Throughout the U.S., trees are dying at an astonishing rate. The reasons for the die-off vary from location to location -- drought, disease, insects and wildfires -- but the root cause in many of these cases is the same: climate change.
The epidemic is even threatening the oldest white oak tree in America, a 600-year-old giant in New Jersey that predates Columbus' visit to the Americas.
The effect is particularly apparent in mountain states like California, where 66 million trees have simply disappeared from the Sierra Nevada range since 2010. The Forest Service blames the years-long drought in the area and the spread of pine beetles.