Our streetlights are causing spring to come one week early

29 Jun 2016

Artificial light is not just a powerful tool for helping us get around at night, but now it seems it’s powerful enough to dictate the fabric of nature by influencing the arrival of spring.

The arrival of spring is a celebratory event not just because it – in theory at least – starts to get warmer from there on in, but it also initiates the return of green leaves to the once inert trees.

However, you might not have noticed that this year it arrived slightly early, around one week or so, thanks to our society’s dependence on artificial light at night.

Future Human

According to new research published in the journal Proceedings of the Royal Society B by a team of biologists from the University of Exeter, an analysis of when a number of tree species began to leaf has found a clear link between their early sprouting and their proximity to large artificial light sources.

They achieved this by comparing the data gathered on trees like the sycamore, oak and ash with correlated satellite imagery showing urban areas with considerable amounts of street lighting.

In all cases, these tree species were sprouting buds up to 7.5 days earlier in areas of high concentration of artificial light, particularly those in trees that naturally bud later.

Knocks ecosystem out of kilter

Rather than just being an interesting phenomenon worth noting, however, the team suggests this could have a damaging cascade effect on our ecosystem, as the early sprouting of leaves will leave it out of kilter with the life cycles of creatures that rely on this predictable sprouting.

Taking one example, the winter moth feeds on fresh emerging oak leaves and, if it misses this time due to the early arrival of buds, this may have some effect on birds in the food chain that rely on it for food.

Calling on further research into the discovery, these initial findings could soon have an impact on a local level in the UK as being worthy of consideration by councils determining the level of lighting emitted and which types of lights will be chosen that could have the least impact.

Speaking of the findings, Prof Richard Ffrench-Constant of the University of Exeter said: “Such results highlight the need to carry out experimental investigation into the impact of artificial night-time lighting on phenology and species interactions.”

Early budding tree image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic