Some of Africa’s largest and most ancient trees have suddenly and unexpectedly died, according to researchers. And they think climate change may be the cause.
Millennia-old baobab trees have borne witness to centuries of history. Commonly found in the sub-Saharan deserts, the behemoth baobab is one of the biggest and the longest-living flowering plant in the world.
The gigantic trees look something out of a fantasy. They have thick, bulbous trunks that rise high towards the sky and are topped with a comparatively tiny crown of leaves. The uncanny shape has given rise to a myth that they are upside down trees. Baobabs occasionally sprout new stems which would grow up into enormous trees.
European explorers claimed the trees could live up to 5,000 years but their true age has been hard to calculate since they don’t always form new growth rings each year. However, radiocarbon dating shows some of the oldest of the species have lived for over 2,500 years — that’s even before Jesus Christ. The trees trunks are, surprisingly, hollow making them impossible to date like other ancient behemoths. However, they have false cavities with bark growing inside them. These cavities form when stems of the tree fuse together as the tree continues to grow. Adrian Patrut, a researcher at Romania’s Babes-Bolyai University, found the wood closer to the middle of the cavities was the oldest, with some samples dating back to over two-and-a-half millennia.
But now, it seems, these ancient monstrous trees are mysteriously dying.
Between 2005 and 2017, researchers who were collecting data on height, girth, age and wood volume of more than 60 trees noted the biggest and oldest baobabs in Zimbabwe, Namibia, Botswana, Zambia and South Africa, collapsed during the 12-year period. Of the 13 oldest trees, nine are either dead or on their way to it. Of the sixth biggest baobabs, five are dead, or almost so, having lost their oldest stems.
The most famous of them, the Chapman baobab stood for an estimated 1,400 years in Botswana and could be seen from miles around the Kalahari Desert. However, in January 2016, the tree crashed to the ground just one day after Botswana experienced it hottest temperature ever.
The Homasi tree of Namibia, which dated back 1,500 years and survived the fall of the Roman Empire, grew to a height of 32 meters. But it suddenly collapsed in 2004 and on New Year’s Day 2005, the last of its stem broke off, ending its one-and-a-half millennia existence.
There is no knowledge about how the baobabs have died in the past centuries. “But when around 70 percent of your 1,500 to 2,000-year-old trees died within 12 years, it certainly is not normal,” said Erika Wise from the University of North Carolina, Chapel Hill. “It is difficult to come up with a culprit other than climate change.”
According to researchers, although the tree have endured a wide variety of elements, including wetter, colder and drier conditions, they are not suited for living in the fastest warming regions of the world.
“We suspect that an unprecedented combination of temperature increase and extreme drought stress were responsible for these demises,” said Adrian Patrut.
More research is needed to see how climate change affect these trees but Patrut said the trees could be more sensitive to rising heat because they need to retain more nutrients and water, in addition to infrequent rains. These trees need to absorb 70 to 80 percent of their volume in water or else they die. That’s what happened to Botswana’s Chapman, which collapsed with only 40 percent of water after a dry season.
The baobabs are expected to suffer more due to climate change and one study indicates global warming will almost completely wipe out the ones in Namibia and Botswana.
“These large trees are incredible natural wonders, like miracles,” said Aida Cuni Sanchez, a postdoc at the University of York. “One should feel extremely lucky to stare at one of these huge trees, which have lived through so many human events. Our children, and grandchildren will not be that lucky.”
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