I went down a rabbithole about this and now I'm really hung up on it. I got curious about how the WWF developed the list of biomes used for their original Global 200 list, and how they were defined, and I can't find any breakdown of their methodology, or what criteria were used to classify an ecoregion as belonging to one biome or another. The most I could gather was that it was based on floral and faunal makeup, and beta diversity, i.e. the same things they looked at when defining the ecoregions. Does anyone know, like, what specifically they were looking at? Was it the type of vegetation, specific adaptations in native organisms, were they factoring in climate at all?