Ecological photopollution created by artificial night lighting can alter animal behavior and lead to population declines and biodiversity loss. Polarized light pollution is a second type of photopollution that triggers water-seeking insects to ovisposit on smooth and dark man-made objects, because they simulate the polarization signatures of natural water bodies. We document a case study of the interaction of these two forms of photopollution by conducting observations and experiments near a lamp-lit bridge over the river Danube that attracts mass swarms of the mayfly Ephoron virgo away from the river to oviposit on the asphalt road of the bridge. Millions of mayflies swarmed near bridge-lights for two weeks. We found these swarms to be composed of 99% adult females performing their upstream compensatory flight and were attracted upward toward unpolarized bridge-lamp light, and away from the horizontally polarized light trail of the river. Imaging polarimetry confirmed that the asphalt surface of the bridge was strongly and horizontally polarized, providing a supernormal ovipositional cue to Ephoron virgo, while other parts of the bridge were poor polarizers of lamplight. Collectively, we confirm that Ephoron virgo is independently attracted to both unpolarized and polarized light sources, that both types of photopollution are being produced at the bridge, and that spatial patterns of swarming and oviposition are consistent with evolved behaviors being triggered maladaptively by these two types of light pollution. We suggest solutions to bridge and lighting design that should prevent or mitigate the impacts of such scenarios in the future. The detrimental impacts of such scenarios may extend beyond Ephoron virgo.

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Lamp-lit bridges as dual light-traps for the night-swarming mayfly, Ephoron virgo: interaction of polarized and unpolarized light pollution.

Based on an earlier observation in the field, we hypothesized that light intensity and horizontally polarized reflected light may strongly influence the flight behaviour of night-active aquatic insects. We assumed that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of these insects than they would have separately. We tested this hypothesis in a multiple-choice field experiment using horizontal test surfaces laid on the ground. We offered simultaneously the following visual stimuli for aerial aquatic insects: (1) lamplit matte black canvas inducing phototaxis alone, (2) unlit shiny black plastic sheet eliciting polarotaxis alone, (3) lamplit shiny black plastic sheet inducing simultaneously phototaxis and polarotaxis, and (4) unlit matte black canvas as a visually unattractive control. The unlit matte black canvas trapped only a negligible number (13) of water insects. The sum (16,432) of the total numbers of water beetles and bugs captured on the lamplit matte black canvas (7,922) and the unlit shiny black plastic sheet (8,510) was much smaller than the total catch (29,682) caught on the lamplit shiny black plastic sheet. This provides experimental evidence for the synergistic interaction of phototaxis (elicited by the unpolarized direct lamplight) and polarotaxis (induced by the strongly and horizontally polarized plastic-reflected light) in the investigated aquatic insects. Thus, horizontally polarizing artificial lamplit surfaces can function as an effective ecological trap due to this synergism of optical cues, especially in the urban environment.

/pdf/phototaxis-and-polarotaxis-hand-in-hand-night-dispersal-23wofj7jck.pdf

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

Photovoltaic solar panels represent one of the most promising renewable energy sources, but are strong reflectors of horizontally polarized light. Polarized light pollution (PLP) associated with solar panels causes aquatic insects to prefer to oviposit on panels over natural water bodies, with potential to negatively impact their global populations as solar energy expands. We evaluate the hypothesis that anti-reflective coatings (ARCs) used to increase the energy efficiency of solar panels will reduce the amount of PLP they reflect, and their attractiveness to aquatic insects. We created artificial test surfaces that mimicked the optical properties of coated and uncoated solar panels and exposed them to wild populations of polarotactic mayflies (Ephemeroptera), horseflies (Tabanidae) and non-biting midges (Chironomidae) used as indicators of PLP. We evaluated the reflection-polarization properties of test surfaces from four different angles of view and under sunny and overcast skies in the visible and ultraviolet parts of the spectrum. Matte (i.e. ARC-coated) sunlit solar panels were strong sources of horizontally polarized light only when the sun was afront and behind, in contrast to uncoated panels which exceeded common polarization-sensitivity thresholds for aquatic insects from all four viewing directions. As predicted by these polarization patterns, horsefly numbers and water-seeking behaviors were significantly reduced by ARCs. Under overcast skies, both matte and shiny (i.e. uncoated) panels were insect-detectible sources of PLP. Matteness modestly reduced the degree of polarization of reflected light, but not sufficiently such that fewer chironomids were attracted to them. Mayflies actually preferred matte panels under overcast skies. ARCs are most likely to reduce PLP and benefit aquatic insects under sunny skies and when used in conjunction with white non-polarizing gridding, but may actually exacerbate the severity of their negative effects under overcast conditions. Consequently, even current ARC technology has a role to play in aquatic insect conservation, but strategic deployment of solar panels away from water bodies and temperate regions may trump these benefits.

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

Funding information Bard College; Australian Research Council; National Science Foundation Abstract Evolutionary traps occur when rapid environmental change leads animals to prefer resources (e.g., food, mates, habitats) that reduce their fitness. Traps can lead to rapid population declines, extirpation, and species extinction, yet they have received little attention within the context of wildlife conservation efforts. We first demonstrate that traps are affecting a taxonomically diverse range of animals including key pollinators and important human food species and commonly impact threatened and endangered species. We then provide a conceptual framework for wildlife scientists and practitioners that outlines: (1) the detectable symptoms of evolutionary traps which require further investigation if a trap is affecting the target of existing conservation management; (2) management options for eliminating traps or mitigating their demographic impacts; (3) case studies illustrating how practitioners have applied these mitigations in specific cases; and (4) a structure for considering how these management options should be integrated into existing decision-making frameworks. Management to eliminate evolutionary traps is a new challenge for conservationist scientists requiring a deeper understanding of the sensory-cognitive world experienced by nonhuman animals. To do so, it will be essential to diagnose the behavioral mechanisms causing traps and then identify solutions to restore adaptive behavior in target populations.

How to disarm an evolutionary trap

In the last decade it has been recognized that the artificial polarization of light can have uniquely disruptive effects on animals capable of seeing it and has led to the identification of polarized light pollution (PLP) as a new kind of ecological photopollution. In this chapter we review some typical examples for PLP and the resulting polarized ecological traps. All such polarized-light-polluting artificial surfaces are characterized by strongly and horizontally polarized reflected light attracting positively polarotactic aquatic insects, the larvae of which develop in water or mud, such as aquatic beetles (Coleoptera), water bugs (Heteroptera), dragonflies (Odonata), mayflies (Ephemeroptera), caddisflies (Trichoptera), stoneflies (Plecoptera) and tabanid flies (Tabanidae), for example. We survey here the PLP of asphalt surfaces, solar panels, agricultural black plastic sheets, glass surfaces, black gravestones and the paintwork of black-, red- and dark-coloured cars. We show how the maladaptive attractiveness (PLP) of certain artificial surfaces to polarotactic insects can be reduced or eliminated. We consider how birds, spiders and bats exploit polarotactic insects trapped by different sources of PLP. We deal with the phenomenon that the vertically polarized mirror image of bridges seen at the river surface can deceive swarming polarotactic mayflies, which is an atypical kind of PLP. We explain why strongly polarizing black burnt-up stubble fields do not attract aquatic insects, which is an example for a horizontal, black polarizing surface that does not induce PLP and thus is an exception proving the rule. Finally, we show that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of night-active aquatic insects than they would have separately. This provides experimental evidence for the synergistic interaction of phototaxis and polarotaxis in these insects.

Anthropogenic polarization and polarized light pollution inducing polarized ecological traps

Asphalt surfaces as ecological traps for water-seeking polarotactic insects: How can the polarized light pollution of asphalt surfaces be reduced?

https://arago.elte.hu/sites/default/files/VikingTwilightBoard_ProcA.pdf

Susanne Åkesson

Papers

Asphalt surfaces as ecological traps for water-seeking polarotactic insects: How can the polarized light pollution of asphalt surfaces be reduced?

fragmentnew interpretation of the Uunartoq artefact sunstones before and after sunset? Twilight board How could the Viking Sun compass be used with