We surveyed 110 country churches in south-western Sweden\udfor presence of brown long-eared bats Plecotus auritus in\udsummer 2016 by visual inspection and/or evening emergence\udcounts. Each church was also classified according to the\udpresence and amount of aesthetic directional lights (floodlights)\udaimed on its walls and tower from the outside. Sixty-one\udof the churches had previously been surveyed by one of us (J.R.)\udbetween 1980 and 1990, before lights were installed on Swedish\udchurches, using the same methods. Churches with bat colonies\udhad decreased significantly in frequency from 61% in 1980s\udto 38% by 2016. All abandoned churches had been fitted with\udflood-lights in the period between the two surveys. The loss of\udbat colonies from lit churches was highly significant and most\udobvious when lights were applied from all directions, leaving\udno dark corridor for the bats to leave and return to the roost.\udIn contrast, in churches that were not lit, all of 13 bat colonies\udremained after 25+ years between the surveys. Lighting of\udchurches and other historical buildings is a serious threat to the\udlong-term survival and reproduction of light-averse bats such\udas Plecotus spp. and other slow-flying species. Bat roosts are\udstrictly protected according to the EU Habitats Directive and\udthe EUROBATS agreement. Lighting of buildings for aesthetic\udpurposes is becoming a serious environmental issue, because\udimportant bat roosts are destroyed in large numbers, and the\udproblem should be handled accordingly. As a start, installation\udof flood-lights on historical buildings should at least require an\udenvironmental impact assessment (EIA).
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