1 . If humans were truly at home under the light of the moon and stars, we would go in darkness happily, the midnight world as visible to us as it is to the vast number of nocturnal (夜间活动) species on this planet. Instead, we are diurnal creatures, with eyes adapted to living in the sun’s light. This is a basic evolutionary fact, even though most of us don’t think of ourselves as diurnal beings. Yet it’s the only way to explain what we’ve done to the night: We’ve engineered it to receive us by filling it with light.

The benefits of this kind of engineering come with consequences — called light pollution — whose effects scientists are only now beginning to study. Light pollution is largely the result of bad lighting design, which allows artificial light to shine outward and upward into the sky. Ill-designed lighting washes out the darkness of night and completely changes the light levels — and light rhythms — to which many forms of life, including ourselves, have adapted. Wherever human light spills into the natural world, some aspect of life is affected.

In most cities the sky looks as though it has been emptied of stars, leaving behind a vacant haze (霾) that mirrors our fear of the dark. We’ve grown so used to this orange haze that the original glory of an unlit night — dark enough for the planet Venus to throw shadows on Earth — is wholly beyond our experience, beyond memory almost.

We’ve lit up the night as if it were an unoccupied country, when nothing could be further from the truth. Among mammals alone, the number of nocturnal species is astonishing. Light is a powerful biological force, and on many species it acts as a magnet. The effect is so powerful that scientists speak of songbirds and seabirds being “captured” by searchlights on land or by the light from gas flares on marine oil platforms. Migrating at night, birds tend to collide with brightly lit tall buildings.

Frogs living near brightly lit highways suffer nocturnal light levels that are as much as a million times brighter than normal, throwing nearly every aspect of their behavior out of joint, including their nighttime breeding choruses. Humans are no less trapped by light pollution than the frogs. Like most other creatures, we do need darkness. Darkness is as essential to our biological welfare, to our internal clockwork, as light itself.

Living in a glare of our own making, we have cut ourselves off from our evolutionary and cultural heritage — the light of the stars and the rhythms of day and night. In a very real sense, light pollution causes us to lose sight of our true place in the universe, to forget the scale of our being, which is best measured against the dimensions of a deep night with the Milky Way — the edge of our galaxy — arching overhead.

4 . The amount of plastic pollution in the oceans is rapidly increasing. This is problematic, as at least 700 kinds of ocean animals—including sharks, whales, seabirds and turtles—can become caught in the stuff or mistake it for a tasty snack.

While we know that some ocean animals seem to catch plastic because it looks like jellyfish or some other food sources, less research has been carried out into what plastic smells like to ocean animals. But now, a study from the University of North Carolina at Chapel Hill has found the coating (涂层) that naturally builds up on ocean plastics causes the rubbish to give off the smell of food.

The researchers took 15 turtles, each around five months old, and placed them in a lab aquarium. They then piped in smells of clean water, clean plastic, turtle food, and plastic that had been soaking in the ocean environment for five weeks. The turtles showed no reaction to the smells of clean water or clean plastic. But when facing ocean soaked plastic or turtle food, they stuck their noses out of the water and showed increased activity.

“This finding is important because it’s the first proof that the smell of ocean plastics causes animals to eat them,” said Dr Kenneth J Lohmann, who took part in the study. It’s common to find a turtle with its stomach full of plastic materials. There are also increasing reports of sea turtles that have become ill and stuck on the beach due to their taking in plastic.”

According to the researchers, areas of the ocean with much plastic may trick turtles and other animals into thinking that there are plenty of food sources, when the opposite is true. “Once these plastics are in the ocean, we don’t have a good way to remove them or prevent them from smelling like food,” said Lohmann. “The best thing we can do is to keep plastic from getting into the ocean at all.”