In this classification, we consider it a large transitional area of the other ecosystems of the eastern region of Paraguay and Humid Chaco. It occupies the central and western region of the eastern region of Paraguay and is the most heterogeneous of all, containing an amalgam of the Atlantic Forest of Alto Parana , Cerrado, Mesopotamian Grasslands and Humid Chaco respectively.

This ecoregion of transitions is the one that has registered the largest number of birds in Paraguay with a total of 594 species, none of them endemic since they can be found in other regions.