With a changing climate, you might think that nature has enough on its plate to deal with. Yet it seems that it is also having to contend with a brighter world. A new study has found that the human use of artificial light has caused spring to arrive a week earlier in the United Kingdom.
With tree buds and flowers opening earlier than is expected, it could have profound impacts on the birds and insects that are ordinarily in sync with the onset of spring. Using data collected by citizen scientists for the Woodland Trust on when people first observed sycamore, oak, ash, and beech trees in leaf, the researchers then correlated this data with satellite images of artificial lighting. By doing this, they found that the trees were budding up to 7.5 days earlier in the brightest areas, and that traditionally later budding trees were most affected.
“Our finding that the timing of bud burst of woodland tree species may be affected by light pollution suggests that smaller plants growing below the height of street lights are even more likely to be affected,” explained Professor Richard ffrench-Constant from the University of Exeter, and co-author of the study published in the Proceedings of the Royal Society B. “Such results highlight the need to carry out experimental investigation into the impact of artificial night-time lighting on phenology and species interactions.”
The data collected by the Woodland Trust has also found that while the onset of spring may have occurred earlier in cities this year, its spread up the country has been dramatically slower. Scientists are able to track the start of spring as it travels north through Britain, and found that it moved at a rate of 1.9 kilometers per hour (1.2 miles per hour), or that of the average iceberg. This, the researchers say, is a rate more in step with what was seen during the Victorian era, and much slower than the preceding decades. Last year, for example, spring moved up the country at a much nippier 3 km/h (1.9 mph).
The impact of the changes in the onset and speed of spring could have profound knock-on effects on wildlife. As seasons become less predictable, animals will struggle to keep up, and as many rely on spring for abundances of food after winter and to mate and/or feed their offspring, it could lead to changes in populations. Many birds, for example, feed on the proliferation of the winter moth, which in turn feeds on emerging oak leaves. If the timing of the leaves is off, so will the moths be, and the cascade will ultimately impact the birds.