Urban Streetlights Give Trees Tougher Leaves, Hurt Insects

CORRECTION: The study cited below focussed on trees that were all exposed to High Pressure Sodium (HPS) lamps. Therefore, the findings can not be generalized to LED streetlights. Special thanks to Jim Levecchi at AECOM for sharing this detail of the study.

Researchers at the Chinese Academy of Sciences have published research showing exposure to high levels of artificial light at night makes tree leaves tougher and more difficult for insects to eat, disrupting urban food chains. The paper was published in Frontiers in Plant Science.

The scientists studied Japanese pagoda and green ash trees to determine if trees receiving higher artificial light put more energy into fighting insects by toughening their leaves and producing greater chemical defenses in those leaves. 5,500 leaf samples, as well as illuminance measurements, were collected from 30 sites. The researchers found that the higher the artificial light exposure, the tougher the leaves were, and less insect herbivory was found, sometimes none.

Reduced insect herbivory can indicate fewer herbivorous insects, which reduces food for other insects, birds, and other species that eat herbivorous insects, up the food chain. It is likely that the recent significant declines in global insect and bird populations are partially attributable to artificial light at night.

David Shiller

David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

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