Universiteit Leiden

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Effects of light at night on plants and their interactions with other species

What is the effect of light at night on plant phenology and physiology, and how does this affect plant interactions with other species?

Ellen Cieraad

Part of this research is conducted in conjunction with the NIOO research programme and experimental sites of Light on Nature and Light on Landscape.

Short abstract

Artificial light at night is the fastest growing type of pollution. Light pollution affects the behavior and ecology of many different species. This project aims to improve our understanding of the effects of light pollution on plant communities, and mechanisms through which light pollution affects interactions between species in the food web.

Light pollution of the Netherlands, as captured by the International Space Station in 2012 | Image credit: ESA/NASA

Project description

While artificial light at night brings many benefits to humankind, it interferes greatly with the natural light environment. For example, more than 90% of the European population lives under polluted skies, and can no longer see the impressive Milky Way in the night sky. This ever increasing light pollution is also affecting the behaviours and ecology of many different species.

Studies into the effects of light pollution have mainly focussed on human health and animal species, but we still know very little about the effects on plants in their natural environment. Plants use light as a key source of energy (through photosynthesis) and information (for example, to correctly time important life stages such as bud burst, flowering and leaf fall). Therefore, there is a strong potential for plants to be affected by light pollution. Since plants are at the base of all terrestrial food webs, such changes can also affect other species and their interactions (for example, herbivorous insects may no longer have access to the same quality or quantity of foliage), and thus cascade through the foodweb.

Have you ever noticed that in spring, trees that are under streetlights tend to show their green leaves before trees that are not directly under a light? In autumn, parts of trees that are lit by artificial lights also retain their leaves longer – here a plane tree (Platanus sp) in Leiden. | photo credit: Liselotte Rambonnet

In this research, we use a multitude of methods, data sources and scales to investigate the different pathways through which light pollution affects plants and the interactions of plants and other species. For example, we measure the impact of artificial light at night of different intensities and colours on the phenology and physiology of plants, in urban, natural and experimental conditions. We use experimental setups to assess to what extent and through which mechanisms artificial light at night of different spectra affects insect herbivory damage and other food web interactions. Using data collected by remote sensing and citizen scientists, we also assess the relative importance of different key drivers of tree phenology, including temperature and light pollution. Moreover, in collaboration with the Department of Industrial Ecology (CML), we aim to integrate the effects of light pollution into the life cycle impact assessment (LCIA) framework.

Societal relevance

While we have been making headway with reducing many forms of pollution over the last decade or more, light pollution continues to grow at a very fast pace. This is at least partially driven by the current transition from incandescent lights to LED’s – it is now inexpensive to run many lights and not switch them off as often. Through increasing the understanding of the effects of the timing, colour and intensity of light on different species and ecosystems, the outcomes of this research will contribute to the formation of strategies to reduce the impacts of light pollution on biodiversity and humans.

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