As urbanisation continues to grow, artificial lights are becoming more and more prominent. As high street shops, factories and hospitality companies continue to operate after sunset, invertebrate populations are taking the fall.

Spiders

A study published in Biology Letters this week reveals that ALAN exposure is shrinking spiders' brains.

ALAN supresses melatonin activity in spiders causing oxidative stress which reduces the volume of brain structures resulting in impaired cognition. Melatonin is an antioxidant essential for metabolism, reproduction and many other bodily function and is formed in the brain.

An imbalance of this hormone is causing a shift in their developmental rate, increased mortality and reduced foraging ability.

Crickets

Last month, some research conducted by Darren Rebar and colleagues in Behavioural Ecology highlighted the impacts of ALAN on crickets.

They found that artificial light exposure is reducing their immunity and preventing them from reproducing. In crickets, it supresses lysosome activity which is responsible for fighting bacteria and viruses, and killing damaged cells.

Moths

Various studies have revealed how ALAN light can impact moth behaviour but a paper published by UK scientists in Insect Conservation and Diversity from 2020 has proved it can also lower their reproductive rates.

ALAN prevents moths detecting mating season as the natural daylight cycle is disrupted. This has a knock-on impact on larval development and hatching.

As moths are nocturnal and easily distracted by ALAN they are losing valuable foraging and mating time at night. Flying into lights can also cause higher mortality and increased predation risk, working as convenient moth-bait for natural predators to indulge.

Since moths use celestial navigation, flying at a particular angle relative to the position of the moon and stars, artificial light disrupts this process. This makes it nearly impossible for moths to navigate long distances, reducing their likelihood of finding food, laying or mating grounds.

Why care?

Invertebrates feed our native bird populations and play a key part in decomposition and the nutrients cycle. Without them, entire ecosystems would collapse alongside the services and resources they provide for the human race.

Fluorescent light which is used in retail, commercial and industrial lighting attracts moths and other invertebrates much more than LED or sodium lamps.

If more research is carried out on its deadly impact then it can be used by policy makers to convince companies to switch their bulbs to insect-safe alternatives.