For the last fifty years, the trees of the boreal forest have been moving north. The Treeline takes us along this critical frontier of our warming planet from Norway to Siberia, Alaska to Greenland, to meet the scientists, residents and trees confronting huge geological changes. Only the hardest species survive at these latitudes including the ice-loving Dahurian larch of Siberia, the antiseptic Spruce that purifies our atmosphere, the Downy birch conquering Scandinavia, the healing Balsam poplar that Native Americans use as a cure-all and the noble Scots Pine that lives longer when surrounded by its family. It is a journey of wonder and awe at the incredible creativity and resilience of these species and the mysterious workings of the forest upon which we rely for the air we breathe. Blending reportage with the latest science, The Treeline is a story of what might soon be the last forest left and what that means for the future of all life on earth.