Epsilon Archive for Student Projects

Abstract

Biodiversity is under threat in Sweden and many species are on the brink of extinction. This is mainly due to the large-scale drainage projects during the 19th and 20th century and the increasingly intensive land use in agriculture and forestry. The intensive land use with sharply defined boundaries between the production units has in many cases led to either overgrazing or overgrowing. As a result many species have been pushed back to "leftover" habitats like shooting ranges, power line corridors, roadsides, dumps, embankments and other similar areas. Therefore the question has been raised, wether or not it is needed to re-introduce large herbivores into the wild in order to maintain the biodiversity that is related to the extensive land use.

This study has been conducted as a literature review and will focus on the European bison’s (Bison bonasus) impact on other species and biodiversity; conditions for reintroducing large herbivores in Sweden are also discussed.

Free roaming populations of large herbivores have a positive impact on plants, insects and many other groups of organisms. From a societal point of view, there may be conflicts with agriculture and forestry; traffic safety also has to be considered. Therefore fences and wildlife crossings may need to be put up. The long term goal of reintroduction of European bison should be a genetically sustainable metapopulation of approximately 1,000 animals, which requires a minimum surface area of 10 000 km2, which corresponds to 100 * 100 kilometres. From an ecological perspective, it is also important to discuss free roaming populations of wild horses, cattle, woodland reindeer (Rangifer tarandus fennicus), and maybe also sheep and goats as the species with their different niches can contribute to a mosaic of habitats which benefit biodiversity.

Suitable areas of reintroduction require further research. In order to achieve maximum benefits, it is desirable to consider solutions where other species are included. Examples of endangered or nationally extinct bird species sharing habitat with the European bison are the middle spotted woodpecker (Dendrocopos medius), white-backed woodpecker (Dendrocopos leucotos) and the black stork (Ciconia nigra). Including herbivores, woodpeckers and storks in the same project could provide very cost effective results as they are umbrella species for many other species in several different habitats; for example plants and insects in open-land areas, beetles in dead wood and amphibians and mosses in wetlands and swamp forests.

In order to locate suitable sites for reintroduction I had
the national power line system (Stamnätet) in mind; this is unproductive land from an economic point of view. The power line corridors are important habitats and hold many endangered species which presumably would benefit further from extensive grazing. Forest land should be protected at appropriate places in the surroundings, it is also important to increase the proportion of wetlands and swamp forests which will benefit both deciduous trees as well as supply of deadwood. Furthermore power line corridors serve as natural migration corridors between suitable habitats. Suggested areas for reintroduction of European bison are the woodlands of Götaland in the southeast of Sweden and the woodlands of Svealand south of Dalälven.