These stunted shrubs mark the tree line, the beginning of the boreal forest, the taiga. The needle-shaped leaves of the conifers are virtually inedible. So this forest supports very little animal life. It’s a silent place where the snow is unmarked by footprints. In the Arctic winter, snow forms a continuous blanket across the land. But as spring creeps up from the south, the taiga is unveiled. This vast forest circling the globe contains a third of all the trees on earth and produces so much oxygen, it changes the composition of the atmosphere.