Land cover changes in Southern Sweden from the mid-Holocene to present day: insights for ecosystem service assessments
Abstract: Climate change and human impact play a huge role in the sustainability and development of ecosystems and the services they offer to societies over temporal and spatial scales. Fossil pollen-based estimates provide unique information on past land cover change, but to date there are not many methods able to create spatially continuous maps and have a fine scale of land cover changes inferred from pollen information. No spatially continuous maps of this type exist for southern Sweden. This studies aim was to evaluate these spatial changes in land cover in Götaland, through a long-term perspective and the related ecosystem services (ES), to determine how land cover may change here going forward and what ES can be expected for society, and how best to manage that land cover to get the most ES for the benefit of future societies. First CORINE land cover data (2012) was mapped in ArcMap 10 representing the present, showing that Götaland is currently 63% forested, 19% arable land and 11% water bodies. Next the Landscape Reconstruction Algorithm (LRA) based on pollen estimates, including pollen records from 41 sites in Götaland covering 25 plant taxa, was used to create land cover maps of the past. To determine the best interpolation method to use with the LRA, 17 methods were assessed in ArcMap for the reconstruction of land cover for five land cover types: conifer forest, broad-leaved forest, shrubs, open land, and arable land, for a period in the past closest to 2012. This involved cross-validation and visual comparison with the CORINE data. Simple kriging with cokriging with an arcsine transformation was determined to be the most suitable method. Spatially continuous maps of land cover were created in ArcMap for 15 time windows in 6 periods: the Mesolithic, Neolithic, Bronze Age, Iron Age, medieval period, and the modern period. These maps were split into 5 counties: Blekinge, Halland, Jönköping, Kronoberg and Skåne for further analysis. The maps showed good concurrence with historical data and other studies from the Holocene for the study site in terms of land cover patterns, with much finer spatial resolution than many other studies. Major land cover patterns were: a decrease in forest cover over the Holocene with an increase in open land and arable land. Intervening periods were somewhat stable with a patch work of land cover types. Forest cover returned in modern times to high levels all over the study site and arable land was concentrated in areas along the coasts. The regional map of Götaland and the more local ones considering the 5 counties were then discussed in terms of changes of ES through time based on the knowledge obtained from an ES assessment matrix for the present. Forests were the main source of ES in the early periods with this decreasing over time with human activities, until modern times where it increases again. ES from open land and arable land become more and more available over the Holocene as technology advances. In intervening periods these improvements in agricultural practices greatly influenced land cover with expansion and contraction of this land cover type and its ES’s due to changes in climate, favourable or not, and other negative impacts on human civilization. The data produced in this Master thesis have a great potential to be further used to assess the respective long-term influences of land-use and climate on the major ES in Götaland. They would therefore be of great interest for effective land management strategies, using for example past disturbance regimes, to face the ongoing and future climate changes.
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