NWO - Impact of light at night: preventing habitat loss and habitat fragmentation by adapting night-time illumination

Artificial light at night continues to increase and there is a clear societal demand for effective measures to mitigate its negative impacts on plants and animals. Illumination of linear infrastructures can severely affect nocturnal species in the relative close proximity of these light sources: effects vary from direct mortality to disruption of species’ natural behaviour. In terms of mitigation, there has so far been much emphasis on light spectra (green and red light) under experimental conditions. This has put forward the potential of reducing the short wave (blue) part of the spectrum for reducing impact on nocturnal species in terrestrial habitats. For effective mitigation in real life situations, there are however a number of knowledge gaps that limit the possibilities for effective mitigation measures. First, there is a fundamental lack of knowledge on how the response of these species depends on light intensity, which likely varies with the light spectrum and the type of behaviour of the animals. This impedes effective conservation measures, as knowledge on critical threshold levels is essential to keep habitat sufficiently dark. The absence of knowledge on threshold light levels is even more urgent for illumination along linear structures, at which many nocturnal species concentrate their movements through the landscape. Above a certain threshold, lighting may have a barrier effect and render suitable habitat inaccessible. Second, information on the impact of novel lighting concepts such as adaptive (traffic dependent) and restricted (with a predetermined nightly intensity schedule) lighting is virtually absent. Here, we propose to study the light intensity dependent habitat loss, and the impact of novel adaptive lighting concepts at a unique, existing experimental setup for testing the impact of light on ecosystems. An additional mobile lighting setup will be applied for light impact assessment at landscape corridors. We focus on nocturnal species that are strongly affected by light at night, and focus on both habitat loss and landscape connectivity for bats and mice, and landscape connectivity for mustelids and amphibians. Bats will be studied with high-resolution, high-speed acoustic tracking with microphone arrays. The activity of mice will be assessed with camera systems and Giving Up Density protocols, and mustelids and amphibians will be studied with advanced camera systems. With this approach, we anticipate to collect essential information to enable effective, practical mitigation measures.