These snow-covered forests encircle the arctic, from scandinavia, through Russia, to Alaska and the rest of North America.
But close to the north pole, the winters are too long and too cold for even the hardiest of trees.
This is the tundra, and it stretches all the way to the shores of the arctic ocean.
Here, conditions are even more extreme than in the forests.
During the two months of winter darkness, temperatures may fall to minus 50 degrees celsius.
The ground deep beneath the snow has been frozen solid since the last ice age.
There is no shelter of any kind. Very few animals can survive here.
But this is one which does. An arctic fox.
It has the warmest fur of any mammal.
And it can survive blizzards that may rage for days on end.
It must nonetheless eventually eat something.
But how is that something to be found when you're all by yourself in this desolation?