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May 17, 2013 3:19 pm
To most people ginkgo is either the tree with the smelly “fruits” or the source of a leaf extract that is good for your memory, but the unmistakable acrid aroma of the fallen seeds, or the pills in the health food store, are only part of what makes ginkgo unique. Ginkgo is common on city streets from Beijing to London, but it is a botanical oddity, with no close living relatives. Its ancestors grew up with the dinosaurs and the single living species has come down to us almost unchanged for 200m years. Ginkgo is one of the world’s most distinctive plants, with one of the longest of botanical pedigrees; there is no other living tree with a prehistory so deeply intertwined with that of our planet.
Once regarded as a cousin of pines, yews and cypresses, ginkgo was later recognised as something quite different. It was first distinguished from conifers in plant classifications of the early 19th century. The evidence that has come to light since – particularly the astonishing discovery made in Japan in 1896 that the intimate details of its reproduction are more like those of a fern than a normal seed plant – has reinforced its isolated position among living plants. So in the 20th century, as the world of plants has come into sharper scientific focus, ginkgo has assumed new evolutionary importance. To borrow a phrase from Darwin, ginkgo has become a platypus for the plant kingdom, and plant palaeontologists have traced its lineage deep into prehistory. Ginkgo is now the most widely recognised of all botanical “living fossils”: a tree that time forgot and an increasingly familiar living link to landscapes of the distant past.
For almost all of its long tenure on our planet ginkgo inhabited a world without people and, for much of that time, a world very different from that of today. For tens of millions of years it lived alongside plants and animals that are long since extinct. Several different kinds of ginkgo-like trees watched as our ancestors transformed from reptiles to mammals. The prehistory of ginkgo goes back to before the Atlantic Ocean existed and before the southern continents broke from Antarctica and went their own ways.
Fossil ginkgo leaves are known from every continent and, despite massive changes on our planet over the past 200m years, ginkgo has proved remarkably resilient. It felt the shock as flowering plants came to dominate the Earth about 100m years ago but it was oblivious to the traumatic events that eliminated the dinosaurs a few tens of million years later. In Asia, Europe, and North America it flourished during the great warmth of 50m years ago and once grew close to the North Pole.
Eventually though, and for reasons that are not fully clear, ginkgo began to suffer. By the time our ancestors diverged from those of other living apes, 5m to 7m years ago, ginkgo was probably already in decline. It was nearly extinguished by the great Ice Ages that gave birth to our own species. When the last great southward push of the northern ice sheet had retreated, ginkgo was barely hanging on, perhaps only in protected valleys scattered across eastern and south-central China. By the time modern people arrived in that part of Asia, perhaps 50,000 years ago, ginkgo was already a relic.
Human dominance on our planet could have meant the end for ginkgo, but unlike many other trees, it has flourished alongside people. In one way or another, it has proved useful; more unusually, it has become revered. In many cultures, in many different ways, ginkgo commands unusual respect. Together, these qualities earned ginkgo a reprieve. The nuts became a delicacy and were used for oil and in medicine. The tree, with its distinctive leaves and great longevity, also took on symbolic meaning in Buddhism, Daoism, and Confucianism. From China and Korea, ginkgo spread to Japan and became incorporated in the indigenous religion of Shintoism. Many of the great ginkgos of China, Japan, and Korea are in the grounds of Buddhist temples or Shinto shrines.
From Asia, again with the assistance of people, ginkgo began its renewal. In the early 18th century, through the Dutch trading colony of Dejima in southern Japan, ginkgo became known in Europe. Soon after, around 1730 to 1750, seeds found their way back to the Low Countries and Britain, probably from both China and Japan, but perhaps also from Korea. Ginkgo then spread quickly to North America and elsewhere as a horticultural novelty. By the early 19th century ginkgo was a familiar symbol of the east in European horticulture. Goethe memorialised it in a famous poem to his muse Marianne Willemer. In just 100 years, ginkgo had returned to many of those places from which it had been extinguished millions of years before.
In the past 50 years ginkgo has been resurgent; interest in growing ginkgo, what it stands for scientifically, and the ways in which it might be useful has never been higher. Ginkgo has become recognised as a valuable street tree that grows well in tough places. Resistant to disease, tolerant of pollution, and able to withstand extremes of heat and cold, it is now familiar in urban landscapes over much of the world. Parts of Tokyo are a near ginkgo forest, and ginkgo is among the most common street trees in Manhattan. In recent decades ginkgo has also found its way into the pharmacy as one of the most popular herbal remedies. Its medicinal properties are the subject of advanced biomedical research into whether it can improve circulation and hold back memory loss. Extracts from ginkgo leaves are the source of a multibillion-dollar pharmaceutical industry.
With its resilience and longevity, ginkgo epitomises much of what we admire about trees and its strong cultural associations underline the strength of that bond. Compared with us, and much else in our modern world, trees such as ginkgo have comforting longevity. They change slowly, almost imperceptibly. They are beacons of timelessness that cross generations. To quote a well-known proverb: “A society grows great when old men plant trees whose shade they know that they shall never sit in.”
Ecologically speaking, trees find a place to live and put down roots; in the parlance of ecology they are site occupiers. They arrive, courtesy of the wind, or perhaps a bird or squirrel, and there they stay. In a densely populated world filled by restless people with ever-escalating demands, such a ponderous lifestyle may not be a winning strategy. Our habits disturb the world on a massive scale and create environments that favour weeds: plants that live fast, reproduce early, and die young. The soothing calm of long-lived trees is easily lost in the turmoil.
The timescales of ginkgo’s vast biography – thousands, millions, tens of millions, hundreds of millions of years – are not easy for us to grasp, but they are perhaps instructive of how we should think about our true place in the world. They should make us pause. Trees, especially trees such as ginkgo, which connect us to the deep history of our planet, help calibrate the speed of current environmental change. They ask us to reflect more carefully about all we lose when the short view rules our world and everything in it. They ask us to think about the future with an eye to the past, and they remind us that while the best time to plant a tree was 20 years ago, the second best time is now.
Edited Extract from ‘Ginkgo: The Tree that Time Forgot’ by Peter Crane (Yale University Press, £25)
Professor Sir Peter Crane is dean of the Yale School of Forestry and Environmental Studies in Connecticut and former director of Kew gardens, London
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