Scientists urge caution after finding that insects fall into 'ecological trap' by mistaking panels for pools of water
David Adam The Observer 6 Jun 10;
Solar panels could wipe out fragile populations of insects, according to a new study that raises fresh doubts about the ecological impact of some forms of renewable energy.
Scientists have discovered that aquatic insects such as the mayfly can mistake shiny photovoltaic panels for pools of water, which they rely on to reproduce. They urge caution on the increasing use of panels until experts work out how they could affect insects and other creatures that feed on them.
"The effect of solar panels on populations of aquatic insects has not yet been researched," said Bruce Robertson, a scientist at the US Department of Energy's Great Lakes Bioenergy Research Centre in Michigan. "It is clear that the worst place to put a solar installation would be in proximity to natural lakes and rivers, where aquatic insects could easily become attracted to them."
The insects mistake the panels for water because both reflect horizontally polarised light – an optical trick in which light waves vibrate in the same direction. Many insects have evolved to detect such polarised light as a sure way to find water, particularly in arid environments.
The insects mate above the panels, which makes them vulnerable to predators, and lay their eggs on their surface, where they perish. Scientists call such natural siren songs "ecological traps". Robertson said: "There is no more severe way to degrade an organism's habitat than by creating an ecological trap. We predict traps should cause rapid population declines where solar panels are common, but it will depend on the extent of solar panels in an area and how many insects are attracted to them. It appears that, once attracted, most die trying to reproduce."
To investigate the scale of the effect, Robertson and colleagues in Hungary set up different designs of solar panels next to a creek in the Hungarian Duna-Ipoly National Park at Domorkapu. They watched insects such as mayflies and stoneflies form swarms to reproduce in the early summer evening.
Reporting their results in the journal Conservation Biology, the scientists say that several species of insect were drawn to the panels and laid more eggs on their surface than on water. They add: "We urge caution in the placement of solar arrays and selection of panel design, particularly where rare or endangered species may be directly or indirectly affected." Solar farms, with large areas of such panels, are rapidly spreading across Europe, Africa and the US, they say.
The scientists found that solar panels which had their shiny surface broken up with white borders or grid designs proved much less attractive to the insects. "They still polarise light, but produce it in smaller patches which is unappealing to aquatic insects that may prefer larger patches of water in which to breed," Robertson said.
"Citizens concerned about the effect of their own solar panels or collectors can use white tape to create a grid on their panels."
