Humans contributed to animal extinctions on Madagascar
doi:10.1038/nindia.2020.166 Published online 24 October 2020
After surviving repeated megadroughts, dodo birds, giant tortoises and other large animals native to Madagascar and Rodrigues, a small volcanic island east of Madagascar, perished because of human activities amid a major drying trend, an international team of climate experts has found1.
The findings suggest that human activities such as hunting, deforestation and agriculture may have contributed significantly to the extinctions.
Madagascar and Rodrigues, which are considered biodiversity hot spots, have lost most of their endemic large animals that weighed more than 10 kilograms in body weight within the past few centuries. However, it has been difficult to prove whether climatic shifts, human activities or both are to blame for such losses.
To find out, scientists, including a researcher from the National Cave Research and Protection Organisation in Raipur, India, analysed isotopes of oxygen and carbon, and trace elements in the calcite deposits isolated from two caves of Rodrigues and Madagascar. Based on these analyses, they reconstructed past climate changes over a period of 8,000 years.
They found that animal extinctions and ecological changes on the islands occurred during a major drying trend over the past two millennia that was punctuated by four megadroughts. This was the same period when humans arrived on the islands, settled and grew in numbers, the researchers say.
Climate reconstruction, they say, reveals that the human arrival and expansion happened during one of the driest spells of the past eight millennia, accelerating the animal extinctions.
1. Li, H. et al. A multimillennial climatic context for the megafaunal extinctions in Madagascar and Mascarene Islands. Sci. Adv.6, eabb2459 (2020)