Wednesday, November 30, 2016

Yes, trees communicate

          The simple profundity of trees: two new books 
                                         
Quiver Tree Forest, Namibia; photograph by Beth Moon from her book Ancient Trees: Portraits of Time (2014). A collection of her color photographs, Ancient Skies, Ancient Trees, has just been published by Abbeville.











 
From the New York Review of Books

The Long, Long Life of Trees 
by Fiona Stafford
Yale University Press, 287 pp., $30.00

                      By Thomas Packenham 

    In 1664 John Evelyn, diarist, country gentleman, and commissioner at the court of Charles II, produced his monumental book on trees: Sylva, or a Discourse of Forest Trees. It was a seventeenth-century best seller. Evelyn was a true son of the Renaissance. His book is learned and witty and practical and passionate all by turns. No later book on trees has ever had such an impact on the British public. His message? A very modern one. We are in desperate need of trees for all kinds of reasons. Get out there with your spade and plant one today.
   Despite the catastrophes that crippled London in the next two years—the great plague and the great fire—Evelyn lived to see the book reprinted four times. A century later it was reissued with elegant copperplate illustrations and an exhaustive commentary to bring it up to date. Later editions of the book (renamed Silva) have followed, and many authors have tried to write in the spirit of Evelyn. But somehow Sylva has always remained head and shoulders above its successors. That is, until the present. The two new books on trees under review are both outstanding. In different ways their authors share many of Evelyn’s best qualities.
   Fiona Stafford’s The Long, Long Life of Trees treads closest in the footsteps of Sylva. Evelyn, it is true, was more adventurous in his choice of trees to be described in detail. He covers an astonishing range: a tally of thirty-one genera, which include newly introduced trees from the American East Coast, like red oaks and Weymouth pines, as well as trees that were seen as exotic in England, such as the cedar of Lebanon and the Irish strawberry-tree. Stafford plays safe by choosing a mere seventeen genera, which represent the common trees of gardens and woods and hedgerows throughout Western Europe as well as North America: oaks, sycamores, chestnuts, hawthorns, and so on. But there is nothing humdrum about her descriptions.
    Stafford is professor of English at Oxford University and writes about novels, poetry, art, and the environment. In her own way she is as learned as Evelyn, and she is a gifted writer. What do trees mean for her? She owes this book, she says, to her “sense of wonder” at trees. She admires their physical beauty. She is astonished by their gift for survival. And most of all, perhaps, she is struck by their extensive cultural associations. She reminds us that it’s easy to take trees for granted. But we must do more than merely admire them. We must go out there, she says, echoing Evelyn’s words, taking our spades to plant new saplings for the future.
   If she plants a tree, her first choice, I feel sure, will be an oak. Most sensible people find the common oak of Europe, Quercus robur, quite irresistible. Ever been inside a Royal Oak? Stafford means the British pub, not the famous oak at Boscobel in which the future Charles II hid from the fury of the Roundheads after his defeat at the Battle of Worcester in 1651. Of course one led to the other, and today there are more Royal Oaks in Britain than any other pubs except Crowns and Red Lions.
   In her chapter on oaks, Stafford explores the tangled history of Britain’s infatuation with the species. It long predates the king’s miraculous escape at Boscobel. The oak was a symbol of power and strength from classical times. It was the tree of Zeus, king of the gods. It was the oracular tree at Dodona in Greece, meaning that it could predict the future. Augustus Caesar, ever conscious of his image, faced the Roman public wearing a civic crown of oak leaves. The tree’s “manly” virtues made it a choice as a symbol for any country, like Britain, seeking to impress its neighbors. Effortlessly it became the national tree of Britain, although the claim was not uncontested. (Many patriotic British people would be surprised to learn that twelve other European countries and the US all claim it as their national tree.)
   “Sturdy, stalwart and stubborn,” Stafford writes,
the oak has always been admired for its staying power…. No other tree is so self-possessed, so evidently at one with the world. Unlike the beech, horse chestnut or sycamore, whose branches reach up towards the sky, the solid, craggy trunk of a mature oak spreads out, as if with open arms, to create a vast hemisphere of thick, clotted leaves.
   It is this copious canopy that provides a home for an astonishing number of small insects, birds, animals, lichens, ferns, and fungi. If you look up at those mossy, fern-encrusted branches, you may well find redstarts and robins and wood warblers searching for insects, while woodpeckers and little owls build their nests in hollows in the trunk. A great oak is a world in itself. “This is the King of the Trees,” Stafford writes exultantly, “the head, heart and habitat of an entire civilisation.”
   How long can a great oak survive? Sober estimates are impossible, since the oldest oaks are invariably hollow, and most of the annual rings are therefore missing. Wild estimates (including my own) vary between six hundred and one thousand years. Fortunately, many of the great oaks of Britain were engraved and described by Jacob Strutt for his pioneering set of tree portraits, Sylva Britannica, first published in 1826. (He borrowed half his title from John Evelyn.) As one would expect, the majority of Strutt’s ancient trees—the Yardley oak, the Bull oak, the Cowthorpe oak—have now been blown down or simply crumbled to dust. Others have been reduced, like the Major oak in Sherwood Forest, to the fate of a cripple supported by steel crutches. But a few of the most famous have survived.
   “Majesty” at Fredville in Kent still stands tall, after perhaps five or six hundred years. The Panshanger Oak in Hertfordshire, much admired by Winston Churchill a century ago, still looks good for several more centuries. Even more remarkable is the Bowthorpe Oak in Lincolnshire. Stafford describes a visit she paid to this aged creature. My guess is that it’s at least seven hundred years old. At any rate its trunk was hollow enough in the eighteenth century for smart dinner parties for seventeen people to be given inside its vast interior. Now it’s only the home of a pony and some chickens. But its generous owner allows visitors. Stafford describes the experience: “like stepping from ordinary domesticity into the presence of some immortal being—ancient, wrinkled, yet oddly welcoming.”
   One of her best chapters deals with the common and much-abused sycamore of Europe. She quotes a comment by William Blake: “Not everybody sees alike: a Tree that moves some to Tears of Joy to other Eyes is just a green thing in the way.” Did Blake have the sycamore in mind when he wrote those lines? Certainly the tree gets a bad press because of its habit of dropping sticky leaves on pavements and railway lines, causing delays and accidents. In fact the “honeydew” that coats the leaves is a mixture of rich, sugary sap and the excrement of aphids that feed on it. And the list of the sycamore’s so-called vices doesn’t end there. It is the tree, as Stafford says, of excess:
For many, the sycamore is too generous a tree altogether. It disturbs people’s sense of proportion and even seems to uncover lurking puritanical anxieties about excess. It is the tree of profusion: too much sap, too many leaves. Too many sycamores, in fact.
   Its propeller-like seeds are a torment to gardeners, infesting lawns and rose beds alike. And worst of all, it is a “tree weed,” an invasive alien, a vicious intruder from Europe.
   Stafford looks coolly at these charges, and makes a powerful case for the defense. She points out that sycamores have flourished in Britain for hundreds of years and, despite their pushy reputation, their numbers there have not increased in the last half-century. In fact they fit neatly into the ecosystem, deftly regulating their own numbers and occupying the spaces where most other trees do not flourish. They are generous in the best sense. They add elegance and comfort to the bleak Yorkshire coastline or the rocky islands of Scotland. As for the claim that they are invasive aliens, Stafford points to the thirteenth-century shrine of Saint Frideswide in the cathedral at Oxford, in which five-lobed sycamore leaves are carved on the boss above her tomb. It would appear that by the Middle Ages the sycamore leaf was already a Christian symbol, perhaps representing the stigmata or Five Holy Wounds. And judging from modern research on fossilized pollen, it is possible that this much-maligned tree is a native after all.
                                         
 ‘The Amorous Baobabs,’ near Morondava, Madagascar; photograph by Thomas Pakenham from his book Remarkable Trees of the World (2002)

   Poets, Stafford continues, are quicker than suburban gardeners to appreciate the virtues of the sycamore. She cites John Clare’s lyrical account of the “splendid sycamore” with its mountain of sunny green foliage. Its sticky leaves, he wrote, were a great gift to the world. We should listen to the “merry bees, that feed with eager wing,/On the broad leaves, glaz’d over with honey-dew.” Stafford also reminds us that Shelley’s bittersweet poem “Ode to the West Wind” was based on his experiences in the autumn of 1819, wandering in the sycamore woods around Florence. Shelley was in a wretched state; two of his young children had just died. That autumn it was the fall of the sycamore leaves that caught his imagination. The dead leaves were driven by the west wind—“Yellow, and black, and pale, and hectic red,/Pestilence-stricken multitudes.” But the trees, he hoped, would “quicken a new birth.” For the west wind was propelling the “winged seeds” as well as the dead leaves. The dead leaves promised new life. “If Winter comes, can spring be far behind?”









   For her chapters on the European ash and horse chestnut, Stafford strikes a more somber note. Both are European species of a worldwide genus: respectively Fraxinus excelsior and Aesculus hippocastanum. Both are now threatened by a pair of lethal diseases from the East. In fact many of the trees commonest in Europe and North America are now facing an apocalyptic threat from Asia. Fifty years ago we lost most of our elm trees to a fungus from China, spread by a beetle laying infected eggs under the bark. (“Dutch” elm disease was a misnomer. The original enemy was Asian, not European.) Today these new enemies—sudden oak death, acute oak decline, beech wilt, sweet chestnut blight, and so on—are decimating our parks and forests.
   The most immediate problem in Europe is Chalara, a fungus that leads to dieback—the death of leaves and branches—in ash trees, believed to have been introduced in the 1990s from Asia on infected crates or pallet wood. In Denmark 80 percent of the European ashes have already died. The plague has now reached Britain and Ireland and is expected to be just as devastating there. Stafford offers little hope for dealing with Chalara. It may be already too late to stop. Control measures should have been taken when the disease was first identified in Eastern Europe. Even if the measures now being taken succeed, there is an even more pitiless Asian enemy behind Chalara—the emerald ash borer, Agrilus planipennis, a bright green Chinese beetle that has already devastated many forests in North America. So Stafford leaves us with the bleak conclusion that there is probably no way out. One way or the other, we shall lose almost all our ash trees and so many of our “familiar wood-lined roads, green parks and sheltered towns will be left, bereft and bare.”
   As for the horse chestnut, half the species in Europe are already believed to be infected by bleeding canker, a bacterial infection that causes a sticky liquid to be secreted from blemishes on the bark, eventually killing the entire tree. Stafford takes a surprisingly relaxed view of this new threat. She says that “bleeding canker may…be a health scare rather than a death sentence. Faking its own death seems just the sort of trick that might engage the horse chestnut….” I wish I could believe her. In Ireland, where I live, many of the finest specimens in parks and gardens have already succumbed. Every year we lose two or three of the largest and most majestic trees in the parkland. There is no defense, no treatment.
   But the good news, which should be of some comfort to Stafford, is that there is after all a way to mitigate these disasters. If the aim is to recreate the lost trees, you must make sure to choose a Chinese or Japanese or Indian species of the same genus. This means planting Himalayan horse chestnut, Chinese elm, Chinese ash, Japanese oak, and so on. For these Asian species evolved millions of years ago side by side with the Asian diseases. Today these species are immune—according to the experts I have talked to. I hope they are right. All will be clear, at any rate, within the next one hundred years.
   Peter Wohlleben’s The Hidden Life of Trees breaks entirely new ground, and John Evelyn would have been delighted with his discoveries. Wohlleben is a professional forester who works for the local community in Hümmel, a small village in the Eifel Mountains of western Germany. For years he managed the forest of beech, oak, pines, and spruce on conventional lines, felling the trees for their timber when they were mature and extracting the logs with heavy machinery. As he puts it, he “knew about as much about the hidden life of trees as a butcher knows about the emotional life of animals.” But gradually he came to look at the trees in a new light. Visitors, he noticed, would admire the trees he dismissed as of little commercial value: the more crooked and gnarled the trees, the better they liked them. His own love of nature, a relic of childhood, was reignited. He began to notice bizarre root shapes and strange patterns of growth. He writes, “Suddenly, I was aware of countless wonders I could hardly explain even to myself.”
   Meanwhile new generations of scientists were exploring his local forest, including a team from Aachen University. And both there and in the university in Vancouver, five thousand miles away in British Columbia, discoveries were made that astounded Wohlleben.
   What both teams discovered was nothing less than a vast underground network, called a mycorrhiza, in which fungi connect trees of different species by passing chemical and electrical signals among the trees’ roots. It was an arboreal Internet—christened the “wood wide web.” Trees could actually communicate by exchanging carbon through their roots. The exchange offered mutual support. Carbon is the food of trees, created by photosynthesis, using the leaves as solar panels. Sometimes one tree would act as mother to its neighbors, giving them more carbon than it received in return. Later the debt would be repaid as the roles were reversed.
   As the subtleties of this underground network were explored, it became clear to scientists that trees not only benefited by mutual exchange of food. They exchanged vital information, warning their neighbors (and children) of threats and advising them of opportunities to seize. For example, if a tree’s leaves are bitten by a caterpillar, it will send a message though the mycorrhiza, prompting other trees in the network to release chemicals that repel caterpillars.
   For Wohlleben these discoveries confirmed what he had come to recognize himself: that, in their own way, trees had feelings, that they knew how to communicate with one another, and that the strong were able to assist the weak. But how to reconcile this with his job as a butcher of trees? Fortunately his employers, the village of Hümmel, were high-minded romantics like himself. They agreed to forgo the income from sales of timber and create a series of tree reserves in the forest. All timber machinery was banned. When a tree had to be felled, only horses were employed in removing the logs. The forest flourished under these generous new rules, and tourists flocked to explore its wonders. Perhaps the high-minded villagers of Hümmel had made a good commercial bargain.
   Today Wohlleben continues to work in the forest. Every day, he says, he makes new discoveries: learning more about how trees live and die, how they live their lives in harmony with their neighbors and with all the rest of the ecosystem. Of course he is now more of a guardian than a manager. He organizes survival tours and has arranged for part of the forest to be set aside as a natural graveyard. And his writings have now made him deservedly famous. The German edition of the book has proved a best seller. For twenty years teams of scientists had been exploring the dark world under trees to find how they share each other’s lives. Peter Wohlleben is the first to explain and expose these discoveries. He has listened to trees and decoded their language. Now he speaks for them.
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