Perpetual "Moonlight” May Be Disrupting Animals’ Life Cycles

Light pollution is increasing rapidly across the planet. This could harm many species that depend on natural light conditions.

By the editorial staff of Park Science magazine

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About this article

This article was originally published in the "Research Roundup" section of Park Science magazine, Volume 39, Number 2, Summer 2025 (August 29, 2025).

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Artificial (left) and natural (right) light levels that affect animal behavior, from sunset (top) to starlight (bottom) conditions. The values along the circumference represent the light levels in millilux (mlux). The animals shown represent some species' responses to natural and artificial light intensities (for full references, see Seymoure et al. [2023]). The night sky scenes were modified with permission from Chadwick A Moore. All other graphics were created by the authors BMS and JMW.

Seymoure and others. 2025. Global artificial light masks biologically important light cycles of animals.  Frontiers in Ecology and the Environment e2832.

Modern society depends on artificial lighting at night. But many wild animals rely on phases of the moon and other natural light cycles. Excess light at night (light pollution) can disrupt the ability of mammals, birds, and other animals to find food or mate.

Researchers reviewed more than 1,300 scientific publications. They culled that number to 120 to help them understand the effect of light pollution on animals. They looked at the effects of nighttime light levels on 136 different animal species. Using the new world atlas of artificial night sky brightness, they mapped artificial light levels reaching the Earth’s surface. The results of their analysis were published in the January 2025 issue of Frontiers in Ecology and Environment.

Their analysis revealed that 85 of the 136 different animal species were affected by light levels between the full moon and “nautical twilight.” In the U.S., nautical twilight is the period about 1 hour before to 30 minutes before sunrise. Thirty-three species were sensitive to light levels between quarter and full moon. And 19 species were affected by light levels between crescent and quarter moon.

The authors also found that light pollution had doubled the brightness of new moon nights—critical to many animal behaviors—for 23 percent of the Earth’s land surface. Up to 77 percent of Global Protected Areas were affected. They estimate that 26 percent of the Earth’s surface is now under “perpetual ‘moonlight’.” And this could reach as high as 50 percent by 2052. They suggest practical actions land managers can take to lessen artificial light at night.

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Seymoure and others. 2025. Global artificial light masks biologically important light cycles of animals. Frontiers in Ecology and the Environment 23(4): e2832.