It seems to me that it depends upon what you are herding. The Swiss manage to herd dairy cows in mountainous areas.
See also
http://www.my-world-journal.com/Greece.html
re: sheep and goat herding.
which of the following environments is conducive to a herding way of life?
a. Swamps.
b. Steppes.
c. Alluvial plains.
d. Uplands.
2 answers
Which of the following environments is conducive to a herding way of life?