Mob varrients and camels not loading in loaded chunks

I have a base in the desert and near a savanna and I have noticed that when I go to the savanna, none of the warm mob variants spawn because I have already visited those chunks. When I go to the desert, no camels spawn naturally. But when I go to new chunks, those mobs will spawn. It is very jarring because sometimes when I’m going through my savanna, for example, it goes from natural mobs to then spawning the warm variants. I wish there was a way for already existing chunks to atleast get the new mob variant spawns, because they really make the world feel more alive.