The Death of the Ancient Giants

Here at Ferrebeekeeper we have delved into giant ancient trees, yet we left out one of the most astonishing and iconic trees of all–the African baobab (Adansonia digitate).  Full grown baobabs are among the most massive flowering plants in the world, and, like the yews, the sequoias, and the great oaks, they can live for an enormously long time—up to 2500 years according to carbon dating.   The African baobabs live on the dry, hot savannas of sub-Saharan Africa.  The trees grow up to 25 m (85 feet) in height, but it is their mass which makes them astonishing: trunks with a diameter of 14 m (46 feet) are not unknown.  Shaped like jugs or squat bottles, these trunks help the trees store precious water during droughts.  Below the ground, the trees are even more astonishing.  The roots grow wider and deeper than the branches which is why enormous baobabs can be found in seemingly parched scrublands.  Their roots seek out secret water basins and find hidden underground rivulets.

Baobabs are also known as “dead rat trees” because of the appearance of their fruit. Admittedly this does not make the fruit sound super appealing, yet it is edible and nutritious and a market is springing up for baobab fruit smoothies.  In addition to providing fruit for humans, the leaves and bark of the tree is important to wildlife on the great savannas.

Although the trees are practically synonymous with the landscape, humans know less about them than one might suspect.  Although the trees are fertilized by pollen born by fruit bats and bush babies, the full process of fertilization is not entirely understood.  Indeed, botanists are increasingly unsure whether   Adansonia digitate is actually just one species.  The other baobab trees are largely native to Madagascar (although there is one Australian species, and a species on the Arabian Peninsula) so it seems like the genus originated on the microcontinent and then spread to the great supercontinent.

As you might imagine, the baobab features heavily in innumerable myths, folktales, and religions of Africa.  It is the magic fairy tree of that land.  My personal favorite story comes from the Zambezi basin, where tribes tell of how the proud baobabs grew so tall and beautiful that they began to rival the gods themselves.  In wrath the gods inverted the trees so that the fat roots now grow into the sky, but the trees were still splendid, till evil spirits put a curse on the strange white flowers.  Now anyone who picks these fantastic blossoms is subject to terrible bad luck…more specifically a lion will kill and eat that person!  That should keep the blossoms safe.

But, of course, in the Anthropocene world, such made-up curses don’t keep the trees safe at all.  There is one true curse on the great baobabs.  Across Africa they are dying.  Trees which were saplings during the fall of the Roman Empire (the western half!) are swiftly succumbing to an unknown scourge.  To quote a tragic article in the Atlantic, “Of the 13 oldest known baobabs in the world, four have completely died in the last dozen years, and another five are on the way, having lost their oldest stems.” The full truth of what is felling the giants is subject to debate, but botanists and arborists agree that the rapid warming of the world is the most likely culprit.  Trees which lived for two millennia in arid wastelands in the heat of equatorial Africa are suddenly dying from high temperatures.  Some of these trees have been landmarks for countless generations of people.  It is as though a mountain died and withered up

I am not sure how to properly quantify something so troubling, but the truly ancient past offers some upsetting clues about what might soon become of the Baobabs’ home (which is humankind’s first home too).  Set aside your tears for the great trees and join me, tomorrow.  We are going to take another trip back to the beginning of the Eocene, the “dawn age” which calls to me again and again. In that sweltering summer world of 56 million years ago, there are clues about what will be the fate of baobab trees and of their home ecosystem. The Eocene was a world without ice.  The arctic oceans were warm year-round. Rainforests filled with unknown marsupials covered Antarctica.  I hope you will boldly join me in going back to that bygone age, but I am worried you will not like what we find, and I am worried we are not going to like what we find in the future either.

God DAMMIT, humankind, can you not even let me end on a chilling note without making it stupid?

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The Long Summer of the Eocene

The Eocene (Illustration by Bob Hynes for the Smithsonian Institution)

The Eocene epoch (which lasted from 56 million ago to 34 million years ago) was hot!  Temperate forests ran all the way to the poles.  Steamy tropical jungles grew in the latitude where Maine is now and the equatorial regions of earth were (probably) sweltering. Tropical reefs formed in the coastal waters around a heavily forested and ice-free Antarctica. Since there was not year-round ice at each pole, the sea levels were much higher.

A Global Map of the Early Eocene (map by Dr. Ron Blakey)

The Eocene was a time when most of the contemporary mammalian orders first appeared.  The earliest artiodactyls, perissodactyls, rodents, bats, probiscideans, sirenians, and primates all originated during this time.  Of course mammals were not the only story: the Eocene was also a time of great diversification for birds and many familiar orders of avians developed then.  Reptiles begin to put the setbacks which marked the end of the Cretaceous behind them and several giant new species emerged including an immense tropical ur-python and a host of crocodiles and turtles. It is harrowing to think that the first wee dawn horses and cute little early atiodactyls were forced to contend with a 13 meter long super snakes and giant crocodilians (which flourished in the great hot swamps of Alaska), but such is the case.

Titanboa with Ancient Crocodilian (painting by Jason Bourque)

The high temperatures of the Eocene are perplexing to scientists.  By contrast, the temperatures of the Paleocene (which was the first era of the Cenezoic and had directly preceded the Eocene) were much more temperate. In fact the temperature spike of 56 million years ago seems to have ended the Paleocene and brought about the diversification of Eocene life.  The rapid warming is known as the Palaeocene-Eocene thermal maximum and scientists have been vigorously debating what caused the climate change.  An immense amount of carbon seems to have entered the atmosphere at this time, which in turn led to greenhouse warming.  It remains controversial as to how such a large quantity of carbon got into the atmosphere.  Comet/meteorite impact, massive peat fires, and volcanic activity have been suggested as triggers, however supporting evidence is lacking.  The release of globally significant quantities of hydrocarbons–which had been trapped in undersea clathrates seems like a more feasible hypothesis, as does the idea that the earth’s orbit brought the planet closer to the sun for a time.

Phenacodus, a goat-sized grazer of the Eocene era (painting by Heinrich Harder)

The end of the Eocene was also linked to the carbon cycle.  Reduced carbon dioxide in the atmosphere seems to have led to global cooling and newly evolved varieties of grasses began to invade large swaths of the world.  Additionally two massive meteor strikes in Siberia and Maryland combined with substantial volcanic activity to finish off the long hot summer. But during the Oligocene, the era which followed the Eocene, the world was a much more familiar place inhabited by orders of animals which are still here with us today (or are us–since primates first evolved during the Eocene).