Reduce grazing intensity on grassland by seasonal removal of livestock
Overall effectiveness category Awaiting assessment
Number of studies: 7
Background information and definitions
Productive grasslands used for livestock production are intensively managed, with permanent grazing resulting in a closely cropped sward (Bubová et al. 2015). While grazing is important for maintaining open grassland, reducing grazing intensity by removing livestock for part of the year allows some vegetation to grow taller, increasing structural complexity and floral diversity (Morris 2000), and this may provide more suitable habitat for some grassland butterflies and moths (e.g. Elligsen et al. 1997).
For studies on reducing grazing intensity by decreasing the number of livestock, see “Reduce grazing intensity on grassland by reducing stocking density”. For studies on reducing grazing intensity alongside other reductions in management intensity, such as reduced chemical input, see “Reduce management intensity on permanent grasslands (several interventions at once)”. For studies on removing grazing entirely, see “Cease grazing on grassland to allow early succession”. For studies on increasing grassland management, see “Increase grazing intensity or cutting frequency on grassland”.
Elligsen H., Beinlich B. & Plachter H. (1997) Effects of large-scale cattle grazing on populations of Coenonympha glycerion and Lasiommata megera (Lepidoptera: Satyridae). Journal of Insect Conservation, 1, 13–23.
Morris M.G. (2000) The effects of structure and its dynamics on the ecology and conservation of arthropods in British grasslands. Biological Conservation, 95, 129–142.
Bubová T., Vrabec V., Kulma M. & Nowicki P. (2015) Land management impacts on European butterflies of conservation concern: a review. Journal of Insect Conservation, 19, 805–821.
Supporting evidence from individual studies
A replicated, randomized, controlled trial in 1997–1998 on permanent pasture at three sites in Dumfries and Galloway, UK (Haysom et al. 2000) found that fencing field headlands to prevent grazing during the summer increased the abundance of caterpillars. After one year, headlands protected from summer grazing had more caterpillars (18 individuals/10 samples) than grazed headlands (1 individual/10 samples). From spring 1997, four treatments were carried out in adjacent plots (10 × 50 m long) on the boundaries of seven pasture fields: fenced (May–September) unsprayed, fenced (May–September) sprayed, unfenced unsprayed, and unfenced sprayed. Unfenced plots were grazed by cattle and sheep during summer, and all plots were intermittently grazed by sheep during winter. In sprayed plots, herbicide (6 l glyphosate/ha) was applied in April 1997 to clear strips to trial a method for increasing foraging access for birds. Insects were sweep net sampled in June and July 1997 and 1998.Study and other actions tested
Referenced paperHaysom K.A., McCracken D.I., Roberts D.J. & Sotherton N.W. (2000) Grassland conservation headlands: a new approach to enhancing biodiversity on grazing land. Grazing Management: the Principles and Practice of Grazing, for Profit and Environmental Gain, within Temperate Grassland Systems: Proceedings of the British Grassland Society Conference, 29 February-2 March, 2000, Harrogate, UK, 159-160.
A replicated, controlled study in 2005–2007 at an upland site in the UK (exact location not given) (Fraser et al. 2008) found that improved grassland from which cattle were excluded in summer had a similar abundance and species richness of butterflies to permanently grazed grassland. In exclusion plots, the abundance (15–67 individuals) and species richness (5–10 species) of butterflies was similar to permanently grazed plots (abundance: 42–156 individuals; richness: 7–11 species). Ten plots of improved perennial rye grass Lolium perenne/white clover Trifolium repens were grazed in spring and autumn, but had livestock excluded from May–September and one silage cut taken. Ten similar plots were grazed throughout the growing season by livestock. Butterfly transect counts were conducted weekly from mid-April to mid-September 2005–2007.Study and other actions tested
A replicated, randomized, controlled study in 2002–2006 on four lowland farms in Devon and Somerset, UK (Potts et al. 2009) found that plots of intensively-managed grassland without autumn cattle grazing did not have a greater abundance or species richness of butterflies, or abundance of caterpillars, than plots which were grazed. On intensively managed silage plots which were not grazed in September, the abundance (1–3 individuals/transect) and species richness (1 species/transect) of butterflies, and the abundance of caterpillars (0–7 caterpillars/transect), was similar to that on silage plots with September grazing (butterfly abundance: 0–2 individuals/transect; richness: 0–1 species/transect; caterpillar abundance: 0–4 caterpillars/transect). In April 2002, six experimental plots (50 × 10 m) were established on permanent pastures (>5-years-old) on four farms. All plots were fertilized (225 kg nitrogen/ha, 22 kg phosphorus/ha, 55 kg potassium/ha) and cut twice/year to 5 cm in May and July. Three plots/farm were then grazed by cattle in September until the sward was 5–7 cm. The remaining plots were not grazed. From June–September 2003–2006, butterflies were surveyed once/month on a 50-m transect through the centre of each plot. In April, June, July and September 2003–2006, caterpillars were counted (but not identified) on two 10-m transects/plot using a sweep net (20 sweeps/transect).Study and other actions tested
A controlled study in 2002–2004 at an upland semi-natural grassland in the Scottish Borders, UK (Cole et al. 2010) found that a summer-grazed area had a higher abundance of caterpillars than an area with year-round grazing. A site which was only grazed in the summer had a higher abundance of caterpillars than a site which was grazed all year (data presented as statistical results). From autumn 2002, two large (>40 ha) plots were grazed by 3–4 sheep/ha: one during June–September only (49.7 ha), and the other year round (74.9 ha). Invertebrates were sampled using pitfall transects (9 traps, 2 m apart) at 15 locations/plot for four weeks during May–June 2004.Study and other actions tested
A replicated, paired, controlled study in 2009–2010 in two semi-natural grasslands in central France (Scohier et al. 2013) found that plots which were not grazed during the peak flowering period had a similar number of butterflies and burnet moths to rotationally grazed plots. In plots where sheep were excluded in summer, the abundance of butterflies and burnet moths (17 individuals/plot) was not significantly different from in rotationally grazed plots (10 individuals/plot). Two grasslands were studied: one which had been extensively managed for 40 years, and one which had been fertilized and grazed at a higher stocking density. From 15 May–30 September 2009–2010, two 5,500-m2 patches/grassland were grazed by five (extensive management history) or seven (intensive management history) 3-year-old ewes/patch. The patches were divided into four plots and sheep were grazed on rotation, spending seven days/plot before moving on. One plot was excluded from the rotation from 26 May–14 July during peak flowering. From June–July 2009–2010, butterflies and burnet moths were surveyed four times on one 30-m transect/plot.Study and other actions tested
A replicated, randomized, paired, controlled study in 2008–2012 on a farm in Berkshire, UK (Woodcock et al. 2014) found that grasslands established with flowering plants where cattle were removed for part of the summer had a greater abundance and species richness of pollinators (including butterflies) than grasslands grazed throughout summer. When sown with a seed mix including legumes or legumes and other non-woody, broadleaved plants (forbs), plots where cows were removed in the summer had a higher abundance (8–56 individuals/plot) and species richness (3–6 species/plot) than plots where cattle grazed throughout the summer (abundance: 3–49 individuals/plot; richness: 2–7 species/plot). In plots sown with grasses alone, pollinator abundance (0–3 individuals/plot) and species richness (0–2 species/plot) were lower regardless of grazing intensity. In spring 2008, forty-eight 875-m2 plots were sown with one of three seed mixes: a “grass only” mix of five species (30 kg/ha, cost: €83/ha); a “grass and legume” mix of five grasses and seven agricultural legumes (34 kg/ha, €120/ha); or a “grass, legume and forb” mix of five grasses, seven legumes and six non-legume forbs (33.5 kg/ha, €190/ha). Half of the plots were lightly grazed (3 cows/ha, May and September–October) and half were more heavily grazed (3 cows/ha, May–October). In May, July and August 2009–2012, butterflies, bees (Apidae) and hoverflies (Syrphidae) were surveyed three times/year on two parallel 20 × 2 m transects/plot.Study and other actions tested
A review in 2015 of 126 studies in Europe (Bubová et al. 2015) reported that reducing grazing intensity on grassland benefitted 41 out of 67 butterfly species of conservation concern. Results were not tested for statistical significance. The review reported that 44 studies found that reducing grazing intensity benefitted 41 butterfly species, but did not distinguish between using seasonal grazing and reducing stocking density. Grazing was most beneficial in autumn (September–November) and spring (April), but was potentially harmful in late spring to mid-summer (data not presented). See paper for information on individual species. Meadows were extensively grazed by different livestock and at different times, sometimes with rotational mowing. The review focussed on 67 butterfly species of conservation concern. The available information was biased towards studies in Northern and Western Europe.Study and other actions tested