Lights blind-side pollinating moths
Switching off your outdoor lights at night will not only save you money on electricity it might also help New Zealand to flourish, research shows. Many of the flowers in our gardens — and many of New Zealand’s food crops including kiwifruit, apples and avocados — depend on pollination by insects to survive.
Pollen, transferred from the anther of one plant to the stigma of another by an airborne insect (a bee for instance) or the wind allows seeds and fruit to form.
Most of us know that bees are great pollinators, but even bees need a rest at night — in fact, honey bees sleep for up to eight hours a day. Less well known is that moths are also important pollinators, and as nocturnal insects they get their work done quietly and through the night.
Moths play a distinctly different pollination role to bees, feeding on the nectar of different plants. With their long, thin proboscises, moths are able to feed from plants that can’t be visited by the shorter-tongued bees. Likewise, moths cover comparatively large distances when compared to the more localised bees, allowing them to pollinate between plants that are relatively far apart.
While most of us only notice moths when they flutter around the outdoor lights in our garden, New Zealand has 1800 moth species, 90 per cent of which are unique to our country.
It seems, though, that our artificial lights are disrupting moths’ ability to pollinate. To navigate from place to place, it is thought they have evolved to use a method called transverse orientation. This is where the moth keeps a light source at a certain position relative to its body to help guide it along a consistent path. When the brightest light source at night was the moon this was reliable for the moth. With the proliferation of electric lighting in our modern world, however, moths are now exposed to hundreds of artificial “moons” which can send them off course.
Artificial lights not only confuse the moths, negatively affecting their ability to feed and therefore pollinate, they also make them more susceptible to being seen — and eaten — by predators.
Research out this week looking at the effect of streetlights on moths and their pollination abilities suggested an interesting compromise where both moths and humans might win.
The study, published in the journal Ecosphere, set up a chain of street lights alongside hedgerows on farmland in the UK. They varied the type of bulbs used, as well as the amount of time that the lights were on during the night. Underneath the
lights they planted female white campions — plants with white flowers that would go on to produce seeds if pollinated.
The researchers found that the light from high-pressure sodium lamps and light-emitting diodes caused pollination of the flowers in the area to drop from 50 per cent to 30 per cent.
However, when the lights were turned on at dusk and turned off again at midnight, it was found that the moths were able to pollinate just as well as when the lights were off all night.
Although unexpected, the results suggest that a compromise — turning streetlights on during busy commuting times when it’s dark, then off again at midnight when most streets are quiet, could allow moths to pollinate normally with the added benefit of helping councils to save on their electricity budget.
In the meantime, just the simple act of turning out outdoor lights and drawing curtains to prevent indoor light from escaping could help our furry moth friends to feed and in turn your garden to grow.