Maintain upland heath/moorland
Overall effectiveness category Awaiting assessment
Number of studies: 3
Background information and definitions
Increased management of upland heath, or moorland, in particular by overgrazing, has led to a reduction in characteristic vegetation cover in favour of more dominant grass species, which are less favoured by sheep (Martin et al. 2013). A reduction in grazing pressure, or a switch to low intensity cutting or burning regimes, may allow moorland vegetation to recover, and in turn potentially support larger populations of heathland butterflies and moths.
See also “Habitat restoration and creation – Restore or create heathland/shrubland”.
Martin D., Fraser M.D., Pakeman R.J. & Moffat A.M. (2013) Impact of moorland grazing and stocking rates. Natural England Evidence Review, Number 006, Report.
Supporting evidence from individual studies
A replicated, randomized, controlled study in 2003–2005 on an upland grassland in Perthshire, UK (Dennis et al. 2008, same experimental set-up as 2) found that the abundance of moth caterpillars was higher in ungrazed plots compared to lightly or commercially grazed plots after 30 months. After 18 months of grazing, there was no significant difference in the number of caterpillars on ungrazed (2.8 individuals/plot), lightly grazed (1.9–2.4 individuals/plot) and commercially grazed plots (2.3 individuals/plot). However, after 30 months, there were more caterpillars in the ungrazed plots (4.9 individuals/plot) than in the lightly grazed (1.9–2.4 individuals/plot) or commercially grazed plots (0.5 individuals/plot). From January 2003, three grazing regimes (light grazing: sheep at 0.9 ewes/ha; mixed grazing: sheep and cattle equivalent to 0.9 ewes/ha; commercial grazing: sheep at 2.7 ewes/ha) and an ungrazed treatment were replicated six times each in twenty-four 3.3-ha plots (in three pairs of adjacent blocks). Caterpillars were sampled by sweep net in 2003–2005.Study and other actions tested
A replicated, randomized, controlled study in 2003–2007 on an upland estate in Scotland, UK (Littlewood 2008, same experimental set-up as 1) found that ungrazed and lightly grazed plots had a higher abundance and species richness of moths than plots grazed at a commercial stocking densities. Plots grazed by sheep at low density had a higher abundance (52 individuals/night) and species richness (12.3 species/night) of moths than plots grazed by sheep at commercial densities (abundance: 34 individuals/night; richness: 10.6 species/night), or plots grazed by sheep and cattle at low density (abundance: 42 individuals/night; richness: 11.3 species/night), and were similar to ungrazed plots (abundance: 48 individuals/night; richness: 13.2 species/night). In January 2003, one of four grazing treatments was established on each of 24 plots (3.3 ha each) on a grazed acid grassland upland estate. The treatments were: low density sheep grazing (3 sheep/plot); commercial high density sheep grazing (9 sheep/plot); low density mixed grazing (2 sheep/plot plus two cows and calves for 4 weeks in autumn); ungrazed control. Moths were sampled between June and October 2007 using four 15 W light traps placed randomly within plots of each treatment, for six or seven sample nights/plot.Study and other actions tested
A controlled study in 2002–2004 at an upland semi-natural grassland site in the Scottish Borders, UK (Cole et al. 2010) found that a site managed with low intensity grazing had a higher abundance of caterpillars than an intensively grazed site. 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). Two large (>40 ha) plots were grazed by 3–4 sheep/ha from autumn 2002: one during June–September only (low intensity grazing, 49.7 ha), the other year round (high intensity grazing, 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