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What Works in Conservation 2021

 | 
William Junior Sutherland
, 
Lynn V. Dicks
, 
Silviu O. Petrovan
, 
et al.

2. Bat conservation

2.2 Threat: Agriculture

Volltext

2.2.1 All farming systems

Likely to be beneficial

Retain or plant native trees and shrubs amongst crops (agroforestry)

1Eight studies evaluated the effects of retaining or planting native trees and shrubs amongst crops on bat populations. Four studies were in Mexico, three were in South America and one was in Tanzania.

2COMMUNITY RESPONSE (7 STUDIES)

3Community composition (1 study): One replicated, site comparison study in Tanzania found different compositions of bat species in coffee plantations with different amounts and types of shade cover.

4Richness/diversity (7 studies): Four of six replicated, site comparison studies in Columbia, Mexico and Costa Rica found a similar number of bat species in shaded and unshaded coffee plantations, and in coffee plantations with different amounts and types of shade cover. The two other studies found more bat species and higher bat diversity in coffee, cacao and banana plantations with varied shade cover, than in plantations with a single shade species or no shade. One replicated, site comparison study in Tanzania found more bat species in shaded coffee plantations than in traditional mixed agroforestry systems with natural forest vegetation.

5POPULATION RESPONSE (6 STUDIES)

6Abundance (5 studies): Two replicated, site comparison studies in Mexico captured more bats in coffee plantations with varied shade cover than in plantations with a single shade species. One replicated, site comparison study in Mexico found higher activity (relative abundance) of forest bat species in plantations with a varied shade cover than in plantations with a single shade species, but the opposite was true for open habitat bat species. One replicated, site comparison study in Costa Rica found no difference in the number of bats captured between cacao and banana shade plantations and unshaded monocultures. One replicated, site comparison study in Tanzania found greater bat occurrence in shaded coffee plantations than in traditional mixed agroforestry systems with natural forest vegetation.

7Condition (1 study): One replicated, site comparison study in Columbia found that great fruit-eating bats captured in ‘silvopastoral’ areas that used agroforestry, along with no chemicals, had higher body weights and body condition scores than those in conventional farming areas.

8BEHAVIOUR (0 STUDIES)

9Assessment: likely to be beneficial (effectiveness 60 %; certainty 53 %; harms 0 %).

https://www.conservationevidence.com/​actions/​963

Use organic farming instead of conventional farming

10Twelve 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.

11COMMUNITY RESPONSE (7 STUDIES)

12Community 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.

13Richness/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.

14POPULATION RESPONSE (12 STUDIES)

15Abundance (12 studies): Five of nine replicated, paired sites or site comparison studies in Europe, the USA, Canada and Chile found that overall bat activity (relative abundance) and common pipistrelle activity did not differ between organic and non-organic farms. The other four studies found higher overall bat activity, bat feeding activity, Brazilian free-tailed bat activity, and activity of four of seven bat species on organic farms than non-organic farms. Two replicated, paired sites and site comparison studies in the UK found 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. One replicated, site comparison study in France found higher activity for two of three bat species over organic fields than two of three types of conventionally managed fields.

16BEHAVIOUR (0 STUDIES)

17Assessment: likely to be beneficial (effectiveness 60 %; certainty 60 %; harms 0 %).

https://www.conservationevidence.com/​actions/​961

Unknown effectiveness

Create tree plantations on agricultural land

18Three studies evaluated the effects of creating tree plantations on agricultural land on bat populations. The three studies were in Australia.

19COMMUNITY RESPONSE (3 STUDIES)

20Richness/diversity (3 studies): Three replicated, site comparison studies in Australia found no difference in the number of bat species in agricultural areas with and without plantations of native trees.

21POPULATION RESPONSE (3 STUDIES)

22Abundance (3 studies): Two of three replicated, site comparison studies in Australia found no difference in bat activity (relative abundance) in agricultural areas with and without plantations of native trees. The other study found higher bat activity in plantations next to remnant native vegetation than in isolated plantations or over grazing land. In all three studies, bat activity was lower in plantations compared to original forest and woodland remnants. BEHAVIOUR (0 STUDIES)

23Assessment: unknown effectiveness (effectiveness 30 %; certainty 30 %; harms 0 %).

https://www.conservationevidence.com/​actions/​958

Engage farmers and landowners to manage land for bats

24One study evaluated the effects of engaging farmers and landowners to manage land for bats on bat populations. The study was in the UK.

25COMMUNITY RESPONSE (0 STUDIES)

26POPULATION RESPONSE (1 STUDY)

27Abundance (1 study): One study in the UK found that during a five-year project to engage farmers and landowners to manage land for bats, the overall population of greater horseshoe bats at four maternity roosts in the area increased (but see summary below).

28BEHAVIOUR (1 STUDY)

29Change in human behaviour (1 study): One study in the UK found that a landowner engagement project resulted in 77 bat-related management agreements covering approximately 6,536 ha of land.

30Assessment: unknown effectiveness (effectiveness 55 %; certainty 20 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1936

Manage hedges to benefit bats

31Two studies evaluated the effects of managing hedges to benefit bat populations. Both studies were in the UK.

32COMMUNITY RESPONSE (1 STUDY)

33Richness/diversity (1 study): One replicated, site comparison study in the UK found that hedges trimmed ≥3 years prior had more bat species recorded along them than hedges trimmed during the previous winter.

34POPULATION RESPONSE (2 STUDIES)

35Abundance (2 studies): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between hedges managed for wildlife on agri-environment scheme farms and hedges on conventional farms. One replicated, site comparison study in the UK found that hedges trimmed ≥3 years prior had higher activity of two of eight bat species/species groups than hedges trimmed during the previous winter. BEHAVIOUR (0 STUDIES)

36Assessment: unknown effectiveness (effectiveness 50 %; certainty 36 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1943

Plant field margins with a diverse mix of plant species

37One study evaluated the effects of planting field margins with a diverse mix of plant species on bats populations. The study was in the UK.

38COMMUNITY RESPONSE (0 STUDIES)

39POPULATION RESPONSE (1 STUDY)

40Abundance (1 study): One replicated, site comparison study in the UK found that the activity (relative abundance) of soprano pipistrelles and barbastelle bats increased with a greater diversity of plant species within field margins, but there was no effect on common pipistrelle activity nor on the occurrence of any of the six bat species studied.

41BEHAVIOUR (0 STUDIES)

42Assessment: unknown effectiveness (effectiveness 50 %; certainty 30 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1941

Reduce field size (or maintain small fields)

43One study evaluated the effects of maintaining small fields on bat populations. The study was in Canada.

44COMMUNITY RESPONSE (0 STUDIES)

45POPULATION RESPONSE (1 STUDY)

46Abundance (1 study): One replicated, site comparison study in Canada found that agricultural landscapes with smaller fields had higher activity (relative abundance) of six of seven bat species than landscapes with larger fields. BEHAVIOUR (0 STUDIES)

47Assessment: unknown effectiveness (effectiveness 60 %; certainty 30 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1939

Retain riparian buffers on agricultural land

48One study evaluated the effects of retaining riparian buffers on agricultural land on bat populations. The study was in the UK.

49COMMUNITY RESPONSE (0 STUDIES)

50POPULATION RESPONSE (1 STUDY)

51Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ along waterways with buffers of vegetation on agri-environment scheme farms and waterways on conventional farms.

52BEHAVIOUR (0 STUDIES)

53Assessment: unknown effectiveness (effectiveness 40 %; certainty 20 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2284

Retain unmown field margins

54One study evaluated the effects of retaining unmown field margins on bats populations. The study was in the UK.

55COMMUNITY RESPONSE (0 STUDIES)

56POPULATION RESPONSE (1 STUDY)

57Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between unmown field margins managed for wildlife on agri-environment scheme farms and field margins on conventional farms.

58BEHAVIOUR (0 STUDIES)

59Assessment: unknown effectiveness (effectiveness 0 %; certainty 10 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1940

Unlikely to be beneficial

Pay farmers to cover the costs of conservation measures (e.g. agri-environment schemes)

60Three studies evaluated the effects of agri-environment schemes on bat populations. The three studies were in the UK.

61COMMUNITY RESPONSE (0 STUDIES)

62POPULATION RESPONSE (3 STUDIES)

63Abundance (3 studies): Two of three replicated, paired sites studies in the UK found that overall bat activity (relative abundance) or the occurrence of six bat species did not differ significantly between farms managed under agri-environment schemes and those managed conventionally. One of the studies found that agri-environment scheme farms had similar activity of five bat species, and lower activity of one bat species, compared to conventional farms. The other study found lower overall bat activity and activity of pipistrelle species on agri-environment scheme farms than conventional farms.

64BEHAVIOUR (0 STUDIES)

65Assessment: unlikely to be beneficial (effectiveness 27 %; certainty 42 %; harms 0 %).

https://www.conservationevidence.com/​actions/​962

No evidence found (no assessment)

66We have captured no evidence for the following interventions:

  • Increase the proportion of semi-natural habitat in the farmed landscape
  • Manage ditches to benefit bats
  • Plant in-field trees
  • Plant new hedges
  • Provide or retain set-aside areas in farmland
  • Retain existing in-field trees
  • Retain remnant forest or woodland on agricultural land.

2.2.2 Livestock farming

Likely to be beneficial

Manage livestock water troughs as a drinking resource for bats

67Two studies evaluated the effects of managing livestock water troughs as a drinking resource for bats. Both studies were in the USA.

68COMMUNITY RESPONSE (0 STUDIES)

69POPULATION RESPONSE (0 STUDIES)

70BEHAVIOUR (2 STUDIES)

71Use (2 studies): One replicated, paired sites study in the USA found that removing livestock modifications from water troughs resulted in bats drinking from them more frequently. One paired sites study in the USA found that livestock water tanks that were larger, full of water or surrounded by sparse vegetation had more bats drinking from them than smaller, half full tanks surrounded by no or dense vegetation.

72Behaviour change (1 study): One replicated, paired sites study in the USA found that when livestock modifications were removed from water troughs, bats approached troughs fewer times before successfully drinking from them. Assessment: likely to be beneficial (effectiveness 67 %; certainty 45 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1951

No evidence found (no assessment)

73We have captured no evidence for the following interventions:

  • Avoid the use of antiparasitic drugs for livestock
  • Manage grazing regimes to increase invertebrate prey
  • Replace culling of bats with non-lethal methods of preventing vampire bats from spreading rabies to livestock.

2.2.3 Perennial, non-timber crops

Likely to be beneficial

Use non-lethal measures to prevent bats from accessing fruit in orchards to reduce human-wildlife conflict

74Two studies evaluated the effects of using non-lethal measures to prevent bats from accessing fruit in orchards to reduce human-wildlife conflict. The studies were in Madagascar and Mauritius.

75COMMUNITY RESPONSE (0 STUDIES)

76POPULATION RESPONSE (0 STUDIES)

77BEHAVIOUR (0 STUDIES)

78OTHER (2 STUDIES)

79Human-wildlife conflict (2 studies): Two replicated, controlled studies (including one randomized study) in Madagascar and Mauritius found that using an organic deterrent spray, hanging plastic flags in trees, or covering individual tree branches with nylon net bags reduced damage to lychees caused by Madagascan flying foxes or Mauritius fruit bats. One of the studies found that ringing bells in lychee trees deterred most Madagascan flying foxes. Assessment: likely to be beneficial (effectiveness 70 %; certainty 50 %; harms 0 %).

https://www.conservationevidence.com/​actions/​1953

No evidence found (no assessment)

80We have captured no evidence for the following interventions:

  • Introduce certification for bat-friendly crop harvesting regimes
  • Prevent culling of bats around fruit orchards
  • Restore and manage abandoned orchards for bats.

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