Jacqueline notes, above, that she does not know exactly which tune is being referred to by the original questioner. However, her recent e-mail newsletter does comment on some of the music she recorded, with others, for that series. Maybe one of these is the one you're looking for??

From Jacqueline Schwab's e-mail newsletter:
"...Ken Burn's new documentary "The National Parks: America's Best Idea,"...
From the musical side of things, you'll hear Kathy
Talvitie's evocative "Red Star Line" and other tunes I recorded with
Jay Ungar, Molly Mason and Matt Glaser, as well as the Gaelic air
"Robaidh dona gorach" (from my "Celtic Dialogue" CD with fiddler
Laura Risk) and the Scottish reel "Keep It Up" (from the demo by New
Rigged Ship, my duo with cellist Reinmar Seidler), and also hear a track
from a CD by tunesmith Larry Unger."