A Natural History of the Senses (38 page)

When you consider something like death, after which (there being no news flash to the contrary) we may well go out like a candle flame, then it probably doesn’t matter if we try too hard, are awkward sometimes, care for one another too deeply, are excessively curious about nature, are too open to experience, enjoy a nonstop expense of the senses in an effort to know life intimately and lovingly. It probably doesn’t matter if, while trying to be modest and eager watchers of life’s many spectacles, we sometimes look clumsy or get dirty or ask stupid questions or reveal our ignorance or say the wrong thing or light up with wonder like the children we all are. It probably doesn’t matter if a passerby sees us dipping a finger into the moist pouches of dozens of lady’s slippers to find out what bugs tend to fall into them, and thinks us a bit eccentric. Or a neighbor, fetching her mail, sees us standing in the cold with our own letters in one hand and a seismically red autumn leaf in the other, its color hitting our senses like a blow from a stun gun, as we stand with a huge grin, too paralyzed by the intricately veined gaudiness of the leaf to move.

The stealth of autumn catches one unaware. Was that a goldfinch perching in the early September woods, or just the first turning leaf? A red-winged blackbird or a sugar maple closing up shop for the winter? Keen-eyed as leopards, we stand still and squint hard, looking for signs of movement. Early-morning frost sits heavily on the grass, and turns barbed wire into a string of stars. On a distant hill, a small square of yellow appears to be a lighted stage. At last the truth dawns on us: Fall is staggering in, right on schedule, with its baggage of chilly nights, macabre holidays, and spectacular, heart-stoppingly beautiful leaves. Soon the leaves will start cringing on the trees, and roll up in clenched fists before they actually fall off. Dry seedpods will rattle like tiny gourds. But first there will be weeks of gushing color so bright, so pastel, so confettilike, that people will travel up and down the East Coast just to stare at it—a whole season of leaves.

Where do the colors come from? Sunlight rules most living things with its golden edicts. When the days begin to shorten, soon after the summer solstice on June 21, a tree reconsiders its leaves. All summer it feeds them so they can process sunlight, but in the dog days of summer the tree begins pulling nutrients back into its trunk and roots, pares down, and gradually chokes off its leaves. A corky layer of cells forms at the leaves’ slender petioles, then scars over. Undernourished, the leaves stop producing the pigment chlorophyll, and photosynthesis ceases. Animals can migrate, hibernate, or store food to prepare for winter. But where can a tree go? It survives by dropping its leaves, and by the end of autumn only a few fragile threads of fluid-carrying xylem hold leaves to their stems.

A turning leaf stays partly green at first, then reveals splotches of yellow and red as the chlorophyll gradually breaks down. Dark green seems to stay longest in the veins, outlining and defining them. During the summer, chlorophyll dissolves in the heat and light, but it is also being steadily replaced. In the fall, on the other hand, no new pigment is produced, and so we notice the other colors that were always there, right in the leaf, although chlorophyll’s shocking green hid them from view. With their camouflage gone, we see these
colors for the first time all year, and marvel, but they were always there, hidden like a vivid secret beneath the hot glowing greens of summer.

The most spectacular range of fall foliage occurs in the northeastern United States and in eastern China, where the leaves are robustly colored, thanks in part to a rich climate. European maples don’t achieve the same flaming reds as their American relatives, which thrive on cold nights and sunny days. In Europe, the warm, humid weather turns the leaves brown or mildly yellow. Anthocyanin, the pigment that gives apples their red and turns leaves red or red-violet, is produced by sugars that remain in the leaf after the supply of nutrients dwindles. Unlike the carotenoids, which color carrots, squash, and corn, and turn leaves orange and yellow, anthocyanin varies from year to year, depending on the temperature and amount of sunlight. The fiercest colors occur in years when the fall sunlight is strongest and the nights are cool and dry (a state of grace scientists find vexing to forecast). This is also why leaves appear dizzyingly bright and clear on a sunny fall day: The anthocyanin flashes like a marquee.

Not all leaves turn the same colors. Elms, weeping willows, and the ancient ginkgo all grow radiant yellow, along with hickories, aspens, bottlebrush buckeyes, cottonweeds, and tall, keening poplars. Basswood turns bronze, birches bright gold. Water-loving maples put on a symphonic display of scarlets. Sumacs turn red, too, as do flowering dogwoods, black gums, and sweet gums. Though some oaks yellow, most turn a pinkish brown. The farmlands also change color, as tepees of cornstalks and bales of shredded-wheat-textured hay stand drying in the fields. In some spots, one slope of a hill may be green and the other already in bright color, because the hillside facing south gets more sun and heat than the northern one.

An odd feature of the colors is that they don’t seem to have any special purpose. We are predisposed to respond to their beauty, of course. They shimmer with the colors of sunset, spring flowers, the tawny buff of a colt’s pretty rump, the shuddering pink of a blush. Animals and flowers color for a reason—adaptation to their environment
—but there is no adaptive reason for leaves to color so beautifully in the fall any more than there is for the sky or ocean to be blue. It’s just one of the haphazard marvels the planet bestows every year. We find the sizzling colors thrilling, and in a sense they dupe us. Colored like living things, they signal death and disintegration. In time, they will become fragile and, like the body, return to dust. They are as we hope our own fate will be when we die: Not to vanish, just to sublime from one beautiful state into another. Though leaves lose their green life, they bloom with urgent colors, as the woods grow mummified day by day, and Nature becomes more carnal, mute, and radiant.

We call the season “fall,” from the Old English
feallan
, to fall, which leads back through time to the Indo-European
phol
, which also means to fall. So the word and the idea are both extremely ancient, and haven’t really changed since the first of our kind needed a name for fall’s leafy abundance. As we say the word, we’re reminded of that other Fall, in the garden of Eden, when fig leaves never withered and scales fell from our eyes. Fall is the time when leaves fall from the trees, just as spring is when flowers spring up, summer is when we simmer, and winter is when we whine from the cold.

Children love to play in piles of leaves, hurling them into the air like confetti, leaping into soft unruly mattresses of them. For children, leaf fall is just one of the odder figments of Nature, like hailstones or snowflakes. Walk down a lane overhung with trees in the never-never land of autumn, and you will forget about time and death, lost in the sheer delicious spill of color. Adam and Eve concealed their nakedness with leaves, remember? Leaves have always hidden our awkward secrets.

But how do the colored leaves fall? As a leaf ages, the growth hormone, auxin, fades, and cells at the base of the petiole divide. Two or three rows of small cells, lying at right angles to the axis of the petiole, react with water, then come apart, leaving the petioles hanging on by only a few threads of xylem. A light breeze, and the leaves are airborne. They glide and swoop, rocking in invisible cradles. They are all wing and may flutter from yard to yard on small
whirlwinds or updrafts, swiveling as they go. Firmly tethered to earth, we love to see things rise up and fly—soap bubbles, balloons, birds, fall leaves. They remind us that the end of a season is capricious, as is the end of life. We especially like the way leaves rock, careen, and swoop as they fall. Everyone knows the motion. Pilots sometimes do a maneuver called a “falling leaf,” in which the plane loses altitude quickly and on purpose, by slipping first to the right, then to the left. The machine weighs a ton or more, but in one pilot’s mind it is a weightless thing, a falling leaf. She has seen the motion before, in the Vermont woods where she played as a child. Below her the trees radiate gold, copper, and red. Leaves are falling, although she can’t see them fall, as she falls, swooping down for a closer view.

At last the leaves leave. But first they turn color and thrill us for weeks on end. Then they crunch and crackle underfoot. They
shush
, as children drag their small feet through leaves heaped along the curb. Dark, slimy mats of leaves cling to one’s heels after a rain. A damp, stuccolike mortar of semidecayed leaves protects the tender shoots with a roof until spring, and makes a rich humus. An occasional bulge or ripple in the leafy mounds signals a shrew or a field mouse tunneling out of sight. Sometimes one finds in fossil stones the imprint of a leaf, long since disintegrated, whose outlines remind us how detailed, vibrant, and alive are the things of this earth that perish.

Polar bears are not white, they’re clear. Their transparent fur doesn’t contain a white pigment, but the hair shafts house many tiny air bubbles, which scatter the sun’s white light, and we register the spectacle as white fur. The same thing happens with a swan’s white feathers, and the white wings of some butterflies. We tend to think of everything on earth as having its own deep-down rich color, but even razzmatazz colors that hit one’s eyes like carefully aimed fireworks are just a thin rind on things, the merest layer of pigment. And many objects have no pigment at all, but seem richly colored nonetheless
because of tricks played by our eyes. Just as the oceans and sky are blue because of the scattering of light rays, so are a blue jay’s feathers, which contain no blue pigment. The same is true of the blue on a turkey’s neck, the blue on the tail of the blue-tailed skink, the blue on a baboon’s rump. Grass and leaves, on the other hand, are inherently green because of the green pigment chlorophyll. The tropical rain forests and the northern woods both sing a green anthem. Against a backdrop of chlorophyll green, earth brown, and sky-and-water blue, animals have evolved kaleidoscopic colors to attract mates, disguise themselves, warn off would-be predators, scare rivals away from their territory, signal a parent that it’s time to be fed. Woodland birds are often drably colored and lightly speckled, to blend in with the branches and sifting sunlight. There are lots of “LBJs,” or “little brown jobs,” as birders sometimes call them.

Abbott Thayer, an early twentieth-century artist and naturalist, noticed what he called
countershading
, a natural camouflaging that makes animals most brightly colored on the parts of their body that are least exposed to sunlight, and darker on those areas that are most exposed. A good example is the penguin, which is white on the breast so that it will look like pale sky when viewed from underneath in the ocean, and black on its back, so that it will blend in with the dark depths of the ocean when viewed from on top. Since penguins are not in much danger from land predators, their obvious two-tone linoleum-floor look doesn’t matter when they’re waddling on shore. Camouflage and display is the name of the game in the animal kingdom. Insects are especially good at disguise; one famous example is the British peppered moth, which took only fifty years to change from a lackluster salt-and-pepper gray to nearly black so that it could blend in with tree bark that had become stained by industrial pollution. Pale moths were easier for a bird to spot as the tree trunks grew darker, and so darker moths survived to produce even darker moths, which in turn survived. Animals will do most anything to disguise themselves: Many fish have what look like eyes on their tails so that a predator will aim its attack on a less vital part of the body; some grasshoppers look so much like quartz they become invisible on
South African hills; clever butterflies sport large, dark eyespots on their wings, so that a songbird predator will think it’s facing an owl; the insects called walking sticks appear dark and gnarly as twigs; Kenyan bush crickets blend in with the lichens on a tree trunk; katydids green up like leaves—some species even develop brown fungusy-looking sections; a Peruvian grasshopper mimics the crinkled dead leaves on the forest floor; the Malaysian tussock moth has wings that resemble decaying leaves: brown, torn, or perforated. Various insects costume themselves as snakes, others as bird droppings; lizards, shrimp, frogs, fish, and a few spiders tint their body color to blend in with their surroundings. Camouflage to a fish means scintillating like the water that surrounds it, breaking up the apparent outline of its body, and vanishing among the corridors of down-welling light. As Sandra Sinclair explains it in
How Animals See:
“Each scale reflects one-third of the spectrum; where three scales overlap, all colors are canceled out, leaving a mirrorlike effect.” All a predator may see is a twisting flash of light. Luminescent squids maneuver at depths where there is little light; swimming through the gloom, they mimic the natural light from above, and can even disguise themselves as clouds floating over the surface of the water in order to become invisible to their prey. They are “stealth” squids. All sorts of animals can change color quickly by shrinking or enlarging their store of melanin; they either spread the color around so much that they look darker, or tug the color into a smaller space so that some underlying pigment becomes visible. In
Speak, Memory
, Vladimir Nabokov writes joyously of his fascination with the mimicry of moths and butterflies: