Magda Sikora

Abstract The aim of the work described here has been to determine the long-term impact of human activities on wetlands. Consideration has been given to such aspects as the development of the drainage network, peat extraction and restoration. The study selected two Nature Reserve wetlands, i.e. the Pobłockie Bog and Kurze Grzędy, both located in the Baltic Sea basin in northern Poland. Both areas were subject to a search for relevant literature and sources in the form of historical maps from the last century, as well as contemporary topographic and thematic maps. Supplementary fieldwork was also carried out (in 2013), as regards the verification of the existing hydrographic and hydraulic engineering network in the area under investigation. The greatest past impact on the analysed wetlands was exerted by a network of ditches and irrigation channels. This revision of the hydrographic network caused departures from the natural water cycle, as drainage became excessive in the face of the loss of the natural drainage system. The consequence was drying and rotting of bog surfaces, with the replacement of original plant species with those of differing requirements as regards hydrological regimes. Attempts to restore more natural water relations to the bogs have been made recently, with appropriate treatment raising the level of groundwater, in order to encourage improved functioning. A measurable effect of this is a reduced number of ditches and irrigation channels, for example from 13.3 to 1.48 km since 2000 in the case of Pobłockie Bog. Hydrographic change associated with drainage of peat deposits is considered the most important reason for changes in swamp habitats, and notably their vegetation. Some plant species have been replaced by others, with certain plant species requiring damp conditions (notably cross-leaved heath Erica tetralix) disappearing altogether with the lowering of the water table. Long-term drainage and the construction of new drainage ditches have led to the encroachment of bog woodland on the originally treeless bog. The effect is a loss of large bog areas, replaced by forest communities. The analysed bogs present clearly visible changes in the hydrographic network. Over the years the formerly waterlogged area has been transformed by human activity from a naturally treeless wetland to a desiccated region with only a small amount of water. The area was drained so that land for agriculture could be acquired, but the area was also used as a source of peat. With the passage of time, human overexploitation of the area ceased, and the approach taken to wetlands today is entirely different from that in place a few decades ago. The uniqueness of these kinds of wetlands has come to be appreciated, and an attempt has thus been made to restore a more natural appearance and function to the areas under study, among others. The first effects of the attempts to repair the environment in the area can now be seen in increasing soil moisture, a shallower water table, and an increased area with permanently visible standing water. Such a rapid pace of change in water conditions has been achieved, not only through human activity, but also by way of a natural factor that is the activity of beavers (Castor fiber).

Magda Sikora

Articles