Conservation of insect diversity in semi-natural habitats in Denmark: Effects of management vs. abandonment

Research output: Book/ReportPh.D. thesis

Insects comprise more than half of all known species, and form the biological basis for terrestrial ecosystems worldwide. Despite this, insects remain neglected in ecological and conservation studies nationally and internationally. The overall objectives of this PhD thesis were to investigate how Danish nature conservation efforts in heathlands and forests affect selected insect taxa, and provide knowledge to conserve insect communities and support conservation decisions. Specifically, this thesis explored whether unmanaged heathland (Paper I & II) and forest (Paper III & IV) areas contributed to richer and more diverse insect communities compared to managed areas. In paper I, we investigated how old-growth unmanaged heathland affected the diversity of multiple insect taxa (bees, crane flies, ground beetles, hoverflies and rove beetles) compared to traditional intensive management regimes. The results show contrasting responses of insect taxa, with some taxa preferring bare soil associated to management and some taxa preferring high dense vegetation associated with old-growth areas. In paper II, we investigated how abandonment of heathland management affected ants, which are ecosystem engineers forming and shaping heathland habitats. The results show varying negative effects of management on ant species richness and abundances of organic mound forming species related to decreasing vegetation complexity. However, ants with mineral mounds benefit from grazing and burning, but not from harvesting. In paper III, we investigated how abandonment of forest management affected crane fly diversity in broadleaved forests. The results show that abandonment of forest management increases crane fly species richness and abundance, and that these responses are mediated through changes in edaphic conditions, particularly increased soil moisture and pH. In paper IV, we build on the work conducted in paper III, and expand the experimental design to include forest wetland habitats. The results show that forest wetland habitats provide species rich crane fly communities, and that abandonment of forest management positively affects saproxylic and soil-inhabiting crane fly diversity across dry, drainage ditches and swamp habitats through changes in soil pH, light and moisture as well as increased microhabitat availability. Altogether, the results presented here demonstrate the importance of abandonment of management in structuring insect communities across different habitats and successional stages. To benefit overall heathland insect diversity, we recommend management regimes resetting the succession and exposing bare soil for specialized heathland insects, but also allowing patches of old-growth vegetation stages to develop and conserving existing ones. To benefit crane fly forest communities we recommend reestablishment of natural hydrology and conservation of oldgrowth swamps in combination with abandonment of management.
Original languageEnglish
PublisherDepartment of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
Number of pages143
Publication statusPublished - 2021

ID: 272725853