Baobabs are dying across southern Africa‚ and climate change may be to blame.

Some of the oldest and largest baobabs in South Africa‚ Zimbabwe‚ Namibia‚  Botswana‚ and Zambia have abruptly died in the past decade‚ say a team of international researchers.

“Nine of the 13 oldest … individuals have died‚ or at least their oldest parts/stems have collapsed and died‚ over the past 12 years‚” they wrote in the scientific journal Nature Plants‚ calling it “an event of an unprecedented magnitude”.

The trees‚ aged between 1‚100 and 2‚500 years‚ may have fallen victim to climate change‚ said a team which included Stephan Woodborne from iThemba Labs in Johannesburg and Grant Hall from the University of Pretoria.

Study leader Adrian Patrut‚ from Babes-Bolyai University in Romania‚ said: “It is definitely shocking and dramatic to experience during our lifetime the demise of so many trees with millennial ages.”

While the cause of the deaths is unknown‚ the researchers “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”.

Patrut said the dead trunks were only 40% water‚ instead of the 75-80% they should have been. Their condition meant they could no longer support the tree’s weight‚ he said.

Between 2005 and 2017‚ the researchers dated “practically all known very large and potentially old” African baobabs – more than 60 in total. After studying data on girth‚ height‚ wood volume and age‚ they noted the “unexpected and intriguing fact” that most of the oldest and biggest trees died during the study period.

The researchers used radiocarbon dating to analyse samples from the trees and found that the baobab trunk grows from up to seven core stems. Four of the trees they studied died completely‚ meaning all their stems toppled together.

The oldest tree which suffered the collapse of all its stems was the Panke tree in Zimbabwe‚ estimated to have existed for 2‚500 years. The biggest‚ Holboom‚ was from Namibia. It stood 30.2m tall and had a girth of 35.1m.

The most famous victim of the die-off was the Chapman's baobab‚ a national monument and tourist attraction in central Botswana that bore the carved initials of explorer David Livingstone. It was named after South African hunter James Chapman‚ who visited it in 1852. On January 7‚ 2016‚ its six trunks all collapsed and died.

“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‚” said the researchers.

“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. However‚ further research is necessary to support or refute this.”

- The baobab is the biggest and longest-living flowering tree‚ and has branches resembling roots reaching for the sky. It serves as a massive store of water and bears fruit that feeds animals and humans. It is sometimes known as the “dead rat” tree‚ after the shape of its fruit. Its leaves are boiled and eaten‚ while its bark is pounded and woven into rope‚ baskets‚ cloth and waterproof hats.