[1] The topography is generally low, extending from sea level up to 500 meters elevation.

There are coastal lagoons along the Atlantic shore including Lagoa dos Patos in Brazil, which rise to rolling hills in the eastern part of the ecoregion.

The western portion of the ecoregion is drained by tributaries of the Uruguay River, including the Ibicuí, Negro, Tacuarembó, Yí, and Queguay.

Grazing mammals include the Pampas Deer (Ozotoceros bezoarticus), the Gray Brocket or Guazuvirá Deer (Mazama gouazoubira), and the capybara (Hydrochoerus hydrochaeris), the world's largest living rodent.

These include the greater rhea (Rhea americana), ochre-breasted pipit (Anthus nattereri), yellow cardinal (Gubernatrix cristata), saffron-cowled blackbird (Xanthopsar flavus) and pampas meadowlark (Sturnella militaris).