Restore or create peatland
Overall effectiveness category Awaiting assessment
Number of studies: 5
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Background information and definitions
Large areas of peatland have been deliberately or unintentionally drained (for example extracting drinking water from below ground lowers the water table over a large area) for human activities. Drained peat can be too dry and chemically unsuitable for peatland plants (Lamers et al. 2002), reducing the suitability of habitat for specialist butterflies and moths. Peatland restoration typically involves raising the water table to rewet the surface peat. This creates more suitable conditions for recolonization by peatland plants (Money & Wheeler 1999; Ritzema et al. 2014), such as bog myrtle Myrica gale, which could benefit butterflies and moths which depend upon them as a caterpillar food source (Fowles et al. 2004). However, the rate at which water levels are raised may need to be controlled, so as not to submerge overwintering caterpillars (Joy & Pullin 1997, 1999). It may also be necessary to rewet the area around a peatland (creating a ‘hydrological buffer zone’) to prevent water simply draining away from the peatland.
A range of techniques may be used to raise the water table to restore peatlands, for example blocking drainage ditches, planting flood-resistant vegetation to slow water flow, blocking underground channels, building raised embankments to retain water, inserting dams below the peat surface to slow subsurface drainage, switching off drainage pumps, felling trees, or restoring inflows. These interventions are all considered in this action. For studies of specific actions for creating, restoring, or managing peatlands, see “Replant native vegetation” and “Employ areas of semi-natural habitat for rough grazing (includes salt marsh, lowland heath, bog, fen)”.
Habitats within this action include peatland, bogs, mires, and wet heathland, where the water table is close to the ground surface. For studies on restoring wet grasslands, fenland and floodplains, see “Restore or create wetlands and floodplains”. For studies on restoring dry heathland and shrubland, see “Restore or create heathland/shrubland”.
Fowles A.P., Bailey M.P. & Hale A.D. (2004) Trends in the recovery of a rosy marsh moth Coenophila subrosea (Lepidoptera, Noctuidae) population in response to fire and conservation management on a lowland raised mire. Journal of Insect Conservation, 8, 149–158.
Joy J. & Pullin A.S. (1997) The effects of flooding on the survival and behaviour of overwintering large heath butterfly Coenonympha tullia larvae. Biological Conservation, 82, 61–66.
Joy J. & Pullin A.S. (1999) Field studies on flooding and survival of overwintering large heath butterfly, Coenonympha tullia, larvae on Fenn’s and Whixall Mosses in Shropshire and Wrexham, UK. Ecological Entomology, 24, 426–431.
Lamers L.P., Smolders A.J.P. & Roelofs J.G.M. (2002) The restoration of fens in the Netherlands. Hydrobiologia, 478, 107–130.
Money R.P. & Wheeler B.D. (1999) Some critical questions concerning the restorability of raised bogs. Applied Vegetation Science, 2, 107–116.
Ritzema H., Limin S., Kusin K., Jauhiainen J. & Wösten H. (2014) Canal blocking strategies for hydrological restoration of degraded tropical peatlands in Central Kalimantan, Indonesia. Catena, 114, 11–20.
Supporting evidence from individual studies
A before-and-after study in 1988–2003 in a raised bog in Ceredigion, UK (Fowles et al. 2004) reported that a re-wetted bog supported a larger population of rosy marsh moth Coenophila subrosea caterpillars than before drains were blocked. Results were not tested for statistical significance. One to five years after the last drains were blocked, 27–88 caterpillars/year were recorded, compared to 8–27 caterpillars/year in the preceding 10 years. From the mid-1980s, large drains surrounding a raised bog were dammed. In 1993 and 1998, shallow peat-cuttings were also blocked, raising the water table at the site from 42 cm to 48 cm over 15 years. In late May 1988–2003, caterpillars were counted once/year, at night, in fourteen 15 × 1 m plots along a transect across the bog.Study and other actions tested
A replicated, site comparison study in 1998–1999 on 68 wet heathland sites in the Netherlands (WallisDeVries 2004) found that raising water levels reduced occupancy by Alcon large blue Maculinea alcon. Fewer recently flooded sites were occupied by Alcon large blue (48%) than non-flooded sites (85% occupancy), and sites where measures had been taken to raise the water level were more likely to be flooded (68%) than sites without such measures (35%). Sixty-eight wet heathland sites in the Netherlands where Alcon large blue was known to have occurred since 1990 were selected. Management information for the last five years was obtained by sending questionnaires to land managers. Changes in management designed to raise water levels had been used at 31% of sites (further details not provided). From mid-July–early September 1998–1999, Alcon large blue eggs were counted in each of three 10 × 10 m plots/site to determine butterfly presence in the plot.Study and other actions tested
A replicated, paired, site comparison study in 2007 in nine boreal mires in Central Finland and Northern Karelia, Finland (Noreika et al. 2015, same experimental set-up as 5) found that mires restored by ditch-filling and tree cutting had moth communities which were intermediate between those found on drained and pristine mires. One–three years after restoration, the moth community on restored mires was intermediate between the communities found on drained and pristine mires (data presented as model results). One of three mire specialist micro-moths (rush marble Bactra lancealana) and one of two specialist macro-moths (Manchester treble-bar Carsia sororiata) were more numerous in restored than drained sites, but were most abundant in pristine sites. However, one specialist micro-moth (Crambus alienellus) and one specialist macro-moth (Arichanna melanaria) were more abundant in the drained sites than restored sites. A third specialist micro-moth (pearl-band grass-veneer Catoptria margaritella) did not differ in abundance between restored, drained and pristine sites (see paper for details). In the 1960s and 1970s, parts of nine mires were drained for forestry. From 2003–2006, some drained areas were restored by filling ditches with peat, damming the ends with logs and peat, and cutting trees. Each mire also contained a pristine, undrained area. In 2007, moths were sampled along two 250-m transects in each restored, drained and pristine area (six transects/mire). From May–August, micro-moths were sampled weekly using 100 sweeps/transect of a 28-cm diameter net at all nine mires. From May–July, macro-moths were counted weekly along each transect at five of the mires.Study and other actions tested
A replicated, paired, site comparison study in 2011 in 12 bogs in County Offaly, Ireland (Flynn et al. 2016) found that protected bogs, some of which had been re-wetted, had a similar total abundance and species richness of moths to unprotected bogs, but individual species showed mixed preferences. The total number of moths recorded on protected bogs was 951 individuals of 67 species, compared to 865 individuals of 73 species on unprotected bogs (statistical significance not assessed). Of the 14 most common species, three were more abundant on protected bogs (dark arches Apamea monoglypha, large yellow underwing Noctua pronuba, dark tussock Dicallomera fascelina), three were more abundant on unprotected bogs (map-winged swift Pharmacis fusconebulosa, narrow-winged pug Eupithecia nanata, spruce carpet Thera britannica), and eight showed no difference (data presented as model results). Of 15 bog-associated species of conservation concern, only three (dark tussock, bordered grey Selidosema brunnearia, garden tiger Arctia caja) were recorded in higher numbers on protected sites than on unprotected sites (statistical significance not assessed). Six raised bogs (74–246 ha) designated as Special Areas of Conservation, and six nearby (1.5–5 km away), highly modified but vegetated undesignated raised bogs (40–578 ha) were selected. At four of the protected sites, restoration work (mostly drain blocking) had taken place. From July–October 2011, moths were sampled five times using a Heath-type actinic 15 W light trap left overnight at each site. Paired sites were sampled on the same night, and all sites were sampled over two nights/visit.Study and other actions tested
A replicated, paired, controlled, before-and-after study in 2003–2014 in 19 boreal mires in Finland (Noreika et al. 2016, same experimental set-up as 3) found that restoring mires by raising the water table and removing large trees increased the abundance and species richness of mire specialist butterflies. On restored mires, the abundance (1.8 individuals) and species richness of mire specialist butterflies was higher than on drained mires (0.8 individuals), and similar to pristine mires (2.9 individuals; data for species richness not presented). Prior to restoration, abundance and species richness were similar in sites to be restored (1.4 individuals) and drained sites (1.7 individuals), but higher on pristine sites (3.6 individuals). See paper for individual species results. Each of 19 mires comprised three habitats: drained sites which were restored during the study, drained sites that remained in forestry use throughout the study, and undrained pristine sites. At restored sites, tall trees were removed and the water table was raised. Nine mires were restored between 2004 and 2006, and 10 were restored from 2011–2013. Six 250-m transects were established in each mire (2 transects/habitat, 80 m apart). Beginning in May, butterflies were surveyed weekly in years before (2003 or 2010) and after (2007 or 2014) restoration at each mire (7–15 visits/site/year), and divided into specialists (species which predominantly occur on mires) and generalists (species which predominantly occur in other habitats).Study and other actions tested
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This Action forms part of the Action Synopsis:Butterfly and Moth Conservation
Butterfly and Moth Conservation - Published 2022
Butterfly and Moth Synopsis