Meet Nature’s Apex Regenerator: The Mighty Baobab Tree

The oldest relationship between humans and ancient trees naturally occurs in Africa. The continent’s longest-lived tree is the largest, too. Amazingly wide for its height, a mature baobab appears otherworldly. Leafless for most the year—an energy conservation strategy—its branches resemble roots marooned in the sky. According to traditional stories, the original baobab was planted upside down as punishment by gods, heroes, or hyenas.

The “upside-down tree” also goes by “elephant tree.” The connection between Africa’s greatest megaflora and megafauna goes beyond size. The calloused bark of a baobab is elephantine in color and texture. Botanists speak of pachycauls (thick-stemmed plants) as a cognate of pachyderms (thick-skinned mammals). Moreover, bush elephants consume the bark. In the dry season, tusked males gouge the trunks, peel away strips, and chew their fibrous trophies.

Baobabs heal over wounds that would kill other trees. They are among nature’s apex regenerators. Their wood contains a high percentage of living cells, and a high percentage of water—up to 80 percent. Contrary to popular belief, a baobab doesn’t perform hydraulic storage like a barrel cactus. Rather, it uses all that watery tissue to prop itself up. The tree is elastic, swelling and shrinking over seasons and stages of life. To keep its spongy mass intact requires a special outer later, like a rind.

From the inside, old baobabs hollow out, producing roomy recesses. Their uses are limited only by imagination. In a haunting Afrikaans-language novel by Wilma Stockenström, a woman escapes enslavement by confining herself in a tree: “You, trusty baobab, confidant, home, fort, water source, medicine chest, honey holder, my refuge, my last resort. . . . You protect me. I revere you.”

The useful emptiness of baobabs had impressed Ibn Battuta, one of the best-traveled persons of the fourteenth century. He saw trees of “great age and girth” on the road to Mali. “I was surprised to find inside one tree, by which I passed, a man, a weaver, who had set up his loom in it and was actually weaving.” In Mali and in Sudan, on the western and eastern edges of the Sahara, Africans introduced baobab, and later generations burrowed out giants to form networks of cisterns—infrastructural trees that in time became war targets.

If humans are destroyers, what explains the coexistence of hominins and baobab over millions of years? The longevity of the relationship can be expressed in economic terms as a dynamic of uselessness and usefulness. The tree’s absorbent tissue barely qualifies as wood—no good for building, burning, or charcoal-making. Besides, a fat-stemmed succulent is unchoppable. One tree can defeat a bulldozer, as British planners discovered during their abortive East African Groundnut Scheme. Baobab never grew as forests that farmers burned for farmland. Instead, isolated giants of the savannah inspired pastoralists and agriculturalists alike to situate their camps and villages nearby, and to plant future giants in the neighborhood. Humans long ago succeeded monkeys as the main dispersers of the species.

In addition to shade, shelter, and storage, African baobab gives foods, medicines, and textiles. Its velvety seedpods contain roastable seeds surrounded by vitamin-rich pulp that can be eaten raw or processed into meal. (In French, the species goes by “monkey bread tree”; in Afrikaans, “cream-of-tartar tree.”) Leaves can be cooked; roots can be nibbled. People peel the bark and convert it into rope for weaving. If debarking is performed properly, and if the tree is allowed to heal, the process can be repeated in future years.

All over sub-Saharan Africa, ethnic groups devised customary rules to manage the utilization of this resource that combined the properties of wild organism, crop plant, and sacred tree. Among the Dogon people of Mali, for example, tree guardians wearing terrifying masks patrolled communal baobabs.

The tree’s genus name, Adansonia, honors French naturalist Michel Adanson. He arrived in Senegal in 1749 and set to work filling his enormous collecting cabinet. He beheld his first baobab on Gorée Island. On another island near Dakar, he observed a huge specimen with overlaid names and dates carved by European voyagers as far back as the fourteenth century—imperial claims of possession. This palimpsest caused Adanson to muse that the lives of these giants “must continue many thousand years, and, perhaps, reach as far back as the deluge.” He called baobab both the “largest vegetable creation in nature” and “the most ancient living monument in the earth.”

In his magnum opus, Familles des plants, Adanson created an idealized growth chart to offer “an idea of the duration of these monstrous trees.” Based on diameter and height, Adanson guesstimated that imposing African baobabs might be 5,150 years old—just shy of the age of the Earth according to biblical chronologies. Adanson made no claim of accuracy, but he promoted the idea that a naturalist could, with sufficient growth data, age-date a tree without relying on unreliable “tradition.”

Ironically, scientific legend grew up around the inscribed baobab in Senegal. In the enhanced version of the story, Adanson makes an incision into the cambium layers adjacent to the dated tree graffiti. By measuring the widths of the excised tree rings, he calculates the annual growth rate for mature baobabs. Separately, he observes the growth rate of young baobabs. These data combined with the tree’s height and girth—exactly measured, of course—allows the naturalist to reliably estimate the age: 5,150 years. Thus, the ingenious Frenchman offers proof of extreme longevity in trees, a topic of speculation since the Greeks and Romans.

This apocryphal story felt veracious to European scientists enraptured with metric precision. French dictionaries and encyclopedias of the postrevolutionary period listed baobab as the “Thousand-Year Tree” (L’arbre de Mille Ans). On the strength of Adanson, Alexander von Humboldt—the most esteemed naturalist of the nineteenth century—called baobab “one of the oldest inhabitants of our globe.” Adanson’s “discovery” lasted in textbooks in spite of debunking by US botanist Asa Gray: “The vitality of an erroneous statement is truly wonderful,” he wryly observed. Charles Lyell sustained this error in his groundbreaking Principles of Geology.

Darwin read Lyell on the Beagle, which made first landfall at the Cape Verdean island Sao Tiago in January 1832. While traversing a valley near Praia, the port city, Darwin beheld his first giant tree, a baobab—a species he knew from Humboldt. “This one bears on its bark the signs of its notoriety—it is as completely covered with initials & dates as any one in Kensington Gardens,” wrote Darwin. He returned to the site with measuring instruments. He doubted any plant could endure 6,000 years, though this one “strikes the beholder that it has lived during a large fraction of the time that this world has existed.” However, the erosion of the valley that sheltered the tree must have taken much longer, he noted. As of 1832, baobab grew at the border of biblical and geological time.

Today, it’s unclear if Adansonia naturally occurred in Cape Verde before the fifteenth century CE. The islands had no human population before the Portuguese turned them into a human trafficking hub. The presence of baobab, introduced or not, marked the islands as African spaces. At Sao Tiago, like Gorée, enslaved persons awaiting their trans-oceanic uprooting would have seen these trees as vestiges of home.

Adanson observed that Wolofs in Senegal wore tobacco pouches on their necks with second pockets for baobab seeds and other treasures. On the Middle Passage, slaves may have carried such pouches, while slavers may have stocked pulpy seedpods as anti-scurvy edibles. On the other side of the Atlantic, in the Caribbean islands, displaced Africans planted slow-growing baobab, specimens of which have survived to this day as landmarks of cultural tenacity.

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The validation of extreme longevity in African baobab only recently moved beyond the musings of Adanson. Because of their great girth and unusual morphology, baobabs have never been well suited for tree-ring dating. Radiocarbon works better, provided that inner tissue can be obtained. Firm evidence that baobabs can live one thousand years came in the 1960s, when two things coincided: the calibration of the radiocarbon dating method, and the construction of Kariba Dam on the Zambezi River, a megaproject that required mass demolition of megaflora.

More recently, a Romanian chemistry professor secured funding to research the maximum age span of angiosperms. The project got off the ground because one of the most famous baobabs—the Grootboom of Namibia—had just collapsed, allowing access to ancient inner wood. The investigation appeared to be prophetic, or cursed: wherever the professor went looking in southern Africa for the oldest baobabs, he found fallen giants. (Strangely enough, he moonlights as an authority on paranormal phenomena.)

In 2018, in a prestigious academic journal, the professor reported that of fourteen known baobab millennials, ten had buckled or perished in the twenty-first century, including iconic specimens in South Africa and Botswana. The outlier had, before its sudden death, reached approximately 2,500 years.

This limited, emblematic sample made climate crisis headlines around the world. “It’s sad that in our short lives, we are able to live through such an experience,” said the primary investigator. A coauthor called the mortality cluster “a canary in the mine.” Botanists questioned aspects of this study, but no one doubted the takeaway: southern Africa will continue to get hotter and drier, shrinking the habitat of baobab.

Long before the global media attention, Zimbabweans spoke anecdotally of baobab decline. According to some, the mysterious “black soot” on trunks was the doing of spirits angered by misbehavior in the present and the past. A Black nationalist, pro-government media source suggested that the “curse” began in 1855, when David Livingstone reputedly carved his name on one or more big baobabs near Victoria Falls (which he brazenly named). These profaned trees held ancestral spirits of the Tonga people. According to microbiologists, the unsightly fungus is endemic, and not by itself fatal. It may signal stressors like drought and overuse. In Zimbabwe, fly-by-night bark collectors have damaged baobabs in violation of customary rules.

The African baobab seems destined for further domestication and, in cities such as Dakar, street tree status. Programs are underway—combining lab science and Indigenous knowledge—to create superior cultivars for propagation as cosmetic and pharmaceutical material, and as crop trees. This is an example of “conservation through utilization.” Baobabs take decades to reach sexual maturity, so the fruit of this research will arrive in the future. In the meantime, the food industry has discovered baobab pulp, another “superfood” additive for discerning consumers of smoothies in the Global North. The harvesting of seedpods, outsourced to village women, brings cash to poor locales, though the market may not be sustainable.

For as long as ecologists have studied baobab—just one century—they’ve noted a paucity of young trees as well as centurial gaps between mature cohorts. This is characteristic of various slow-growing, long-lived trees. What explains it? The multiyear co-occurrence of atmospheric and soil conditions needed for seedling recruitment simply happens rarely. Now that people and livestock have greater footprints and hoofprints—and now that industrial countries have irrevocably altered the climate of the planet—who knows when that optimal sequence will recur in Africa?

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From Elderflora, by Jared Farmer, courtesy Basic Books. Copyright 2022, Jared Farmer.