 Heaths and pastures are, respectively, low shrublands and grasslands where forest growth is hindered by human activity but not the climate.Tall grasslands, including the tallgrass prairie of North America, the north-western parts of Eurasian steppe (Ukraine and south of Russia) and the Humid Pampas of Argentina, have moderate rainfall and rich soils which make them ideally suited to agriculture, and tall grassland ecoregions include some of the most productive grain-growing regions in the world.The expanses of grass in North America and Eurasia once sustained migrations of large vertebrates such as buffalo ("Bubalus bubalis"), saiga ("Saiga tatarica"), and Tibetan antelopes ("Pantholops hodgsoni") and kiang ("Equus hemionus").