PROJECT DESCRIPTION
BACKGROUND
The "Wieden en Weerribben" form the biggest low-lying peat bog complex in north-western Europe. Peat excavation over a period of centuries has created a linear pattern of ridges where the peat was dried and open ditches from where it was cut. Aquatic plants that gradually took hold in the ditches have evolved into reed beds, quaking bogs and, eventually, marshy woodland. This activity produced a particularly varied landscape with rich fauna. It has between 20 and 30 breeding pairs of bittern, the largest colony in the EU of the pond bat (Myotis dasycneme) and black tern (Chlidonias niger) among other species. In the second half of the twentieth century this ecosystem was threatened, mainly as a result of more intensive farming. The water table in the surrounding polders was lowered, with the result that the low-lying bog areas dried up, the reed beds became acidified, and, in many places, nitrate-rich water drained from the polder was allowed to come into contact with the peat ditches. This considerably accelerated the natural process whereby rich low-lying bog biotopes changed into marshy woodland with poor biodiversity. Although a number of measures subsequently improved the quality of the water, the ecological clock would have to be turned back in order to stimulate the succession which determines the biodiversity of low-lying bogs. For every hectare which becomes marshy woodland, a hectare of open water or young reedbeds needs to be created. Either the acidified top layer of peat is removed in order to restore reedbeds with a variety of flowering plants, or the floating vegetation in the ditches is completely removed, creating stretches of open water. Every piece of land benefiting from 'cyclical management' has to be rejuvenated once every 30 to 100 years. This was tried in the 1980s with the help of Community funds made available via the ACE programme. It was discovered that it was preferable not to leave the dredged material in the vicinity. Unfortunately, such transport operations would considerably increase the cost of cyclical management, which is already expensive because of the intensive use of labour and equipment.
OBJECTIVES
The beneficiary, Natuurmonumenten (de Wieden) would join forces with the public forestry organisation Staatsbosbeheer (de Weerribben) to achieve a cyclical management of more than 100 ha and the necessary steps to improve the ratio between the different stages in the succession. As part of the project, an oxidation test would be conducted to determine whether by allowing the dredged material to compact on the spot the high cost of transporting it could be reduced. Lower transportation costs would make the cyclical management more feasible. In addition to the environmental benefits, the rejuvenation of the ecosystem was intended to benefit the local reed cutters (who are an important part of the local economy), commercial fish farming (improved conditions for breeding) and the possibilities for recreation (a more attractive landscape).
RESULTS
The project successfully restored open waters, young reedbeds and calcareous fens. In total more than 100 ha were restored. Legal and administrative procedures to obtain permits, however, resulted in delays to most of the projects in Flanders and The Netherlands. The procedures also incurred high costs. Restoration work resulted in a good conservation status of rare and endangered habitats such as quaking bogs with great fen sedge (Cladium mariscus). It also helped consolidate the Natura 2000 network through the development of a dense network of plots of endangered habitats and species. Restoration also increased the mobility of the species thus resulting in bigger populations. As part of the project, a peat oxidation experiment was carried out. In the experiment, the top layer of floating fen vegetation (‘kragge’) is cut away by machines, flipped over like a pancake and left to dry in long bands of material. This allows the peaty material to oxidise. The leftovers can then be removed to the depot. While the experiment appears to have been successful, further monitoring and a precise financial evaluation are necessary Finally, the project aided the development of new equipment and know-how including the kraggevreter and watermaster. The results of the project could be applied to other similar sites in Western Europe with the same conservation and management problems. The project successfully restored open waters, young reedbeds and calcareous fens. In total more than 100 ha were restored. Legal and administrative procedures to obtain permits, however, resulted in delays to most of the projects in Flanders and The Netherlands. The procedures also incurred high costs. Restoration work resulted in a good conservation status of rare and endangered habitats such as quaking bogs with great fen sedge (Cladium mariscus). It also helped consolidate the Natura 2000 network through the development of a dense network of plots of endangered habitats and species. Restoration also increased the mobility of the species thus resulting in bigger populations. As part of the project, a peat oxidation experiment was carried out. In the experiment, the top layer of floating fen vegetation (‘kragge’) is cut away by machines, flipped over like a pancake and left to dry in long bands of material. This allows the peaty material to oxidise. The leftovers can then be removed to the depot. While the experiment appears to have been successful, further monitoring and a precise financial evaluation are necessary Finally, the project aided the development of new equipment and know-how including the kraggevreter and watermaster. The results of the project could be applied to other similar sites in Western Europe with the same conservation and management problems.
