The Tree
Authors: Colin Tudge
CONTENTS
List of Illustrations and Figures
1. Trees in Mind: Simple Questions with Complicated Answers
5. Trees Without Flowers: The Conifers
6. Trees with Flowers: Magnolias and Other Primitives
7. From Palms and Screw Pines to Yuccas and Bamboos: The Monocot Trees
8. Thoroughly Modern Broadleaves
9. From Oaks to Mangoes: The Glorious Inventory of Rose-like Eudicots
10. From Handkerchief Trees to Teak: The Daisy-like Eudicots
12. Which Trees Live Where, and Why
To my grandchildren
ILLUSTRATIONS AND FIGURES
The Buddha receiving enlightenment under a peepul tree
The Names and Times of Ages Past
Magnolias and Other Primitives
Coastal redwoods rerooting themselves
Original drawings by Dawn Burford
PREFACE
AT BOSCOBEL IN
Shropshire in the English Midlands stands the Royal Oak, where the provisional King Charles II is alleged to have hidden from Cromwell’s men after the Battle of Worcester, which ended his premature attempt to restore the monarchy. Why not? All this happened only about three and a half centuries ago (1651) and oaks may live for two or three times as long as that. Robin Hood and his Merry Men are said to have feasted beneath the Major Oak in Sherwood Forest in Nottinghamshire—and so they might have, for if they existed at all it was in the time of Richard I, in the late twelfth century, and the Major Oak was alive and well at that time. A yew I met in a churchyard in Scotland has a label suggesting that the young Pontius Pilate may once have sat in its shade “and wondered what the future held.” It’s an audacious claim. But the tree was there, even if Pilate wasn’t—already some centuries old at the time of Christ.
There’s a kauri tree in New Zealand called Tane Mahuta (the oldest and biggest kauris are given personal names), with a trunk like a lighthouse, that was four hundred years old when the Maoris first arrived from Polynesia. For the first nine hundred or so years of Tane Mahuta’s life, the moas, related to ostriches but some of them half again as tall, would have strutted their stuff around its buttressed base, threatened only by the commensurately huge but short-winged eagles that threaded their way through the canopy to prey upon them. Now the moas and their attendant eagles are long gone but Tane Mahuta lives on. Many a redwood still standing tall in California was ancient by the time Columbus first made Europe aware that the Americas existed. Yet the redwoods are striplings compared to some of California’s pines, which germinated at about the time that human beings invented writing and so are as old as all of written history. These trees out on their parched hills were already impressively old when Moses led the Israelites out of Egypt, or indeed when Abraham was born. So it is that some living trees have seen the rise and fall of entire civilizations.
Trees inspire: the Buddha received enlightenment under a peepul tree.
Some redwoods, Douglas firs, and eucalypts are as tall as a perfectly respectable skyscraper, and there’s an extraordinary banyan in Calcutta that would cover a football field. Many are host to so many other creatures that each is a city: as cosmopolitan as Delhi or New York and far more populous than either. Creatures of all kinds may feed on trees, or maraud among their branches. At least, I know of no arboreal octopuses—but there could be, out in the mangroves. There’s many a tree-happy crab in the mangroves, as I have seen for myself, and the robbers of the Pacific islands, giant hermit crabs, come on land (as many crabs do) to feed on coconuts. When the Amazon is in flood—deep enough to submerge well-grown trees entirely, over an area not far short of England—the fish feed on fruit and river dolphins race through the upper branches of what should be the canopy, while monkeys hop and swim from crown to crown like ducks. In New Zealand little blue penguins nest in the forest at night with ground parrots (or at least they do on the sanctuary of Maud Island). In the 1970s, in the crown of one fairly modest tree in Panama a scientist from the Smithsonian Institution counted eleven hundred different
species
of beetle—yet he didn’t bother with the weevils, although they are beetles too, or look closely at the host of creatures that are not beetles, or those that were living in the roots. I once found myself in an old kapok tree in Costa Rica in which biologists had thus far listed more than four thousand different species of creatures.
Yet a tree cannot afford simply to serve as someone else’s monument and feeding ground. From the moment the seed falls on to the forest floor (or the sand of the savannah, or a fissure in some mountain crag, or a glacier’s edge, or a lakeside, or a tropical seashore) to the moment of its final demise, perhaps a thousand years later, the tree must compete through every second—for water, nutrients, light, and space; and to fend off cold, heat, drought, flood, toxicity, and the host of parasites and predators of all conceivable kinds (from a tree’s point of view, squirrels or giraffes are “predators”). A village or a civilization may choose to make a tree their symbol. The entire nation of Brazil is named after a tree—for brazilwood was known to Europeans before the country was. But however we may choose to ennoble it, the tree must fight its corner, a creature like all the rest. If it did not fight it would be dead. Even when it sheds its leaves to ride out frost or drought, its cells are still busy beneath its armored bark. Were it not so, the leaves could not burst out as they so spectacularly do when the temperate spring or the tropical rains return—or sometimes in advance of the rains, to the delight of camels and goats, which thus may find green fodder in the depths of drought. In many trees, too, tropical and temperate, the flowers emerge before the leaves, which keeps the path clear for pollinating winds, bees, or bats. Since there are no leaves to provide nourishment, the flowers must be fed from the tree’s reserves in its trunk and roots. The living timber is multipurpose: a prop, a conduit, a larder.
Flowers, of course (and the cones of conifers), meet life’s other demand: not simply to survive and grow but to reproduce. Here, the trees’ immobility is a particular drawback. Many trees reproduce without sex, commonly though not exclusively by root suckers, but all trees (to my knowledge) practice sex as well. For sex, gamete must meet gamete: sperm and egg in the case of animals and primitive plants, pollen and ovule in the case of conifers and flowering plants. Since many flowers of many trees are hermaphroditic (male stamens and female carpels on the same flower), and many trees (like oaks and many conifers) are monoecious (the individual flowers are exclusively male or female, but both kinds occur on the same tree), it may seem easy enough for trees to pollinate themselves. But on the whole they don’t. One of the botanical surprises of recent decades (finally proven by genetic studies) is the length to which most trees go to avoid self-fertilization. “Outcrossing” is the norm: pollination of, and by, other individuals who, of course, are of the same species but preferably are not too similar genetically. To achieve outcrossing, trees must elicit the help of the wind—or bribe or otherwise coerce a variety of animals, from flies and beetles and bees to birds and bats—to carry their pollen for them. Some temperate trees (like apples and horse chestnuts) are pollinated by animals, though most (like oaks and birches and beeches) are content to use the wind. But in tropical forests, where most kinds of trees live, animal pollination is the norm; and because life is competitive, the mechanisms that have evolved for this have become more and more elaborate. Thus for every one of the 750 different fig species there is a corresponding specialist wasp species to pollinate it; and each wasp knows its own fig (although, as recent studies have shown, the relationship between figs and their wasps is not quite so cozy as had been supposed). When the ovules are fertilized and become seeds, encased in fruits (or some other kind of fruiting body) they must then be dispersed—sometimes again by wind but often by another, entirely separate, suite of animal accomplices—birds and fruit bats and rodents and orangutans, whose help must again be actively co-opted.
Thus life is perforce competitive: hordes of creatures of thousands of different kinds are all after the same things, and most live directly at the expense of others. But it is also, just as inescapably, cooperative. Trees are good competitors. But they are also among the world’s most exemplary cooperators, forming a host of mutualistic relationships for one purpose or another with an enormous variety of different creatures, from the bacteria and fungi that help them to feed to the many, many different kinds of animals that help them with different stages of their reproduction. Trees do not seem to be aware, as dogs and monkeys are aware. They do not have brains. But they are sentient in their way; they gauge what’s going on as much as they need to, and they conduct their affairs as adroitly as any military strategist. Why be “aware” when you can simulate all that awareness brings? They surely don’t think, as animals do. But they orchestrate their fellow creatures nonetheless. A forest is a forest because it has trees in it, not because it may have sloths and toucans or squirrels or chimpanzees. The trees are the prime players and the animals are the dependents.
The human debt to trees is absolute. Modern evolutionary theory has it that we owe our brains—our art, our inventiveness, and presumably much of our deviousness—to our sexuality. We dance and paint and joke and tell stories to impress potential mates—or such at least was the crude beginning of our wits, on which we have built. But pigs and squirrels and elephants are clever too. They also must attract mates. So why have pigs produced no concert pianists or professors of jurisprudence? Another ingredient is needed—one suggested a long time ago by more conservative biologists. Our brains and our dexterity evolved together: they are an exercise in coevolution. Pigs are clever, but their hands are hoofs: nothing there with which to express their dreams and insights. We, by contrast, can translate our thoughts into action: our artifacts (as Robert Pirsig put the matter in
Zen and the Art of Motorcycle Maintenance
) are ideas in space. Brains are expensive organs (they require a huge amount of energy), so unless they produced some immediate payoff, natural selection would have selected against them. But because we have hands (at the end of long, strong, extremely mobile arms), brains did provide payoffs, manifest not least in a thousand kinds of tools with which to effect further manipulations. Hands provided the encouragement, the selective pressure, to make our brains even brainier; and the growing brains in turn encouraged more dexterity. But the only reason we have such dexterous hands and whirling arms is that our ancestors had spent eighty million or so years (so some zoologists calculate) in the trees. Arboreal life requires dexterity and hand-eye coordination. Squirrels almost became intellectuals, but not quite. Monkeys and apes came closer—but they stayed up in the trees, where they are obliged to squander their fabulous skills just on getting around. Our ancestors, somewhere in Africa, came to the ground when the climate dried up and the trees retreated. They learned to walk on two legs (which no other primate or any other mammal of any kind has learned to do convincingly), freeing their versatile hands and arms for other purposes. Were it not for that pedigree we would remain as intellectually frustrated as elephants and dolphins sometimes seem to be.
Archaeologists speak of the Stone Age, and the Bronze Age and the Iron Age and the Steam Age, and now we have the age of the internal combustion engine and nuclear power and space and IT. But every age has been a Wood Age—ours at least as much as any in the past; and perhaps the decades to come will be even more so. Ice Age Russians made houses from the bones of mammoths, the Inuit use ice, and the people of the Bronze Age Orkneys built remarkable villages, with restaurants and mausoleums, from slabs of rock. But great architecture demands wood. The ruins that survive from classical times are all of stone, but that’s only because wood rots. Architecture in stone and bricks evolved from timber architecture, and needed wooden-handled tools and wooden scaffold for its construction—and timber roofs and rafters. Wood, in this energy-conscious age, may well begin to replace all or some of the steel used in the grandest buildings.
Wood was the first serious fuel, too—and human beings clearly learned the use of fire at least 500,000 years ago, long before we were as big-brained as we are now. No fuel: no smelting—so no Bronze Age or Iron Age or modern machines. No wood: no ships. No ships: no ocean travel—no human beings in Australia, New Zealand, or any other island that could not be reached simply by hitching a lift on floating vegetation (as many a beast is thought to have done, from rats to monkeys and tortoises). No ocean travel: no empires: no modern politics. A woodless world would have had advantages. But we could also say no wood: no civilization.
Yet timber is not the end of it. Trees are the source of drugs, unguents, incense, and poisons for tipping arrows, stunning fish, and killing pests; of resins, varnishes, and industrial oils, glues and dyes and paints; of gums of many kinds, including chewing gum; of a host of fibers for the rigging and hawsers of great ships (whether made of wood or not) and for the stuffing of cushions; and of course, perhaps above all these days, for paper. All that, plus a thousand (at least) kinds of fruits and nuts and—in traditional agrarian societies—a surprising amount of fodder for animals, including cattle and sheep, which most of us assume live primarily on grass. As a final bonus, the wooden husks of many a tree fruit make instant household pots and drums and ornaments.
In short, without trees our species would not have come into being at all. And if trees had disappeared after we had hit the ground, we would still be scrabbling like baboons (assuming the baboons had even allowed us to live).