Nairobi, June 12 – Scientists have reported that 9 of the 13 oldest and five of the six largest African baobab trees have died, or at least their oldest parts/stems have collapsed and withered, over the past 12 years and the cause of the mortalities remains unclear.

According to the findings of a research paper published in the journal Nature Plants, the deaths of the trees “is an event of an unprecedented magnitude.”

“These deaths were not caused by an epidemic and there has also been a rapid increase in the apparently natural deaths of many other mature baobabs. We suspect that the demise of monumental baobabs may be associated at least in part with significant modifications of climate conditions that affect southern Africa in particular,” the scientists wrote in their paper.

“Further research is necessary to support or refute this supposition,” the researchers from universities in South Africa, Romania and the United States added.

The African baobab is the biggest and longest-living angiosperm tree. By using radiocarbon dating the researchers identified the stable architectures that enable baobabs to reach large sizes and great ages.

The trees that have died or are dying were found in Zimbabwe, Namibia, South Africa, Botswana and Zambia. They are all between 1,000 and more than 2,500 years old.