Even a little artificial light endangers ecosystems

Modern societies rely on artificial lighting at night. This is often at the expe
Modern societies rely on artificial lighting at night. This is often at the expense of nearby ecosystems. Photo: Jürgen Vieweg/Pixelio

A new collection of studies on artificial light at night shows that the effects of light pollution are more far-reaching than thought. Even small amounts of artificial light can disrupt species communities and entire ecosystems. The special issue of 16 scientific studies published in the journal Philosophical Transactions of the Royal Society B looks at the effects of light pollution on complex ecosystems, including soil, grassland and insect communities. In the special issue, scientists from the German Center for Integrative Biodiversity Research (iDiv) and Friedrich Schiller University Jena emphasize the domino effect that light pollution can have on ecosystem functions and stability.

Artificial lighting is increasing worldwide - and the night sky is also becoming brighter as a result. Light pollution, which increases by up to ten percent every year, interrupts the natural light cycles that have been largely constant throughout the history of the earth. These cycles are vital for organisms that rely on light as a source of energy and information. To date, studies that have examined the effects of light pollution have largely focused on human health and individual species. In contrast, the study of entire ecosystems, in which species are linked by multiple interactions, has mostly been left out."Species do not exist in isolation, but interact in multiple ways," explains Myriam Hirt of iDiv and the University of Jena, who co-edited the special issue with Remo Ryser. , "Our goal was to better understand how the brightening of the night sky affects entire ecosystems and the associated ecosystem services."

With the help of the iDiv Ecotron, which consists of several controllable ecosystems (so-called EcoUnits), the researchers simulated and modified nighttime lighting conditions. The most important results in this context include:

  • The effects of artificial light also reach belowground soil communities and affect soil respiration and carbon use efficiency
  • Artificial light affects insect activity, resulting in, among other things, higher predation rates at night, so there was more hunting behavior
  • Artificial light leads to a reduction in plant biomass and diversity, as well as changes in plant characteristics, such as the hairiness of leaves
  • Artificial light can shift or align the periods during which species are active, leading to greater overlap in their activity and ultimately affecting the persistence of species

The studies also showed that even low intensities of light pollution - less than a full moon - have profound effects, not only on the behavior and physiological responses of individual species, but are also reflected at more complex levels, such as in communities and ecological networks, such as food webs. "How individual species respond to artificial light and how they relate to each other affects how the entire ecosystem responds. For example, a shift in the activity of diurnal and crepuscular species to the night changes the extinction risks in the entire species community," says Remo Ryser of iDiv and the University of Jena.

Another study in the special issue examined how artificial light causes indirect cascade effects that also affect humans. For example, artificial light at night can influence the frequency and behavior of mosquitoes. The study shows that artificial light leads to changes in the timing of important mosquito behaviors, such as host seeking, mating and flight activity. This could have far-reaching consequences for the transmission of diseases such as malaria. Another study examined how different lighting strategies can mitigate the negative effects of artificial light. However, the researchers note that mitigating light pollution requires a nuanced approach, as the effects on different species can vary widely. Accordingly, preventive measures may not be universally applicable.

Due to the steady increase in artificial lighting around the world, fewer and fewer regions can be found where it is truly dark - with potential impacts on human health and ecosystems. With this special issue, the authors hope to stimulate further research and action that will not only help mitigate the harmful effects of light pollution, but also take into account the needs of society and nature. "Of course, artificial light at night has many advantages," says Myriam Hirt. "But we must not ignore its negative effects either."

In several studies, the iDiv-EcoTron was used to simulate and modify lighting conditions at night.