Christmas is tied to the magical north and to the reindeer — creatures of mythical power that fly through the night across the world, helping to distribute happiness and good will. But reindeer do exist — we call them caribou in North America — and these animals and their home in the boreal woodlands and on the barren-ground tundra are in trouble.

For the past decade, I have been conducting aerial surveys of caribou herds. As I sit strapped in small planes in minus-20-degree temperatures, it amazes me that that they survive against the challenges of their environment — particularly the females. These animals spend most of the year on the move and live in places that seem intolerably harsh. They undertake long journeys of hundreds or thousands of miles and return to give birth in the same traditional areas. Such large-scale migrations are an ecological phenomenon that, sadly, is fast disappearing across the planet.