The terrain consists mostly of grassy plains and wooded hills in the eastern region. To the west are mostly low, marshy plains. Paraguay contains six terrestrial ecoregions: Alto Paraná Atlantic forests, Chaco, Cerrado, Humid Chaco, Pantanal, and Paraná flooded savanna. It had a 2019 Forest Landscape Integrity Index mean score of 6.39/10, ranking it 74th globally out of 172 countries. The Guarani Aquifer is an important exorheic basin to the region.