Some wonderful bad news is emerging. The kind that easily converts to good news.

A powerful toxin is now sprawling across land, water and sky. This pollutant degrades everything from phytoplankton to entire food webs, water quality, climate, human physiology and mental health, including our consciousness of a larger universe.

The great news: It costs nothing to remove.

In fact, detoxing from this pollutant would happily cut household, business and government overhead; energy and health care costs; carbon emissions; water pollution; cancer rates; even the epidemic depressions, addictions and joylessness that so dim human life on the planet today.

And this toxic cleanup is laughably easy. We could do it in our sleep.

That’s because the toxin is artificial light—the kind that should not be shining all night, for reasons we've been in the dark about until recently.

“We humans would like night to be day,” said Travis Longcore, an ecology professor at the University of California, Los Angeles Yet “for millions of years we've had a dark night. We can mess with that, but it comes at a cost.”

That cost isn’t just “the light bill,” as my grandparents called the scant toll for their mild electrical use—even if that cost itself is astronomical today.

The International Dark-Sky Association estimates that the U.S. alone wastes $2.2 billion and emits an extra 14.1 million tons of carbon dioxide per year, simply from excessive or redundant night lighting.

But the larger costs are ecological and health-related—the kind we always get billed for later.

We’ve long known that man-made lights disrupt nocturnal bird migrations. We’ve known likewise that shore lights distract sea turtle hatchlings away from their vital seaward crawl, luring them perilously toward the inland glare of roads and houses.

Now biologists are finding that artificial lighting disrupts myriad other vital cycles, from reproduction to metabolism, reforestation to water ecology.

Take the prolific algal blooms currently sucking life out of the Chesapeake Bay and Gulf of Mexico.

Normally, deeper-dwelling zooplankton would swim upward at night to feed on a fat supper of algae. But man-made lights—magnified by water surface—keep these microorganisms from surfacing, and the algae grow undeterred.

Night lighting also impairs water quality inland. It hampers the survival of trees, whose clocks are set by seasonal darkness, discourages bat species vital to reforestation, lures aquatic insects away from streams, inhibits amphibian reproduction and throws off biological cycles of microbes, fish, reptiles and birds.

And it affects mammals—like us.

Our all-nighters of faux daytime are now considered a powerful endocrine disruptor, linked to insomnia, stress, cancer, stunted growth, depression, accelerated aging and obesity.

Night lighting also impairs vision, ironically. It’s not just our lost views of the ancient, distant stars our ancestors knew, though this in itself is surely an inspiration-suppressant. Light pollution also taxes our basic visual equipment of rods and cones.

Studies have found night shift workers are nearly twice as likely to develop breast cancer as day workers. The World Health Organization now considers night shift work a probable carcinogen.

Other studies find nocturnal light exposure strongly associated with higher blood sugar levels, diabetes and weight gain.

T.S. Wiley, author of “Lights Out: Sleep, Sugar and Survival,” explains that humans evolved to seek sweetness “when the light is long and the fruit is out there.”

By contrast, in winter, “when the light is short … you don’t. But we never have short light, so we crave Ho Hos and Ding Dongs. Endless summer creates an endless appetite for carbohydrates.”

Where does light relate to carbs?

Everywhere—from photosynthesis to food webs to the world’s ancient “carb” deposits we’re suddenly consuming in one big blaze of a carbon binge.

Just turning out the lights each night could significantly modify that carb spree, slow climate change and give some well-deserved rest to our exhausted biosphere.

That’s the suggestion of astrophysicist Eric Vandernoot, of Florida Atlantic University. “When one considers the damaging effects it causes us and the animals out in the wild, one realizes that light pollution is just as damaging as a toxic chemical spill across the land.”

The difference, Vandernoot points out, is that we keep actively paying for this pollution we could so easily quit creating.

How? “Stop harming yourself and others in society. Just turn the lights off.”

A brilliant, obvious, low-impact solution, right?

But such a practical act would require the use of an older lighting source: the inner luminary of human reason. These days, that’s the last light we seem willing to turn on.