Story | 05/17/2013 09:34:00

Marshland restoration as a standard approach

Sami Oksa

Marshes are ecosystems that produce peat. Peat is partly composed of non-biodegradable biomass made up of plant materials that do not decompose in anaerobic conditions.

The high number of marshlands is one of the characteristics of the Finnish environment – a third of the country's surface area is marshes and peatlands. Marshes produce peat at approximately ten cubic metres per hectare, as the annual growth in peat thickness is somewhere around one millimetre. Forest drainage was introduced in the post-war period and reached its peak after the 1950s. Practically no new drainage ditches have been dug since the 1990s, and the early 2000s saw a strong move toward restoration of marshland nature.

In fact, the industry has paid particular attention to nature conservation from the 1990s, digging almost no new drainage ditches. Land with a lower tree production potential and marshlands, valuable for biodiversity, have long been excluded from ditch network maintenance projects as a general guideline. This is also a criterion of PEFC certification.

The current Finnish Forest Act, from 1997, includes provisions for the protection of marshland environments. Natural fens to the south of Lapland, luxuriant woodlands and open mires are still covered by the regulations of the Act. The new forest act draft also defines Lapland fens as well as cloudberry and wood horsetail areas as conservation sites.

By diggers and man-power

Restoration aims to return marshlands to their natural, pre-drainage state, and it has become the standard approach in recent years. Restoration work has been carried out both by diggers and workers. On some sites, ditches have been filled using diggers alone, while elsewhere labour has been used to construct dams from materials found nearby. This raises the water level and restarts the paludification process.

In collaboration with Birdlife Finland, UPM has been working on the restoration of a marshy area it owns in Keuruu, creating dams in ditches to stop the water flow and boost the paludification process. We also removed trees grown in nearby areas after the ditches were dug. As we reduce the water-evaporation effect of trees, more water starts to collect in marshy areas.

Another aim of restoration work at Keuruu was to strengthen the willow grouse population that had dwindled in the south of the country. The growth of trees resulting from ditches had reduced the habitat suitable for willow grouse, and the project aims to reverse this development by removing trees and raising water levels. In fact, some sightings have already been reported since the start of the restoration work; one male bird, for instance, was seen in full courtship display on top of a dam.

However, marshland restoration should not always be taken for granted, as highly decayed peat may cause leakage into waterways in areas where major restoration projects are carried out. New waterlogging of terrain can also cause other effects, such as increases in the phosphorus load. Therefore, marshland restoration should be considered and planned carefully, starting from the selection of sites, to avoid any undesirable consequences. Nature conservation work is not always simple or free from emissions or leakages.