The speaker pushes back against the idea that death is the great villain. Death, they say, gets too much credit. People are the ones who make themselves targets, drawing a bull's-eye wherever the bomb lands, tying ropes, sealing themselves away, and clearing real forests only to put up "forests of stone." The tone is dry and a little bitter, and the humor is blunt, as in the comparison of human decline to "spent erections."
The second half shifts to a stranger picture of humans as creatures built to stand upright, looking like termite mounds in the noon heat, giving the sun as little surface as possible. While predators rest, we stretch out like shadows toward whatever they or the wind have dropped. The poem suggests we are scavengers, resourceful and a bit exposed. The mood is wry and unsentimental, with a kind of grudging admiration. We bring much of our trouble on ourselves, but we also adapt in odd, stubborn ways.