The mysterious life (and death) of Africa’s oldest trees
By Jaime Lowe
3 January 2019
(Topic) – The baobab trunks are thick and bulbous and fat. The bark is shiny and red. The trees don’t sway. They don’t whistle with the wind. Movement is slow and barely perceptible, if they move at all. Baobabs can grow to 100 feet tall; their diameters can reach up to 40 feet. For the most part their leaves appear for just a few months during the wet season and look like the unnatural hair that emerges from a chia pet. Their most dynamic motions are during the roughly five minutes at dusk when their night-blooming flowers open for the bats and moths who drink their pollen, and in death, when they topple suddenly and dramatically in just a few hours.
In June 2018, a study was published by the scientific journal Nature Plants; it stated simply that the baobabs are dying. The scientists involved do not know why, but they suspect increased drought and climate change. For decades, villagers in Botswana have witnessed the depletion of baobabs because of human encroachment—cattle grazing and farmland have taken over areas once roamed by hunter-gatherers. The introduction of agriculture and changes to the soil have produced a negative effect on the trees. These trees, which are some of the oldest on the planet, are rooted so solidly into the African horizon, they appear invincible, as if the sun couldn’t set without the silhouettes of their gnarly branches reshaping the line where land meets sky. […]
In 2005, the scientists involved in the Nature Plants study—Stephan Woodborne, associate professor at the University of Pretoria and a researcher at iThemba LABS in Johannesburg, along with six others—set out to study baobabs. This collaboration has yielded a number of different papers, but it was only the last one, in 2018, that captured the global imagination. Woodborne wanted to relate climate models to the samples collected in the field, and Adrian Patrut, the paper’s lead scientist and a professor of chemistry at Romania’s Babeș-Bolyai University, was aiming to carbon-date the trees. They bored holes in old specimens, hoping to find information about the weather over the past millennia. They had heard rumors that some baobabs might be as old as 6,000 years, maybe even older. After cataloguing so many collapsed baobabs, they made another conclusion: that the trees were in peril. They published the ages of trees in the peer-reviewed Nature Plants, along with the alarming fact that nine of the 13 oldest and five of the six largest baobabs that they sampled had died or partly collapsed in the past 12 years. The reports of the old trees’ deaths led to shocking headlines. The New York Times published a story titled “Last March of the ‘Wooden Elephants’: Africa’s Ancient Baobabs Are Dying”; the Guardian titled its piece “Climate change is wiping out the baobab, Africa’s ‘tree of life’”; National Geographic wrote, “Africa’s Oldest Trees Are Dying, and Scientists Are Stumped.” Patrut told NPR, “Such a disastrous decline is very unexpected. It’s a strange feeling, because these are trees which may live for 2,000 years or more, and we see that they’re dying one after another during our lifetime.”
When visiting iThemba LABS this past October, Woodborne told me that the baobabs he’d studied had appeared healthy and strong, and then they “just fell.” He said, “There is an indescribable stillness—the baobab is just no longer a baobab. And within a year, it disintegrates. There’s just a depression in the earth where the tree was.” In the six or so months since his research was published, Woodborne has lectured extensively around the world about the results. “You give the presentation and people want a happy ending,” he said. “They want to hear that everything will be OK, but it’s not.” […]
The mainstream news stories about baobab demise immediately connected the death of the trees to our current climate crisis. The articles tended to leave out any nuance about what we know, and what we don’t, about the current state of baobabs. The tree was clearly in danger before the results were published; several species of baobabs are on the International Union for Conservation of Nature Red List of Threatened Species because of human encroachment. The headlines also left out an important detail of the recent revelations: the published research centered on the tree’s growth within the margins of its territory in the southern parts of the African continent, in Botswana, Namibia, South Africa, and Zimbabwe, where temperatures are already warming faster than the global average and drought is intensifying with each year. But the baobab is actually thriving in many parts of northern Africa. Are the baobabs from the study dying because of rising temperatures or because they are old, or both? Does their decline indicate the decline of the species? And what does this mean for the surrounding landscape? [more]
The Mysterious Life (and Death) of Africa’s Oldest Trees
ABSTRACT: The African baobab is the biggest and longest-living angiosperm tree. By using radiocarbon dating we identified the stable architectures that enable baobabs to reach large sizes and great ages. We report that 9 of the 13 oldest and 5 of the 6 largest individuals have died, or at least their oldest parts/stems have collapsed and died, over the past 12 years; the cause of the mortalities is still unclear.
