Madagascar used to be house giant birds and mammals, giant tortoises, and even giant lemurs, but today, these massive animals are not found on the island anymore. There had been an endless debate about whether climate change or human activities are to be blamed for the loss.
Recently, a study of cave deposits on an Indian Ocean island provided the much-awaited answers: The dry conditions made it difficult for the large animals to thrive, but the last straw was the human activities.
Researchers Xi'an Jiaotong University geochemist Hai Cheng and graduate student Hangling Li studied the climate condition and impact of human activities concerning Madagascar's megafauna's extinction. The findings were published in Science Advances on October 16.
Mysterious Madagascar
Madagascar is located 425 kilometers off the southeastern coast of Africa. Researchers believed that it was among the last places humans settled until two years ago when Paleoecologist James Hansford discovered the butchered elephant bones. The bones dated 10,500 years back, indicating that humans and giant mammals coexisted millennia before the megafauna became extinct. The extinction of the megafauna was believed to be 1,500 years ago.
Studying the Climate of Madagascar
Pieces of evidence of the region's climatic history were studied in the caves of Rodrigues, a small, remote island 1600 kilometers east of Madagascar.
The island was in pristine isolation until the recent century. The place became an ideal area to study the speleothems, stalactites, and stalagmites that can record ancient climates.
Segments of the deposits were dated, which build new layers over time, similar to tree rings and ice circles. The study team was able to record decade-by-decade resolution dating back to 8,000 years ago. Heavy oxygen, carbon, and trace elements revealed changes from layer to layer, indicating how wet the climate was at a given point in time.
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Climate Change, Human Activities, and Mass Extinction
The study showed that the southwestern Indian Ocean had four significant droughts over the entire period. The team also found out that an arid condition coincided with the megafauna's mass extinction 1500 years ago.
The study finding indicates that Madagascar's megafauna survived from previous dry spells. Thus, Cheng suggests that human activity, either from overhunting or habitat destruction, might have been the "last straw" of the megafaunal extinction.
Significance of the Study
The new study sheds light and provided researchers "a really clear picture" of the overall climate in the region, Kristina Douglass, an anthropologist at Pennsylvania State University, University Park said. She also thought that studying Rodrigues was innovative.
However, Madagascar is vast; thus, there is a wide variety of topography and local climates and various human habitation degrees. This would imply that extinction may vary in different places. This would require further localized studies, Douglas said.
Hansford deems that the extinction may have increased after establishing the human population, such as the rise of farming and urban centers, which also destroyed animals' natural habitat. Human-induced activities such as fire, hunting, disease, and introduction of native species may still have played a role in the extinction of Madagascar's giant birds and animals.
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