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Providing evidence to improve practice

Action: Exclude or remove livestock from degraded peatlands Peatland Conservation

Key messages

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  • Ten studies evaluated the effects on peatland vegetation of excluding or removing livestock from degraded peatlands. Seven studies were in bogs, two in fens and one in an unspecified peatland. Three studies were based on the same experimental set-up in the UK.
  • Plant community composition (2 studies): Of two replicated, paired, controlled studies in bogs in the UK, one found that excluding sheep had no effect on the development of the plant community. The other found no effect in wetter areas of the bog, but that in drier areas excluding sheep favoured dry moorland plants.
  • Herb cover (9 studies): Seven studies ­(including six replicated, paired, controlled) in bogs in the UK and Australia and fens in the USA found that excluding or removing livestock typically had no effect on cover of key herb groups. Five of five studies found that excluding livestock typically had no effect on cottongrass cover. Two of two studies reported no effect on sedge cover. However, one before-and-after study in a poor fen in Spain reported that rush cover increased after cattle were excluded (along with other interventions). One site comparison study in Chile found that excluding livestock (along with other interventions) increased overall herb cover, but one replicated, paired, controlled study in bogs in Australia found that excluding livestock had no effect on overall herb cover.
  • Moss cover (6 studies): Five replicated, paired, controlled studies in bogs in the UK and Australia found that excluding livestock typically had no effect on Sphagnum moss cover. Responses sometimes varied between species and sites. Three of the studies in the UK also found no effect on cover of other mosses. One before-and-after study in a poor fen in Spain reported that Sphagnum moss appeared after excluding cattle (and rewetting).
  • Tree/shrub cover (8 studies): Four replicated, paired, controlled studies in bogs in the UK and Australia found that excluding livestock had no effect on shrub cover (specifically heather or a heathland community). One replicated, paired, controlled study in a bog in the UK found that excluding sheep had no effect on heather cover in wetter areas, but increased heather cover in drier areas. Three studies (including two site comparisons) in bogs in the UK, fens in the USA and a peatland in Chile found that excluding or removing livestock increased shrub cover.
  • Vegetation structure (1 study): One replicated, paired, controlled study in a bog in the UK found that excluding sheep increased total vegetation, shrub and bryophyte biomass but had no effect on biomass of grass-like herbs.

Supporting evidence from individual studies

1 

A replicated, paired, controlled, before-and-after study in 1953–1975 in a grazed blanket bog in England, UK (Rawes & Hobbs 1979) found that excluding sheep typically had no effect on heather Calluna vulgaris or cottongrass Eriophorum spp. cover, but had mixed effects on moss cover. In two of three sites, plots from which sheep had been excluded had similar cover to grazed plots of heather (exclusion: 60–70%; grazed: 50–60%) and cottongrasses (exclusion: 7%; grazed: 7%). Meanwhile in a third site, around a bog pool, cover increased over 21 years of sheep exclusion for both heather (from 40 to 54%) and cottongrasses (from 0 to 2%). Moss cover showed mixed responses to sheep exclusion: both Sphagnum and other moss cover were lower in exclusion plots than grazed plots in one site (exclusion: 3%; grazed: 4–5%), similar in exclusion and grazed plots in one site (exclusion: 1%; grazed: 1%), but showed mixed responses by species around the bog pool. In 1953 or 1968, sheep were excluded from part of each site with 20 cm mesh fencing. The rest of each site remained grazed (<0.3 sheep/ha). Vegetation cover was recorded after 7, 18 or 12 years of exclosure (and immediately before exclosure in the bog pool site).

2 

A replicated, randomized, paired, controlled study in 1954–1973 in a grazed and recently burned blanket bog in England, UK (Rawes & Hobbs 1979) found that excluding sheep typically had no effect on vegetation cover, but did increase the number of heather Calluna vulgaris shoots and stems. For 32 of 37 plant groups, cover never significantly differed between plots from which sheep had been excluded and plots that remained grazed. These included Sphagnum mosses (exclusion: 5–19%; grazed: 2–8%), six of seven other moss species (exclusion: 1–38%; grazed: 1–46%), cottongrasses Eriophorum spp. (exclusion: 6–62%; grazed: 9–67%) and live heather (exclusion: 30–82%; grazed: 19–70%). However, exclusion plots did contain a greater density of heather shoots and stems than grazed plots. In 1954, four areas of a grazed bog (<0.3 sheep/ha) were burned once. Within each area, a random three of six 1,000 m2 plots were fenced to exclude sheep. In each area, one fenced and one unfenced plot were burned again in 1965. In 1972, vegetation cover was estimated by recording, in each plot, plants touching 250 randomly placed pins. This study was based on the same experimental set-up as (7) and (8).

3 

A replicated, paired, controlled, before-and-after study in 1966–1980 in two grazed blanket bogs in England, UK (Rawes 1983) found that excluding sheep increased shrub cover, but typically had no effect on cover of moss or herb species. In exclusion plots, cover increased of heather Calluna vulgaris (before: 0–4%; after 14 years: 2–21%) and crowberry Empetrum nigrum (before: 7–17%; after: 27–42%). These changes were significant in two of four comparisons, with a similar trend in the others. Cover of two other shrub species did not decline. There was no significant change in cover of six of six moss species, including two Sphagnum (before: 0–10%; after: 1–21%) or in 8 of 11 comparisons involving herb species, including black sedge Carex nigra (before: 6%; after: 4%) and cottongrasses Eriophorum spp. (before: 18–72%; after: 16–69%). Vegetation cover generally did not change in grazed control plots (except for a decrease in heather cover in one site, from 6% to 3%). In 1966, 0.1 ha of each bog was fenced to exclude sheep. An adjacent plot in each bog, with similar vegetation, was left open to grazing (<0.5 sheep/ha). In 1966 and 1980, vegetation cover was measured using 500 systematically placed pins in each plot.

4 

A replicated, paired, controlled study in 1980–1996 in two grazed bogs in Australia (Wahren et al. 2001) found that excluding cattle with fences had no effect on vegetation cover. Over 15 years, cover of different vegetation types changed similarly in exclusion and grazed plots. Although Sphagnum moss cover increased in exclusion plots (from 15–20% to 23–24%), it also increased in grazed plots (from 16–18% to 19–20%). In one bog where heathland vegetation cover increased, it did so in both exclusion plots (from 5 to 30%) and grazed plots (from 4 to 23%). Herb cover did not change in exclusion plots (from 54–77% to 54–70%) or grazed plots (from 49–81% to 52–77%). In 1980–1981, one pair of plots was established in each grazed bog. Two plots (one plot/pair) were fenced to exclude free-ranging cattle. The other plots remained open to grazing. In 1981 and 1996, vegetation cover was recorded along 5–15 transects/bog, each 20–70 m long.

5 

A site comparison study in 1977–1997 in three historically grazed sedge meadows in Wisconsin, USA (Middleton 2002) reported that after cattle grazing was stopped, vegetation structure and species richness became more like a meadow that had never been grazed, but shrub cover less so. Most of these results were not tested for statistical significance. Between four and twenty years after grazing was stopped, average vegetation cover and height increased (data reported as graphical analyses) whilst the number of plant species decreased (from 43 to 34). For these measures, the previously grazed meadow became more like a never-grazed meadow and less like a heavily grazed meadow. In contrast, cover of red twig dogwood Cornus sericea increased significantly in the previously grazed meadow (from 0 to 9%) but not in the never-grazed meadow (from 0 to 2%). Total sedge Carex spp. cover did not change significantly over time in any site. In 1977 and 1997, three sedge meadows were studied: one previously grazed (heavily grazed until 1973, when grazing stopped), one that remained heavily grazed, and one effectively never grazed (lightly grazed until the 1960s). Sedge meadows are sedge-dominated peatlands, fed by ground water. Cover and height of every plant species were recorded in 20–28 quadrats (0.2 m2) per meadow.

6 

A replicated, paired, controlled study in 1988–2002 in a grazed bog in England, UK (Smith et al. 2003) found that excluding sheep changed the plant community composition and vegetation cover in drier parts of the bog, but had no effect in wetter parts of the bog. Exclusion and grazed plots developed different plant communities over 14 years in drier areas, but retained similar communities to each other in wetter areas (data reported as graphical analyses). After 14 years, exclusion plots in dry areas had greater cover of heather Calluna vulgaris than grazed plots (exclusion: 7%; grazed: 1%) and less cover of Magellan’s bog moss Sphagnum magellanicum (exclusion: 8%; grazed: 23%). In both wet and dry areas, excluding sheep did not affect cover of other common plant species including cottongrasses Eriophorum spp. (exclusion: 4–23%; grazed: 6–19%) and other Sphagnum moss species (exclusion: 4–21%; grazed: 3–36%). In 1988, ten pairs of 20 x 20 m plots were established in a grazed bog: five pairs in the wetter central part of the bog and five pairs in the drier margins. Five plots (one plot/pair) were fenced to exclude sheep. The other plots remained grazed (0.65 sheep/ha). In 1988 and 2002, vegetation cover was visually estimated in ten 1 m2 quadrats/plot.

7 

A replicated, paired, controlled study in 1954–2004 in a grazed and recently burned blanket bog in England, UK (Ward et al. 2007) found plots fenced to exclude sheep contained more total vegetation, shrub and bryophyte biomass than grazed plots, but similar biomass of grass-like herbs. After 50 years, above-ground vegetation biomass was greater in exclusion plots (240 g/m2) than grazed plots (192 g/m2). This included greater biomass of shrubs (mainly heather Calluna vulgaris; exclusion: 194; grazed: 161 g/m2) and bryophytes (mainly red-stemmed feather moss Pleurozium schreberi; exclusion: 37; grazed: 18 g/m2). However, exclusion and grazed plots contained similar biomass of grass-like herbs (mainly sheathed cottongrass Eriophorum vaginatum; exclusion: 10; grazed: 13 g/m2). In 1954, sixteen 1,000 m2 plots were established (in four blocks of four) on a grazed bog. Eight plots (two plots/block) were fenced to exclude sheep. The other eight plots remained open to summer grazing (0.04 sheep/ha). All plots were burned once in 1954, with half also burned every 10 years thereafter. In 2003–2004, live above-ground vegetation was cut from one 25 cm2 quadrat/plot, then dried and weighed. Samples were taken in spring, summer, autumn and winter. This study was based on the same experimental set-up as (2) and (8).

8 

A replicated, randomized, paired, controlled study in 1954–2001 in a grazed and recently burned blanket bog in England, UK (Lee et al. 2013) found that excluding sheep had no effect on plant community composition, cover and species richness. Between 1972 and 2001, the overall plant community composition changed in both grazed and ungrazed areas, from liverwort-rich to heather- or cottongrass-rich (depending on whether they were also burned). However, community development was not significantly affected by grazing (data reported as graphical analyses). Over the experimental period, exclusion and grazed plots contained a similar number of plant species and Sphagnum moss species, and similar cover of heather Calluna vulgaris and cottongrasses Eriophorum spp. (amongst other species; data not reported). In 1954, four 60 x 90 m areas of a grazed bog received an initial burn. Then, sheep were excluded from half of each area whilst the other half remained open to grazing (0.1–0.3 sheep/ha). Of three plots within each grazed and ungrazed area, two were burned again during the study period (every 10 or 20 years). Vegetation cover was measured in 1972, 1982, 1991 and 2001 by recording, in each area, plants touching 300 randomly placed pins. This study was based on the same experimental set-up as (2) and (7).

9 

A site comparison study in 2014 in a peatland in Chile (Cabezas et al. 2015) found that a protected area (fenced to exclude livestock and where moss harvesting was prohibited) had greater vegetation cover and taller vegetation, but lower vascular plant richness and diversity, than an adjacent unprotected (grazed and harvested) area. The protected area had greater cover than the unprotected area of total vegetation (87 vs 62%), herbs (68 vs 51%) and shrubs (19 vs 11%) and contained taller vegetation (65 vs 13 cm). The protected area had lower vascular plant species richness than the unprotected area (7 vs 11 species/4 m2) and lower diversity (reported as a diversity index), but also contained fewer non-native species (<0.1 vs 1.9 species/4 m2). In 2014, vegetation cover and height were recorded in forty-four 2 x 2 m quadrats. Fifteen quadrats were in 5.5 ha of protected peatland, fenced to exclude oxen for eight years and with no moss harvesting for at least 20 years. The study does not distinguish between the effects of these interventions. Twenty-nine quadrats were in 10.5 ha of unprotected peatland, grazed by four oxen and harvested monthly.

10 

A before-and-after study in 2008–2013 in a historically grazed poor fen in Spain (Peralta de Andrés et al. 2015) reported that after building fences to exclude cattle (along with rewetting), cover of rushes Juncus spp. increased and new populations of Sphagnum moss appeared. No statistical tests were carried out. Before intervention, the fen was covered by dryland grasses and forbs, with no Sphagnum. Four years after intervention, 81% of the peatland area contained rushes: common rush Juncus effusus with some sharp-flowered rush Juncus acutiflorus. Sphagnum mosses also appeared in 3 of 10 monitored quadrats. In 2009, fences were built to exclude cattle. At the same time, the fen was rewetted by blocking/removing drainage channels and building a new inflow ditch. The study does not distinguish between the effects of cattle exclusion and rewetting. Vegetation cover before (2008) and after (2013) intervention was mapped from aerial photos and recorded in ten permanent quadrats (size not reported).

Referenced papers

Please cite as:

Taylor N.G., Grillas P. & Sutherland W.J. (2018) Peatland Conservation. Pages 329-392 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2018. Open Book Publishers, Cambridge, UK.