/fillbiome

Syntax

/fillbiome <from> <to> <biome> [replace <filter>]

Argument	Kind of value	What to type
<from>	Block position	One corner of the area, as block coordinates X Y Z.
<to>	Block position	The opposite corner of the area.
<biome>	Game id	The id of the biome to set, for example minecraft:cherry_grove. The id of a biome.
<filter>	Game id or tag	For replace: the biome to replace, as a biome id or a biome tag starting with #. The id of a biome, or a #tag of them.

Permission level	2: operators, worlds with cheats on, command blocks and functions
Works in	Operators on multiplayer servers, singleplayer worlds with cheats enabled, and command blocks and functions.
Result	Reports how many biome entries were set and the corners of the area. The number /execute store saves is the number of biome entries changed.
4 block grid	Biomes are stored in cells of 4 by 4 by 4 blocks. Both corners are rounded down to this grid, so the changed area can differ slightly from the coordinates given.
replace	With replace, only cells whose current biome matches the filter are changed.
Size limit	The volume of the area may not exceed the game rule max_block_modifications (default 32768 blocks). A larger area fails with "Too many blocks in the specified volume".
Loaded area	All chunks in the area must be loaded, otherwise the command fails with "That position is not loaded".
Nothing changed	Fails with "No biome entries were changed" if the area already has that biome or nothing matches the filter.

/fillbiome ~-8 ~-8 ~-8 ~8 ~8 ~8 minecraft:cherry_grove

Turns the area around you into a Cherry Grove.

/fillbiome ~-8 ~-8 ~-8 ~8 ~8 ~8 minecraft:desert replace minecraft:plains

Turns only the Plains parts of the area into Desert.

/fillbiome ~-8 ~-8 ~-8 ~8 ~8 ~8 minecraft:mushroom_fields replace #minecraft:is_forest

Turns every forest biome in the area into Mushroom Fields.