It is best to treat this dated but pleasant documentary as entertainment. Paul Smith's music is incredibly evocative, especially at the birth of a bison and during the fury of a flash flood.
The tone of the narration is often downbeat, referring to qualities of this unique environment soon to be lost forever. To keep from being sucked down into this negativity, keep in mind that recent interest in preserving the prairie environment is being matched with federal assistance, and hopefully the "Vanishing Prairie" won't vanish after all.
The photography is by all accounts excellent. Disney enlisted the help of world-class nature photographers who endured hardships, disappointments, and seemingly-eternal stakeouts behind a camera lens to get just the right shot. When you see it on the screen it all looks too easy. Folks, it's not easy at all! And remember that these films were pioneering firsts that pre-dated Animal Planet, the Crocodile Hunter, and even Wild Kingdom. It started here, and it started with style.
