User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-6050823-20131027165736/@comment-6050823-20131028015335

The reason why so many monsters appear in the Unknown Sea of Trees is because, the Unknown Sea of Trees is inbetween multiple areas(Ruins Field, Primeval Forest, and the Great Desert and, I'm talking about the Low Rank Unknown Sea of Trees)and some monsters use it to cross other areas. While others like Gravios and afew other monsters may breed in the Unknown Sea of Trees besides moving to other areas. The High Rank Unknown Sea of Trees is supposely in the mountains of the Heavenly Mountains(Atleast, thats where it is believed to be and is in-game)close to the Frozen Sea and Ruins Field(The Underground Caves/Volcano is close to the Frozen Sea).