Is there really such a thing as “light pollution?” Can artificial light actually be harmful to people or animals? Well, it very well might be, at least according to a new study from the people at Tel Aviv University (TAU).
According to what the TAU people described as an extensive study at Tel Aviv University’s School of Zoology, researchers tested the impact of prolonged low-intensity light pollution on two species of desert rodents: the diurnal golden spiny mouse, and the nocturnal common spiny mouse. The researchers said that their findings were highly disturbing in that, on two different occasions, entire colonies exposed to ALAN (Artificial Light At Night) died within days, and reproduction also decreased significantly compared to control groups.
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“Our results show clearly for the first time that light pollution can be extremely harmful to these species, and suggest they may be harmful to ecosystems, biodiversity, and even human health,” said the researchers.
There are animals that thrive at night and so prefer the darkness. So any light, even in small amounts from a distance, can disrupt their very existences. This includes light emanating from a city at a far distance away.
The study was led by Prof. Noga Kronfeld-Schor, Chief Scientist of Israel’s Ministry of Environmental Protection, and PhD student Hagar Vardi-Naim, both from TAU’s School of Zoology and the Steinhardt Museum of Natural History. The paper was published in Scientific Reports.
Prof. Kronfeld-Schor explained, “We have been studying these closely related rodent species for years. They both live in Israel’s rocky deserts: the golden spiny mouse (Acomys russatus) is diurnal, and the common spiny mouse (A. cahirinus) in nocturnal. The two species share the same natural habitat but use it at different times to avoid competition. By comparing closely related species that differ in activity times, we gain new insights into the biological clock and its importance to the health of both animals and humans.”
In the study, the researchers placed 96 spiny mice of both species, males and females in equal numbers, in eight spacious outdoor enclosures at TAU’s Zoological Research Garden. The enclosures simulated living conditions in the wild: all animals were exposed to natural environmental conditions, including the natural light/dark cycle, ambient temperatures, humidity, and precipitation. Each enclosure contained shelters, nesting materials and access to sufficient amounts of food. The experimental enclosures were exposed to low-intensity ALAN (similar to a streetlamp in urban areas) of different wavelengths (colors) for 10 months: two enclosures were exposed to cold white light, two to warm white (yellowish) light, and two to blue light, while two enclosures, remained dark at night and served as controls. All animals were marked to enable accurate monitoring of changes in behavior and physical condition. The experiment was conducted twice in two successive years.
Additional tests revealed that exposure to ALAN caused physiological and hormonal changes – most significantly in the level of cortisol, an important stress hormone involved in the regulation and operation of many physiological pathways, including the regulation of the immune system. Lab tests indicated that exposure to blue light increased cortisol levels of golden spiny mice, while white light reduced cortisol levels of golden spiny mice males in winter.
