The correct option is option D. A dismal prospect of total devastation of the natural environment.
When the speaker talks about:
"When a vast image out of Spiritus Mundi
Troubles my sight: somewhere in sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds. "
Is in fact referring to the birds as a symbol for Nature in its sharpest, cleanest sense. Humankind is destroying the Nature and has to face the consequences, in today's world that translates in the effects of climate change and global warming the humans provoked, bringing deserts where once were rivers and falls.