The Ecology of the Earth's Grazing Ecosystems

Abstract

A s recently as 150 years ago, most of Earth's grasslands supported large migratory populations of hoofed herbivores belonging to the Artiodactyla, Perissodactyla, and Proboscidea-that is, ungulates. These herbivores included bison (Bison bison) on the North American plains, saiga antelope (Saiga tatarica) on the Eurasian steppe, wildebeest (Connochaetes taurinus) and zebra (Equus burchelli) on the African savanna, and the ecologically equivalent kangaroos (Macropodidae) on the Australian savanna. As a result of the post-industrial global expansion of cropland and cattle ranching, most grasslands grazed by Pleistocene megaherbivores were eliminated. Today, they are restricted to the world's few large grassland reserves that protect all seasonal ranges of the animals. In this article, we describe profound functional similarities between two of the most celebrated of these remaining habitats, the Serengeti ecosystem of east Africa and Yellowstone National Park (YNP) of the North American intermountain west, which previously have been considered to