The Japanese believe in the kodama, or spirit, that lives inside the broadleaf forests of snowy Hokkaido. The 600-year-old redcedars of British Columbia have evolved an underground neural network that communicates via a highway of fungus. And the famously hardy bristlecone pines that cling to the rocky cliffs of the Great Basin Ranges have persisted since the pyramids were built. Clearly, there’s a lot humans can learn from trees. Treeline follows skiers, scientists and a tree doctor as they explore our connection to some of the oldest living species on the planet.