Provide or retain set‐aside areas in farmland

Supporting evidence from individual studies

1. A replicated, site comparison study in 1990–1991 on five arable farms in Hampshire and Wiltshire, UK (Moreby & Aebischer 1992) found that the abundance of caterpillars was similar on fallow set-aside and wheat fields. The number of caterpillars of butterflies, moths and sawflies (Lepidoptera and Symphyta combined) was not significantly different on set-aside (0.4 individuals/sample) and wheat fields (0.7 individuals/sample).  A total of 44 fields on five farms in the first year of the UK’s five-year set-aside scheme (left fallow or drilled with grass) were sampled in June 1990.  In 1991, fifteen fields at two of the farms were re-sampled to evaluate second-year fallow set-aside.  Caterpillars were collected using a D-Vac suction sampler in the headlands of fields, 3 m from the field edge. Five samples of 0.5 m² were taken at each site.

   Study and other actions tested

   Referenced paper

   Moreby S.J. & Aebischer N.J. (1992) Invertebrate abundance on cereal fields and set-aside land - implications for wild gamebird chicks. British Crop Protection Council Monographs, 50, 181-186.

2. A replicated, site comparison study in 1992 in agricultural land in Baden-Württemberg, Germany (Steffan-Dewenter & Tscharntke 1997) found that naturally regenerated set-aside had a higher species richness of butterflies than either set-aside sown with lacy phacelia Phacelia tanacetifolia or cereal crops, and that butterfly species composition changed with set-aside age. Butterfly species richness was higher in naturally regenerated set-aside (11–13 species) than in sown set-aside (7 species) or cereal crops (4 species), but lower than in old meadows (20 species).  Species richness did not differ with set-aside age (11–13 species), but species composition did. Butterfly species found in older set-aside tended to be less migratory, spend longer as caterpillars (1-year-old: 61 days; 4-years-old: 105 days), and have fewer generations/year (1-year-old: 2.5 generations/year; 4-years-old: 1.9 generations/year). In 1992, four fields in each of seven management types were studied: former cereal fields left to naturally develop as set-aside for each of 1, 2, 3 and 4 years, 1-year-old set-aside sown with lacy phacelia, old meadows (>30 years old), and cereal fields (rye Secale cereale or wheat Triticum aestivum). Set-aside fields and old meadows were mown once/year in July. From May–October 1992, butterflies were counted along transects nine times/field.

   Study and other actions tested

   Referenced paper

   Steffan-Dewenter I. & Tscharntke T. (1997) Early succession of butterfly and plant communities on set-aside fields. Oecologia, 109, 294-302.

3. A replicated, paired, site comparison study on 30 arable farms in southern and eastern England, UK (Moreby & Southway 2000) found that stubble set-aside fields had a similar abundance of caterpillars to wheat fields. The number of caterpillars of butterflies, moths and sawflies (Lepidoptera and Tenthredinidae combined; 0.2–0.5 individuals/sample) did not differ between set-aside and wheat fields. Additionally, cutting set-aside (to 10–15 cm) tended to decrease invertebrate numbers (including Lepidoptera) compared to topping it (to 25 cm) or leaving it uncut (data not presented). Set-aside fields were naturally regenerated after harvest. Wheat fields received pesticides. Invertebrates were sampled using a D-Vac suction sampler in 51 set-aside fields and 51 adjacent wheat fields on 30 farms in June–July (year not given).

   Study and other actions tested

   Referenced paper

   Moreby S.J. & Southway S. (2000) Management of stubble-set-aside for invertebrates important in the diet of breeding farmland birds. Aspects of Applied Biology, 62, 39-46.

4. A replicated, site comparison study in 2002 in 12 fields in County Laois and County Kildare, Ireland (Bracken 2004) found that set-aside did not support a higher abundance or species richness of butterflies than arable crop or pasture fields. The abundance of butterflies was similar in set-aside fields (16.3 individuals), arable crop (15.5 individuals) and pasture (14.5 individuals). The species richness of butterflies was also similar in set-aside (6 species), arable crop (4 species) and pasture (6 species) fields. See thesis for abundance of individual species. Four fields of each of three farmland habitats, set-aside, arable crop and cattle-grazed pasture, were studied. Set-aside fields were non-rotational, and had been out of production for at least three years. Set-aside and arable crop fields were paired close to each other on the same farms. From April–September 2002, butterflies were surveyed seven times along one 250-m transect in each field.

   Study and other actions tested

   Referenced paper

   Bracken F. (2004) The diversity of birds and butterflies in Irish lowland landscapes with special reference to the effects of set-aside management on birds in the breeding season.

5. A replicated, site comparison study of 31 rotational set-aside fields in England, UK (Moreby, 2007) found that caterpillar abundance was similar in set-aside fields and uncultivated field boundaries. The number of butterfly and moth caterpillars was similar in set-aside fields and uncultivated field boundaries (data not presented). Caterpillars were sampled in the uncultivated field boundary (0 m) and at 3 m and 50 m in to each of 31 rotational set-aside fields in mid-May (year not given).

   Study and other actions tested

   Referenced paper

   Moreby S.J. (2007) Invertebrate distributions between permanent field boundary habitats and temporary stubble set-aside. Aspects of Applied Biology, 81, 207-212.

6. A site comparison study in 1999–2000 in two agricultural regions in Geneva and Valais, Switzerland (Revaz et al. 2008) found that sites within an intensively cultivated region with set-aside areas had a similar abundance and biomass of butterflies and moths to a traditional, extensively cultivated region. The abundance and biomass of adult butterflies and moths (abundance: 5.2 individuals/site; biomass: 6.9 mg/site) and caterpillars (abundance: 2.4–2.8 individuals/site; biomass: 23.1–28.3 mg/site) in set-aside strips in an intensively farmed landscape was not significantly different from sites in an extensively farmed landscape (adults: 1.5 individuals/site, 3.9 mg/site; caterpillars: 1.5–2.3 individuals/site, 3.9–57.6 mg/site). From 1991–1998, a total of 83 set-aside strips (10-m wide, totalling 19 ha) were established across one 500-ha agricultural region. A second, 360-ha region was extensively cultivated. Between March and September 1999 and 2000, grass-dwelling arthropods (including butterflies, moths and caterpillars) were surveyed by hand-netting along 30-m transects at each of five locations within set-aside strips in an intensive arable region, and six locations along irrigation canals and ditches in an extensively farmed region. Ground-dwelling arthropods (including caterpillars) were sampled for seven days using 15 pitfall traps next to each transect.

   Study and other actions tested

   Referenced paper

   Revaz E., Schaub M. & Arlettaz R. (2008) Foraging ecology and reproductive biology of the stonechat Saxicola torquata: Comparison between a revitalized, intensively cultivated and a historical, traditionally cultivated agro-ecosystem. Journal of Ornithology, 149, 301-312.

7. A replicated, site comparison study in 2008 in a mixed farming region in Hungary (Kovács-Hostyánszki et al. 2011) found that sown set-aside fields had a higher abundance and species richness of butterflies than cereal fields, and this did not change with set-aside age. In set-aside fields both the abundance (28–33 individuals/field) and species richness (7–9 species/field) of butterflies were higher than in winter wheat fields (abundance: 4 individuals/field; richness: 2 species/field). There was no difference between 1-, 2- and 3-year-old set-aside fields (see paper for details). See paper for details of individual species. Seventeen set-aside fields were sown with one legume and two grass species in autumn 2005–2007, had no chemicals applied, and were mown once/year in June. Sixteen winter wheat fields were fertilized (70 kg/ha/year nitrogen), sprayed once/year in spring with herbicide and insecticide, and harvested in June. From May–August 2008, butterflies were surveyed on fixed transects four times in each field. Each field was surveyed for 10, 20 or 30 minutes, depending on field size.

   Study and other actions tested

   Referenced paper

   Kovács-Hostyánszki A., Kőrösi Á, Orci K.M., Batáry P. & Báldi A. (2011) Set-aside promotes insect and plant diversity in a Central European country. Agriculture, Ecosystems & Environment, 141, 296-301.

8. A replicated, randomized, controlled study in 2003–2004 in an arable field in Jokioinen, Finland (Kuussaari et al. 2011) found that second-year set-aside plots sown with less competitive grasses had a higher abundance and species richness of butterflies and day-flying moths than first-year set-aside or second-year set-aside sown with competitive grasses. On set-aside plots sown the previous year with less competitive grasses, both the abundance (30 individuals/1,000 m) and species richness (4.2 species/plot) of butterflies and day-flying moths were higher than in plots sown with competitive grasses (5 individuals/1,000 m; 0.7 species/plot) or plots sown that spring with competitive (2 individuals/1,000 m; 0.5 species/plot) or less competitive grasses (3 individuals/1,000 m; 0.7 species/plot). However, there was no significant difference from plots where competitive (9 individuals/1,000 m; 2.0 species/plot) or less competitive (21 individuals/1,000 m; 2.9 species/plot) grasses had been sown under the crop in the previous year, or from stubble fields (17 individuals/1,000 m; 4.2 species/plot). No butterflies or moths were recorded in cereal plots. In 2003, a 16.5-ha field was divided into four blocks, each containing eight 0.3-ha plots. Plots were assigned to eight treatments: grass mix sown in 2003 and left to develop in 2004, spring barley sown in 2003 followed by grass mix sown in 2004, spring barley sown in 2003 with undersown grass mix which developed in 2004, spring barley sown in 2003 and left as stubble in 2004, and spring barley sown in both years. Two grass mixes, containing more and less competitive species, were used. In June–July 2004, butterflies and day-flying moths were recorded four times, two weeks apart, on one 250-m zig-zag transect through each plot.

   Study and other actions tested

   Referenced paper

   Kuussaari M., Hyvonen T. & Härmä O. (2011) Pollinator insects benefit from rotational fallows. Agriculture, Ecosystems & Environment, 143, 28-36.

9. A replicated, site comparison study in 2009–2014 in eight farm set-asides and two native prairies in Wisconsin, USA (Kleintjes et al. 2017) found that set-aside fields sown with grasses and non-woody broadleaved plants (forbs) had a similar number of butterflies to native prairies in the first year, but lower numbers after 2–5 years. For the first year after establishment, set-aside areas had a similar number of butterflies (8–52 butterflies/200 m) to native prairie (5–42 butterflies/200 m). However, 2–5 years after establishment, the number of butterflies on set-aside (5–20 butterflies/200 m) was lower than in native prairie (22–68 butterflies/200 m). The total number of species recorded on set-aside (31 species, of which six were not seen on prairies) was similar to prairie sites (35 species, of which 10 were not seen on set-aside). In spring 2009, fields (average 6.8 ha) on eight farms enrolled in a set-aside program were pre-treated with glyphosate and seeded with a mix of six grasses and 11 forbs using a no-till seed drill. They were compared with two native dry sand prairies in a powerline right-of-way, managed to suppress woody vegetation. From May–August 2009–2012, butterflies were surveyed 2–4 times/year on one 200-m transect/farm. In 2013–2014, just four farms and the two native prairies were surveyed twice/year.

   Study and other actions tested

   Referenced paper

   Neff P.K., Locke C. & Lee-Mader E. (2017) Assessing a farmland set-aside conservation program for an endangered butterfly: USDA State Acres for Wildlife Enhancement (SAFE) for the Karner blue butterfly. Journal of Insect Conservation, 21, 929-941.