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.

Popular Abstract

Nature provides us with all we need to survive on this planet. Yet there have been times when the climate has not been so favourable, or we as a species did not yet have the tools to efficiently take advantage of this bounty. Are there ways to see how we faired over time? To see how we impacted the land and how we progressed in terms of our control over nature in the deep past? Nature shows us how. By laying down pollen in lake beds and bogs and storing it in these low oxygen conditions, windows of past vegetation are preserved. Thousands of years later cores taken meters down into these habitats raised this past again.

It is not enough to just count these fossilized pollen samples though to get past vegetation cover. You have to use models specifically made to factor in all the ways the pollen from different species behaved. The most advanced tool to do this today is called the Landscape Reconstruction Algorithm. This model was applied to dozens of pollen records taken from sites all over southern Sweden to produce vegetation estimates for this region throughout the deep past.

Until recently this vegetation cover of the past has been represented in coarse ways. Mapping techniques had not yet been developed to give detail fine enough to be usable to locally based agencies for land management strategies. A mapping software called ArcMap was used in this study along with the above modelled pollen estimates to recreate past land cover in southern Sweden. 17 different methods were trialled comparing todays land cover with that in the near past and the method that compared the best was chosen. This was applied to 15 time periods going back to 7250 years ago. At the same time the services nature provides in the present were compiled for this region, and using the recreated past land cover along with historical data, the same for the past was done.

The maps produced agree well with history, showing past land cover and changes in a detail never produced before for southern Sweden. They were able to show where and when humans first started changing the landscape, opening up the forests. They showed when Bronze Age communities nearly stripped the landscape clear of forest cover. Until climate changes and civilization collapse, mixed with human diseases in the Iron Age put a halt to this progress, bringing the forests back. What was also seen was an increase in agricultural land in the Iron Age when things stabilized, with again the decrease in forest cover until these practises became more efficient, needing less land.

Forests in the deep past provided the most services to people, with this decreasing over time with human activities, until modern times where it increases again. Services from open land and arable land become more and more available as technologies improved. In intervening periods these improvements in agricultural practices greatly affected land cover with expansion and contraction of arable land and its services due to changes in climate, and various impacts on human civilization.

The world is getting hotter and weather patterns less predictable. At the same time the population is continuing to grow and so will need more resources. By using the maps from this study to see how the landscape changed based on human behaviour and climate changes, we can better plan for the future.

• author: O'Dwyer, Robert
• supervisor: Anna Maria Jönsson; Laurent Marquer
• organization: Dept of Physical Geography and Ecosystem Science
• course: GISM01 20192
• year: 2019
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: Geography, Geographical Information Systems, GIS, Physical Geography, Götaland, Landscape Reconstruction Algorithm, Fossil Pollen, Ecosystem Services
• publication/series: Master Thesis in Geographical Information Science
• report number: 109
• language: English
• additional info: Supervisor Laurent Marquer, Research Group for Terrestrial Palaeoclimates; Max Planck Institute for Chemistry, Mainz, Germany
• id: 8997920
• date added to LUP: 2019-11-19 14:00:34
• date last changed: 2019-11-19 14:00:34