Why Fall Color Will Fade



One leaf was as orange as flame, undoused by the burgundy at its edges. Another was brighter and purer than yellow gold. A third could have inspired Jackson Pollock, its spatters of yellow, green, and red were so bright and random. Would Pollock snap that his art was not random? The universe could make the same argument. The effect looks random, though, playful and carefree. Like a six-year-old, I choose with furrowed brow, gather my leaves at the stem, and carefully carry them home. I want to own a piece, however temporary, of this beauty.

“Fall foliage tours” might sound like bus trips for retirees, but the other day I cursed a tailgater for silently pressuring me to speed up on the back roads, each S-turn opening a new blaze of color, late afternoon’s light slanting through the leaves and turning them translucent. No longer craving shade, I hike to high places just to gaze down at the treetops.

Why? Elizabeth Barrett Browning should have tackled this one. I love fall leaves because they crunch underfoot and walking feels like stomping grapes for wine, my boots helping crush next spring’s compost. I love fall leaves because they catch fire in the firepit and coax the logs to burn. I love that the leaves are pointy or oval or rounded or intricately scalloped—and they turn the color of sunset, blood, or rubies—and nobody tells leaves of a particular shape or color that they are only welcome on part of the ground.

I love them because I never lost the school kid’s habit of seeing autumn as the new year. The marketing miracle of pumpkin spice owes a debt to our obsession with this season, the time we can finally put on our favorite old sweatshirt and stay outside all day, under a sky as blue as cornflowers, without getting sweaty and cranky. Fall foliage is beautiful for technical reasons, too, its palette a color-wheel complement to the blue sky above and the green grass below. Navy and teal foliage would not work nearly so well.

And fall is extra poignant because it is a last hurrah, a chance to hang out with friends at a winery or go apple-picking or sit around a bonfire before winter descends and we all scurry back to our dens. Crisp air and chilly nights predispose us to the Danes’ hygge: cozy get-togethers, comfort food, soft throws, snuggling on the sofa. Cooler temperatures are also said to bring mental clarity, and they certainly calm tempers. Violence rises with the mercury, heat making us irritable, impatient, existentially miserable, and so bleary we cannot think things through.

Another thought, though: what if we love fall color because we need a break from all that lush, verdant, monotonous green? It cools us in summer and gives us hope. But just as we occasionally need to buy the sort of dress we have never worn before or chalk our hair pink for the fun of it, trees need to shake it up a little, too. Pretty up and strut their stuff, make sure we see them. “Everything want to be loved,” Alice Walker writes in The Color Purple. “…. You ever notice that trees do everything to git attention we do, except walk?”

Is Walker anthropomorphizing, or just pointing out facts? The scientists can tell us that that fall leaves’ glowing yellow comes from carotenoid pigments, and the reds and purples emerge with the accumulation of anthocyanins. Until now, I avoided thinking about the chemistry, sure that it would ruin my favorite season as surely as physics ruined the rainbow. But there is a new reason to learn and worry (as there is in virtually every aspect of nature in the Anthropocene). The climate’s mercurial shifts are about to change both the timing and the tone of autumn.

Researchers are not exactly sure how it will all play out. Some say that warmer temperatures will mean longer growing seasons, so a later start to fall foliage. Others say that if trees start photosynthesizing earlier, they may turn color sooner.

Moving a little color up earlier would not end the world, I tell myself. A little color later would be okay, too. So what if the show starts while the audience members are still fanning themselves and fizzles out after most have gone home? A synchronized burst is more dramatic, but this will lengthen the window….

Then I learn that sheer curtains are about to dim our view. Warmer falls will not only change the timing of the leaves’ turn but will make the colors less brilliant. Why? Because the warmer it is in early fall, the less anthocyanin the leaves will produce, meaning we will see less of those rich, saturated reds and purples.

We flock to New England for fall foliage tours because it gets cold faster up there. “If the first frost comes later than it used to, the brilliant foliage will appear later than it used to,” notes botanist Susanne Renner, an honorary professor of biology at Washington University and emeritus professor at the University of Munich.

And the brilliant foliage will also be less brilliant.

How do you even measure that? Moses might have thought the bush was burning because he was feeling especially optimistic that day. Sadly, though, the effect has already been demonstrated in studies of sugar maples. Chill the air, and they pump out more anthocyanin and turn brighter colors. Warm the air, and….

The sugar maple is one of the nation’s most beloved trees, claimed by New York, Wisconsin, West Virginia, and Vermont as their state tree. Its prevalence in New England is another reason the foliage is best there. On a sunny day, sugar maples look lit from the center. For color, they do not force you to choose: they can be yellow, burnt orange, crimson, purplish red, or a little of all of that in stages. Their transformation starts in tiny clumps at the top of the tree, up where the microclimate is colder. Crimson moves down the tree and sneaks into that glowing center from the sides. On the individual leaves, yellow spreads from edge to center, displacing the green, which lingers to outline the veins, then cedes to yellow altogether. The yellow then darkens to orange, staying gold in the center but with edges turning a vivid red that gradually moves across the entire leaf. Watch a sugar maple through October, and you are watching alchemy.

But just as the old Kodachrome photos faded, the sugar maples’ colors are about to lose their intensity. Renner’s team used satellite data to analyze the “greenness” in forests in the Northern Hemisphere. They found that for every degree (Celsius) of warming, trees lose their greenness about one and a half days sooner. That might mean they change color sooner (and less vibrantly). It might also mean that the leaves just fall off and begin to rot. Because the planet still has a huge variety of trees, we will see all sorts of responses to the climate crisis. Even when our seasons had a rhythm, trees that did a lot of nitrogen fixing never bothered to turn colors; maybe they will be our new stalwarts? Or maybe they will shed even their green leaves sooner. Robert Frost warned us: “Nothing gold can stay.” Master gardeners have begun to urge us to look for plants that can tolerate heat and drought. We may also find ourselves looking for trees that can still muster a bit of glorious color—or making our peace with the trees that stay green—or appreciating the sculptural forms in bare branches.

The shift will take some time. For now, soak in the fall color. The trees are asking for attention—and they, too, might sense a last hurrah.


Read more by Jeannette Cooperman here.