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Recently it was claimed that the increase in artificial light at night was a significant contributor to the 'ecological armageddon' of decreasing insect populations. It was further argued that the transition to more blue light emitting LEDs made the situation even worse than the isolated increase in light alone.

Drastic declines in insect populations, ‘Ecological Armageddon’, have recently gained increased attention in the scientific community, and are commonly con- sidered to be the consequence of large-scale factors such as land-use changes, use of pesticides, climate change and habitat fragmentation. Artificial light at night (ALAN), a pervasive global change that strongly impacts insects, remains, however, infrequently recognised as a potential contributor to the observed declines. Here, we provide a summary of recent evidence of impacts of ALAN on insects and discuss how these impacts can drive declines in insect populations in light-polluted areas. ALAN can increase overall environmental pressure on insect populations, and this is particularly important in agroecosystems where insect communities provide important ecosystem services (such as natural pest control, pollination, conservation of soil structure and fertility and nutrient cycling), and are already under considerable environmental pressure. We dis- cuss how changes in insect populations driven by ALAN and ALAN itself may hinder these services to influence crop production and biodiversity in agricul- tural landscapes. Understanding the contribution of ALAN and other factors to the decline of insects is an important step towards mitigation and the recovery of the insect fauna in our landscapes. In future studies, the role of increased nocturnal illumination also needs to be examined as a possible causal factor of insect declines in the ongoing ‘Ecological Armageddon’, along with the more commonly examined factors.

M. Grubisic: "Insect declines and agroecosystems: does light pollution matter?", Annals of Applied Biology, 2018. DOI

This seems a bit dubious to me. The world is steadily urbanising, meaning that humans flock together more than ever in fewer places than before. In these places the nights seem to become much brighter than ever before.
I do not doubt that ALAN may contribute to the decline of insects, but only in those places were ALAN is found and does increase. That seems plausible from the start.
I doubt that this is a significantly bad effect for insects in every case, as we probably do not need them that much in cities (green city/urban gardening as increasingly important exceptions) and most of us certainly do not want them in cities (killing every mosquito on sight seems common practice, even if methods change).

That situation is of course different in rural areas, or agricultural areas, or nature reserves, or just the wilderness. Insects are an integral part of ecosystems. It seems as if ALAN did not, can not increase that much in such areas. An unstated assumption until now was of course that most insects are not found urban areas but repopulate these areas quickly from the natural reserves surrounding those.

Did artificial light at night contribute significantly to the observed decline in insect populations?

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