User blog comment:Kogath/Monster Hunter: World Discussion/@comment-25083735-20190720031910/@comment-5158920-20190720084459

The maps we go on are only a portion of the biome. Although the Highlands and Rotting Vale have more of a limit than other biomes. If you look at the Ancient Forest and Wildspire from Astera you will see they're far larger than the maps we go on especially the Ancient Forest. You can also see the Wildspire mud section expanding further when you look beyond Jyuratodus starting location.