Abstract
Megaherbivores fulfilled a number of important ecological function in terrestrial ecosystems and behaved as ecological engineers since 300 million years until around 12,000 years ago. The late Pleistocene extinction led to the loss of important ecological functions that were partially restore by agriculturists humans through an ecological replacement. Understanding better the differences and similarities in the ecological impact of megaherbivores and agricultural humans should help to predict the future of terrestrial ecosystems.
Highlights
Nowadays, very large terrestrial herbivores with adult body weights larger than 1,000 kg occur only in some tropical areas of the world, in Africa and Asia, and they are counting only a handful of species (Owen-Smith, 1988)
Since the late Triassic, all species of megaherbivores belonged to the dinosaurs, until they became eradicated during the Cretaceous-Paleogene mass extinction event, around 66 million years ago (Weishampel and Norman, 1989). This is the best-known example of megaherbivore replacement that led to the global extinction of all late Cretaceous megaherbivores and the radiation of large herbivorous mammals that derived from much smaller species
Megaherbivores are larger versions of their smaller relatives, their large size allows them to perform different ecological functions that are poorly performed by smaller herbivores (e.g., Fritz, 1997; Owen-Smith, 2013), even when these smaller herbivores are present in equivalent biomass as the megaherbivores (Owen-Smith, 1988)
Summary
Very large terrestrial herbivores with adult body weights larger than 1,000 kg (the socalled megaherbivores, in the sense of Owen-Smith, 1988) occur only in some tropical areas of the world, in Africa and Asia, and they are counting only a handful of species (Owen-Smith, 1988). Even if one considers the historical distribution of these megaherbivores, before the recent shrinkage of their distribution due to intensified encroachment of their habitat and active hunting by humans, these very large terrestrial herbivores had still a relatively restricted distribution on the continents before the invention of firearms. This restricted geographical and climatic distribution of terrestrial very large herbivores is an exception when one looks at the terrestrial biosphere during geological times. The chronological coincidence between megaherbivore extinctions and the arrival of modern humans in Australia, North and South America, as well as on large islands such as
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