Perilous Plastic.

• Position: THE BIG PICTURE

Marine life is in danger all over the world. Why? Plastic litter is clogging Earth's oceans--from the icy Arctic to the tropical Pacific. Each year, an estimated 8 million tons of discarded plastic bags, straws, cups, bottles, and other products end up in the ocean, where they can harm and even kill fish and other animals. Some, like this turtle in the Mediterranean Sea, get trapped in plastic netting; others ingest pieces of plastic or even microscopic particles--called microplastics--that form when chemical pollutants react with salt water and sunlight.

But the world is starting to take action to curb plastic pollution. In November, Boston's city council approved a plastic bag...