Now, more than 80% of people live under light-polluted skies, and that number continues to rise.

The vast majority of artificial light is not needed by humans, and every extra streetlight or perpetually lit office building contributes to light pollution. Over 33% of the world’s population cannot see the Milky Way galaxy due to light pollution, and for birds that navigate using the stars, this hazy sky is causing deadly results. This International Dark Sky Week, learn why we need the dark, and discover how the Smithsonian National Museum of Natural History’s newest exhibition “ Lights Out: Recovering Our Night Sky,” utilizes the museum’s extensive collections to illustrate the ecological implications of light pollution.

But the signal is becoming increasingly dim as artificial lights blur the line between day and night. This pattern acts as a cue, telling different species when to eat, sleep, mate and migrate. Since the dawn of biological history, organisms on Earth have evolved under the consistent cycle of light and dark. Occasionally an unexpected “Thud” pierces through the ambient noise and shudders the glass windows: migratory birds brought to a sudden stop on their long journeys, never to reach their final destinations. Ovenbirds ( Seiurus aurocapillus) are commonly found on city streets after an evening migration, and saving specimens in the museum’s ornithology collection allows researchers to monitor the species’ population decline.Ĭity buildings are filled with the sounds of shuffling papers, ringing phones and the dull buzz of artificial lights that illuminate the structures deep into the night.

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