If you are ever moved to be needlessly cruel to someone hunkered down for the winter in a dull, drafty place, you might send them a picture of Heron Island. A lush, sand-fringed freckle several hours by boat from Gladstone, Australia, it looks like a screensaver version of paradise. Adorably dour-looking black noddies perch in Pisonia trees; green and loggerhead turtles stumble from the turquoise water each year to bury their eggs in the sand. But the most astonishing feature of the island is offshore—a portion of the Great Barrier…
