A report, jointly published last year by Butterfly Conservation, the UK Centre for Ecology and Hydrology and Newcastle University, revealed a surprising link between night-time artificial lighting and the populations of moth caterpillars in southern England. The surveys, at 27 pairs of lit and unlit sites, included night-time sweep netting of grass verges and the daylight beating of hedges and revealed that caterpillars were 33% less abundant in lit grass verges and 47% less abundant in hedges subject to artificial lighting. Even worse, the drive to reduce energy consumption through the use of modern white LED lights had reduced caterpillar populations by 43% in grass verges and 52% in hedges when compared to unlit sample areas.
The sampling of hedges was undertaken during daylight and demonstrates conclusively that fewer caterpillars live in hedges which are subject to light pollution at night. On the other hand, the sweep-netting surveys captured only those caterpillars which had climbed into the upper layers of the grasses to feed at night. It is therefore possible that the reductions found in areas subject to night-time lighting are in part because the illumination discourages some caterpillars from climbing, rather than because they aren’t in the lit area at all. Nevertheless, it remains reasonable to observe that the night-time lighting of grasslands and hedges is reducing the feeding habitat available to moth caterpillars.
This study adds to the data, principally obtained through laboratory trials, which show that night-time lighting affects moth populations by preventing them flying and through interfering with their mating and reproduction processes. Overall, therefore, light pollution is having a significant impact on UK moth species. Unfortunately, we must add to these factors the reductions in habitat through the loss of hedges and grasslands and the effects of pesticides and herbicides – small wonder, perhaps, that our moth populations have crashed so heavily in the past 50 years or so.
Sadly, the reductions in numbers of moths and their caterpillars also adversely affects the populations of birds, bats and other creatures higher in the food chain, thus magnifying the resultant biodiversity loss. It is thus in everyone’s interests that we should adopt sound artificial lighting policies as part of the mitigation strategy when planning our future development projects.
JP Ecological Services 