Most of the Birmingham Zoo is within the Southern Shale Valleys level IV ecoregion, which itself is nested within the Ridge and Valley level III ecoregion, one of the major level III ecoregions of the Southern Appalachian Mountains. The terrain of the Southern Shale Valleys is dominated by stream valleys and low hills predominantly of shale. Thus, the original soils in this area were probably acidic (possibly circumneutral in some areas) and harbored a different community of plants than limestone-rich Jones Valley to the north.
The hilly northern portion on the north edge of the Zoo property is within the Southern Limestone/Dolomite Valleys and Low Rolling Hills level IV ecoregion. The terrain of this ecoregion is one of karst topography interrupted occasionally by hills of chert and sandstone. Despite the name, the portion of the Zoo in this ecoregion is on a foundation of sandstone.