Conservation Biology in Agricultural Habitat Islands

During the last 50 yr the Scandinavian landscape has been considerably altered because of changes from traditional agricultural practices to modern and efficient techniques. This change has resulted in large areas of monocultures (e.g., cereals, oil seed) but also abandonment of areas which earlier were used for grazing or hay production. Following this development, common problems for a sustainable biological diversity of agricultural land are habitat disappearance, decrease in habitat quality, influences on dispersal and interspecific interactions and increased importance of stochastic events. The five case studies presented in this paper focus on the effects of modern agriculture on animal and plant populations: 1) Species richness and diversity of carabid beetles were highest along edges between agricultural fields and woodland, and on habitat islands; 2) Bird species number, in relation to abundance, was higher on small than large forest-like habitat islands, due to edge conditions or habitat variability on the small islands; 3) Predation on blackbird nests was higher on small woodland islands than on larger ones, and this was particularly related to young and subordinate breeding blackbirds being forced to choose smaller islands as nesting sites; 4) Traditional agricultural environments supported a richer pollinator fauna than isolated habitat islands in an efficiently utilized agricultural landscape, and as a result of poor pollination seed set was also lower in the latter environment; 5) Grazing is an important factor in the pollination of the rare herb Senecio integrifolius. Even though seed set was positively correlated with population size, grazing may be detrimental to seed production or favourable to seed germination. Generalizing, species in boreal agricultural land are either derived from steppe environments with present source areas within this farmland or from the boreal forests and then often with sink populations within the farmland.