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Providing evidence to improve practice

Action: Use organic farming instead of conventional farming Bat Conservation

Key messages

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  • Twelve studies evaluated the effects of using organic farming instead of conventional farming on bat populations. Eight studies were in Europe, two in the USA, one in Canada and one in Chile.

COMMUNITY RESPONSE (7 STUDIES)

  • Community composition (1 study): One replicated, paired sites study in the USA found that the composition of bat species did not differ between organic and non-organic farms.
  • Richness/diversity (7 studies): Five of seven replicated, paired sites or site comparison studies in Europe, the USA, Canada and Chile found that the number of bat species did not differ between organic and non-organic farms. The other two studies found more bat species on organic farms than non-organic farms.

POPULATION RESPONSE (12 STUDIES)

BEHAVIOUR (0 STUDIES)      

Supporting evidence from individual studies

1 

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 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). Brandt’s and Bechstein’s bat activity did not differ in pasture, arable or woodland habitats, or for any other bat species, between organic and conventional farms (see original paper for detailed results). 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 1.5 h from 1 h after sunset. Two farms within a pair were sampled on consecutive nights in June–September 2000 or 2002.

2 

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. A greater number of bat passes and bat species were recorded on organic farms (abundance index 6–75% higher; species density 8–65% higher) than conventional farms (numbers not reported). 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.

3 

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 paper 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 1.5 h from dusk. Surveys were repeated on three nights/site in June–August 2006.

4 

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).

5 

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 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 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.

6 

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 in total (see original paper 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 4 h from sunset.

7 

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 paper 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.

8 

A replicated, site comparison study in 2015–2016 at three organic and three conventional rice farms near Vercelli, Italy (Toffoli & Rughetti 2017) found that organic farms had higher overall bat activity and bat feeding activity than conventional farms. The average number of bat passes was higher on organic rice farms (178 bat passes/hour) than conventional rice farms (50 bat passes/hour). The same was true for the average number of feeding buzzes (organic farms: 27 buzzes/hour; conventional farms: 1 buzz/hour). Twelve bat species were recorded in total although 95% of the recordings were Pipistrellus spp. (see original paper for data for individual species). Surveys were carried out on three organic rice farms (rice paddies certified organic and not treated with synthetic pesticides) and three conventional rice farms (rice paddies regularly treated with pesticides and chemical fertilizers). Bat activity was recorded with a bat detector at one sampling point/farm for three nights in May–September 2015 or 2016.

9 

A replicated, site comparison study in 2016 of 19 wheat fields in the Île-de-France region, France (Barré et al 2018) found that organic fields had higher activity for two of three bat species than two of three types of conventionally managed fields. Activity of Kuhl’s pipistrelle Pipistrellus kuhlii and common pipistrelle Pipistrellus pipistrellus was higher over organic tillage fields than conventional tillage fields with two herbicide applications and conventional ‘conservation tillage’ fields with three herbicide applications, but not over conventional ‘conservation tillage’ fields with two herbicide applications (data reported as statistical model results). The activity of Nathusius’ pipistrelle Pipistrellus nathusii did not differ significantly between organic fields and any of the three conventional field types. Surveys were carried out at 12 sites in two organic fields (tillage to 30 cm depth and no herbicides) and 13–18 sites in 5–7 of each of the three types of conventionally managed fields (tillage with two herbicide applications, or superficial ‘conservation tillage’ with two or three herbicide applications). Bat detectors were used to simultaneously survey 1–4 sites/treatment on each of eight nights in June 2016.

10 

A replicated, paired sites study in 2014 at 18 pairs of farms in California, USA (Olimpi & Philpott 2018) found that organic farms had similar bat activity, species richness, diversity and species composition to conventional farms. Overall bat activity did not differ significantly between organic (average 45 bat passes/night) and conventional farms (average 40 bat passes/night). The same was true for the activity of bat species adapted to cluttered habitats (organic: average 10 bat passes/night; conventional: 4 bat passes/night) and open habitats (organic: average 31 bat passes/night; conventional: 33 bat passes/night). Bat species richness, bat diversity and species composition also did not differ significantly between organic and conventional farms (data reported as statistical indices). Eleven bat species were recorded in total (see original paper for data for individual species). Each of 18 pairs of fields in certified organic farms and conventional farms was surveyed simultaneously with one bat detector/field for 6–7 nights in June–September 2014.

11 

A replicated, paired sites study in 2017 of 16 pairs of soybean Glycine max fields in Canada (Put et al 2018) found that organic fields had higher overall bat activity and activity of four of seven bat species than conventional fields, but the number of bat species did not differ. Overall bat activity (bat passes) and the activity of four bat species (big brown bat Eptesicus fuscus, hoary bat Lasiurus cinereus, little brown bat Myotis lucifugus, silver-haired bat Lasionycteris noctivagans) was higher over organic fields than conventional fields (data reported as statistical model results). The activity of three other bat species (eastern red bat Lasiurus borealis, northern long-eared bat Myotis septentrionalis, tri-coloured bat Perimyotis subflavus) and the number of bat species recorded did not differ over organic and conventional fields (data reported as statistical model results). Sixteen soybean fields on certified organic farms were paired with 16 soybean fields on conventional farms (fields treated with neonicotinoid pesticides) according to field size, local habitat and surrounding landscape. Two locations at the edge of each of 32 fields were surveyed with bat detectors for two nights in June–July 2017.

12 

A replicated, paired sites study in 2016–2017 at 11 paired plots on organic and conventional vineyards in Buin and Paine, Chile (Rodríguez-San Pedro et al 2018) found that organic vineyards had more bat species and greater activity of Brazilian free-tailed bats Tadarida brasiliensis than conventional vineyards. A higher number of bat species were recorded on organic (average 2 bat species/sampling point) than conventional vineyards (average 1 bat species/sampling point). Organic vineyards had greater activity of Brazilian free-tailed bats (average 24 bat passes/sampling point) than conventional vineyards (average 10 bat passes/sampling point). Eleven pairs of plots on organic and conventional vineyards were matched by adjacent habitats and surrounding land cover types. Organic vineyards had been certified for 15–20 years, did not use agrochemical treatments (except fungicides) and had cover crops, flowers and weeds between rows. Two sampling points/plot (edge and interior) were surveyed simultaneously using bat detectors for 30 minutes on each of three nights in January–March 2016 and 2017.

Referenced papers

Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2019) Bat Conservation. Pages 67-140 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.