Action: Revert arable land to permanent grassland
- All five studies looking at the effects of reverting arable land to grassland found no clear benefit to birds. The studies monitored birds or grey partridges in the UK and wading birds in Denmark (4). They included three replicated controlled trials.
- One of the studies, a controlled before-and-after study from the UK, showed that grey partridge numbers fell significantly following the reversion of arable fields to grassland.
This intervention involves changing from an arable crop to sown agricultural grassland, to be used for grazing or silage. It is not the same as the creation of species-rich or other semi-natural grasslands, which is discussed in the chapter on habitat restoration and creation.
See also ‘Provide or retain set-aside areas’ for some studies where non-rotational set-aside land was sown with grass, but managed as set-aside rather than as permanent agricultural grassland.
Supporting evidence from individual studies
A controlled before-and-after study in 1970-94 in a 28 km2 area of arable farmland in Sussex, England (Aebischer & Potts 1998), found that grey partridge Perdix perdix numbers declined rapidly on arable fields in 1987-94, following their reversion to grassland, beginning in 1987 (average of 6.5 coveys/km2 in 1970-86 vs. 1.1 coveys/km2 in 1987-94). There was a considerably smaller decline on arable fields that were not reverted to grassland (average of 4.9 coveys/km2 in 1970-86 vs. 2.5 coveys/km2 in 1987-94). The reversed fields went from being more favoured by partridges before reversion to less favoured afterwards, equating to a 23% per year decrease in relative habitat quality on the reversion fields.
A replicated, controlled study in the winters of 1994-7 on farmland in southern England (Wakeham-Dawson & Aebischer 1998) found that Eurasian skylark Alauda arvensis, corn bunting Miliaria calandra and meadow pipit Anthus pratensis were not consistently more abundant on arable land reverted to grassland than on intensively managed permanent grassland or winter wheat fields (4-11 birds/km2 for skylarks on reverted fields vs. 0-10 and 1-8 birds/km2 for permanent grassland and winter wheat; values were 0.1-0.2, 0 and 0-1 birds/km2 for buntings and 0-1.1 0 and 0-4 birds/km2 for pipits). Densities of rooks Corvus frugilegus did not differ across field types. Reverted arable fields were sown with agricultural grass mixtures and managed under specific guidelines, whilst the permanent grassland fields were mown frequently and fertilised. This study also describes the effects of ‘Habitat restoration/creation’ and is discussed in ‘Create open patches or strips in permanent grassland’.
A replicated, controlled study in the spring and summer 1994-6 on 40 farms in southern England (Wakeham-Dawson et al. 1998) found that arable fields reverted to permanent grassland held similar densities of Eurasian skylarks Alauda arvensis as winter wheat and intensively managed permanent grassland, except in summer 1994, when they held significantly higher densities, and summer 1995, when they held lower densities than winter wheat (summer 1994: 11.9 birds/km2 on 65 reverted fields vs. 2.6 and 4.4 birds/km2 for 29 and 47 fields of permanent grassland and winter wheat, respectively; summer 1995: 2.1 birds/km2 for 15 reverted fields vs. 3.0 and 11.0 birds/km2 for seven and 26 fields of permanent grassland and winter wheat; other seasons: 5.7-9.1 birds/km2 vs. 3.6-4.0 and 8.5-13.0 birds/km2). Densities of carrion crows Corvus corone tended to be higher on reverted land, significantly so in some seasons (1.8-4.8 birds/km2 on reverted fields vs. 0-3.0 and 0-1.1 birds/km2 for grassland and wheat) and rooks C. frugilegus were never found on winter wheat. Between 65 and 82 reverted arable fields were surveyed, each sown with agricultural grass mixtures and managed under specific guidelines, whilst the 15-29 permanent grassland fields were frequently mown and fertilised. Between 38 and 47 winter wheat fields were surveyed. This study is also described in ‘Undersow spring cereals’, ‘Reduce grazing intensity on permanent grasslands’, ‘Habitat restoration and creation: Grasslands’ and ‘Provide or maintain set-aside areas in farmland’.
A replicated, controlled study in 615 grassland fields in Jutland, Denmark (Kahlert et al. 2007), found that the populations of four waders (northern lapwing Vanellus vanellus, black-tailed godwit Limosa limosa, common redshank Tringa totanus and Eurasian oystercatcher Haematopus ostrolagus) did not increase on restored grasslands (formerly croplands), whether or not they were under a scheme designed to increase water levels in fields. There were increases on some other field types. This study is discussed in detail in ‘Raise water levels in ditches or grassland’.
A replicated site comparison study on 1,031 agricultural sites across England in 2004-8 (Ewald et al. 2010) investigated the impact of the restoration of different grasslands on grey partridge Perdix perdix. However, the study does not distinguish between the impacts of grassland restoration, scrub restoration and control and rough grazing. Sites with more of the combined intervention had a lower proportion of young partridges in the population in 2008. This study describes the effects of several other interventions, discussed in the relevant sections.
- Aebischer N.J. & Potts G.R. (1998) Spatial changes in grey partridge (Perdix perdix) distribution in relation to 25 years of changing agriculture in Sussex, U.K. Gibier Faune Sauvage, Game Wildlife, 15, 293-308
- Wakeham-Dawson A. & Aebischer N.J. (1998) Factors determining winter densities of birds on environmentally sensitive area arable reversion grassland in southern England, with special reference to skylarks (Alauda arvensis). Agriculture, Ecosystems & Environment, 70, 189-201
- Wakeham-Dawson A., Szoszkiewicz K., Stern K. & Aebischer N.J. (1998) Breeding skylarks Alauda arvensis on Environmentally Sensitive Area arable reversion grass in southern England: survey-based and experimental determination of density. Journal of Applied Ecology, 35, 635-648
- Kahlert J., Clausen P., Hounisen J. & Petersen I. (2007) Response of breeding waders to agri-environmental schemes may be obscured by effects of existing hydrology and farming history. Journal of Ornithology, 148, 287-293
- Ewald J.A., Aebischer N.J., Richardson S.M., Grice P.V. & Cooke A.I. (2010) The effect of agri-environment schemes on grey partridges at the farm level in England. Agriculture, Ecosystems & Environment, 138, 55-63