Can modified solar panels disarm an ecological trap?

Solar power plant in Serpa, Portugal. On the heels of increasing evidence that wind energy and ethanol can cause serious ecological impacts, a new study in Conservation Biology raises concerns over “polarized light pollution” from polarizing photovoltaic solar panels.

The study, led by Hungarian researcher Gábor Horváth, shows that solar panels can act as ecological traps for aquatic insects potentially leading to population decline or even local extinction.

The good news is that the study also showed that modifications in the design of solar panels can substantially reduce the negative impact.

An ecological trap occurs when sudden environmental changes cause species to become attracted to habitat areas that are poor quality. 

For positively polarotactic aquatic insects such as mayflies, stoneflies, dolichopodid dipterans and tabanids, adults emerge from aquatic ecosystems to mate and then lay eggs in water.

The insects rely on smooth water to reflect polarized light as an indicator of suitable habitat (i.e. lakes and streams) to lay eggs.

Previous work has shown that other surfaces reflecting horizontally polarized light, such as dry asphalt and dark coloured cars, are often mistaken as suitable locations for ovipositing.

The researchers found the black surfaces of photovoltaic solar panels emit near total polarized light (d≈100%) regardless of orientation and elevation and are much more efficient at polarizing light than water (d≈30-70%) potentially leading polarotactic aquatic insects to select these artificial surfaces over adjacent natural water bodies.

Past research has shown that polarization-induced attraction of these insects to artificial surfaces can result in reproductive failure of eggs, death from exhaustion, and increased risk of predation.

On the positive side, the new study also found that the effects may be easily reduced.

Horváth and his co-authors observed that black solar panels framed or partitioned with a white non-polarizing surface significantly reduced the attractiveness of the panels to insects.

Their study possibly represents the first to demonstrate the elimination of an ecological trap.

Although gridding reduces the energy generation capacity of the solar panel in proportion to the amount of area lost to the white gridding, the benefits far outweigh the cost.

According to the study, a 1.8% reduction in generation capacity significantly reduces the attractiveness of the panel to polarotactic insects 10 to 26 fold.

--by Ian Adams

HORVÁTH, G., BLAHÓ, M., EGRI, A., KRISKA, G., SERES, I., & ROBERTSON, B. (2010). Reducing the Maladaptive Attractiveness of Solar Panels to Polarotactic Insects Conservation Biology DOI: 10.1111/j.1523-1739.2010.01518.x