This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Two of this atlas's best known ecosystems, the Serengeti and Brazil's Cerrado, were filed under the Grassland biome from the founding wave onward, and by the ordinary meaning of the word, that was not unreasonable: both are open, sun struck expanses of grass stretching to the horizon. But ecology draws its categories from climate and structure, not appearance, and by that measure both places have always been something more specific than grassland. The Cerrado's own description already called it, without qualification, the most biodiverse savanna ecosystem on Earth, and carried the alias Brazilian Savanna. The Serengeti's own description already called it a savanna grassland ecosystem. The biome record simply had not caught up to what the entities themselves already said.
The distinction matters because temperate grassland and tropical savanna form under different climates. A savanna stays warm to hot year round and has a rainy season and a dry season, with most of its rain falling in just a few months; that long dry season is what keeps the grassland from closing over into forest. A temperate grassland, the prairie of the American Midwest or the steppe of Central Asia, is instead defined by real seasonal swings in both temperature and precipitation across the year, a different climate pattern that produces a superficially similar grass dominated landscape by a different route.
The Serengeti's own wildfire, nitrogen cycle and decomposition facts, and the Cerrado's own wildfire demonstration, already described exactly this savanna dynamic before either was reclassified: seasonal drought curing the grass into fuel, fire recycling nutrients and holding back tree cover, a new flush of growth on the next rain. Reclassifying both ecosystems under the newly minted Savanna biome does not change a single fact already on either page. It corrects the shelf they sit on to match what was already written on the label.