What is the poet's intent and message in the poem "Flower-Fed Buffaloes" by Vachel Lindsay?

In "The Flower-Fed Buffaloes," Vachel Lindsay is singing a
lament (i.e., a mournful song of sorrow)  in poetry for the buffalo which were driven
off or hunted to extinction by the advent of the power of Western civilization's
Industrial Revolution and the engines it porduced. Lindsay's intent is to mourn the
passing of the buffalo and all that sustained them, the "prairie flowers" and the
"perfumed grass," along with all those whom they sustained, the "Blackfeet" and the
"Pawnee" tribes, now "lying low." Lindsay's intent is bound up with his message, which
is that while Western civilization progresses forward and gives increasing opportunity
to Western people, there is a cost attached to the forward push in which "locomotives
sing" and the natural environment is "swept away by wheat." The cost is in reduced life
and freedom for animals, the buffalo; flora, the prairie flowers; natural habitat, the
"tossing, blooming, perfumed grass"; and other human beings, non-Western human
beings:

With
the Blackfeet lying low,
With the Pawnee lying
low.