Thursday, February 24, 2022

Feeling Young and Feeling Old in Nature

Tailgates opened and closed, and women chattered as we milled around the parking area after a snowshoe hike. I stood in a sort of receiving line as the hike participants—mostly retirees—stopped by to ask a few more questions or share a recent encounter with nature.

One woman, with a sparkle in her eye, just wanted to thank me “for making us feel young.” I thought back to the steep hills and sometimes uneven trail, the cold wind off the lake, and the stiffness that was already creeping in to my (much younger) lower back. “Oh, the fir-rari and mentioning C.S. Lewis,” she said in response to my questioning look.

I smiled, happy to know that she also appreciated two of my favorite teaching tidbits. “Firs are flat and friendly, and they have racing stripes like a FIR-rari,” I’d lectured with a smile while holding a sprig of balsam fir. The stomata (doorways for gas exchange) in their needles are sunken in to two whitish stripes on the bottom of the needles. It’s something to look for if you’re comparing the fir with a spruce.

C. S. Lewis is the author of The Lion, the Witch, and the Wardrobe, and inventor of a magical land called Narnia. I read The Chronicles of Narnia series many times over as a kid. Earlier in the day, after we’d talked about the actual science of the Subnivean Zone (visit my blog if you need a refresher), I’d spotted a place where a mouse had popped out of the subnivium, hopped across the snow, and then re-entered through the little space next to a fallen log. “Look, it’s a wardrobe!” I’d stage-whispered to the people closest to me in line, referencing one of the magical portals into Narnia.

While neither of my jokes were the laugh-out-loud type, even moderate chuckling can help us relax, improve circulation, and reduce pain. Learning new things keeps your brain happy and healthy, too. Those benefits, and others, combine to make us feel younger. I thought back to the article I wrote about sliding—while I was in the midst of planning a sledding party for my 40th birthday—and how being playful with friends made us all feel younger. Play is essential to kids, of course, and increases survival. Play also benefits adults—essentially by making us feel like kids.

Papa and Zac discover something new together. Photo by Emily Stone.

Later, as I sat on the yoga mat in my long johns, feeling old and stretching out sore muscles before they stiffened up completely, I thought about the contradictions. Outdoor adventures can be physically taxing, but being out in nature mostly makes me feel young. Jumping in a puddle, sliding (purposefully) on ice, splashing in the lake, squishing mud between my toes, talking about animal poop, laughing about the gross, ridiculous, or amazing things that animals do, or even just soaking up sunshine brings a lightness to my spirit.

“What makes you feel young in nature?” I asked friends. With shining eyes, one woman told me a story about skinny dipping in a private pond, blue sky and sunshine, and no one else around for miles. The fun of letting your curiosity and imagination run wild—especially if you have an actual kid with you—popped up several times. Experiencing awe and wonder were recurring themes—their health benefits supported by data. Another friend mentioned the wind on her face, and the way that you can escape from societal expectations in the woods and just be yourself—more like the unselfconscious, unburdened days of childhood.

As for nature making us feel old, several answers revolved around the sadness of not being able to do favorite activities anymore. Sometimes the changes aren’t in our bodies, but in the places we love. Childhood haunts are paved over, and a favorite lake turned green with algae. Planting and growing things came up, too, since the life cycles in our garden plants are so short, and becoming a gardener can also mean taking on the role of your grandmother.

Grandma and Zac plant the garden. Photo by Larry Stone.

I also think about my age in relation to critters who live fast and die young. Many moths and butterflies complete their entire life cycle in a matter of weeks. If they are one of the generations who must survive the winter, then their life might last a whole year, with a long dormancy in the middle. The flowers they feed on also race through life. Many songbirds and small mammals can’t live more than a single decade, while here I am starting on my fifth one!

If I want to feel young, though, I look up. In the shade of a centuries-old white pine, my daily doings seem smaller in scale. And then there are the stars. A human at any age is young within the universe.

One of my wisest friends boiled it down to the fact that: “When I feel joy, I feel young; when I don’t feel joy, I feel old.” For him—for many of us—nature is that reliable source for joy.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Visit our Mysteries of the Night exhibit before it closes at the end of February. Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, February 17, 2022

Why is grass green?

Why are most plants green? The answer is more complex—and unknown—that you might think. Photo by Emily Stone.

I felt a little sad last week as I peered through my computer screen at the sixth graders clustered in front of the web cam in their classroom. I first met most of these kids in Miss Bonney’s 4K classroom at Drummond Elementary School many years ago. In those days, I would bring a MuseumMobile tub full of furs, bones, books, toys, or a giant turtle shell into their circle on the carpet. Sitting there among the wiggling, adorable children, I envisioned them growing up to be little naturalists. I also recoiled reflexively when the kid seated next to me sneezed. Oh, the days!

As the kids moved up through the grades, I taught them about spiders, brought them owl pellets to dissect, and even dressed them up as fish. Even as we were focused on one subject, they’d blurt out questions about something completely different. If there was time, I’d answer whatever questions they threw my way, often with unbridled enthusiasm for their curiosity and the incredibly weird nuances of nature.

Last week, though, was my final MuseumMobile visit with these students. We spent thirty minutes discussing the results of their goldenrod gall dissection experiment. Then, hoping to capitalize on the rapport I’d developed with supporting their curiosity over the years, I asked, “What questions do you still have about nature?”

After a long discussion about why wolf scat would or wouldn’t be exciting to dissect, I noticed a kid in the back who had been raising his hand throughout. When called on, he asked “Why is grass green?” A giggle rippled through the class. Was he being a smart aleck, I wondered? But he’d waiting politely until he was called on, so I gave him the benefit of the doubt. It’s a surprisingly interesting question.

Grass is green because it contains the pigment chlorophyll, of course. The chlorophyll is there to conduct photosynthesis. And it appears green because that wavelength of light is reflected back to our eyes. I gave them a quick explanation of color and vision.

And then our time was up. But the question was still niggling at me. Didn’t I read something once that pointed to a more nuanced answer? It was time to go Googling.

The first basic search turned up exactly what I’d always been taught, and what I told the students. Chlorophyll looks green because it absorbs blue light and red light and reflects green light.

Then, an article from the Journal of Biological Education caught my eye. “Chlorophyll does not reflect green light – how to correct a misconception,” read the title. The author, Olli Virtanen of the University of Turku in Finland, did some tests on the reflectivity of leaves, and determined that leaves look green not so much because they are reflecting green light, but because they are so very good at absorbing red and blue light.

All of this seems like a little bit of semantics to me, so I did a some more digging.

An article in Science confirmed that chlorophyll, in partnership with carotenoid pigments also in leaves, absorbs almost every single photon of red and blue light. In contrast, the leaves “only” absorb 90% of green photons. If light isn’t absorbed, it must be reflected, right? The nuance seems to be that leaves aren’t reflecting ALL the green light; they are just reflecting more of it than the other colors of light in the spectrum. Even though green light might just be the “leftovers,” our eyes are really good at seeing green because it’s at the center of our visible spectrum.

But that isn’t the only way to answer the question, “Why is grass green?” There’s another angle, best understood by turning things around and asking, “Why aren’t leaves blue or fuchsia or any other color?”

At a chemical level, it probably has something to do with the fact that the molecule of chlorophyll has magnesium at its center. A molecule of heme (the pigment that makes our blood red) is very similar…except that it contains iron. I’m not sure what effect those metal ions have on color, but surely they do something.

We can also think about color in terms of its role in making photosynthesis effective. A few sources purport that the Sun gives off less green light, and that’s why it’s beneficial for plants to reflect light of that color. That’s not true, however: the Sun radiates as much or more energy in green wavelengths as in the others.

Maybe the Sun is giving off too much green light for the plants to handle? Nathaniel Gabor, a physicist at the University of California, created a model to help understand the problem. He found that by using mostly red and blue wavelengths of light, chlorophyll is feeding itself a steady diet of photons—just enough to power photosynthesis, and not so many that the cells are damaged by excess. The stable stream of photons is maintained even as sunlight flickers through the canopy in varying amounts. If plants focused on using green light, they would be alternately overwhelmed by and starved of energy.

If we ask the question with evolutionary history in mind, a few more hypotheses pop up. One is that ancient organisms who filled the oceans before chlorophyll came onto the scene did focus on using green light—and filtered it out of the surface waters. Red and blue wavelengths were all that were left to power photosynthesis. Also, blue light penetrates most deeply into the ocean and would be the best source of energy down there even without green-light competitors above. At some point, tides turned, and the red-and-blue-light photosynthetic organisms became dominant—eventually creeping out of the oceans and into our lawns.

So, why is grass green? Science isn’t 100% sure yet, but at least I can be proud that my MuseumMobile students know how to ask interesting questions.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Visit our Mysteries of the Night exhibit before it closes at the end of February. Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, February 10, 2022

Hemlock and Paper Birch: An Odd Couple

At the trail intersection I turned left, looked up, and paused for just a moment to appreciate the dark green lace of the hemlock thicket in front of me. Several “redwoods of the east” towered elegantly in a grove. Beneath them, broken-topped boles wore the same dark brown furrowed bark. And filling in between were young hemlocks of all ages lending a shimmer of green to the mostly black-and-white forest.

This is one of my favorite spots along the trails of the Forest Lodge Estate. Mary Griggs Burke, the Cable Natural History Museum’s founder, bequeathed her 872-acre retreat on the south shore of Lake Namakagon to the Forest Service for research and education. Northland College manages access. I often guide hikes. The crunching of a dozen snowshoes behind reminded me that I wasn’t alone in this special spot.

Why is a grove of bushy baby hemlocks so special? Here in northern Wisconsin, we are at the far edge of eastern hemlock range. Just a few outliers exist farther west and north, but the heart of their habitat extends up Appalachia to the northeast. Perhaps the trees just haven’t had time to migrate back after the most recent glaciation plowed them away—only 14,000 years ago or so—or maybe the moisture runs low as the rain shadow of the Rocky Mountains creeps in across the plains. Even in places where hemlocks are abundant, white-tailed deer often nibble the young ones to death and regeneration can be spotty.

We admired the thicket—that has somehow escaped the deer—and breathed in the magical, primordial air (is that being overly dramatic?). Then a bitter gust off the icy lake set us moving again.

Just around the corner two grayish, old paper birch trees caught my eye.

At first glance paper birch and eastern hemlock are about as different as trees can get. There’s the bark, of course: smooth, pale, relatively thin and peeling, vs. thick, dark, corky ridges. Also their leaves, and the fact that birches lose their broad, bright green suncatchers each fall while hemlock holds on tight. Hemlock holds onto life a lot longer in general—growing for hundreds of years—while birches live a more human-scale existence of mere decades.

Over those centuries, the acid in hemlock needles washes nutrients out of the soil, while the rapid decomposition of birch leaves results in soils enriched in Ca, Mg, K, Mn, Fe…an alphabet soup of minerals.

One of the first things I learned in botany class was that hemlocks are the most shade tolerant tree in their range, while paper birches are at the other end of the spectrum, only exceeded by aspen and pin cherry in their demand for sun. Plus, paper birch is near the southern end of its range here but extends north to the edge of the treeless tundra. In contrast, yellow birch’s range, shade tolerance, and ecology more closely match that of hemlock—so much so that “hemlock-yellow birch” is an official cover type. 

I wouldn’t have been surprised to see yellow birch in this forest, and yet here instead was its sun-loving relative growing among the hemlocks.

A few more steps down the trail, I spotted one of my favorite teaching spots. Under heaps of snow were the spiked turrets and sloping sides of a hemlock stump, likely rotting since 1888 when this area was clearcut by the Northern Wisconsin Lumber Company. From that stump rose a slender young hemlock tree, only a few inches in diameter and maybe twice as tall as me. And, brushing away the snow, I revealed another piece in the puzzle: the grayed bark of a long-dead birch tree, it’s knee still hooked over the edge of the old stump where it had once grown, too. Not even steps away, this odd couple had almost been hugging.

This scene tells not of the trees’ differences, but what they have in common. Hemlocks bear their seeds in tiny cones, not unlike the cylindrical catkins of birch, which are just more fragile and ephemeral. And inside each structure are tiny seeds flanked by papery wings. Those seeds mature in late summer, and drop throughout the winter, sometimes skittering over crusty snow in a race to get farther from the crushing shade of their parent tree. While both species produce lots of seeds almost every year after they reach age 15, they face equally poor odds that any one seed will ever germinate, survive seedlinghood, or become a new tree.

Inside this tiny eastern hemlock cone are even smaller seeds that need a little bit of luck to ever become a tree. Photo by Emily Stone

The tiny seeds contained within hemlock cones are winged -- almost like mini maple seeds. Photo by Emily Stone.

Inside the cone-shaped catkins of birch are their tiny, winged seeds. Four-pointed bracts protect the seeds until it all falls apart. Photo by Emily Stone.

One thing that increases the odds of successful germination in hemlock and the birches is a lucky landing on the spongy surface of a rotting log or stump. Here—like on my friend who died in 1888—the moist environment, relatively warmer temperatures above ground level, and protection from pathogenic fungi—result in a cozy nursery. Without the benefit of a nurse log or nurse stump, the trees would need bare soil, consistent moisture, and a lot more luck. 

Nurse stumps are warm, damp places where seeds of hemlock, birch, and more can find a slightly more hospitable place to germinate. As the stump rots away under the new tree, roots often form funny looking knees. Photo by Emily Stone.

With that in mind, maybe it’s not so crazy to think that the hemlock grove we passed earlier—where they have somehow, against the odds, sprouted like crazy—does have a little magic in the air.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Visit our Mysteries of the Night exhibit before it closes at the end of February. Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, February 3, 2022

Admiring Pileated Woodpeckers

Conversation hummed around the office as Museum staff chatted with an old friend. I couldn’t stay focused, though. Movement outside the office window had caught my eye, and it was too good to ignore. “Hey!” I broke in. “There’s a pileated woodpecker outside the office window!”

These big, red-capped woodpeckers aren’t uncommon in the Northwoods, but it did seem a little special to have one right outside. Conversation paused and we all turned to look.

Male pileated woodpeckers like this one have both a red crest and a red mustache. Photo by Joshlaymon - Own work, CC BY-SA 3.0, https.commons.wikimedia.orgwindex.phpcurid=70700524

With a body length of up to 19 inches and a wingspan up to 30 inches, pileateds are the largest woodpeckers in the United States. Which is why it was a little odd that this guy was dangling almost upside down from some rather spindly boxelder twigs in a posture more suited to a chickadee. Sure, they only weigh 11 ounces, but that’s still 22x what a chickadee weighs. Twigs bent and bounced as his big bill nibbled at something.

While conversation began again, I kept watching. I could identify the woodpecker as male because in addition to his red crest, his mustache (scientists call it a malar stripe) was also scarlet. On females, this cheek stripe is black. But what was he eating?

Typically, carpenter ants and their larvae constitute anywhere from 40% to 97% of a pileated woodpecker’s diet, with beetle larvae, fruits, nuts, seeds, and even poison ivy berries rounding out the rest. None of those foods seemed logical for his current location. Golden-crowned kinglets find enough tiny caterpillars frozen onto winter twigs to fuel their 0.19 oz metabolism. Ruffed grouse get their energy from eating tree buds, but have a gizzard to grind them up and special bacteria to break down the cellulose. Boxelder seeds are toxic to horses, but have been reported as an emergency food for red squirrels. “Hey, buddy,” I wanted to shout, “What’s for lunch?”

Most of the time, we see pileated woodpeckers on big, dead trees. First, they listen for the sounds of insects moving and chewing, then they use their chisel-like beak to excavate rectangular holes, or sometimes just shred an area of punky wood. Then, they extend their barbed tongue into the hole, use it to grab a 6-legged morsel, and retract it into their mouth.

With how noisy a woodpecker’s drumming can be, I’m a little surprised that they are still able to hear such quiet sounds. I suppose there are a couple reasons for this. First, their loudest drumming is reserved for communication. When you hear their resonant tapping echoing through the forest, that’s a message to other pileateds that a pair is defending a territory. While pileated woodpeckers defend the same territory all year, they are less vocal about it in the winter. Feeding happens every day, of course, but feeding is usually much quieter and sounds like dull thuds—if you’re even close enough to hear it.

Second, woodpeckers don’t just use their tongues to extract prey; tongues also protect their brain by wrapping around the back of the skull. A Y-shaped bone called a hyoid apparatus helps support the tongue and helps it extend—and also acts like a seatbelt for the brain. Even the structure of their beak is important. The upper half of a woodpecker’s beak is longer, but the bone inside extends farther into the lower beak. The lower beak ends up taking more of the impact and transferring force to the body instead of the noggin.

In addition, woodpeckers have less space and fluid between their brain and their skull. While this may seem counterintuitive, it helps reduce movement of the brain during pecking—the same type of movement that gives humans a concussion in a fender bender. All of these adaptations help protect the woodpecker’s brain and hearing while they pound on trees.

It's easy to find evidence of pileated woodpeckers feeding this time of year. Piles of wood chips accumulate under trees where pileateds are active, and even their past exploits are more visible without leaves in the understory. Weathered snags perforated by woodpecker feeding holes are always fun to see. They illustrate well the meaning of the woodpecker’s genus name Drycopus, which comes from the Greek for “tree cleaver.”

Wood chips on the snow indicate recent activity in the winter woods. Pileated woodpeckers create these rectangular holes in order to get at insects. Nest holes have a much smaller entrance. Photo by Emily Stone.

So, whether you spot a pileated dangling awkwardly from twigs or pounding away at a trunk, I hope you pause your conversation, take a moment, and admire them.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Follow us on Facebook, Instagram, YouTube, and to see what we are up to.