Minecraft wiki entry for Updating_old_terrain, associated text: MCEdit has a plugin to select chunks by biome so that we can delete them. It is also possible to protect regions of your world, in case you need to preserve existing builds in those biomes.[2] As this method depends on MCEdit, it only works for worlds opened in Java Edition 1.7.2 to 1.12.2. If you have opened the world in 1.13, you need to retrieve the older save from the backups folder.