Abstract
Emerging lighting technologies provide opportunities for reducing carbon footprints, and for biodiversity conservation. In addition to installing light-emitting diode street lights, many local authorities are also dimming street lights. This might benefit light-averse bat species by creating dark refuges for these bats to forage and commute in human-dominated habitats. We conducted a field experiment to determine how light intensity affects the activity of the light-opportunistic Pipistrellus pipistrellus and light-averse bats in the genus Myotis. We used four lighting levels controlled under a central management system at existing street lights in a suburban environment (0, 25, 50 and 100% of the original output). Higher light intensities (50 and 100% of original output) increased the activity of light-opportunistic species but reduced the activity of light-averse bats. Compared to the unlit treatment, the 25% lighting level did not significantly affect either P. pipistrellus or Myotis spp. Our results suggest that it is possible to achieve a light intensity that provides both economic and ecological benefits by providing sufficient light for human requirements while not deterring light-averse bats.
Highlights
Over the last 60 years, artificial light at night (ALAN) has increased globally on average by 6% per annum [1]
Our results are broadly consistent with our hypotheses, that higher light levels (50% and 100%) increased the activity of light-opportunistic species such as P. pipistrellus, but reduced the activity of light-averse species such as Myotis spp
Lower light levels (25%) do not affect activity levels of either lightopportunistic or light-averse species of bats compared to the unlit treatment (0%)
Summary
Over the last 60 years, artificial light at night (ALAN) has increased globally on average by 6% per annum [1]. ALAN is the result of a number of artificially lit sources, but street lights are one of the main contributors as they are installed in most towns and cities across the world [3,4]. LED street lights offer a number of advantages over older lighting technologies, including increased energy efficiency, flexibility and longevity [6]. As well as installing LED lights, many local authorities are implementing strategies to save money and reduce their carbon footprints, such as partnight lighting and dimming. Dimming LED street lights is typically carried out by pulsewidth modulation, which manipulates the duty cycle of a signal, so that the amount of ‘on’ time is reduced, but the spectral output of the light is unchanged [10,11]
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