge, bow sedge and rosebay willowherb grow.

The dominant vegetation here is a deciduous spruce forest. Pine forests grow on the ridges. The abundance of deciduous trees can be explained by recurring floods, as well as mowing and grazing. Aspen and birch dominate. Here and there, there are quite a few oak and linden trees.

Many Species, Including Unusual Ones

The islands are home to many rare species of lichens and wood-decay fungi that thrive on the abundance of dead wood. This area also boasts a very rich insect fauna, where the rare wood-dwelling beetles in particular have attracted attention.

Among all the species, those that benefit from flooding are worth mentioning: the river meadow runner, the beach skin lichen, and the hairy claw moss. Many different species—including insects, birds, mosses, and lichens—benefit from the abundant supply of aspen. On the oak trees, for example, one can find the fungus Rutskinn, which is found only on Vidön in the entire Dalarna region.

The bird life is rich in both species and individuals. Woodpeckers leave a strong mark on the area through nest-building and foraging in the old trees.

Cultural Conditions

The Bysjöholmarna islands are uninhabited, but they have long been of great value as hayfields and pastures. On land-allotment maps from 1801, most of the land is listed as “sva,” “kärrslog,” or “starrslog.” Some areas are called “backe,” which likely refers to rocky, difficult-to-cultivate land that probably contained some forest.

Otherwise, the islands must have been almost entirely open, with the exception of the old oak and pine trees, which are so ancient that they were already there at that time. On Vidön, one area is called “the hill with the barns,” but otherwise there appears to have been no settlement. Haymaking likely ceased as early as the beginning of the century, but grazing continued well into the 1950s.

On Lammön, there was also fairly intensive gravel quarrying, which left large scars on the ridge. However, these areas have begun to regrow with pine trees, so they are not very noticeable today.

Getting to the Islands

The Bysjöholmarna islands can only be reached by boat. Remember that you may only moor your boat for 24 hours. Lammön is a popular destination and the island best suited for leisurely strolls. There is also a marked trail here.

All photos: Anders Heurlin, Dalarna County Administrative Board.