Guys, gals, let`s get our thinking caps on.
The solution is simple--Punctuated Creation!
When God saw all that prime real estate lying empty post-Flood, He kicked the ole Creation machine back into gear and popped out new critters (and plants) for each vacancy. It`s all spelled out in the second book of the Bible--Profundicus--right between Genesis and Exodus. Not in your Bible? Damn, that Eusebius has a lot to answer for.
Btw, do I get a prize?