What are the underlying themes of the poem "Ten Thousand" by Roo Borson?

The main theme of "Ten Thousand" is Borson's contrarian view of being alive. The logical conclusion of this contrarian view is that all that is valued or desired is the unknown future. Borson begins establishing the contrarian perspective in his descriptions of nature: the birds "dive up"; the "leaves off the ground" become "wheels"; "branches [are] planted against the sky." Things are not as expected. The end result of this contrarianism is that the empty void ahead is pitted against the meaningless hollowness behind:

All those memories,
you wouldn't want them over again, there's no point.
What's next, you ask yourself.
You ask it ten thousand times.

A second illustrative theme is that of nature illuminating human nature. The scenes in nature as described by Borson, though contrary to expectation and, in some ways, to reason, correlate to humankind's experience. What is usually felt to be experiences that connect a person to Earth and to living and to one's own place in reality, like "feet on the earth" or touching one's own hand ("the way your hands / sometimes touch each other") are merely things you wouldn't care to experience again:

All those memories,
you wouldn't want them over again, ....

All that signifies is the empty void ahead versus the meaningless hollowness behind:

What's next, you ask yourself.
You ask it ten thousand times.