Plastic can take centuries to break down, and instead of quietly disappearing beneath the waves, it has a way of coming back to haunt us. Almost 1 million shoes and over 370,000 toothbrushes were among more than 400 million pieces of plastic recently found washed up on a remote group of islands in the Indian Ocean. Great chunks of plastic have been found inside the stomachs of everything from seabirds to whales, while tiny microplastics are eaten by fish and…