Action: Use organic farming instead of conventional farming
- Seven studies evaluated the effects of using organic farming instead of conventional farming on bat populations. Six studies were in Europe, and one in the USA.
COMMUNITY RESPONSE (4 STUDIES)
- Richness/diversity (4 studies): Three of four replicated paired sites or site comparison studies in the UK, USA and France found that the number of bat species did not differ between organic and non-organic farms. The other study found more bat species on organic farms than non-organic farms.
POPULATION RESPONSE (7 STUDIES)
- Abundance (7 studies): Four of five replicated, paired sites or site comparison studies in Europe and the USA found that total bat activity (relative abundance) and common pipistrelle activity did not differ between organic and non-organic farms. The other study found significantly higher total bat activity on organic farms than non-organic farms. Two replicated, paired sites and site comparison studies in the UK found significantly higher activity of Myotis species over water and rivers on organic farms than non-organic farms, but no differences were found for other species or habitats.
USAGE (0 STUDIES)
Organic farming is an agricultural system that excludes the use of synthetic fertilizers and pesticides and relies on techniques such as crop rotation, compost and biological pest control. Organic standards are strictly regulated in many countries prohibiting the use of chemicals and providing recommendations for management to conserve biodiversity. Organic farming may include combinations of several separate interventions (as discussed separately in this chapter). The studies below examine the effects of organic farming overall.
For an intervention that relates specifically to organic pest control, see ‘Threat: Pollution – Agricultural and forestry effluents – Use organic pest control instead of synthetic pesticides’. For interventions that involve reducing the use of synthetic pesticides and fertilisers, see ‘Threat: Pollution – Agricultural and forestry effluents – Reduce pesticide, herbicide or fertiliser use’.
Supporting evidence from individual studies
A replicated, paired sites study in 2000–2002 on 24 pairs of farms in southern England and Wales, UK (Wickramasinghe et al 2003) found that water habitats on organic farms had higher activity for two of 11 bat species than on conventional farms, but bat activity did not differ in pasture, arable or woodland habitats, and a similar number of bat species was recorded on both farm types. The activity of Brandt’s bats Myotis brandtii and Bechstein’s bats Myotis bechsteinii was significantly higher over water habitats on organic farms (Brandt’s bat: 66 bat passes; Bechstein’s bat: 7 bat passes) than on conventional farms (Brandt’s bat: 2 bat passes; Bechstein’s bat: 0 bat passes). Bat activity did not differ in pasture, arable or woodland habitats, or for any other bat species, between organic and conventional farms. A similar number of species was recorded on organic (14 species) and conventional farms (11 species). Certified organic farms (established 1–2 years) were paired with nearby conventional farms with similar habitats (pasture, arable, water and woodland), size and type of business. No details are reported about the type or origin of water habitats; water may have originated from outside of the farms. Each of 48 farms was surveyed with bat detectors rotated between three random points for an hour and a half from one hour after sunset. Two farms within a pair were sampled on consecutive nights in June–September 2000 or 2002.
A replicated, paired sites study in 2002–2003 on 65 pairs of farms in England, UK (Fuller et al 2005) found that organic farms had higher bat activity and a greater number of bat species than conventional farms. Significantly more bat passes and more bat species were recorded on organic farms than conventional farms (abundance index 6–75% higher on organic farms; species density 8–65% higher). Organic farms with >30 ha of arable land were paired with nearby conventional farms matched by crop type and cropping season. Habitat data collected across all 130 farms showed that organic farms had a higher density of hedgerows, a greater proportion of grassland than crops, smaller fields and wider, taller hedgerows with fewer gaps than conventional farms. Each of 130 farms was surveyed using bat detectors along a 3 km triangular transect in June–August in 2002 and 2003.
A replicated, paired sites and site comparison study in 2005 in six pairs of olive Olea europea groves and six native woodlands on Zakynthos island, Greece (Davy et al 2007) found that organic olive groves had similar bat activity and foraging activity to non-organic olive groves. Overall bat activity and foraging activity did not differ between organic (average 0.8 bat passes/min, 0.04 feeding buzzes/min) and non-organic olive groves (1.1. bat passes/min, 0.06 feeding buzzes/min). Bat activity in organic and non-organic olive groves also did not differ significantly to that in three native oak Quercus spp. woodland patches (1.5 bat passes/min) and three native pine Pinus halipensis woodland patches (2.5 bat passes/min). Eleven bat species were recorded in total (see original reference for data for individual species). Six organic olive groves were paired with six non-organic olive groves similar in size, age, density of trees and altitude. Organic olive groves used organic pest control (scent and sticky traps) and no chemicals. Non-organic groves were treated with a yearly insecticide spray. Six native, untreated woodland patches were also surveyed (three oak, three pine). Each of 18 sites was surveyed with bat detectors rotated between four random points for an hour and a half from dusk. Surveys were repeated on three nights/site in June–August 2006.
A replicated, paired sites study in 2003 on eight paired farms near Bristol, UK (Pocock & Jennings 2008) found that organic cereal fields had similar common pipistrelle Pipistrellus pipistrellus activity to nearby conventionally farmed fields. Common pipistrelle activity did not differ significantly between organic cereal fields (total 96 bat passes) and nearby conventionally farmed fields (total 152 bat passes). Pairs of fields were matched to control for habitat variables and were sampled simultaneously during one night in May–August 2003. At each of 16 sites, bat detectors recorded bat activity from 45 minutes after sunset for 20 minutes at each of four points along a transect (two points within fields, two along field boundaries).
A replicated, site comparison study in 2009–2011 of 5–13 organic and 10–30 non-organic farms in Wales, UK (MacDonald et al 2012) found that rivers on organic farms had significantly higher activity of Daubenton’s bats Myotis daubentonii than rivers on non-organic farms, but the activity of five other bat species in fields and along hedgerows did not differ between organic and non-organic farms. The average number of bat passes for Daubenton’s bats was significantly higher over rivers on organic farms than non-organic farms (data reported as statistical model results). However, a similar number of bat passes/year were recorded on organic and non-organic farms for common pipistrelles Pipistrellus pipistrellus, soprano pipistrelles Pipistrellus pygmaeus, common noctules Nyctalus noctula, greater horseshoe bats Rhinolophus ferrumequinum and lesser horseshoe bats Rhinolophus hipposideros (data reported as statistical model results). Organic farms were part of an organic farming scheme. The number of farms included in the analysis varied for each bat species from 5–13 for organic and 10–30 for non-organic farms. Some farms (organic and non-organic) were also part of agri-environment schemes. No details are reported about the origin of the rivers; water may have originated from outside of the farms. Transects or static detector surveys were carried out at each farm once or twice/year between June and September in 2009, 2010 and 2011.
A replicated, site comparison study in 2009–2010 at four organic and four conventional apple orchards in Michigan, USA (Long & Kurta 2014) found that organic orchards had similar bat activity, number of bat captures and species diversity as conventional orchards. The average number of bat passes recorded did not differ significantly between organic (37 bat passes/night) and conventional orchards (51 bat passes/night). The number of bats captured also did not differ significantly between organic (1.5 captures/night) and conventional orchards (2.2 captures/night). The same was true for species diversity (data reported as the Simpson’s Index). Four bat species were recorded (see original reference for data for individual species). Four organic and four conventional apple orchards (small dwarf or semi-dwarf varieties, 6–24 ha in size) were surveyed between June and August 2009, and May and August 2010. One bat detector/orchard recorded nightly bat activity, and was moved to random locations within each orchard each week. Mist netting was carried out 3–5 times/week at one orchard/night for four hours from sunset.
A replicated, paired sites study in 2015 at 21 pairs of organic and conventional vineyards in the south of France (Froidevaux et al 2017) found that organic farms had similar bat activity and species richness to conventional farms. Bat activity for the most abundant group of bat species (mid-range echolocating bats) did not differ significantly on organic (average 35 bat passes/site) and conventional farms (47 bat passes/site). Numbers for other groups of bat species were too low for statistical analysis. Species richness was also similar between organic and conventional farms (average 5 species/site for both). Ten bat species were recorded in total (see original reference for data for individual species). Twenty-one pairs of organic and conventional vineyards were matched according to local and landscape scale criteria, such as altitude, slope, aspect, presence of linear habitat features, vineyard area and proportion of semi-natural habitats. Conventional vineyards were assumed by the authors to have high pesticide use, although details were not reported. Each of 21 pairs of sites were sampled simultaneously with two bat detectors for one full night in August–September 2015.
- Wickramasinghe L.P., Harris S., Jones G. & Vaughan N. (2003) Bat activity and species richness on organic and conventional farms: impact of agricultural intensification. Journal of Applied Ecology, 40, 984-993
- Fuller R.J., Norton L.R., Feber R.E., Johnson P.J., Chamberlain D.E., Joys A.C., Mathews F., Stuart R.C., Townsend M.C., Manley W.J., Wolfe M.S., Macdonald D.W. & Firbank L.G. (2005) Benefits of organic farming to biodiversity vary among taxa. Biology Letters, 1, 431-434
- Davy C.M., Russo D. & Fenton M.B. (2007) Use of native woodlands and traditional olive groves by foraging bats on a Mediterranean island: consequences for conservation. Journal of Zoology, 273, 397-405
- Pocock M.J.O. & Jennings N. (2008) Testing biotic indicator taxa: the sensitivity of insectivorous mammals and their prey to the intensification of lowland agriculture. Journal of Applied Ecology, 45, 151-160
- MacDonald M.A., Morris A.J., Dodd S., Johnstone I., Beresford A., Angell R., Haysom K., Langton S., Tordoff G., Brereton T., Hobson R., Shellswell C., Hutchinson N., Dines T., Wilberforce E.M., Parry R. & Matthews V. (2012) Welsh Assembly Government Contract 183/2007/08 to Undertake Agri-environment Monitoring and Services. Lot 2 – Species Monitoring. Final report: October 2012.
- Long B.L. & Kurta A. (2014) Activity and diet of bats in conventional versus organic apple orchards in southern Michigan. Canadian Field-Naturalist , 128, 158-164
- Froidevaux J.S.P., Louboutin B. & Jones G. (2017) Does organic farming enhance biodiversity in Mediterranean vineyards? A case study with bats and arachnids. Agriculture, Ecosystems & Environment, 249, 112-122