Problem with biome

Hello,

I have actually a local server with a city on the map, but the problem is that's there is a part of my city in the desert and a other part in the forest so the rain don't fall everywhere.

But i don't remember it was sand before, and i have grass everywhere so i don't understand..
So i ask to you guys, is it possible to change the biome with a plugin or something like that ?

It will be very interesting for me, thank you

Have a nice day