Adding to Vercetti's interpretation, I would like to add Mann's own thoughts in his rather good commentary track for COLLATERAL where he says, paraphrase-wise, that the human civilization that L.A. displays, despite the structural acheivement by our species, it won't last forever, while nature itself flourished before our species escaped from being ape-man beasts, and will indeed run wild(pun intended) once mankind has had its day in the sun.