User blog comment:Gen. Grievous1138/The Biomes Initiative/@comment-25101089-20150531003001/@comment-25101089-20150531135822

Yes there is, the file LOTRBiome.class (in world/biome) lists every single biome in the mod, alongside their IDs. Also, many biomes have been removed and re-added as biome variants to save IDs (such as the Lothlórien Clearing).