What Works in Conservation 2021
| , , ,2. Bat conservation
2.3 Threat: Energy production
Texte intégral
2.3.1 Wind turbines
Beneficial
Increase the wind speed at which turbines become operational (‘cut-in speed’)
1Twelve studies evaluated the effects of increasing the wind speed at which turbines become operational (‘cut-in speed’) on bat populations. Ten studies were in the USA and two were in Canada.
2COMMUNITY RESPONSE (0 STUDIES)
3POPULATION RESPONSE (12 STUDIES)
4Survival (12 studies): Ten of 12 studies (including 10 replicated, randomized, controlled studies and one before-and-after study) in the USA and Canada found that increasing the wind speed at which turbines become operational (‘cut-in speed’), or increasing the cut-in speed along with preventing turbine blades from turning at low wind speeds (‘feathering’) resulted in fewer bat fatalities than at conventionally operated turbines. The other two studies found that increasing cut-in speeds did not reduce bat fatalities, but sample sizes were small or treatments were applied for short periods only.
5BEHAVIOUR (0 STUDIES)
6Assessment: beneficial (effectiveness 80 %; certainty 72 %; harms 0 %).
https://www.conservationevidence.com/actions/1960
Prevent turbine blades from turning at low wind speeds (’feathering’)
7Six studies evaluated the effects of preventing turbine blades from turning at low wind speeds on bat populations. Five studies were in the USA and one was in Canada.
8COMMUNITY RESPONSE (0 STUDIES)
9POPULATION RESPONSE (6 STUDIES)
10Survival (6 studies): Five of six studies (including five replicated, controlled studies and one before-and-after study) in the USA and Canada found that preventing turbine blades from turning at low wind speeds (‘feathering’), or feathering along with increasing the wind speed at which turbines become operational (‘cut-in speed’) resulted in fewer bat fatalities than at conventionally operated turbines. The other study found that automatically feathering turbine blades at low wind speeds did not reduce bat fatalities. BEHAVIOUR (0 STUDIES)
11Assessment: beneficial (effectiveness 82 %; certainty 70 %; harms 0 %).
https://www.conservationevidence.com/actions/970
Likely to be beneficial
Automatically reduce turbine blade rotation when bat activity is high
12Two studies evaluated the effects of automatically reducing turbine blade rotation when bat activity is high on bat populations. One study was in Germany, and one in the USA.
13COMMUNITY RESPONSE (0 STUDIES)
14POPULATION RESPONSE (2 STUDIES)
15Survival (2 studies): Two replicated studies (one randomized, controlled and one paired sites study) in Germany and the USA found that automatically reducing the rotation speed of wind turbine blades when bat activity is predicted to be high resulted in fewer bat fatalities for all bat species combined and for five bat species.
16BEHAVIOUR (0 STUDIES)
17Assessment: likely to be beneficial (effectiveness 80 %; certainty 60 %; harms 0 %).
https://www.conservationevidence.com/actions/971
Slow rotation of turbine blades at low wind speeds
18One study evaluated the effects of slowing the rotation of turbine blades at low wind speeds on bat populations. The study was in Canada.
19COMMUNITY RESPONSE (0 STUDIES)
20POPULATION RESPONSE (1 STUDY)
21Survival (1 study): One replicated, randomized, controlled study in Canada found that bat fatalities were reduced when turbine blades were slowed at low wind speeds.
22BEHAVIOUR (0 STUDIES)
23Assessment: likely to be beneficial (effectiveness 60 %; certainty 40 %; harms 0 %).
https://www.conservationevidence.com/actions/2939
Unknown effectiveness
Apply textured coating to turbines
24One study evaluated the effects of applying a textured coating to turbines on bat populations. The study was in the USA.
25COMMUNITY RESPONSE (0 STUDIES)
26POPULATION RESPONSE (1 STUDY)
27Abundance (1 study): One paired sites study in the USA found that applying a textured coating to a turbine did not reduce the activity of four bat species or the number of bats observed.
28BEHAVIOUR (0 STUDIES)
29Assessment: unknown effectiveness (effectiveness 0 %; certainty 22 %; harms 0 %).
https://www.conservationevidence.com/actions/1957
Deter bats from turbines using ultrasound
30Four studies evaluated the effects of deterring bats from wind turbines using ultrasound on bat populations. The four studies were in the USA.
31COMMUNITY RESPONSE (0 STUDIES)
32POPULATION RESPONSE (3 STUDIES)
33Survival (3 studies): Three replicated, randomized, controlled studies (one with a before-and-after trial in the second year) in the USA found mixed results. In the first year of one study, 21-51 % fewer bats were killed at turbines with an ultrasonic deterrent fitted than at control turbines, but in the second year, from 2 % more to 64 % fewer bats were killed at turbines with ultrasonic deterrents fitted. One study found that using an ultrasonic deterrent emitting a constant or pulsed signal had mixed effects on the fatality rates of three bat species. One study found that using ultrasonic deterrents resulted in fewer fatalities for two of three bat species.
34BEHAVIOUR (1 STUDY)
35Behaviour change (1 study): One paired sites study in the USA found fewer bats flying near one of two wind turbines with an ultrasonic deterrent compared to turbines without, but the effect of the deterrent overall was not significant. Assessment: unknown effectiveness (effectiveness 40 %; certainty 35 %; harms 10 %).
https://www.conservationevidence.com/actions/968
No evidence found (no assessment)
36We have captured no evidence for the following interventions:
-
Close off potential access points on turbines to prevent roosting bats
-
Deter bats from turbines using low-level ultraviolet light
-
Deter bats from turbines using radar
-
Modify turbine placement to reduce bat fatalities
-
Paint turbines to reduce insect attraction
-
Remove turbine lighting to reduce bat and insect attraction
-
Retain a buffer between turbines and habitat features used by bats.
2.3.2 Mining
Trade-off between benefit and harms
Install and maintain gates at mine entrances to restrict public access
37Nine studies evaluated the effects of installing gates at mine entrances on bat populations. Eight studies were in the USA and one in Australia.
38COMMUNITY RESPONSE (1 STUDY)
39Richness/diversity (1 study): One replicated, before-and-after study in the USA found that fewer bat species entered mines after gates were installed. POPULATION RESPONSE (3 STUDIES)
40Abundance (3 studies): Two replicated, site comparison or before-and-after studies in the USA and Australia found fewer bats in mines or at mine entrances after gates were installed. One replicated, controlled, before-and-after study in the USA found that bat activity (relative abundance) remained stable or increased at five of seven gated mines, and decreased at two gated mines. BEHAVIOUR (6 STUDIES)
41Use (2 studies): One before-and-after study in the USA found that 43 of 47 mines continued to be used 12 years after gates were installed, however bats abandoned four mines with ‘ladder’ design gates. One replicated study in the USA found that gate design and time since gate installation had varied effects on the presence of four bat species.
42Behaviour change (4 studies): Four replicated, before-and-after or site comparison studies in the USA and Australia found that bats at mine entrances circled more and entered mines less after gates were installed.
43OTHER (2 STUDIES)
44Collisions with gates (1 study): One replicated, controlled, before-and-after study in the USA found that up to 7 % of bats at mine entrances collided with mine gates.
45Assessment: trade-off between benefit and harms (effectiveness 50 %; certainty 50 %; harms 46 %).
https://www.conservationevidence.com/actions/1963
Unknown effectiveness
Maintain microclimate in closed/abandoned mines
46One study evaluated the effects of maintaining the microclimate in an abandoned mine on bat populations. The study was in the USA.
47COMMUNITY RESPONSE (0 STUDIES)
48POPULATION RESPONSE (1 STUDY)
49Abundance (1 study): One before-and-after study in the USA found that modifying the microclimate of an abandoned mine by closing a man-made entrance resulted in a greater number of bats hibernating within the mine. BEHAVIOUR (0 STUDIES)
50Assessment: unknown effectiveness (effectiveness 45 %; certainty 20 %; harms 0 %).
https://www.conservationevidence.com/actions/1964
Restore bat foraging habitat at ex-quarry sites
51One study evaluated the effects of restoring bat foraging habitat at ex-quarry sites on bat populations. The study was in France.
52COMMUNITY RESPONSE (0 STUDIES)
53POPULATION RESPONSE (1 STUDY)
54Abundance (1 study): One replicated, site comparison study in France found that gravel-sand pits had higher overall bat activity (relative abundance) 10 years after restoration than gravel-sand pit sites before or during quarrying.
55BEHAVIOUR (0 STUDIES)
56Assessment: unknown effectiveness (effectiveness 50 %; certainty 35 %; harms 0 %).
https://www.conservationevidence.com/actions/2286
No evidence found (no assessment)
57We have captured no evidence for the following interventions:
-
Exclude bats from roosts prior to mine reclamation
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Provide artificial subterranean bat roosts to replace roosts in reclaimed mines
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Relocate bats from reclaimed mines to alternative subterranean roost sites
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Reopen entrances to closed mines and make suitable for roosting bats
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Retain access points for bats following mine closures.
Table des illustrations
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