The water is heavily decorated by the wetlands plant known as the common reed. This plant is a good indicator of an abundance of nutrients (nitrate and phosphate) in the water. As a rule, this reflects contamination by agricultural run off or sewage. But, reeds also help to counteract this contamination. The reed has its own “treatment plant” as it takes up nitrate from the water through its roots and releases nitrogen gas to the atmosphere.
In many cases the extra nutrients from agriculture stimulates biological production in the water, such that the plant- and animal life becomes both more abundant and more diverse. But, in Lake Bjellandsvatnet, so much vegetation had grown in that the living conditions for several species had become threatened.
In 1995, Lake Bjellandsvatnet was protected as a nature preserve, mainly because of its birdlife. It was the responsibility of the environmental regulatory agencies to ensure that the conditions in the preserve were maintained at the same level as they were when the lake became a nature preserve. But, one could clearly see that the reeds grew so dense that the area was no longer suitable for ducks and other swimming wetland birds.
In 1996, therefore, a channel was dug through the thickest part of the reeds on the east side of the lake. It was not a pretty sight the first few years afterward, but the measure was successful. Living conditions improved for several types of water birds, and after five years, there was scarcely anything to be seen of the channel.
Today there are good living conditions for several types of ducks, such as the mallard, teal and the Eurasian wigeon. In 1979, the rare horned grebe was found nesting in Sveio for the first time ever in southern Norway. In addition, the area represents the northern boundary for the reed warbler’s nesting distribution in Norway. In the winter, swans and Canada geese are a usual sight.
A bird observatory was built at Lake Bjellandsvatnet in 2001.
