Simultaneous extinction of Madagascar's megaherbivores correlates with late Holocene human-caused landscape transformation

Reconstructing the dynamics and drivers of late Quaternary megafaunal extinctions requires direct radiometric date series that are assessed within probabilistic statistical frameworks. Extinction chronologies are poorly understood for many tropical regions, including Madagascar, which had a diverse, now-extinct Holocene large vertebrate fauna including a megaherbivore guild of endemic hippopotami and elephant birds. Madagascar's megaherbivores likely played vital roles in regulating ecosystem structure and nutrient cycling, but few direct dates are available for megaherbivore specimens identified to species level, with uncertainty over when and why different representatives of this guild disappeared. Here, we conduct a new investigation into Malagasy megaherbivore extinction dynamics, including 30 new AMS dates and 63 audited published dates. We use Gaussian-resampled inverse-weighted Mclnerny (GRIWM) analysis to estimate species-specific extinction dates for three elephant bird species (Aepyornis hildebrandti, Mullerornis modestus, Vorombe titan), eggshell representing Aepyornis or Vorombe, and two hippo species (Hippopotamus lemerlei, H. madagascariensis), and to estimate extinction dates for megaherbivore communities in different biomes. Megaherbivores persisted for millennia after first human arrival. Extinction date estimates vary significantly between biomes, with disappearance from dry deciduous forest over a millennium earlier than other biomes, possibly reflecting local variation in megaherbivore population densities or human pressures. However, megaherbivore communities including all elephant bird and hippo species persisted elsewhere across Madagascar until similar to 1200-900 BP, when they collapsed suddenly. Extinctions are closely correlated in time with intensive conversion of forests to grassland at similar to 1100-1000 BP, probably associated with a shift to agro-pastoralism and representing a radical change in sustainability of prehistoric human interactions with biodiversity. Crown Copyright (C) 2021 Published by Elsevier Ltd. All rights reserved.

Automated summary

The extinction dynamics of Megaherbivores in Madagascar varied significantly between different biomes, with disappearance from dry deciduous forest occurring over a millennium earlier than in other biomes. Megaherbivore communities, including all elephant bird and hippo species, persisted elsewhere across Madagascar until around 1200-900 BP, before collapsing suddenly, closely correlated in time with a shift to agro-pastoralism and intensive forest conversion to grassland around 1100-1000 BP.