A complex of shallow, nutrient-rich wetlands south of the town of Outokumpu, surrounded mainly by farmland, but also by young deciduous forests which regularly flood. Areas of formerly quite extensive open, muddy marshes are now overgrown by sedge, grasses and Salix bushes. In shallow water, large beds of reed Phragmites are abundant.
Nationally important for breeding Botaurus stellaris (7-9 males), Circus aeruginosus (5-6 pairs). In 1984, the first evidence of breeding Tringa stagnatilis inwestern Europe was found in the area; it has since bred twice.
Pressure/threats to key biodiversity
Overgrowth of the wetland is a threat. The area suffers from intense hunting pressure in autumn, and fishing also causes disturbance in some parts, especially to Cygnus cygnus and Anser fabalis. Excessive nutrient pollution is a serious threat to the whole site; sewage is no longer discharged there, but the inflow of nutrients from surrounding farmland, especially during spring floods, is heavy. Oxygen-generating equipment was installed in Sysmäjärvi lake some years ago to help address this problem. There are several birdwatching towers in the area.
National None International Partial767 ha of IBA covered by Special Protection Area (Sysmäjärvi).