Artificial light is Another Form of Pollution
Artificial light should be treated like other forms of pollution because its impact on the natural world has widened to the point of systemic disruption, research says. Human illumination of the planet is growing in range and intensity by about 2% a year, creating a problem that can be compared to climate change, according to a team of biologists from the University of Exeter.
Hormone levels, breeding cycles, activity patterns and vulnerability to predators are being affected across a broad range of species, they write in a paper published in the journal Nature Ecology and Evolution.
From reduced pollination by insects and trees budding earlier in spring, to seabirds flying into lighthouses and sea turtles mistakenly wandering inland to bright hotels in search of the dawn sun, their study-of-studies brings together 126 previous papers to assess the extent of the impact.
In all the animal species examined, they found reduced levels of melatonin – a hormone that regulates sleep cycles – as a result of artificial light at night.
Behavioural patterns were also disturbed in both nocturnal and diurnal creatures. Rodents, which mostly forage at night, were active for a shorter duration, while birds started singing and searching for worms earlier in the day.
The outcomes were not purely negative. The scientists said certain species in certain locations benefited from night-time light: some plants grew faster and some types of bats thrived. But they said the overall effect was disruptive, particularly to the insects drawn to singeing bulbs or fast-moving car lamps.
Satellite images of the Earth at night show how rapidly the problem is expanding geographically, but lights are also becoming more intense as expensive soft amber bulbs are replaced by greater numbers of cheap bright white LEDs. This is biologically problematic because the white light has a wider spectrum, like sunlight.
Unlike the climate crisis, however, solving the lighting problem would save rather than cost money. If people use fewer lights, it would mean lower costs, less electricity and lower emissions. But it would require a change of mindset.