Java Edition:Birch Forest M
Birch Forest M, also known as Mutated Birch Forest or Tall Birch Forest, and now called Old Growth Birch Forest, is a biome with tall birch trees. This biome is a recontinued feature that previously did not generate.
Discontinuation
The biome did not generate from 16w02a (1.9 snapshot) to 16w42a (1.11 snapshot) due to a bug.[1] In 16w02a (1.9 snapshot), no mutated biomes generated at all. The later bug was caused by a simple mix up in the code that was implemented in fixing the 16w02a bug.[2] The (pseudo)code was supposed to be:
convert some birch forest into mutated birch forest convert some birch forest hills into mutated birch forest hills
Instead it read:
convert some birch forest into mutated birch forest convert the same locations of birch forest into mutated birch forest hills
Because of this error, all tall birch forest that was to mutate would be mutated into mutated birch forest hills, and birch forest hills were not mutated at all. The mutated birch forest hills were effectively overriding the regular mutated birch forest biome.
Obtaining
Birch Forest M can be obtained from its addition in 13w36a (1.7 snapshot) to 15w51b (1.9 snapshot). It is discontinued from 16w02a (1.9 snapshot) to 16w42a (1.11 snapshot), and recontinued when the bug was fixed in 16w43a (1.11 snapshot). It has been obtainable once again ever since.
Name
This biome was called "Birch Forest M" from 13w36a (1.7 snapshot), when it was added, to 18w15a (1.13 snapshot). In 18w16a (1.13 snapshot) it was called "Mutated Birch Forest" and the ID was set to mutated_birch_forest. From 18w19a to 21w39a (1.18 snapshot), it was called "Tall Birch Forest". The ID was updated from mutated_birch_forest to tall_birch_forest in 1.13-pre5. Finally, in 21w40a (1.18 snapshot) it was renamed "Old Growth Birch Forest" and the ID was changed to old_growth_birch_forest. Old Growth Birch Forest is the current name.
See also
References