(Credit: Andris Tkacenko/Shutterstock) When cities light up the night, it confuses the trees. In places where night-time light pollution is at its worst, trees burst into bloom a week earlier than trees rooted under dark skies, according to a 13-year study from researchers at the University of Exeter in the United Kingdom. Ringing in spring earlier in urban areas could have important ramifications for entire ecosystems, as changes in tree health send ripples throughout local food chains.