Providing evidence to improve practice

Action: Employ areas of semi-natural habitat for rough grazing (includes salt marsh, lowland heath, bog, fen) Farmland Conservation

Key messages

Supporting evidence from individual studies

1 

A site comparison study in the Shetland Islands, Scotland (Grant 1992) found that areas of heath seeded with grass to improve them for livestock grazing were mostly avoided by nesting whimbrels Numenius phaeopus in favour of unimproved heathland. In 1986 and 1987, this study monitored whimbrels in five areas of heathland that had been partly seeded, four on the island of Fetlar, one on Unst. Eighty-nine percent (111 nests) of the nests were found in unseeded heathland. Most nests were on hummocks and amongst heather. Seeding with grass after ploughing or harrowing resulted in the loss of hummocks and most heather Calluna vulgaris, and created a predominantly grassy habitat. Surface-seeding, without ploughing or harrowing, created less marked changes, with hummocks and heather retained, although hummock height was lowered, and in some areas only dead or dying heather was present.

 

2 

At the same study sites as (Grant 1992), (Grant et al. 1992a) found that areas of heath seeded with grass after ploughing or harrowing, and older pastures, were the main early spring feeding areas for at least 90% of whimbrel Numenius phaeopus pairs in the study. They monitored habitat use by individually marked whimbrels, during the pre-laying period in spring 1987 and 1988, on five Shetland Island heathlands. The birds made little use of unimproved heathland (where most nest) or heathland areas seeded without ploughing/harrowing. The greatest quantities of prey species - earthworms (Lumbricidae) and larval crane-flies (Tipulidae) - were found in the soil of ploughed/harrowed seeded areas of heath and older pastures, with more recently seeded areas holding the highest masses of crane-fly larvae.

 

3 

In a third study using the same Shetland Island heaths as (Grant 1992), (Grant et al. 1992b) found no significant difference in whimbrel Numenius phaeopus chick survival between chicks that used areas of heathland re-seeded with grass and those that did not. Individually marked chicks were monitored after hatching in 20, 23, and 26 broods in 1986, 1987 and 1988 respectively. In each year 35-65% of all chicks remained on heathland, while others (usually broods over 12 days old, from nests within 200 m of the alternative habitat) moved into other habitats.

 

4 

A study of northern lapwing Vanellus vanellus nests on 12 grazed and six ungrazed marshes within an Environmentally Sensitive Area over one year in England (Hart et al. 2002) found that ungrazed marshes had greater clutch size and nest survival than those that were grazed. Clutch size was larger on ungrazed than grazed marshes and nest survival was significantly higher for four-egg clutches (57%) than three-egg clutches (21%). Overall, nest survival was 64% on ungrazed marshes compared with 34% on grazed marshes. On grazed marshes 58% of nests were lost to predation compared with 36% on ungrazed marshes, and 20% of unpredated nests were trampled by livestock. Incubating birds also left their eggs significantly more frequently on grazed compared to ungrazed marshes, because of disturbance. All marshes had been grazed the previous year. Sheep or cattle were introduced to 12 marshes at low stocking densities (i.e. 0.20-0.51 livestock units/ha). Lapwing nest data were collected between April and June 1997.

 

5 

A 2006 review (Middleton et al. 2006) describes the results of six studies that evaluated the impact of cattle-grazing on fens in Europe. Two studies found that excluding cattle from formerly grazed fens reduced the number of plant species (Bakker & Grootjans 1991, Matějková et al. 2003), with a shift to trees and shrubs sometimes occurring after 10-15 years of abandonment. Benefits of cattle-grazing to fen biodiversity are likely to depend on the level of grazing, although one freshwater wetland study found that grazing intensity hardly affected the number of invertebrate species (Steinman et al. 2003). The authors suggest that low to moderate levels of cattle grazing could maintain or increase the biodiversity of nutrient-rich fens that have not been overgrazed in the past. However, trampling associated with high grazing pressure can lead to soil degradation and two studies found, respectively, that the low stocking density required to avoid negative trampling impacts will often be too low to maintain biodiversity (Schrautzer et al. 2004), and additional measures to remove excess biomass (such as mowing) remain necessary (Kleyer 2004). One study found that mowing resulted in higher species richness than grazing in undrained chalk/limestone (calcareous) fens (Stammel et al. 2003).

Additional references:

Bakker J.P. & Grootjans A.P. (1991) Potential for vegetation regeneration in the middle course of the Drentsche Aa brook valley (The Netherlands). Verhandlungen der Gesellschaft für Ökologie, 20, 249-263.

Matějková I., van Diggelen R. & Prach K. (2003) An attempt to restore a central European species-rich mountain grassland through grazing. Applied Vegetation Science, 6, 161-168.

Stammel B., Kiehl K. & Pfadenhauer J. (2003) Alternative management on fens: Response of vegetation to grazing and mowing. Applied Vegetation Science, 6, 245-254.

Steinman, A.D., Conklin, J., Bohlen, P.J. & Uzarski, D.G. (2003) Influence of cattle grazing and pasture land use on macroinvertebrate communities in freshwater wetlands. Wetlands, 23, 877-889.

Kleyer M. (2004) Freie Beweidung mit geringer Besatzdichte und Fräsen als alternative Verfahren zur Pflege von Magerrasen [Free grazing at low stocking rates and infrequent rototilling as alternative conservation management systems for dry nutrient-poor grasslands]. Schriftenreihe für Landschaftspflege und Naturschutz, 78, 161-182.

Schrautzer, J., Irmler, U. & Jensen, K. (2004) Auswirkungen großflächiger Beweidung auf die Lebensgemeinschaften eines nordwestdeutschen Flusstales [Effects of extensive grazing on species biotic communities of a northwest German river valley]. Schriftenreihe für Landschaftspflege und Naturschutz, 78, 39-62.

6 

A replicated trial in the UK (Vale & Fraser 2007) found that songbirds and invertebrate-feeding birds were recorded more often on semi-natural rough grazing than on upland improved pasture, but the opposite was true for crows (Corvidae). Bird numbers and species were recorded in plots of improved upland pasture grazed by cattle and sheep (with and without seasonal removal of grazing in summer, 10 replicates for each) and in plots of semi-natural rough grazing grazed by cattle from June to September (six replicates). The proportion of surveys where songbirds and invertebrate feeders were recorded was greater on semi-natural rough grazing than on improved pasture. However, the effect on the number of individuals varied over the year. The number of birds of invertebrate-feeding species was greater on semi-natural grassland between May and July (338 birds, compared to 52 and 41 on improved treatments, with and without seasonal grazing removal), but greater on improved treatments between October and January (5,833 and 1,458 birds on improved treatments compared to 606 birds on semi-natural grassland). There were fewer birds of species in the crow family on semi-natural rough grazing plots at all times of year, but the difference was greatest during July to September (16 birds on rough grazing, compared to 496 and 77 on improved plots). The location of the study was not given.

 

7 

A replicated trial in 2005-2007 of cattle grazing on six experimental plots of semi-natural upland grassland dominated by purple moor grass Molinia caerulea in the UK (Fraser et al. 2008) found more butterfly (Lepidoptera) species and significantly more individual butterflies than on permanently or partially grazed plots of improved pasture. Between 15 and 17 butterfly species (905-1938 individual butterflies) were recorded on the semi-natural plots in each year, compared to 7-11 species (42-156 butterflies) on ten continually grazed and 5-10 species (21-67 butterflies) on ten partially grazed plots of improved pasture. The semi-natural plots were grazed from June to September, while the partially grazed improved plots were grazed in spring and autumn, but had livestock excluded from May to September and one silage cut taken. Butterfly transect counts were conducted weekly between mid-April and mid-September in 2005, 2006 and 2007.

 

8 

A replicated site comparison study from 2004 to 2008 in England (Ewald et al. 2010) investigated the impact of rough grazing on grey partridge Perdix perdix and found a negative relationship between a combined intervention (grazing, scrub control and the restoration of various semi-natural habitats) and the proportion of young partridges in the population in 2008. The study does not distinguish between the individual impacts of grazing, scrub control and the restoration of various semi-natural habitats. Spring and autumn counts of grey partridge were made at 1,031 sites across England as part of the Partridge Count Scheme.

 

 

Referenced papers

Please cite as:

Dicks, L.V., Ashpole, J.E., Dänhardt, J., James, K., Jönsson, A., Randall, N., Showler, D.A., Smith, R.K., Turpie, S., Williams D.R. & Sutherland, W.J. (2017) Farmland Conservation Pages 245-284 in: W.J. Sutherland, L.V. Dicks, N. Ockendon & R.K. Smith (eds) What Works in Conservation 2017. Open Book Publishers, Cambridge, UK.