Increased floodlighting reducing bat populations in Sweden's churches

phys.org | 8/9/2017 | Staff
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(Phys.org)—A trio of researchers, two from Sweden and one from Spain has found that installing floodlighting around rural churches drives away roosting bats. In their paper published in Royal Society Open Science, Jens Rydell, with Lund University, Johan Eklöf, with Graptolit Ord och Natur and Sonia Sánchez-Navarro with Estación Biológica de Doñana-CSIC describe their comparison of church bat populations over the course of several decades.

Bats in Sweden are generally welcomed because they eat destructive insects and tend to hide at night. But bats have a unique history in the country, as well, because Sweden does not have many caves—instead, most of the bats live in the warm towers and belfries of rural churches. But, the researchers suggest, a recent lighting trend has put the bats at risk, and their numbers are falling.

Rydell - Bats - Years—back - Surveys - Specimens

Rydell has been interested in bats for many years—back in the 1980s, he conducted surveys of specimens living in 61 churches in southwest Sweden, making population charts. In this new effort, he and his colleagues revisited those churches along with 50 others, counting the number of brown long-eared bats.

The researchers concluded that bat populations had remained stable in churches that lacked floodlighting. But in churches with such lighting, populations dwindled depending on how much lighting had been installed. In churches where floodlights were installed on all four sides of a building, there were no bats left at all.

Floodlights - Researchers - Decades - Church - Staff

Installing floodlights, the researchers note, became popular over the past few decades as church staff sought to show off the unique architecture at night. The contrast of the usually stark white buildings lit against a deep black sky offers an inspiring visage, but, it also makes resident bats much more vulnerable to predation by owls, hawks and cats.

The researchers note that bats are protected in Sweden—it is against the law to harm...
(Excerpt) Read more at: phys.org
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