Reducing the Maladaptive Attractiveness of Solar Panels to Polarotactic Insects

Abstract

Human-made objects (e.g., buildings with glass surfaces) can reflect horizontally polarized light so strongly that they appear to aquatic insects to be bodies of water. Insects that lay eggs in water are especially attracted to such structures because these insects use horizontal polarization of light off bodies of water to find egg-laying sites. Thus, these sources of polarized light can become ecological traps associated with reproductive failure and mortality in organisms that are attracted to them and by extension with rapid population declines or collapse. Solar panels are a new source of polarized light pollution. Using imaging polarimetry, we measured the reflection-polarization characteristics of different solar panels and in multiple-choice experiments in the field we tested their attractiveness to mayflies, caddis flies, dolichopodids, and tabanids. At the Brewster angle, solar panels polarized reflected light almost completely (degree of polarization d ≈ 100%) and substantially exceeded typical polarization values for water (d ≈ 30-70%). Mayflies (Ephemeroptera), stoneflies (Trichoptera), dolichopodid dipterans, and tabanid flies (Tabanidae) were the most attracted to solar panels and exhibited oviposition behavior above solar panels more often than above surfaces with lower degrees of polarization (including water), but in general they avoided solar cells with nonpolarizing white borders and white grates. The highly and horizontally polarizing surfaces that had nonpolarizing, white cell borders were 10- to 26-fold less attractive to insects than the same panels without white partitions. Although solar panels can act as ecological traps, fragmenting their solar-active area does lessen their attractiveness to polarotactic insects. The design of solar panels and collectors and their placement relative to aquatic habitats will likely affect populations of aquatic insects that use polarized light as a behavioral cue.

Phototaxis and polarotaxis hand in hand: night dispersal flight of aquatic insects distracted synergistically by light intensity and reflection polarization

“…asphalt roads, oil lakes, black plastic sheets used in agriculture, shiny dark-coloured cars, solar panels and collectors) -mimicking the reflection-polarization characteristics of water surfaces -may confuse flying, water-seeking polarotactic water insects. These man-made polarizing reflecting surfaces cause daylong polarized light pollution, that has disastrous consequences for polarotactic insects (Horváth and Zeil 1996;Kriska et al 2006;Bernáth et al 2001;Horváth et al 2009Horváth et al , 2010a.…”

Polarized light pollution of matte solar panels: anti-reflective photovoltaics reduce polarized light pollution but benefit only some aquatic insects

“…3, Supporting Fig. S2 Horváth et al 2010aHorváth et al , 2011 suggest that ARC's were not sufficiently effective to 380 reduce chironomid attraction. 381…”

“…Moreover, vertical artificial polarizers are just as effective at triggering maladaptive 398 behavior as horizontal ones (Kriska et al 2008) and so the orientation of panels at angles perpendicular 399 to the direction of the mid-day sun is not likely to either mitigate or exacerbate the patterns we have 400 seen here. Previous research has shown that one solution to this problem is to manufacture PV panels 401 with a dense grid of thin white lines (Horváth et al 2010a Because polarized light pollution triggers severely maladaptive behavior in nearly every single 407…”

“…Insect species that have evolved in 418 more xeric, less-often overcast systems like deserts in which large-scale photovoltaic installations are 419 placed may have more consistent and positive responses to matte (anti-reflective) coatings, but more 420 research is needed to examine how a broader array of aquatic arthropod taxa respond to similar 421 reductions in PLP. Because white, non-polarizing gridding on solar panels are known to reduce the 422 attractiveness of artificial polarizers to aquatic insects (Horváth et al 2010a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 …”

“…Photovoltaic solar panels are strong sources of a form of photopollution known as polarized 73 light pollution (PLP, Horváth et al 2009Horváth et al , 2010a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 Observers counted reaction groups (how many times a horsefly individual reacted to a given 177 test surface with aerial looping, touch-down, or landing, excluding repetitions by the same individual 178 before flying away) and reaction items (how many times a given reaction element -looping, touching, 179 landing -was performed by a given horsefly, including repetitions by the same individual before flying 180 away). For example, if 4 horseflies reacted with aerial looping and each horsefly performed 3 loops 181 above a test surface, then reaction groups = 4, and reaction items = 4 × 3 = 12.…”