Reduce field size (or maintain small fields)

Supporting evidence from individual studies

1. A before-and-after study in 1987–1991 on an arable farm in Saarland, Germany (Reck 1993) reported that reducing field size (by increasing the length of field edges), in combination with increasing the area of meadows and field margins, increased the species richness of butterflies and burnet moths. Results were not tested for statistical significance. Four years after field edges were increased and meadows and field margins created, 24 species of butterflies and burnet moths were present on the farm, compared to 20 species before creation. Marbled white Melanargia galathea were present at eight survey sites in 1991, compared to one site in 1987. In 1987, on an intensively managed 30-ha farm with large fields, the length of field edges was increased from 7,200 m to 17,420 m. Semi-natural meadows and field margins were created by sowing regional plant species including rosebay willowherb Epilobium angustifolium, danewort Sambucus ebulus, heather Calluna vulgaris and regional meadow seeds. From May–August 1987–1988 and 1991, butterflies and burnet moths were surveyed at sample sites (number not specified) across the whole farm.

   Study and other actions tested

   Referenced paper

   Reck H. (1993) Creating new habitats on intensively used farmland, the ‘Pappelhof’ in Saarland: A project supported by the German government. Natur und Landschaft: Zeitschrift fur Naturschutz und Landschaftspflege, 68, 394-403.

2. A replicated, site comparison study in 2003–2004 on 24 arable farms in Scania, Sweden (Rundlof & Smith 2006) found that farms with smaller fields in more diverse landscapes had a higher abundance and species richness of butterflies and burnet moths than farms with larger fields in intensively farmed landscapes. Both the abundance (3.6–4.5 individuals/50 m) and species richness (1.4–1.6 species/50 m) of butterflies and burnet moths on farms with small fields in more diverse landscapes were higher than on farms with larger fields (abundance: 0.4–1.7 individuals/50 m; richness: 0.3–0.9 species/50 m). Twelve arable farms with small fields (average: 31,600 m²) in diverse landscapes (15% arable land, 19% pasture), and 12 arable farms with large fields (average: 60,200 m²) in intensively farmed landscapes (70% arable land, 3% pasture) were selected. From June–August 2003 and May–August 2004, butterflies and burnet moths were surveyed 5–6 times/year along 400–750 m routes along cereal field boundaries. Individuals occurring 5 m into the crop and in adjacent 2-m uncultivated margins were counted.

   Study and other actions tested

   Referenced paper

   Rundlöf M. & Smith H.G. (2006) The effect of organic farming on butterfly diversity depends on landscape context. Journal of Applied Ecology, 43, 1121-1127.

3. A replicated, site comparison study in 2009 in two arable farmland areas in Opava-Raciborz, Czech Republic and Poland (Konvicka et al. 2016) found that land farmed with smaller field sizes had twice as many individual butterflies and butterfly species than land farmed with larger field sizes. Both the abundance (14 individuals/visit) and species richness (3 species/visit) of butterflies were higher where field sizes were small (in Poland) than where field sizes were large (in the Czech Republic; abundance: 6 individuals/visit, richness: 2 species/visit). See paper for individual species results. In Poland, the land had been managed as small, family farms for decades, whereas in the Czech Republic the field sizes were on average 10-times larger than in Poland (average field sizes not given). From May–September 2009, butterflies were recorded for five minutes, once/month, in a 10-m diameter circle at each of 20 points/country. Survey points were within 500 m of the state border, at least 200 m apart, and adjoined more than one crop.

   Study and other actions tested

   Referenced paper

   Konvicka M., Benes J. & Poláková S. (2016) Smaller fields support more butterflies: Comparing two neighbouring European countries with different socioeconomic heritage. Journal of Insect Conservation, 20, 1113-1118.

4. A replicated, site comparison study in 2009–2011 in 133 mixed farms in the Central Plateau, Switzerland (Stoeckli et al. 2017) found that farms with more, smaller fields had a higher abundance, but not species richness, of butterflies than farms with fewer, larger fields. The abundance of butterflies on farms with more, smaller fields was higher than on farms with fewer, larger fields, but there was no difference in butterfly species richness (data presented as model results). A total of 133 farms (17–34 ha, 13–91% arable crops) were surveyed. From May–September 2009–2011, butterflies were surveyed six times on 10–38 transects/farm, totalling 2,500 m/farm. Each transect ran diagonally through a single crop or habitat type, with all available crops and habitats represented. All visits to a farm were completed in a single year, and the species richness was summed across all visits. Total abundance of butterflies was calculated from the number recorded in each habitat, and the availability of each habitat across the farm.

   Study and other actions tested

   Referenced paper

   Stoeckli S., Birrer S., Zellweger-Fischer J., Balmer O., Jenny M. & Pfiffner L. (2017) Quantifying the extent to which farmers can influence biodiversity on their farms. Agriculture, Ecosystems & Environment, 237, 224-233.

5. A replicated, site comparison study in 2010–2014 in 50 agricultural areas in the Swiss Plateau, Switzerland (Zingg et al. 2018) found that landscapes with smaller average field sizes had a higher abundance, but not species richness, of butterflies than landscapes with larger fields. Agricultural areas with average field sizes <1.5 ha had a higher abundance, but not species richness, of butterflies than areas with average field sizes >1.5 ha (data presented as model results). Fifty mixed farming areas (1 km²) were selected which had average field sizes from 0.55 to 2.70 ha. Butterflies were surveyed seven times along a 2.5-km transect through each 1-km² area in one of five years (2010–2014).

   Study and other actions tested

   Referenced paper

   Zingg S., Grenz J. & Humbert J. (2018) Landscape-scale effects of land use intensity on birds and butterflies. Agriculture, Ecosystems & Environment, 267, 119-128.