“Ecological effects of artificial light at night on wild plants,” published in the Journal of Ecology, is a call to the ecological community to take a look at a very poorly understood environmental impact of urbanization: night light and its effects on plants.
Reports of trees in North America and Europe that are sensitive to direct street light illumination are well documented. Among the effects are changes in bud break in the spring or how long leaves are retained on deciduous trees in the fall. Known sensitive species include Aesculus hippocastanum, Betula pendula, Liquidamber styraciflua, Populus canadensis, Platanus sp., Populus nigra, Salix fragilis and Ulmus americana.
Artificial light affects plants in multitudes of ways. Horticulturists know that daylength-sensitive plants are easily manipulated into flower or vegetative state with short periods of low-intensity night lighting (5 lux or less). Chrysanthemums are the poster plant for using lighting to time flowering; it’s possible to flower mums any time of the year using lighting. Knowing that artificial light affects plants begs the question: How are artificial lights at night that are becoming more and more common affecting budbreak, flowering, leaf abscission and even nighttime pollinators?
In one experiment, researchers showed that Lotus pedunculatus, a highly sensitive plant to daylength, flowered less under simulated street lighting. Plants produced 10% to 25% fewer flowers. In yet another report, soybeans in a field in Ohio adjacent to a prison with bright floodlights didn’t develop normally.
Darkness may be important for plant stress recovery. In one study, longer days at simulated street light intensity caused more ozone damage on three types of clover.
The British authors note that Britain alone has an estimated 571,000 acres of roadside – more than double the area of natural or semi-natural grassland in the countryside. Planting pollinator habitat along British highways is increasingly popular. How do the passing car lights affect flowering plants growing there? Pollinators?
How night light pollution affects the functional urban landscape and our wild spaces is largely unknown. The authors argue that it’s time to incorporate the effects of artificial light into studies taking a look at how plants and animals are adapting to environmental stresses such as climate change, pollution and habitat loss to name a few.
Ecological effects of artificial light at night on wild plants by Bennie, J., Davies, T. W., Cruse, D. and Gaston, K. J. in the Journal of Ecology 2016, 104, 611-620. DOI: 10.1111/1365-2745.12551
NewTerrain June 1 2016.