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Across the last 50,000 years land vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass over 1,000 kg) survived to the present. Debate on the causes has been ongoing for over two centuries.
Svenning et al. show that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence; conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-Homo sapiens hominins prior to the Late Pleistocene. Image credit: Svenning et al., doi: 10.1017/ext.2024.4.
“The large and very selective loss of megafauna over the last 50,000 years is unique over the past 66 million years,” said Aarhus University’s Professor Jens-Christian Svenning.
“Previous periods of climate change did not lead to large, selective extinctions, which argues against a major role for climate in the megafauna extinctions.”
“Another significant pattern that argues against a role for climate is that the recent megafauna extinctions hit just as hard in climatically stable areas as in unstable areas.”
Archaeologists have found traps designed for very large animals, and isotope analyses of ancient human bones and protein residues from spear points show that they hunted and ate the largest mammals.
“Early modern humans were effective hunters of even the largest animal species and clearly had the ability to reduce the populations of large animals,” Professor Svenning said.
“These large animals were and are particularly vulnerable to overexploitation because they have long gestation periods, produce very few offspring at a time, and take many years to reach sexual maturity.”
The analysis shows that human hunting of large animals such as mammoths, mastodons, and giant sloths was widespread and consistent across the world.
It also shows that the species went extinct at very different times and at different rates around the world.
In some local areas, it happened quite quickly, while in other places it took over 10,000 years.
But everywhere, it occurred after modern humans arrived, or in Africa’s case, after cultural advancements among humans.
Species went extinct on all continents except Antarctica and in all types of ecosystems, from tropical forests and savannas to Mediterranean and temperate forests and steppes to arctic ecosystems.
“Many of the extinct species could thrive in various types of environments,” Professor Svenning said.
“Therefore, their extinction cannot be explained by climate changes causing the disappearance of a specific ecosystem type, such as the mammoth steppe — which also housed only a few megafauna species.”
“Most of the species existed under temperate to tropical conditions and should actually have benefited from the warming at the end of the last Ice Age.”
The researchers point out that the loss of megafauna has had profound ecological consequences.
Large animals play a central role in ecosystems by influencing vegetation structure (e.g., the balance between dense forests and open areas), seed dispersal, and nutrient cycling.
Their disappearance has resulted in significant changes in ecosystem structures and functions.
“Our results highlight the need for active conservation and restoration efforts,” Professor Svenning said.
“By reintroducing large mammals, we can help restore ecological balances and support biodiversity, which evolved in ecosystems rich in megafauna.”
The study is published in the journal Cambridge Prisms: Extinction.
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Jens-Christian Svenning et al. 2024. The Late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene. Aarhus University. Cambridge Prisms: Extinction 2: e5; doi: 10.1017/ext.2024.4
This article was adapted from an original release by Aarhus University.
