The Paleoecological Impact of Grazing and Browsing: Consequences of the Late Quaternary Large Herbivore Extinctions

Abstract

As recently as ~50,000 years ago, a great diversity of large-bodied mammalian herbivores (species >44 kg) occupied nearly all of Earth’s terrestrial realms. Outside of sub-Saharan Africa, the vast majority of these species had disappeared by the Pleistocene-Holocene boundary ~11,700 years ago, either from human impacts, climate change, or some combination of both. Though research has focused on the causes of the late Quaternary extinctions since the nineteenth century, only recently has attention shifted to understanding their downstream consequences for the structure and functioning of terrestrial ecosystems. In this Chapter, we synthesize the available paleoecological datasets bearing on late Quaternary extinctions and corresponding ecosystem change in Australia, North America, and northern Eurasia. We show that across these regions, the disappearance of large herbivorous mammals had far-reaching impacts, including enhanced fire regimes and vegetation state shifts, reductions in seed dispersal and near-extinction of large fruiting plants, downsizing and diversity loss in invertebrate communities relying on herbivore dung, and the collapse of predator guilds relying on large mammal prey. Collectively, these late Quaternary paleoecological lessons emphasize that large herbivores are cornerstones of ecosystems and play major roles in both maintaining stability and driving state shifts. We conclude our Chapter by discussing how these lessons feed into conservation biology today and efforts to mitigate the effects of continued range contraction and extinction of large mammals over the next century.