Outdoor sports were often impractical at night until the 20th century, when electric floodlights began to spark a new fascination with night games. The first night game in professional baseball was a 1930 minor-league contest in Iowa, followed by Major League Baseball's first night game five years later in Cincinnati. Today, countless ball fields, tennis courts and other athletic facilities are regularly bathed in artificial light after dark — sometimes from dusk until dawn, even if no one is using them.
There can be good reasons to leave on outdoor lights at night, like deterring crime or improving safety in public places. There are also good reasons to turn them off, however, especially if they're powerful floodlights illuminating an empty baseball field at 2 a.m. It would save energy, of course, but it could also save a variety of wild animals from the growing scourge of light pollution.
Light pollution often comes up in the context of astronomy and stargazing, since many urban areas are now so awash in electric lights that barely any stars are visible. Yet while we've obscured our views of the night sky, wildlife typically has much more to lose. Lots of bird species migrate or hunt at night, for example, and are now commonly confused by electric lights to the point of exhaustion or death. A similar fate awaits some baby sea turtles, which can be lured away from the ocean by beachfront lighting. And for a wide range of other nocturnal animals, outdoor lights have all but erased the darkness where their ancestors evolved.
"Predators use light to hunt, and prey species use darkness as cover," Christopher Kyba, a German researcher who studies light pollution, tells the International Dark-Sky Association (IDA). "Near cities, cloudy skies are now hundreds or even thousands of times brighter than they were 200 years ago. We are only beginning to learn what a drastic effect this has had on nocturnal ecology."
Light pollution comes from many different sources, but since overnight floodlights at sports facilities tend to be very bright and unnecessary, they could be relatively low-hanging fruit. In the U.S. alone, more than 2,000 outdoor sports lighting complexes are either retrofitted or installed every year, according to the IDA, in places like schools, parks and community recreation centers. These light towers can be a nuisance for nearby residents as well as a hazard for wildlife, so in 2018 the IDA introduced its first set of guidelines to help sports facilities cut back on superfluous lighting and become better neighbors.
Lighting technology has come a long way in the last century, and modern LEDs offer far more precision and control than the incandescent, metal-halide and sodium lamps of decades past. With the right equipment and management, a sports complex can tailor its lights to target only the field of play, reducing problems like spillage and glare that contribute to sky glow.
The IDA has also developed best practices for sports facilities, such as using automatic or remote-control systems to make sure lights are turned off at local curfew times — which should be no later than 11 p.m., the guidelines state. Facilities should also use separate lighting systems for different areas like sports fields, parking lots and concessions, according to the IDA, and provide readily accessible controls so lights can be adjusted as needed for various events.
Even if you don't own a sports complex, the IDA wants your help spreading this message. "To promote lighting that helps protect the nighttime environment, we recommend contacting city council members, community representatives, homeowner associations, and parks and recreation authorities," the IDA suggests. Ask if they know about the IDA's Criteria for Community-Friendly Outdoor Sports Lighting (PDF), and if not, let them know why embracing a little darkness can be a bright idea.