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Past climate change reduced lemur population in Madagascar

Climate threat to lemurs

Daraina region in Madagascar. Background image from Google Earth.

Climate change that took place 4,000-10,000 years ago may have contributed to the endangered status of one of Madagascar’s rarest lemurs by reducing the extent of its habitat, argues a new study published in the journal Proceedings of the Natural Academy of Sciences.

The research, conducted by a team of French scientists, used remote-sensing analyses and population genetics modeling to reconstruct the historical distribution of golden-crowned sifaka (Propithecus tattersalli), a forest-dwelling lemur, in the Daraina region in northern Madagascar. They found the lemur’s habitat underwent a sharp contraction during dry periods caused by climate change.

The findings are significant because they indicate the species suffered a population drop prior to the arrival of humans some 1500-2000 years ago. Humans, through their use of fire, are usually seen as responsible for large-scale vegetation change across the island nation, but the study adds to a growing body of evidence suggesting that Madagascar may not have been as forested as conventionally believed at the time of human colonization.

Golden-crowned Sifaka (Propithecus tattersalli). Photo by Jeff Gibbs.

“Prehuman Holocene droughts may have led to a significant increase of grasslands and a reduction in the species’ habitat,” write the authors. “This contradicts the prevailing narrative that land cover changes are necessarily anthropogenic in Madagascar but does not preclude the later role played by humans in other regions in which recent lemur bottlenecks have been observed.”

In other words, while climate change may have triggered the observed decline in the golden-crowned sifaka’s forest habitat, the authors say that humans could have been responsible for forest loss on other parts of the island. For example, satellite data and aerial photography show that forest cover has indeed declined significantly in the past 50 years across large areas of the island due to agricultural conversion and land-clearing to establish cattle grazing areas.

Nevertheless, the authors note that in their particular study area, forest cover has remained stable for 60 years, indicating that the local population is not necessarily responsible for the golden-crowned sifaka’s endangered status.

“There is no doubt that humans have played a major role in driving several Malagasy species to extinction, since their arrival on the island,” co-author Lounès Chikhi of the Université Paul Sabatier said in a statement. “Although our findings relate to a specific region in Madagascar, they shine the spotlight on how important it is that conservation projects account for regional differences. The presence of humans, we have demonstrated, may not be the only cause for loss of biodiversity. It is risky to alienate local communities by excluding them from their territories, rather that bringing them on as precious allies to help conservationists find local answers for sustainable resource management.”

CITATION: Erwan Quéméré, Xavier Amelot, Julie Pierson, Brigitte Crouau-Roy, and Lounès Chikhi (2012). Genetic data suggest a natural prehuman origin of open habitats in northern Madagascar and question the deforestation narrative in this region. PNAS 2012: 1200153109v1-201200153.

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