Saturday, 14 April 2012

Bats and Lighting of the FB's

Light pollution is a complicated issue for some bat species. It was dealt with unsatisfactorily within the Hydro Environmental Statement, with little reference to literature and no citations of the relevant bat studies, particularly those undertaken in the last 6 years. There has been  overall an unsatisfactory survey evaluation, due to a poor understanding of URBAN ECOLOGY, coupled with a determination to employ many different types of light arrangement  at the  FB's regardless of the survey findings, in order to ensure the Health and Safety of any future riparian residents.

2012 Bat Surveys commissioned at the FB's, should record how bats use the basins for foraging purposes. This habitat could be protected under European Law if it is found to be a significant feature that bats rely on in order to  feed and nurture their young (see earlier post on Habitats Regs). The timing of these surveys is CRITICAL. Surveys carried out during the full moon for example should be invalid. The moon phase and other light sources, can influence how bats utilise open areas.
Fulham FC lights over the London Wetlands Centre

LIGHT EFFECTS ON FORAGING BATS
During August, 2010 London and Herts. & Middlesex Bat Groups took part in a Moon Phase survey. A total of twenty one people, at eight sites across the region participated in bat counts at open areas around water -bodies during ‘No Moon’ (10.8.10) and the ‘Full Moon’ (24.8.10). Standing at a spot in an open area, participants counted the number of Daubenton’s bat passes obtained using a torch with a red filter or red cellophane. During the full moon phase, an additional note was taken of the amount of cloud cover (0-8 cloud cover with 0 equating to a clear sky). When the number of passes was compared, it was found that (at sites where data was obtained) that the full moon reduced the overall activity by almost 2/3 (63%). The full results can be read on the London Bat Group Website or I can supply the full PDF.

Table 1: Number of Daubenton’s bat passes during different moon phases.

Number of Daubenton’s bat passes during ‘No Moon’
10.8.10
Number of Daubenton’s bat passes during the ‘Full Moon’
24.8.10
Oakmere Lake, Potters Bar
3 stations
83
31

273
103

370
187
Pen Ponds, Richmond
3 stations
260
0

60
0

160
119
Kelsey Park , Beckenham
9.9.10
24.810

241
102
Total no of passes
1447
542


Light pollution at Richmond Bridge wildlife corridor?
LIGHT EFFECTS ON COMMUTING BATS
Anthropogenic light pollution is an increasing global problem. Emma Stone and Gareth Jones (2009) installed high pressure sodium lights to mimic the intensity and light spectra of street lights along commuting routes of lesser horseshoe bats Rhinolophus hipposideros. Bat activity was reduced dramatically and the onset of commuting behaviour was delayed in the presence of lighting . The results of the study demonstrated that light pollution has a significant impact of the selection of flight routes of bats. 
Not all species are affected in the same way. Emergence times from roosts appear to act as an indication of the differing light tolerance through the range of species. Those bats which emerge late in the evening include Myotis, particularly the Natterer’s and Daubenton's bat, which have a reduced tolerance to lighting. 

Fair do's .....Kingston Bridge
As intensity of light increases, even relatively light tolerant species are delayed in emergence from their roost. Larger, high flying bat species such as Noctule bat, are not as affected by light pollution. They will often fly during the daytime and feed above installations where security lights attract a variety of insects 

GUIDANCE ON LIGHTING AND BATS
A conference hosted by the Bat Conservation Trust on Lighting and Mitigation for Bats (2007) resolved that: Where any bat species are found, care should be taken to ensure that roosts, foraging areas, and corridors for movement of these species are not affected by light pollution.

• All bat species are adversely affected by the roost access being lit.

• Noctule, serotine, Leisler’s and pipistrelle species commonly feed around lights.

• All other species are generally adversely affected by foraging areas being lit.

• The positive feeding opportunity for some species is not positive overall for bats.


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