Discovery Channel bought and repackaged the BBC program, Planet Earth, which primarily consists of HD footage of the animal kingdom. The BBC version was narrated by David Attenborough. The American version mixes up the footage and replaces David with a voiceover by Sigourney Weaver.
In the original episode "From Pole to Pole" focus shifts from the taiga to Japan. In the American version, for some reason, it shifts much farther south, to tropical rainforests (a birds of paradise segment) which minimizes the pole-to-pole theme.
At this point [about 15 minutes into the episode] our helpful American media decide to educate us with something that didn't exist in the BBC narrative: "Earth's journey around the sun creates the four seasons..."
You can see and hear the original BBC broadcast, which contains accurate information here on YouTube, at the 3:00 minute mark.
On the Discovery Channel website, the episode synopsis correctly attributes the seasons to "the sunward tilt of Earth's orbit," etc., which is even more frustrating. They copied the show from the BBC as well as the synopsis: they had all of the correct information there at hand, but decided to replace portions of it with incorrect information!
Here is the original Bad Astronomy explanation: What Causes the Seasons?