Artificial light at night affects plant–herbivore interactions

Abstract

1. Artificial light at night (ALAN) affects species' physiology and behaviour, and the interactions between species. Despite the importance of plants as primary producers, it remains poorly understood whether and how effects of ALAN on plants cascade through the food web.2. We assess the extent to which ALAN of different spectra result in plant-mediated insect herbivory damage. In a 6-month field experiment, we exposed plants of differing palatability to three colours of ALAN and a dark control, and assessed plant traits (growth rate, leaf size, foliar density and thickness) and insect herbivory (represented by insect damage as loss of foliage to leaf-chewing insects, and gall abundance by phloem-feeding herbivory).3. We found evidence for plant trait-mediated ALAN effects on herbivory for oak, but not for blueberry. In oak, ALAN of different colours changed the direction of relationships of insect damage with relative growth rate and with leaf thickness. Moreover, we found that the effects of ALAN on herbivory damage differed markedly between forest types within the same locale, particularly in the red light treatment. 4. Synthesis and applications. Our results provide evidence that continuous nighttime light, as provided by street lighting around the world, affects food web interactions. The nature of these effects differed by species and appeared to depend on forest type and the light spectrum employed, thus underlining the context dependency of ALAN in different ecosystems and environmental settings. These findings highlight the complexity of using spectral manipulation as a mitigation measure, and the need for further consideration of ALAN in environmental management and planning, to limit the exposure and impact of cascading effects of artificial light at night on food webs and communities.

Long-term exposure to experimental light affects the ground-dwelling invertebrate community, independent of light spectra

“…Less information is available on how light spectrum impacts community composition, but effects have been shown for plants [42] and moths [41]. Effects of light spectrum on community composition were expected as these have shown to differentially alter trophic interactions between many species [43][44][45][46]. Typically, the impact of light spectra on, for example, nocturnal insect and mammal species, is relatively short wavelength (blue light) biased [19,20,43], but effects between different spectra on community composition remain less clear.…”

Part-night exposure to artificial light at night has more detrimental effects on aphid colonies than fully lit nights

“…First, the organisms experience a lit night, which may be seen as the first stressor, which is then followed by a severely reduced dark recovery period, i.e., further stress, although the mechanism is unclear. However, we argue that the ecological consequences of specific mitigation strategies need to be studied before they are readily implemented, as despite good intentions, they may sometimes have unexpected side effects (Cieraad et al 2022).…”

Part-night exposure to artificial light at night has more detrimental effects on aphid colonies than fully lit nights

“…further stress, although the mechanism is unclear. However, we argue that the ecological consequences of specific mitigation strategies need to be studied before they are readily implemented, as despite good intentions, they may sometimes have unexpected side effects [74].…”