It seems obvious enough why God feels grief at man’s evil, and this is why he might wish to destroy man; but why “beast, and the creeping thing, and the fowls of the air” (Gen 6:7)?

There may be two reasons. The broader animal kingdom was created for man, who had responsibility for it; with man destroyed, it would make sense to destroy animals. A second reason, perhaps, is that these creatures too had been corrupted in the Fall, even as the land has sprouted “thorns and thistles.” A remark in Gen 6:11 is consistent with this: “all flesh”—not just human flesh—“had corrupted his way upon the earth.” That would certainly be true if the wolf originally lay down with the lamb, but became a carnivore after the Fall. This is suggested by the notion that nature would once again live in peace in the new creation: “The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them.” (Isa 11:6)