Fingrid to utilise the results of research by Outi Hiltula and Terhi Lensu in the planning of clearing of transmission line areas

Can transmission line areas become “reserves” for degenerated populations of daytime butterflies and plants preferring bogs as their habitat? A pro gradu thesis by Outi Hiltula and Terhi Lensu indicates that transmission line areas serve as an alternative habitat for bog daytime butterflies and plants whose living environments are diminishing. Ditching of bogs and other human activity impair and destroy the living environments and food plants of daytime butterflies which inhabit bogs.
Pro gradu thesis “Voimajohtoaukeiden raivauksen merkitys ojitettujen soiden päiväperhosille ja kasvillisuudelle” (Significance of clearing of transmission line areas for daytime butterflies and vegetation in ditched bogs) made for the Department of Biosciences and Environmental Sciences of the University of Jyväskylä focused on 15 ditched bogs with trees located in transmission line areas and on 5 bogs in natural condition located close to transmission line areas on the 220 kilovolt lines Petäjävesi - Nuojua and Petäjävesi - Haapavesi in the area between Uurainen and Karstula in Central Finland.

Many of the almost 100 regular daytime butterflies in Finland are encountered in bog environments, and nine butterfly species are specialised to live exclusively in bogs. These species are highly bound to their living environment, and bog butterflies do not tend to fly outside their territory. The range of daytime butterfly species inhabiting bogs has declined in recent decades and even disappeared in places. This is mostly due to human activity. Extensive ditching of bogs, peat extraction and intensified management and use of forests have caused most damage. Intensified land use, expansion of housing areas as well as construction of populated areas and traffic areas have also undermined the living space available to butterflies. Other factors which have had a negative impact on the living conditions of daytime butterflies include reduction in the amount of open ditches and headlands, weed control, and abandoning grazing.

A total of 27 daytime butterfly species were found in the area covered by Outi Hiltula’s and Terhi Lensu’s research. All seven species of bog daytime butterflies which fly on even years were discovered. The results show that the number of bog butterfly species and individual butterflies is equal in transmission line areas and natural bogs while other daytime butterflies prefer transmission line areas. Clearing reduces evaporation and shadowing in transmission line areas and increases moisture and amount of light. There were considerably less butterflies in the adjacent reference areas.

“The distinct conclusion to be drawn from this research is that transmission line areas managed through clearing have a positive impact on the preservation of bog daytime butterflies and bog plants,” says Professor Janne Kotiaho, who supervised the research.

A few years ago, Fingrid commissioned a study on the significance of transmission lines for meadow plants and butterflies, which opened a new angle to the importance of transmission line areas in preserving biodiversity. “The current research on bog daytime butterflies indicates that transmission line areas are much more than just a band-like opening in the forest. In many cases, these areas enrich the natural environment by providing a habitat for increasingly rare or endangered plants and insects which no longer can find proper living environments in managed forests or ditched bogs,” says Ari Levula, who is responsible for the clearing of transmission line areas at Fingrid Oyj. He says that the results of the research will be used immediately in the planning of clearing. “Our goal is that the clearing guidelines and clearing intervals are based on information obtained through research. As a result of the earlier study commissioned by Fingrid, we shortened the clearing intervals by approximately one year. The current research shows that there is no reason to use longer clearing intervals at bogs than in areas of mineral soil even though the slower growth of trees in bogs would enable this.”

Janne Kotiaho says that the role of transmission line areas as a part of the natural environment should be studied more extensively. This is why Fingrid and the University of Jyväskylä have launched a joint research project where Fingrid is co-financing Terhi Lensu’s doctoral thesis on the biodiversity impacts of transmission line areas.

Further information:
Ari Levula + 358 (0)30 395 5505, + 358 (0)400 648 522
Janne Kotiaho + 358 (0)50 5946881
Terhi Lensu + 358 (0)40 718 9648