Solitära bin i kulturlandskapet. En undersökning av förutsättningar för den rödlistade arten fibblesandbi (Andrena fulvago) vid 1700-talets slut och dess förutsättningar idag

Abstract

Most studies made on wild solitary bees in recent time shows that their numbers are declining. This essay examines the change in life conditions over time for a red-listed (NT) species of mining bee (Andrena fulvago), reported in 2008 from the Lerdala-area situated in the north eastern part of Västra Götaland-county, Sweden. It also explores the requirements of Andrena fulvago to breed, feed and disperse and their coherence with the human-induced as well as nature given landscape conditions, in order to develop landscape management regimes that support the bees. The condition of the late 18th century in two nearby areas in Lerdala was examined trough digitalized maps from one of the great Swedish land reforms. Other kinds of historic maps were consulted to investigate the change over time. A literature study was performed on solitary bees in general, as well as the particular species and a minor field-study was made to explore today’s landscape. The historic maps reveal a typical three-field rotational agricultural system in the first area and a grazed scanty forest common in the second area. Mining bees need sun-exposed sandy soil to build nests, a fair amount of hawkbit flowers, structure-forming landscape element for warm micro-climate and connection to similar habitats for the sake of gene replacement - all of which would have been common here in the 17-hundreds. The fact that many structure-giving fences and small stony fields of the field rotational system has turned into rational agricultural land and also that the large areas of open forest-commons nowadays are dark and overgrown are negative changes for the solitary bees. There are still some positive landscape elements left in the two areas, such as a few open sandpits and sandy slopes where the turf is torn by tramping domestic cattle and/or recreational humans. Management regimes such as making sun exposed sandpits under the power line that connects the two areas, planting hawkbit flowers and a resumption of the forest grazing in the second area is proposed bee conserving measures in the area.