And all flesh died that moved upon the earth
That had animal life in them, of which motion was a sign:
both of fowl, and of cattle, and of beast, and of every
thing that creepeth on the earth;
excepting those that were in the ark. This general destruction of the creatures, as it was for the sins of men, whose they were, and by whom they were abused, and is expressive of God's hatred of sin, and of his holiness and justice in the punishment of it; so, on the other hand, it is a display both of the wisdom of God, in causing a decrease of the creatures, in proportion to the decrease of men, who now would not need so many; and of the goodness of God to those that were spared, that so the beasts of the field, especially the wilder sort, might not multiply against them, and prevail over them, see ( Exodus 23:29 )
and every man:
except those in the ark; and the number of them is supposed to be as great, if not greater, than of the present inhabitants of the earth, by those who are skilful in the calculation of the increase of men. It is thought it may be easily allowed, that their number amounted to eleven billion; and some have made their number to be eighty billion F16. The Apostle Peter calls them, the world of the ungodly, ( 2 Peter 2:5 ) .
F16 Scheuchzer. Physica Sacra, vol. 1. p. 55.