Landskap i förändring: Våtmarker i Helsingborgs kommun 1820-2016

Sammanfattning: This thesis discusses the landscape changes of Helsingborg municipality in Scania, southern Sweden. The aim of this thesis is to compare the occurrence of wetlands in the early 1800’s with the contemporary occurrence. The findings will be presented from three angles: the total wetland area, presence of different wetland types, and spatial distribution of the wetlands. To assess this change over time is important, since wetlands are involved in the hydrological cycle, and serve to sustain biodiversity. As the wetland distribution changes, such ecosystem services might also get altered. By using a GIS programme, I compared data of past and contemporary wetlands. The wetlands of the early 1800’s are obtained from the military map The Scanian Recognisance map (1812-20). The County Board of Scania, the Swedish National Land Survey, and Helsingborg municipality have mapped the contemporary wetlands. The results show that just under 0.3 % of Helsingborg municipality is wetland in 2016. 200 years ago, 11 % of the area was mapped as wetland. There were 131 wetlands in 1820, and 83 in 2016. The wetland types mire and swamp were tremendously reduced in area and in share of the total. Artificially created wetlands constitute almost 60 % of the total wetland extent 2016. The median distance between wetlands almost doubled over the 200 years, from 220 m in 1820 to 466 m in 2016. The reduced number of wetlands in 2016, as well as the reduced total area, implies fewer habitats for wetland biota. Also, the wetland’s water retention capacity, and potential for water quality improvement, is reduced. The changes in wetland types and distribution have negative effects on the local biota and hydrology, whereas the contemporary work with creation of wetlands is a means to mitigate eutrophication, create habitat for wetland species, and make valuable space for recreation.