Increase grazing intensity or cutting frequency on grassland

Supporting evidence from individual studies

1. A site comparison study in 1994 in 19 traditional hay meadows in Bavaria, Germany (Dolek & Geyer 1997) found that the abundance of all butterflies, and of threatened species only, was lower in a more intensively grazed meadow than in extensively mown or grazed meadows. A meadow which was grazed throughout the summer had fewer butterflies of all species, and of threatened species alone, than meadows grazed for a few weeks/year or mown once/year (data not presented). However, the extensively managed meadows had a higher abundance and species richness of butterflies than three abandoned meadows. Nineteen meadows, which had been managed in the same way for at least 5–20 years, were compared. One former hay meadow was grazed by sheep throughout the summer (intensive management), nine meadows were extensively grazed with sheep, cattle or horses for a few weeks each summer, six traditionally managed hay meadows were mown once/year in July or early August, and three meadows were not managed (abandoned). From June–August 1994, butterflies were surveyed along a fixed transect five times in each meadow.

   Study and other actions tested

   Referenced paper

   Dolek M. & Geyer A. (1997) Influence of management on butterflies of rare grassland ecosystems in Germany. Journal of Insect Conservation, 1, 125-130.

2. A replicated, site comparison study in 1996 in 18 grasslands in Schleswig-Holstein, Germany (Kruess and Tscharntke 2002) found that species richness and abundance of adult butterflies and burnet moths at intensively grazed sites was lower than at sites with low or no grazing, but the responses of caterpillar richness and abundance to grazing intensity were mixed. Butterfly species richness and abundance were lower at intensively grazed sites (average richness = 2; average abundance = 1 ) than low intensity grazing (average richness = 4; average abundance = 8) and ungrazed (average richness = 7; average abundance = 21) sites. Caterpillar species richness was statistically similar in intensively grazed (average = 2) and low intensity grazing (average = 4) sites, but lower in both than in ungrazed sites (average = 7). Caterpillar abundance was statistically similar between intensively grazed (average = 1) and low intensity grazed (average = 9) sites, but intensively grazed sites had lower abundance than ungrazed sites (average = 12). Intensively grazed sites (6) had an average stocking density of 1.4 cattle/ha annually from May–November, low intensity grazed sites (6) had an average density of 5.5 cattle/ha annually from April–October, and ungrazed sites (6) had not been stocked for 5–10 years. From May–September 1996, at each site separate transect walks were conducted once monthly for adult butterflies and burnet moths (45-minute transects) and caterpillars (45-minute transects in grazed sites and 60-minutes in ungrazed sites).

   Study and other actions tested

   Referenced paper

   Kruess A. & Tscharntke T. (2002) Grazing intensity and the diversity of grasshoppers, butterflies, and trap-nesting bees and wasps. Conservation Biology, 16, 1570-1580.

3. A before-and-after study in 1980–2006 in a forest-steppe landscape in the White Carpathians, Czech Republic (Konvicka et al. 2008) reported that increasing cutting frequency on grasslands decreased the abundance of Danube clouded yellow Colias myrmidone. Results were not tested for statistical significance. In the first year of increased cutting, only 11 observations of 26 individual Danube clouded yellows were recorded, compared to 2,345 records in the eight years immediately prior to increased cutting, and 3,838 records in the previous 15 years. In the second and third years of increased cutting, only five and two individuals were recorded, respectively, and these observations were from abandoned pasture outside of the reserves. From the 1970s to the mid-1990s, infrequent mowing and scrub removal were used to prevent succession on 2,457 ha of grassland reserves. From the mid-1990s to 2004, reserves were mown uniformly using national funding, and since 2004 this was increased to two cuts/year on all but 355 ha of grassland. Historical butterfly records were compiled for 1980–1994 and 1995–2002, and butterflies were recorded 3–6 times/year on systematic surveys at prescribed sites.

   Study and other actions tested

   Referenced paper

   Konvicka M., Benes J., Cizek O., Kopecek F., Konvicka O. & Vitaz L. (2008) How too much care kills species: Grassland reserves, agri-environmental schemes and extinction of Colias myrmidone (Lepidoptera : Pieridae) from its former stronghold. Journal of Insect Conservation, 12, 519-525.

4. A replicated, randomized, paired, controlled study in 2005–2007 in four tallgrass prairies in Missouri, USA (Moranz et al. 2014) found that increasing cattle grazing reduced the abundance of regal fritillary Speyeria idalia, particularly after recent burning. The number of regal fritillaries in grazed prairie (0–14 individuals/ha) was lower than in ungrazed prairie (1–25 individuals/ha) throughout the summer. However, the difference was greatest in prairies which had been burned earlier the same year (grazed: 0–2 individuals/ha; ungrazed: 3–22 individuals/ha). From 2000–2004, four remnant prairies were burned on rotation and occasionally hayed or lightly grazed. In 2005, half of each prairie was randomly assigned to one of two treatments: grazing and rotational burning, or rotational burning only. Each half was sub-divided into three plots (20–34 ha), which were randomly assigned to be burned in either March 2005, 2006 or 2007. The grazed sites were stocked with cattle (2.2 ha/animal unit) annually from April–August. From June–July 2006–2007, butterflies were surveyed three times/year on a transect through each plot.

   Study and other actions tested

   Referenced paper

   Moranz R.A., Fuhlendorf S.D. & Engle D.M. (2014) Making sense of a prairie butterfly paradox: The effects of grazing, time since fire, and sampling period on regal fritillary abundance. Biological Conservation, 173, 32-41.

5. A replicated, paired, site comparison study in 2014–2015 on a farm in Galilee, Israel (Berman et al. 2018) found that heavily grazed paddocks had fewer spring webworm Ocnogyna loewii caterpillar nests than moderately grazed paddocks, but grazed paddocks had more nests and solitary individuals than ungrazed paddocks. After 20 years of grazing, the number of caterpillar nests in heavily grazed paddocks (transects: 2.8; plots: 2.1–8.5 nests) was lower than in moderately grazed paddocks (transects: 10.0; plots: 7.1–14.1 nests), but higher than in ungrazed paddocks (transects: 1.1; plots: 0.5–6.1 nests). The number of older, solitary caterpillars was higher in heavily (transects: 23.5–77.0; plots: 2.7 individuals) or moderately (transects: 32.3–36.5; plots: 3.0 individuals) grazed paddocks than in ungrazed paddocks (transects: 6.4–14.2; plots: 1.5 individuals). From 1994, a 1,450-ha farm was divided into paddocks managed permanently by heavy (1.1 cows/ha) or moderate (0.55 cows/ha) grazing, or left ungrazed. In January 2015 and March 2014–2015, caterpillar nests (January) and individuals (March) were counted once/year on three 20-m-long transects in each of two heavily grazed and two moderately grazed paddocks (~27 ha) and in four ungrazed paddocks (0.5–4 ha). Within each of the four grazed paddocks, cattle were excluded from five fenced, 10 × 10 m plots for >10 years. In January 2014–2015, all caterpillar nests were counted in each fenced, ungrazed plot and a paired, grazed plot 3 m away in the surrounding paddock. In March 2015, individual caterpillars were counted in three 30 × 30 cm sub-plots in each grazed and ungrazed plot.

   Study and other actions tested

   Referenced paper

   Berman T.S., Ben-Ari M., Henkin Z. & Inbar M. (2018) Immediate and long-term facilitative effects of cattle grazing on a polyphagous caterpillar. Agriculture, Ecosystems & Environment, 261, 45-53.