Individual study: Organic farming increases the diversity and abundance of wild bees on annually mown fallow strips in Soester Boerde, Leine Bergland and Lahn-Dill-Bergland, Germany
Holzschuh A., Steffan-Dewenter I. & Tscharntke T. (2008) Agricultural landscapes with organic crops support higher pollinator diversity. Oikos, 354-361
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Convert to organic farming
Also in the same study, Holzschuh et al. (2008) report higher bee abundance and diversity on permanent fallow strips next to organic winter fields, compared to fallow strips next to conventional wheat fields. On average, 2.6 m wide annually mown fallow strips next to organic fields had 6.3 bee species, 8.5 bumblebee individuals and 2.6 solitary bees/100 m in total over four surveys, compared to 4.0 species, 3.7 bumblebees and 1.1 solitary bees/100 m on strips next to conventional fields.
Create uncultivated margins around intensive arable or pasture fields
A replicated paired site comparison study in 2003 in three regions of Germany (Holzschuh et al. 2008) found that 21 uncultivated fallow strips adjacent to organic wheat fields had an average of 6.3 bee (Apidae) species, 2.6 solitary bee individuals/100 m2 and 8.5 bumblebee Bombus spp. individuals/100 m2/. Uncultivated fallow strips adjacent to conventional wheat fields had an average of 3.9 bee species, 1.1 solitary bee individuals/100m2 and 3.7 bumblebees/100m2. Bee species richness was 60% higher on uncultivated strips adjacent to organic wheat fields than those adjacent to conventional wheat fields, and had 136% more solitary bees and 130% more bumblebees. Strips adjacent to organic wheat fields also had more flowering plant species and higher flower cover. Species richness and abundance of bees in fallow strips appeared to be limited by foraging resources, which were more abundant when adjacent fields were organic. However, only bees that gather pollen from a range of plants were found on fallow strips during surveys. Specialist bees did not appear to benefit from fallow strips, suggesting that they do not completely compensate for missing semi-natural habitats. Bees were surveyed along 100 m transects four times in May-June 2003 in 42 paired fallow strips adjacent to organic/conventional fields. Flowering plants were surveyed in bee transects and in two transects along the centre and edge of the adjacent field. All fallow strips were mown once a year, with an average width of 2.6 m.