Bats are deserting floodlit churches, researchers in Sweden have found.
A new study that compared the prevalence of long-eared bats today with a survey taken in the 1980s found that they had deserted many rural churches where floodlighting has been introduced. In churches that remain unlit at night, the bats continue to thrive.
The growing popularity of floodlighting – driven partly by improvements in lighting technology – seems to have had a serious impact on bat colonies. Of the 110 rural churches surveyed, the proportion that were home to bat colonies has fallen from 61% to just 38%.
The study, published this week in Royal Society Open Science, said: “The loss of bat colonies from lit churches was highly significant and most obvious when lights were applied from all directions, leaving no dark corridor for the bats to leave and return to the roost… We never saw a long-eared bat passing through or even near a light beam.”
Rural churches provide great opportunities for bats to roost, but to avoid predators, the creatures are highly averse to light. The study concluded that floodlighting of churches and other historic buildings “is a serious threat to the long-term survival and reproduction of light-averse bats”.
Environmental impact assessments should be conducted before installing floodlights on historic buildings, the researchers advise.
Researchers in the UK have also called for a reduction in streetlighting and outdoor lighting of homes, to reduce the impact on bats.