This is possible to a degree by using in-game commands made available by enabling cheats. However, this command won't necessarily change a biome's blocks, but an area's biome classification.

Commands in Minecraft can often make the game a lot more fun. Sometimes it's enjoyable to just run around, explore and do things without needing to struggle to do so.

How To Be a Superhero in Minecraft using Only One Command! Using this awesome one command creation, you can turn into Ant Man in minecraft and use Ant-Man's powers to make to shrink in size!