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Madagascar, known for its unique biodiversity, faces a critical conservation crisis. Over the past 1,000 years, the great “Red Island” has lost many of its large-bodied native vertebrates, including hippos, crocodiles and giant lemurs — some the size of orangutans and gorillas. A new review led by Laurie Godfrey, professor emerita in the Department of Anthropology and published in “Cambridge Prisms: Extinction,” explores how human activity and climate change affected Madagascar’s late Holocene extinctions, offering insights into current conservation challenges.

The paper, co-authored by Stephen J. Burns, professor emeritus in the Department of Earth, Geographic and Climate Sciences, recounts that Madagascar’s first human colonizers, foragers who relied on fishing and hunting, had a minimal impact on the island’s ecosystems. However, the later transition to growing crops and raising livestock was pivotal. This shift led to widespread habitat modification, increased hunting and the eventual collapse of Madagascar’s large vertebrates.

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The effects of climate change varied across the island. Droughts significantly impacted species in Madagascar’s dry southwest, pushing some toward extinction. However, climate change alone was not the main driver of the island-wide decline. Some species adapted by altering their behaviors or retreating to habitats less affected by climate change. It was the combined pressures of human activity and environmental changes that sealed their fate as part of a global phenomenon of large vertebrate Quaternary extinctions, known as the Sixth Mass Extinction.

Godfrey makes a distinction between population collapse — marked by a decline, which can occur over a long period — and extinction, when a species completely disappears.

“Climate was a trigger for megafaunal collapse in the driest part of Madagascar, but we believe it was the spread of agropastoralism, and with that the expansion of the human population and hunting, that ultimately led to extinctions,” she explains.

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The review also highlights varying extinction trajectories around the island. In the wetter zones, the rapid spread of farming and subsequent habitat destruction played a key role in triggering the decline of larger species. In contrast, increasingly drier and more arid conditions played a more substantial role in the southwest. Despite these differences, the ultimate outcomes were similar: threats to large native vertebrates increased as people introduced non-native plants and vertebrate species (e.g., cattle, dogs, sheep and goats) to the island and human populations expanded. 

The authors assert that the growth of farming and herding was the decisive factor, rather than excess hunting by earlier foragers. The research also reveals that genetic bottlenecks, influenced by both natural causes and human activity, occurred regularly in Madagascar’s past. However, recovery from these bottlenecks became increasingly difficult as human pressures grew.

This analysis provides important lessons for the island’s current biodiversity crisis. As global trade and human livelihoods continue to evolve, unsustainable practices like deforestation and increased hunting threaten the survival of smaller-bodied species, including the remaining lemurs, nearly all of which are classified as endangered. The paper argues that addressing these threats requires not only protecting the remaining biodiversity but also ensuring the sustainability of human livelihoods.