The light pollution produced by street lamps, advertising boards, flood lights and our homes is so bad that 80% of the world’s population lives in the haze of a perpetual glow in the hours of darkness.
It started like any other day for Stephen Maciejewski. He woke up at 04:30 and by 05:30 he was in downtown Philadelphia ready to start his patrol. Maciejewski – a volunteer with the conservation non-profit Audubon Pennsylvania – has walked the exact same route for years, looking for birds lying on the pavement.
The unfortunate creatures end up there after crashing into the city’s brightly-lit skyscrapers. Maciejewski bags and labels dead birds and scoops up those that are simply dazed, moving them out of the way of hurrying commuters.
But the morning of Friday 2 October 2020 was different. Maciejewski was kneeling on the pavement picking up a clutch of dead birds when someone ran up and pointed out another cluster around the corner. A few minutes later, someone else told him about a pile further up the street.
“After a while I just couldn’t keep up… it got so overwhelming that I stopped putting them in individual bags,” he says. “I just put them in a big plastic bag.” It was clearly upsetting for Maciejewski – his voice cracks with emotion as he reveals that he ended up collecting around 400 dead birds that day. Usually he would expect to pick up 20.
The deaths were the result of a mass collision event, caused by a combination of overnight conditions: a low cloud ceiling, fog and rain. “The birds were flying fairly low,” says Jason Weckstein, the associate curator of ornithology at the Academy of Natural Sciences of Drexel University. Normally migratory birds use celestial cues such as the stars to help them navigate. Disorientated by cloud and fog, however, they are thought to have been drawn off course by the city lights and smashed into the glass buildings. In total, around 1,500 birds died that night. “They were able to see the [city] lights and the lights attract them in,” says Weckstein.
Pictures taken by Maciejewski of the colourful neotropical birds lying on the city streets, travelled around the world. It was a turning point for Philadelphia, says Connie Sanchez, the program manager for bird-friendly buildings at the National Audubon Society. “There was a lot of media attention, the public truly noticed.”
The deaths were a catalyst for a city-wide effort to tackle the impact of light pollution on birds. In March, a coalition including the Audubon Society and the Academy of Natural Sciences of Drexel University announced “Lights Out Philly”, where building owners, managers, residents and tenants agreed to turn off or dim city lights between midnight and 06:00 during key migration periods. Between April and the end of May and again from August to November, the city’s skyline will dim along with 39 “Lights Out” initiatives across the US.
It is estimated that between 100 million and one billion birds die every year from flying into buildings in the US, with artificial lights thought to play a major role in the death toll. But the effects of light pollution on the natural world is thought to be far greater still.
The light that beams from skyscrapers, office blocks, streetlights and homes scatters into the atmosphere, creating a sky glow that can extend around 150 miles
It “is not a national issue, it’s not a state issue, it’s not a city issue – this is a worldwide issue,” says Weckstein. And it’s not just affecting birds.
The Sun is basically like a clock, says Brett Seymoure a behavioural ecologist at Washington University in St Louis. The reliable rhythm of night and day gives plants and animals signals for natural cycles of feeding, mating, migrating and navigating. Humans are altering this natural rhythm by flooding the world with artificial light.
The era of electric lighting, which began in the late 19th Century, allowed humanity to extend days into the night with the flick of a switch. As technology has progressed, it has only become simpler and cheaper to light up the world more brightly.
But the light that beams from skyscrapers, office blocks, streetlights and homes doesn’t just light what we need – it spills into the habitats of animals and it scatters into the atmosphere, creating a sky glow that can extend around 150 miles (241km) from large towns and cities.