“Cemeteries are full of life,” says biologist Anne Pringle as she walks through the Forest Hill Cemetery in Madison, Wisconsin. It’s a bright, early October day and sunlight filters through the still-green leaves, catching strands of spider silk spun over tombstone crosses. Speckled mushrooms stand sentry over the manicured grass as squirrels chatter overhead. But the form of life that brought Pringle here is subtler: Her work focuses on the green and rust-colored splotches growing on the headstones.