This visually stunning nature series wraps up Season 1 with the finale "Alaska: Last American Frontier," which is set primarily in the southeast portion of that state. It's home to one of the richest temperate rain forests on the planet, as well as the salmon run, an annual migration that attracts the greatest concentration of grizzly bears on Earth. The salmon run is responsible for adding crucial nutrients into the landscape, enhancing the survival of the region's animal and plant life, including giant trees. Helen Bonham Carter narrates.