Bavarian Forest
National Park

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Renaturation of mires

Renaturation of mires (Photo: Hans Kiener)

Bog forests and open mires belong to the ecologically most valuable habitats in the national park. They host many rare and highly specialised species and as such are genuine biodiversity hotspots. In addition, under the Habitats Directive they are defined as priority habitats and thus particularly worthy of protection.

The duty to maintain or renaturalise derives from both the Bavarian Nature Conservation Law and the National Park Regulation. Detailed measures are described in the Natura 2000 Management Plan and in the National Park Plan Annex “Renaturation"

In the case of many drained mires it can be assumed that the earlier damaging interventions will balance themselves out in foreseeable periods of time. In fens containing trees in the natural zone it is to be expected in many cases, that sooner or later through dying and collapse of the current generation of trees the drainage system will become ineffective without human assistance. As a rule renaturation is not necessary here.

In the drained fens on the edge of the national park a one off opportunity arises in the emergence of cleared areas in the course of bark beetle management to water these areas again, without neglecting the required care of the surrounding private forests.

Numerous peat bogs in the national park were more or less successfully drained in the last century, with the consequence that their plant population has been altered significantly. In such drained peat bogs where there is no remarkable tree growth, an extremely long timeframe is likely to be needed for natural regeneration. Here, targeted measures should speed up the regeneration of the mires.

Mire areas make an important contribution to climate protection, in that they store large amounts of carbon in their peat. The drainage of the mires leads to mineralisation of the peat, which produces harmful carbon dioxide. Renaturation measures can stop this development, or at least slow it down. If the renaturation of the mire is successful and it becomes a “growing peat bog", it makes an active contribution to storing carbon and thus reduces the CO² content in the air.

The Bavarian Forest National Park acts in accordance with the usual processes in other mire areas, whereby after the preparatory installation of drain blocking devices, ditches are filled with chopped and stored timber and brushwood acquired in the course of bark beetle management, so that the natural hydrological balance can be regulated again and a natural peat moss cover can grow. According to the most recent findings and current experiences a further depletion of the peat can be avoided and to a certain extent a further wetting can be attained, but not a revitalisation as growing peat bog. For this reason in 2008 a method was applied for the first time, in which drainage ditches were dammed by solid, elevated transverse structures and the stored water channelled laterally in to the bog areas. If this method proves successful then follow up works will begin on other renaturated mires.