Abstract
Introduction and goals: The world’s population is now passing 8 billion, and urbanisation is one of the main threats to biodiversity globally. Oslo, the capital of Norway, has densified considerably within the city zone during the last decades. The landscape effects on biodiversity of urbanisation in Oslo, however, is not well known. The aim of this master thesis is therefore to: 1) Map and quantify the vegetation changes from 1980s to 2021 2) Interpret and discuss the ecological impact of the registered changes, and 3) Increase the understanding of the process of urbanization with respect to vegetation changes and nature management. Material and methods: To achieve the aim, detailed vegetation maps (1:10 000) from Oslo, published in the early 1980s, were digitized and remapped in 2021. The three selected vegetation maps from Oslo, represent an east-west gradient, covering the map sheets of Grorud, Grefsen and Holmenkollen. The protected rangeland forest surrounding Oslo (Oslomarka) was excluded. The remapping was done in-situ with aerial photos, with QGIS in a field-computer with GPS. Land cover transformations and area statistics were estimated using QGIS, whereas analyses on ecological impacts were measured using landscape ecology metrics from FRAGSTATS. Results: Within the re-mapped parts of Oslo, between 1980 and 2021, large areas with vegetation types were lost to urbanisation. Cultivated land, bilberry spruce forests, abandoned species rich meadows and low herb spruce forest decreased most in terms of area. In terms of percentage reduction, moist meadow, weeds, cultivated land and abandoned species rich meadows were most reduced. For the landscape metrics, many index values were reduced from 1980 to 2021. For the class indices, the values show clear directions. The total area of each class (CA) and the mean patch area (AREA_MN) decrease, whereas the mean of Euclidean nearest-neighbor distance (ENN_MN) increases. Housing, apartment buildings, golf courses, industrial areas and business and office premises are the urban types that has expanded most in terms of area. Discussion: The loss of cultivated land is probably of minor importance for biodiversity conservation, except when there is a trajectory towards rewilding, which is positive in terms of management. Most other losses of vegetation types will influence the capability of sustainable management of biodiversity. Noticeable, the other vegetation types have smaller and fewer polygons, which is lowering the connectivity and increasing the fragmentation.