Finland weighs defence benefits of restoring drained mires

Finland is examining whether restoring drained mires near its border with Russia could support national defence, while a 20-year study shows that the ecosystems are still recovering, Yle reports.

Researchers are reviewing the long-term results of mire restoration in the Elimyssalo nature reserve in Kuhmo, near the Russian border. Forest ecology professor Anne Tolvanen began monitoring the restoration project there 20 years ago.

The mire was drained in the 1970s to enable forestry. After Elimyssalo became part of Natura, the European Union’s nature protection network, authorities decided to restore a total of 75 hectares of mires.

The restoration aimed to increase biodiversity, bring back species associated with natural mires and reduce the water pollution caused by drainage ditches. Trees that had grown after drainage were removed, and the ditches were filled so that water would remain on the mire.

Before the work began, researchers established measuring points to record trees, vegetation and groundwater levels. They also took photographs for long-term monitoring. Each restored mire was given 20 to 30 study plots.

Twenty years later, researchers are systematically revisiting every measuring point. The water level has risen and mire vegetation has begun to return, but Tolvanen says the recovery is still far from complete.

“It looks quite like a natural pine mire to me,” Tolvanen says. Without the old, blocked drainage ditches, which are now difficult to see, it would be hard to tell that the area had ever been drained.

Recovery does not proceed steadily. Young trees can begin growing on a mire, increasing water evaporation and slowing the return to wet conditions. This has also happened at Elimyssalo.

Tolvanen says the growth of young trees has recently been observed on natural mires as well. She says this may be linked to higher average temperatures and increased drought.

Mires in Finland began to be drained extensively in the 1950s to make them suitable for growing forests. Drainage reduced biodiversity and released carbon dioxide from the soil. Restoration began experimentally in the 1990s and became more widespread in the 2000s, supported by funding from the EU’s Life programme.

Restoration was initially viewed mainly as a way to increase biodiversity. Its climate effects and possible defence benefits have since also become part of the discussion, although its climate benefits are not considered straightforward.

A working group from the environment and defence ministries published a report on the defence implications in June. It said restoring mires along the border with Russia could provide significant national defence benefits by making them wetter and more difficult to cross, including for heavy vehicles.