What species is the tallest tree in the world, produces fog, and provides habitat for many organisms?
Adrianna Drindak
Let me introduce you to this ecosystem, beginning with a moment of meeting.
The metal boardwalk presses into my back, creating small indentations along my spine. A few meters away, a stream whispers, with the sound of swirling eddies lingering in my ears as the water glides and splashes. The surrounding ecosystem dazzles with green as the ferns dance from the nudge of a passing breeze. There is a deep silence in this forest. A silence that penetrates your soul, a true peace that quiets every internal murmur. Your attention drifts away from both the mundane and real challenges of the world, and shifts to look one way – up.
Now, let’s go for a walk to see the tallest trees in the world.
Adrianna Drindak
We step foot into the forest, with gigantic trees limiting our vision of the sky above. Today we’ll be meandering through the forest, stopping to explore and learn more about the vitality of the coast redwoods and the critical roles they play in this environment. But what does a redwood look like? The tallest known coast redwood is 379 feet (115 m) tall, which is similar to about 38 regulation height NBA hoops stacked on top of each other. This tree has a diameter of up to 26 ft (8 m) which is the equivalent to the length of about one stretch limousine. Recent research has found that there is more carbon stored aboveground in old-growth redwood networks than any other forest system.
Where did these enormous trees, towering above our heads, come from?
There are three species of redwoods found around the world, with each organism populating different biomes: Coast Redwood (Sequoia sempervirens), Dawn Redwood (Metasequoia glyptostroboides), and Giant Sequoia (Sequoidendron giganteum). The redwoods originated from conifers that grew alongside dinosaurs in the Jurassic period, about 145 million years ago. With shifts in the climate, the redwoods became constrained to their present geographic regions. Today the Dawn Redwood is found in central China and the Giant Sequoia thrives in the rugged terrain of the Sierra Nevada Mountains in California. The Coast Redwood is distributed along the coast of southern Oregon and northern California, and stands as the tallest known tree species on the planet.
Adrianna Drindak
We are walking down a gentle dirt path, deep within a redwood forest along the California coast, with our necks craned upwards to the giants above. As we wander amongst the trees, some over 2,000 years old, the branches above our heads are draped with lush greenery. Ferns, saplings, lichens and mosses rest within the tree; not causing harm, rather living peacefully from a higher viewpoint. These plants reposed in the canopy of the coast redwood are referred to as epiphytes. The quiet flutter of other biota sounds from above, such as the endangered Marbled Murrelets chirping from a nest and Wandering salamanders leaping between branches. The rumbling of a stream nearby is a reminder that while we cannot see below our feet, the redwoods are also building relationships below. Coast redwoods shade these aquatic environments and reduce erosion, which cools these areas for salmon populations. In exchange, the salmon provide marine nutrients to the ecosystem and the coast redwoods as they reproduce and decay.
Fog weaves through the afternoon sunlight, making our vision of the path ahead hazy. We pause, with one of the redwoods extending far below our feet, roots entangled with a neighbor, and many meters above our heads, branches draped. This redwood does not only provide habitats for a wide range of organisms, but also facilitates the local climate to support them. Redwoods play a central role in the water cycle of this coastal ecosystem, particularly through their relationship with fog. Coast redwoods require increased moisture levels to reach such extraordinary heights, and use a chemical called terpene to remove moisture from the air. This chemical causes these water droplets to condense, which creates low-lying clouds. This cycle of fog production, fueled by the nearby ocean, sustains the growth of redwood forests.
Adrianna Drindak
The fog slowly lifts and we continue our walk on the dirt path. The forest rustles as we reach a fallen redwood, obscuring part of our trail. The giant lies on its side, resting, with an immense root system exposed. There are ferns and mosses that have grown from the tree and a banana slug inches across the surface, leaving a slimy trail on the rough bark. Fallen redwoods give back to the community in many ways. The Yurok people have cultural traditions that involve working with fallen redwoods to create canoes and other structures. David Eric Stevens, a Yurok Canoe Builder, tells us the story of how the redwood canoe originated. “There’s a story of a redwood tree that wanted to live among humans, and the creator gave him the opportunity to live among humans by giving us canoes.” The canoes carved from fallen redwoods can take approximately seven years to create. Canoe Captain Julian Markussen describes, “If you take care of them properly, they can last for over 100 years.” These fallen redwoods continue to live even after falling, whether that be as habitat for organisms or in an extended life as canoes.
We step past the fallen redwood to continue our meander, dodging the ferns sprouting from the decaying bark. But as we walk, something changes in the forest. The redwoods seem to reach further and expand wider. The vegetation is more vibrant and green than anywhere else in the forest. The sunlight trickles through the branches above, dancing between lichen-covered branches. This is an old-growth redwood forest. Old-growth forests are hubs of biodiversity, with these trees acting as central to underground communication networks, providing habitat, and facilitating an interconnected ecosystem. The few trees that surround us are some that have been protected from historical logging in the region, as only 5 percent of these ancient coast redwood forests remain. We pause here and take a step back in time. There are hundreds of years of history captured in the lush undergrowth and full canopy.
We have reached the end of the path, emerging from the cool shade. We turn to look back, marveling once more at the incredible organisms we had the opportunity to meet. Coast redwoods regulate this vibrant, green ecosystem, endless beyond our sight. It is time to leave this magical forest, with the magnificent, ancient giants that shoot up out of our eyes’ reach. We have peered into an interconnected world, where these trees interact with the atmosphere, flourishing plant life, and abundant critters. There is a pause before we turn to go. What does this forest teach us?
I think back to that moment of meeting, lying on the boardwalk looking up. My first encounter with the coastal redwoods was magical, to say the least. There are no words to describe the might of these ancient beings, as their uppermost branches, or crown, beckon you to look up. In the sharing of gentle silence, as I laid down on the boardwalk surrounded by an ecosystem teeming with life, I dared my eyes to look farther and memorize every detail. I felt a deep desire to cherish and protect these organisms, and to share my joy for the incredible ways they shape their ecosystems and our planet. Most of all, the redwoods revived a deep sense of wonder. This wonder, inspired by such magnificent organisms, pulls you to be present. Just by nature of being and interacting with the redwoods, these trees inspire care, generosity, and resilience. How lucky we are to walk amongst such powerful beings.
Adrianna Drindak is a rising senior at Dartmouth College studying Environmental Earth Sciences and Environmental Studies. Prior to interning at Bio4Climate, she worked as a field technician studying ovenbirds at Hubbard Brook Experimental Forest and as a laboratory technician in an ecology lab. Adrianna is currently an undergraduate researcher in the Quaternary Geology Lab at Dartmouth, with a specific focus on documenting climate history and past glaciations in the northeast region of the United States. This summer, Adrianna is looking forward to applying her science background to an outreach role, and is excited to brainstorm ways to make science more accessible. In her free time, Adrianna enjoys reading, baking gluten free treats, hiking, and backpacking.
The first time I saw the vibrant blossoms of the ‘ōhi’a lehua tree, I was walking on a dirt path in Kauai’s Waimea Canyon State Park, gaping down at the most colorful red and green gorges I had ever seen. Needing a breather from the steep visual plunge, I looked up from the canyon and noticed bright red flowers on the side of the path. As I got closer and could see the plant more clearly, the first thought that popped into my head was how similar the flowers looked to those fiber optic light toys I had played with as a kid. (If you don’t know what fiber optic light toys look like, look them up. You’ll see exactly what I mean.)
After my trip to Waimea Canyon, I saw ‘ōhi’a lehua everywhere. When I drove along the coast between the beach and the sloping mountains, when I hiked the volcanic craters of Haleakala, and when I visited parks and gardens across the islands that protect native plants and animals. ‘Ōhi’a lehua is the most common native tree in Hawaii, so seeing its fiery red, orange, or yellow blossoms every day felt so very ordinary. But ‘ōhi’a lehua is far from ordinary.
Let Me Introduce You to My New Friend, ‘Ōhia Lehua
Endemic to the six largest islands of Hawaii, ‘ōhi’a lehua is the dominant tree species in native forests, present in approximately 80% of the total area of these ecosystems and covering close to one million acres of land across the state. Depending on where exactly it grows, its size can vary widely, from a small shrub to a large tree. Found only in the Hawaiian archipelago, ‘ōhi’a lehua grows at elevations from sea level to higher than 9000 feet, and in a variety of habitats like shrublands, mesic forests (forests that receive a moderate amount of moisture throughout the year), and more wet, or hydric, forests.
You can easily identify the ‘ōhi’a lehua blossoms by their mass of stamens – the part of the flower that produces pollen – which are slender stalks with pollen-bearing anthers on the end. It’s what made me think the ‘ōhi’a lehua looked exactly like those fiber optic light toys. These powder puff-like flowers are most often brilliant shades of red and orange, but yellow, pink, and sometimes even white ones can be found.
‘Ōhi’a lehua grows slowly, reaching up to 20-25 meters (66-82 feet) in certain conditions.
With a little help from the wind, the seeds of ‘ōhi’a lehua travel from the tree and settle in cracks in the ground of young lava rock. It is, in every sense, a true pioneer plant. As one of the earliest plants to colonize and grow in fresh lava fields, ‘ōhi’a lehua stabilizes the soil and makes it more habitable for other species.
Even though ‘ōhi’a lehua can blanket Hawaii’s native forests, this flowering tree also grows alone, as you can see in the photograph below. Plants like ‘ōhi’a lehua fill me with happiness because they are able to grow in the most harsh, barren, and disrupted places, and they make it possible for other species to do the same. Plants like ‘ōhi’a lehua fill me with surety that even though sometimes poorly treated, the natural world will continue to be strong. Plants like ‘ōhi’a lehua make me believe in the resilience of nature.
Biodiversity forms the web of life we depend on for so many things – food, water, medicine, a stable climate, and more. But this connection between human beings and natural life is not always clear, understood, or appreciated. But there is a concept in Hawaiian culture called aloha ‘āina, or love of the land, which teaches that if you take care of the land, it will take care of you. The ‘ōhi’a lehua in particular takes care of the Hawaiian people in a pretty special way.
One of the most important characteristics of this flowering evergreen tree is that it’s a keystone species, protecting the Hawaiian watershed and conserving a great amount of water. The way I see it, ‘Ōhi’a lehua is an essential glue that holds Hawaii’s native ecosystems together. The leaves of ‘ōhi’a lehua are excellent at catching fog, mist, and rain, replenishing the islands’ aquifers and providing drinking and irrigation water for Hawaiian communities. ‘Ōhi’a lehua’s ability to retain water, particularly after storms, not only makes that water accessible for other plants, but it helps mitigate erosion and flooding. The tree provides food and shelter for native insects, rare native tree snails (kāhuli), and native and endangered birds like the Hawaiian honeycreepers (‘i’iwi, ‘apapane, and ‘ākepa). ‘Ōhi’a lehua trunks protect native seedlings and act as nurse logs, providing new plants with nutrients and a growing environment.
‘I’iwi, the Scarlet Hawaiian Honeycreeper, perched on an ‘ohi’a tree (Image Credit: Nick Volpe)
The Myth of ‘Ōhi’a Lehua
‘Ōhi’a lehua may have a disproportionately large effect on Hawaii’s ecosystems as a keystone species, but its presence as a meaningful part of Hawaiian culture could be even larger. There are many versions of mo’olelo (story) about the origin of the ‘ōhi’a lehua tree, but the most common one is about young lovers named Ōhi’a and Lehua. Pele, the goddess of the volcano, changed herself into a human woman and tried to entice ‘Ōhi’a. When he denied her, Pele became enraged and transformed ‘Ōhi’a into a tree. When Lehua found out, she was so heartbroken that she prayed to the gods to somehow help her reunite with him. Answering her prayers, the gods transformed Lehua into a flower and placed her on the ‘ōhi’a tree’s limbs. To this day, it’s believed that whenever a lehua flower is picked, the skies will open up and rain will fall, because the lovers have been separated.
‘Ōhi’a Lehua as a Cultural Symbol
In Hawaiian culture, the ‘ōhi’a lehua is a symbol of love, resilience, and ecological harmony. The transformation of Ohia and Lehua into tree and flower represents the inseparable bond between two people who love each other, and between the tree and its flowers. The term pua lehua, or lehua flowers, is often used to describe people who express the same grace, strength, and resilience of the ‘ōhi’a lehua. Pilina, a Hawaiian word that means “connection” or “relationship,” is an important value in Hawaiian culture because it is a critical way for people to connect with and understand the world around them. The ‘ōhi’a lehua tree is a symbol of pilina, and embodies this relationship between the Hawaiian landscape and its people.
Hula dancers performing at the Merrie Monarch Festival Thomas Tunsch (CC BY-SA )
The ‘ōhi’a lehua is also incredibly important to hula. Hula is the narrative dance of the Hawaiian Islands, and it is an embodiment of one’s surroundings. Dancers use fluid and graceful movements to manifest what they see around them and tell stories about the plants, animals, elements, and stars. ‘Ōhi’a lehua trees and forests are considered sacred to both Pele, the goddess of the volcano as you may recall, and Laka, goddess of hula. To enhance their storytelling and evoke the gods, dancers traditionally wear lehua blossoms or buds in lei, headbands, and around their wrists and ankles.
The Dependability of ‘Ōhi’a Lehua
‘Ōhi’a lehua has long been a part of daily life. Historically, the hardwood of the tree was used for kapa (cloth) beaters, papa ku’i ‘ai (poi pounding boards), dancing sticks and ki’i (statues), weapons, canoes, and in the construction of houses and temples. Today, the tree’s wood is used for flooring, furniture, fencing, decoration, carving, and firewood. ‘Ōhi’a lehua blossoms decorate altars for cultural ceremonies and practices. Flowers, buds, seeds, and leaves form the base of medicinal teas that can stimulate appetite and treat childbirth pain.
Threats to ‘Ōhi’a Lehua
As a native tree, ‘ōhi’a lehua competes with invasive species for moisture, nutrients, light, and space. Plants like the strawberry guava plant (Psidium cattleyanum) grow in dense thickets and block the growth of ‘ōhi’a seedlings. The invasive fountain grass (Pennisetum setaceum) can dominate barren lava flows, making it difficult for ‘ōhi’a to compete. ‘Ōhi’a lehua is also threatened by non-native animals. Hooved animals like pigs, cattle, goats, and deer disturb the soil, eat sensitive native plants, and trample the roots of ‘ōhi’a lehua trees.
The most dangerous threat to ‘ōhi’a lehua is a virulent fungus called Ceratocystis fimbriate, which attacks the tree’s sapwood, preventing it from uptaking water and nutrients, and killing the tree within weeks. It’s been given the name Rapid Ohia Death (ROD) because of how quickly it suffocates the tree, turning the leaves yellow and brown and the sapwood black with fungus. Infections spread through a wound in the bark, which can be caused by animals trampling roots, lawn mowing, or even pruning, and can be present in the tree for up to a year before showing symptoms. ROD is spread by an invasive species of wood boring Ambrosia beetle that infests the tree and feeds off the fungus. When colonizing trees, the beetle produces a sawdust-like substance made of excrement and wood particles called frass, which can contain living fungal spores that get carried in wind currents and spread by sticking to animals and human clothes, tools, and vehicles.
Since its discovery in 2014, ROD has killed more than one million ‘ōhi’a lehua trees across 270,000 acres of land, making it a significant threat to biodiversity and cultural heritage. The International Union for Conservation of Nature (IUCN) classifies ‘ōhi’a lehua’s conservation status as vulnerable, and has recorded a decline in mature trees since 2020. Because ROD can spread long distances, it has the potential to wipe out ‘ōhi’a lehua across the entire state. If ‘ōhi’a lehua disappears, it will lead to a collapse of the Hawaiian watershed and radically change the ecosystem.
How the Hawaiian People Care for ‘Ōhi’a Lehua
Scientists, researchers, and native Hawaiians are working together to ensure the long-term health and resilience of ‘ōhi’a and Hawaii’s native forests by mitigating the spread of Rapid Ohia Death. Hawaii’s Forest Service monitors the land to track the spread of ROD and mortality of trees, has developed sanitation and wound-sealing treatments, and collaborates with hunters and game managers to reduce disease transmission. Scientists rigorously test ‘ōhi’a trees to understand the disease cycle, find out how it can be broken, and to identify trees resistant to the infection that could be used in potential reforestation efforts.
To prevent the spread, Hawaii has announced quarantine restrictions, travel alerts, and sanitation rules. If you are shipping vehicles between islands, you should clean the entire understory with strong soap to remove all mud and dirt from the tires and wheel wells. People who go into ‘ōhi’a forests are advised to avoid breaking branches or moving wood around, to clean their shoes and clothes, and to decontaminate any tools used with alcohol or bleach to kill the fungus. Even hula practitioners are forgoing the use of ‘ōhi’a lehua.
Mālama the ‘āina is a phrase that means to care for and honor the land. ‘Ōhi’a lehua is a wonderful representation of the interconnection between people and nature and I hope learning about this beautiful tree has encouraged you to appreciate the relationship we have with the Earth and what the natural world does for us.
Remember, if you take care of the land, it will take care of you.
Abigail
Abigail Gipson is an environmental advocate with a bachelor’s degree in humanitarian studies from Fordham University. Working to protect the natural world and its inhabitants, Abigail is specifically interested in environmental protection, ecosystem-based adaptation, and the intersection of climate change with human rights and animal welfare. She loves autumn, reading, and gardening.
What Mediterranean tree is uniquely equipped to withstand wildfires with armor-like bark and high, out of reach, branches?
The stone pine!
The stone pine in Casa de Campo, Madrid. (image by author)
In his 1913-1927 novel, In Search of Lost Time, French writer Marcel Proust described the power of a soft, buttery madeleine cookie dipped in tea to transport the story’s narrator back to his childhood, unlocking a flood of vivid memories, emotions, and senses. Since then, the term “Proustian memory” has come to describe the sights, smells, sounds, or tastes that bring us back to a particular place in time, one that reminds each of us that we are home.
This is how my partner talks about the stone pine (Pinus pinea) in Spain. Raised in Madrid, she moved to the U.S. when she was twenty-three. For the next decade she’d go long stretches without returning home (blame grad school, work, a global pandemic, and high airfare).
But on those occasions where she was able to return home for a visit, before that first sip of cafe con leche, it was the stone pines flickering past the taxi cab window that brought her back to the youth she’d spent running beneath them, and told her soul that she was home.
There are few markers more reliable than the stone pine to remind you that you are in the Mediterranean. Its branchless trunk rises 25-30 meters from the dry ground. Deep grooves run up the thick, rugged bark in shades of rust and ash-gray. It is bare all the way up to a rounded crown that seems to hover above the landscape. Branches bearing clusters of slender needles splay out horizontally and cast large soft shadows on the ground, giving the tree its nickname, the parasol (umbrella) pine. Its high canopy offers nesting sites and vantage points for many birds of the Med, like Eurasian Jays and Red Kites.
The stone pine’s unique silhouette foreshadows its individuality among its relatives in the genus Pinus.
stone pine bark detail. (Photo by dmcd25)(CC-BY-NC via iNaturalist)
The Parasol Pine
It is a resilient tree with few natural predators. High branches keep its cones away from most ground-dwelling herbivores, and that hardy bark helps shield against both prying insects and wildfire, perhaps its most common threat in the Mediterranean. The clustering of branches high above the brush also helps it withstand fire events more successfully than other species in the area. That said—it’s important to understand that pests (like the pine tortoise scale) and runaway fires do remain serious threats, even if the stone pine is better prepared to meet them.
The tree also stands apart from other species of pine in its lack of hybridization—that is, its failure to crossbreed with other pine species, despite existing in close proximity. It does not demonstrate a tendency to interbreed with its neighbors like Pinus halepensis (Aleppo pine) or Pinus pinaster (maritime pine), and that is unusual among pines. It’s really just out here doing its own thing.
This pattern of genetic isolation is a product of circumstances. The stone pine’s pollination window doesn’t often line up with other species and, even when they do, the tree’s genetic makeup has remained distinct enough (while others have hybridized) that fertilization is increasingly improbable.
And unlike other pine species, stone pine seeds are not effectively dispersed by the wind, perhaps contributing to this isolation. Instead, they rely on the few animals that can reach them, particularly birds, to shake them free and drop them elsewhere.
I hope we’ve established that the stone pine is one tough, rugged cookie, designed from the root up to thrive in a variety of ecosystems around the Mediterranean. But what’s going on below the surface?
To really understand any tree, you’ve got to look down. When we talk about “siliceous” soils, we’re talking about soils that are made up mostly of silica—essentially a mineral of silicon and oxygen that comes from rocks like quartz and sandstone. These soils are characteristically sandy and drain water quickly, but offer fewer nutrients—making them less fertile and more inhospitable for many trees. They also tend to be more acidic.
On the other half of the pH scale (which measures the acidity of acids on one end, and alkalinity of bases on the other) are what are known as “calcareous” soils—that is, soils rich in calcium carbonate from sources like limestone or chalk, but light on most other important nutrients.
Both of these types of soil are found along the rocky Mediterranean. And while its preference is for the former, more siliceous soils, the stone pine does well in both. In fact, it’s this ability to thrive in these rocky soils that earned the tree its name, the stone pine. Of course, the tree’s deep roots alone are not always enough to survive in these nutrient-deficient soils. Like other pines around the world, Pinus pinea benefits from ectomycorrhizas, the symbiotic relationship between the tree and fungi in the ground that help facilitate nutrient exchange in soils where they are harder to come by. It’s a fascinating relationship that certainly deserves its own essay, but it is important to understand the critical role Ectomycorrhizal fungi (EMF) play in maintaining thriving forest ecosystems. They form mutually beneficial relationships with trees, where the fungi exchange those coveted soil nutrients for carbon compounds produced by the trees during photosynthesis. This natural partnership supports nutrient cycling and enhances tree health and growth, allowing pines just like the stone to survive under more challenging soil conditions.
Explore visualizations of how Ectomycorrhizal fungi support forest growth.
In the course of human events
We know quite a bit more about where the stone pine is, rather than where it’s from. Pinpointing its native range has proven difficult because the tree has been harvested, traded, and replanted by human since prehistory—first for their edible pine nut seeds, then by later civilizations like the Romans for their ornamental status. Even today, it is common throughout the region to find a street or garden lined with the distinctive tree.
Today, pine nuts from the stone pine remain big business, and their cultivation has been seen as an alternative crop in regions where the arid soil would make other agricultural endeavors too difficult.
Pine nuts served on a dish of roasted peppers. Via Pexels.
I’ve realized there is more to learn about the stone pine than I could ever hope to fit on a page. In my naivety or ignorance, I did not expect that. Its deceptively simple silhouette belies a complex story of resilience, symbiosis, and ancient history and, for at least one Spaniard, a reminder that she’s home.
Brendan began his career teaching conservation education programs at the Columbus Zoo and Aquarium. He is interested in how the intersection of informal education, mass communications and marketing can be retooled to drive relatable, accessible climate action. While he loves all ecosystems equally, he is admittedly partial to those in the alpine.
The Cork Oak is a unique tree species whose bark is an ancient renewable and biodynamic material that supports a valuable Portuguese industry. Portugal produces 50% of the world’s cork, thanks to the abundance of the native Cork Oak that covers 8% of the country’s total land area and makes up 28% of its forests.
The harvested cork is made into the wine stoppers we all know, but cork is also used to create flooring, furniture, a variety of household items, and has even broken into the fashion industry in the form of clothing and accessories. Across Portugal, (where the Cork Oak is the National Tree), you’ll find locals sporting cork backpacks, wallets, sandals, and belts, to name a few.
On a recent trip to the Douro Valley in northeastern Portugal, I was inspired by the locality of the wine-making process, exemplified by the roadside Cork Oaks whose harvested bark was used to plug the bottles of Portuguese wine made with grapes grown on the same hills.
The material is gaining more international recognition as a highly renewable and biodegradable resource that can replace traditional, more carbon intensive materials like wood, plastic, leather, and cotton in a wide variety of settings.
The Cork Oak, or Quercus Suber, is an evergreen oak species native to the Mediterranean region, most commonly in Portugal, Spain, Italy, Algeria, Morocco, and Tunisia. A lover of full sun, mild winters, and well-drained soil, the Cork Oak grows to a height of 40-70 feet. Its rounded crown consists of ovular, four-inch leaves that are dark green and leathery on top with a fuzzy, gray underside. The tree is characterized by its recognizable, fissured bark.
Cork Oaks are environmental stalwarts, working hard to prevent erosion and increasing the moisture level in the soil. These services are crucial: Cork Oaks are on the front lines as desertification creeps northward in Africa. These Mediterranean Forests are home to surprisingly biodiverse ecosystems with nearly 135 plant species per kilometer, including other oaks and wild olive trees. These forests shelter a wide variety of animal species and are final strongholds for crucially endangered species like the Iberian Lynx and Imperial Eagle. Their acorns serve as food for native birds and rodents, their yellow flowers feed pollinators, and their unique ability to regenerate their bark makes them a valuable resource for humans.
What sets Cork Oaks apart is their thick, fissured bark with the rare capacity to regenerate every 9-12 years. Its harvest is a heavily regulated process in Portugal that takes place between May and August each year. Laws allow the harvest of a single tree only once every nine years starting at age 25. The process leaves the tree standing, and allows time for the bark to regenerate completely between harvests. Large swaths of the outer bark is cut and peeled off by hand, exposing the tree’s striking, reddish-brown trunk. The last number of the harvest year is then marked on the tree in white paint, as seen below with a tree in the Douro Valley whose bark was harvested in 2023. This tree will be ready for another harvest in 2032, nine years later. With a lifespan of around 200 years, a single cork oak can be harvested up to 15 times!
Photo by Morgan Moscinski (Douro Valley, Portugal)
Once the cork has been aged slightly, pressurized, and boiled (a six-month process), it becomes the lightweight and elastic material we find in our wine bottles. Naturally impervious to liquid while allowing a little air movement over time (this helps wine mature), the Ancient Greeks were the first to use cork as a bottle stopper over 2,000 years ago! It remains the preferred closure solution of contemporary winemakers.
With immense environmental and economic value, the Cork Oak is a unique species working hard to keep the deserts at bay and the wine drinkers happy. A protected species in Portugal since the 13th century, the ancient practice of cork bark harvesting is more important than ever. The tree is not harmed by this process; it actually helps it become a larger carbon sink. The photosynthesis required to regrow its bark results in additional carbon dioxide drawn down from the atmosphere after each harvest. This fascinating process is a rare win-win in the search for biodynamic and sustainable materials. How will we use it next?
So, the next time you celebrate a special occasion, share a bottle with friends, or enjoy a glass of Douro Valley Moscatel after dinner (something I recommend), take a moment to think about the wonderful uniqueness of the material at play. And don’t forget to compost those corks at the end of the night!
Off I pop! Ryan
Ryan Pagois is a climate advocate and systems thinker serving as an Associate Director at Built Environment Plus, helping to drive sustainable building solutions in MA. He is passionate about urban ecology, carbon balance, and rewilding cities. He is excited to pursue a Masters of Ecological Design at the Conway School starting this fall, to explore how low-impact urban development can be our greatest climate solution and community resilience tool. He grew up in Minnesota and studied environmental policy and international relations at Boston University.
In the lush landscapes of North America, the Northern Red Oak stands as a timeless symbol of strength, resilience, and enduring beauty. Revered for its towering stature, vibrant foliage, and essential ecological contributions, this iconic species holds a cherished place in both natural ecosystems and human communities.
The state tree of New Jersey, the Northern Red Oak is sometimes referred to as the “champion oak,” and it certainly qualifies as a biodiversity and climate champion!
The Northern Red Oak, or Quercus rubra, is an impressive hardwood tree that graces the forests of Eastern and Central North America. Its grandeur is exemplified by its towering height, often reaching between 70 to 90 feet, and its robust, straight trunk. Adorned with deeply lobed, glossy green leaves, the Northern Red Oak undergoes a breathtaking transformation in the autumn, as its foliage turns into a symphony of red, russet, and orange hues, captivating onlookers and adding a burst of color to the landscape.
I got to know my oaks over the past few years as I’ve dived more deeply into the native ecology of New England. Like maples and tulip trees, oaks have fairly recognizable leaves, and make an accessible place to start with species identification. It took me a bit longer to discern between different types of oaks, from the sharp edged Northern Red Oak leaves to the rounded edges of the Swamp White Oak leaves, but it’s a satisfying journey to take to get to know these hallmarks of the landscape better. As I learn trees’ names, patterns, life cycles, and roles, I get to establish a greater kinship with these beings, and witness the beautiful ways they interact with the people, birds, insects, and animals in the ecosystem.
Beyond its visual allure, the Northern Red Oak plays a crucial role in maintaining the health and balance of its ecosystems. Its extensive root system helps prevent soil erosion, and improves the soil sponge for water infiltration, buffering against the intensifying drought and flood cycles affecting our environments. These trees also provide essential food and habitat for a biodiverse array of wildlife.
As many scientists and foresters are beginning to recognize in greater numbers, the more we can preserve and plant keystone native species of our ecosystems, the more deeply and powerfully those ecosystems can mitigate the extreme effects of climate change and global warming. Healthy ecosystems are full of complexity, and in part it is the relationships between different species of vegetation, fungi, microbes, and wildlife that make the whole so successful. Northern Red Oaks are particularly valuable bulwarks of the forest ecosystems of the Eastern and Central US, where they support almost 500 different of butterfly and moth species, which in turn feed the larger food chain. These trees’ acorns also directly supply vital sustenance for many types of wildlife, including blue jays, woodpeckers, turkeys, squirrels, raccoons, and deer. Finally, as old trees begin to decay and die, their trunks and branches go on to house many animals’ dens and nests, continuing to provide throughout the stages their life cycle.
The Northern Red Oak has traditionally been valued for its economic significance, which characterizes a lot of the information you can find on this beautiful tree. Revered for its durable wood, the Northern Red Oak is a prized timber species, notable for its strength, durability, and attractive grain pattern. Its wood can be found in various woodworking applications, including furniture, cabinetry, flooring, and veneer. So next time you see a product boasting its oak hardwood, imagine the long history of that material that lies beneath the surface.
Image by Nicholas A. Tonelli from Northeast Pennsylvania, USA, CC BY 2.0 via Wikimedia Commons
Vital and Versatile
Adaptability is another hallmark of the Northern Red Oak, as these trees thrive in a wide range of soil types and environmental conditions. From lush forests to urban parks, this resilient species can flourish in diverse habitats, underscoring its importance as a cornerstone of biodiversity.
In urban forestry and landscaping, Northern Red Oaks are treasured for providing shade, natural beauty, and environmental benefits to parks, streetscapes, and residential areas. Sometimes, biodiversity value and hardiness to poor soil conditions and urban stressors are thought of as tradeoffs that urban foresters must navigate. However, the Northern Red Oak (and many other remarkable trees) prove that sometimes, you can have it all.
Northern Red Oak sapling in our Danehy Park Miyawaki Forest (Image by Maya Dutta)
Despite its resilience, the Northern Red Oak faces threats from pests, diseases, and habitat loss from logging, degradation, and fragmentation, underscoring the need for transforming our relationship to forests and vegetation, these powerful systems for cooling and carbon sequestration. By protecting and preserving Northern Red Oak populations, prioritizing biodiversity and holistic ecosystem health in our climate resilience efforts, we can make a cooler, greener, healthier world for ourselves and the many species we share our home with.
May we make that dream a reality,
Maya
Maya Dutta is an environmental advocate and ecosystem restorer working to spread understanding on the key role of biodiversity in shaping the climate and the water, carbon, nutrient and energy cycles we rely on. She is passionate about climate change adaptation and mitigation and the ways that community-led ecosystem restoration can fight global climate change while improving the livelihood and equity of human communities. Having grown up in New York City and lived in cities all her life, Maya is interested in creating more natural infrastructure, biodiversity, and access to nature and ecological connection in urban areas.
What Nat King Cole, Mel Tormé and Bing Crosby Were Singing About
According to legend, songwriter Robert Wells, trying to stay cool during the hot summer of 1945, put to paper his favorite parts of winter, eventually turning those thoughts into “The Christmas Song.” First on his list – “chestnuts roasting on an open fire.”
Now maybe, if you are like me, you find that a curious choice. Were chestnuts really that important to the Christmas experience? Before yuletide carols and Jack Frost? Before turkeys and mistletoe and tiny tots who can’t sleep because “SantaSantaSanta?” Why, when penning his favorite parts of winter, did his first thought turn to chestnuts?
Which brings us to the Columbian Exchange.
What is the Columbian Exchange?
The Columbian Exchange, for those who don’t know, refers to the massive transfer of plants, animals, germs, ideas, people, and more that occurred in the wake of Christopher Columbus’ arrival in the Americas. While a detailed analysis of all the impacts of the Columbian Exchange is far beyond the scope of this piece, from a strictly biological standpoint, it began a fierce evolutionary battle as previously unseen species entered new territory for the first time.
One of the most notable victims of this exchange turned out to be the American Chestnut Tree.
For more than 2,000 years, the American Chestnut dominated the mountains and forests of the Eastern United States, allowing adventurous squirrels to travel, according to legend, from Georgia to New England without ever touching the ground or another species of tree. Each year it provided much of the diet for many species, including black bears, deer, turkeys, the (now extinct) passenger pigeon and more.
The chestnuts, which grew three at a time inside the velvety lining of a spiny burr, contained more nutrients than other trees in the East, making them especially valuable to Indigenous peoples who relied on them as a food source and used them in traditional medicines. Europeans would later use the nuts as feed for their animals, or forage to use them for food or trade. In addition, since the trees grew faster than oak and were highly resistant to decay, the lumber was highly-prized for construction—to this day American chestnut, reclaimed from older buildings, is sometimes used to create furniture.
Harvesting an American chestnut at TACF’s Meadowview Research FarmsOpen bur of an American chestnut Young green burs at Meadowview Research FarmsWild American chestnut seedling in NY
The chestnuts were, in fact, such a staple that, in the late fall and early winter after the trees had delivered their harvest, city streets would be lined with carts roasting the nuts for sale. They are reported to be richer and sweeter than other varieties of chestnut and were a much sought-after wintertime treat. Today, roasted chestnuts are typically imported, and either European or Chinese chestnuts are used and, if our great-grandparents are to be believed, those species are just not as good. In addition, the loss of the American Chestnut deprived the United States of an important export.
So, What Happened?
After Columbus arrived, a fella by the name of Thomas Jefferson danced into his Virginia home-sweet-home with some European chestnuts to plant at Monticello. Somebody else imported Chinese chestnuts and, before too long, ink disease had practically eliminated the American chestnut in the southern portion of its range.
Then, in 1876, Japanese chestnuts were introduced into the United States in upstate New York and, a few decades later, a blight was discovered at the Bronx Zoo (then known as New York Zoological Park) that, by 1906, had killed 98% of the American chestnuts in the borough. Since Asian chestnuts, and to a lesser extent European chestnuts, had evolved alongside the blight, they were able to survive. But the American Chestnut tree (and its cousin the Allegheny Chinquapin) could not. Over the coming decades the airborne fungus, which could spread 50 miles in a year and kill an infected American Chestnut within ten years, had rendered the American Chestnut functionally extinct.
Canker and blightBlight on young chestnut trees.
What Does That Mean, “Functionally” Extinct?
While the American Chestnut may be “functionally” extinct, that is not the same as being extinct. The root systems of the trees in many cases have survived, as the blight only kills the above-ground portion, and the below-ground components remain. Every so often a new shoot will sprout from the roots not killed when the main tree stem died. These shoots are only able to grow for a few years before they are infected with the blight, and they never reach a point of bearing fruit and reproducing, but they do grow. For that reason, the tree is classified as “functionally” extinct, but not extinct. In addition, isolated pockets of the species have been found, or planted, west of the trees’ historical range where the blight has not yet reached.
A Tufted Titmouse sits on the limb of an American chestnut
Red-spotted purple butterfly on an American hybridGray Tree Frog in Chestnut Tree
Will I Ever Get to Eat a Roasted American Chestnut?
While you probably won’t get to have the full roasted chestnuts experience as Robert Wells once did, there is hope for this species and hope that maybe your grandchildren will enjoy them as your great-grandparents once did. Programs at several universities such as the University of Tennessee and the State University of New York along with the USDA, US Forest Service and some non-profits like the American Chestnut Foundation are actively working to bring the species back by either cross pollinating blight-resistant specimens or combining them with more resistant species. You can learn more about these efforts toward resilient chestnuts by exploring the sources below.
Ho ho ho,
Mike
Mike Conway is a part-time freelance writer who lives with his wife, kids, and dog Smudge (pictured) in Northern Virginia.
You’ve never heard of Pando? Neither had I, till Paula Phipps here at Bio4Climate suggested it as a Featured Creature!
Pando is a 108-acre forest of quaking aspens in Utah, thousands of years old, in which all of the trees are genetically identical! These trees are all branches on a shared root system that is thousands of years old, so the whole forest is one single organism!
Known as the “Trembling Giant,” Pando is more than just your average arbor. It’s so unique it has a name. In a sense, Pando “redefines trees,” says Lance Oditt, who directs the nonprofit Friends of Pando (you will see his name on some of the photos in this piece). Pando also has symbolic significance to many people. Former First Lady of California Maria Shriver puts it this way: “Pando means I belong to you, you belong to me, we belong to each other.”
Aerial outline of Pando, with Fish Lake in the foreground. Lance Oditt/Friends of Pando (Wikimedia Commons)
Pando (Latin for “I spread”) is a single clonal organism, i.e., it is one unified plant representing one individual male quaking aspen (Populus tremuloides). This living organism was identified as a single creature because its parts possess identical genes with a unitary massively-interconnected underground root system. This plant is located in the Fremont River Ranger District of the Fishlake National Forest in south-central Utah, United States, around 1 mile (1.6 km) southwest of Fish Lake. Pando occupies 108 acres (43.6 ha) and is estimated to weigh collectively 6,000 tonnes (6,000,000 kg), making it the heaviest known organism on earth.
Its age has been estimated at between 10,000 and 80,000 years, since there is no way to assess it with any precision due to the irrelevance of branch core samples to the age of the whole creature. Its size, weight, and prehistoric age have given it worldwide fame. These trees not only cover 108 acres of national forestland, but weigh a shocking six million kilograms (13 million pounds). This makes Pando the most massive genetically distinct organism. However, the title for the largest organism goes to “the humongous fungus,” a network of dark honey fungus (Armillaria ostoyae) in Oregon that covers an amazing 2,200 acres. I had no idea such single living organisms could exist! I was instantaneously intrigued, and wanted to learn more about this curious entity.
Deer eating Pando shoots. (Lance Oditt/Friends of Pando)
Pando is also in trouble, because older branches (since it is not composed of individual “trees” despite its appearance, but sprouts from one extensive root system) are not being replaced by young shoots to perpetuate the organism. The reason is difficult to determine, between issues of drought, human development, aging, excessive grazing by herbivores (cattle, elk and deer), and fire suppression (as fire benefits aspens). The forest is being studied, and fencing has been put up around most of the area to prevent browsing animals from entering the forest and eating up the young shoots sprouting from this unified root system. Scientists believe that both the ongoing management of this area and uncontrolled foraging by wild and domestic animals have had deeply adverse effects on Pando’s long-term resilience. Overgrazing by deer and elk has become one of the biggest worries. Wolves and cougars once kept the numbers in check of these herbivores, but their herds are now much larger because of the loss of such apex predators. These game species also tend to congregate around Pando as they have learned that they are not in any danger of being hunted in this protected woodland.
An Epic History
Despite its fame today, the Pando tree was not even identified until 1976. The clone was re-examined in 1992 and named Pando, recognized as a single asexual entity based on its morphological characteristics, and described as the world’s largest organism by weight. In 2006 the U.S. Postal Service honored the Pando Clone with a commemorative stamp as one of the “40 Wonders of America.”
Genetic sampling and analysis in 2008 increased the clone’s estimated size from 43.3 to 43.6 hectares. The first complete assessment of Pando’s status was conducted in 2018 with a new understanding of the importance of reducing herbivory by mule deer and elk to protect the future of Pando. These findings were also reinforced with further research in 2019. But Pando is constantly changing its shape and form, moving in any direction the sun and soil conditions create advantages. Any place a branch comes up is a new hub that can send the tree in a new direction. If you visit the tree and see new stems, you are witnessing the tree moving or “spreading” out in that direction.
Botanists Burton Barnes and Jerry Kemperman were the first to identify Pando as a single organism after examining aerial photographs and conducting land delineation (basically, tracking its borders). They revealed their groundbreaking discovery in a 1976 paper.
Today, perhaps the person who knows the most about Pando’s genetics is Karen Mock, a molecular ecologist at Utah State University in Logan. She and three other scientists ground the aspen’s leaves into a fine powder and then extracted DNA from the dried samples. “When we started our research, I was expecting that it wouldn’t be one single clone,” as is the case with other systems, Mock says. “I was wrong. Pando is a ginormous single clone.” They published their findings in a 2008 study. The group also confirmed that this quaking giant is male, creates pollen and constantly regenerates itself by sending new branches up from its root system in a process called “suckering.”
“The original seed started out about the same size as an aphid,” Mock says. “It’s tiny, and to think that it started this one little tree, its roots spreading and sending up suckers to become one vast single clone.” For context, Pando’s current size is about 10-11 times bigger than that!
Their research has forever changed the way that the scientific community approaches Pando and helped raise public awareness of this unique clone growing in southern Utah while providing it additional protection. For example, Friends of Pando has fixed numerous broken fences that were allowing deer access to the tree.
A wintry vista on Monroe Mountain gives us an idea of what the land the Pando Seed sat down in may have looked like (Lance Oditt/Friends of Pando)
Speculating about how Pando started, biologists have woven a rough image of its early origins. They describe Pando as a tree that transcends nearly every concept of trees and natural classifications we have today. Pando is simultaneously the heaviest tree, the largest tree by land mass, and the largest quaking aspen (Populus tremuloides). A masterpiece of botanical imagination, how Pando came to be is even more improbable than the challenge of classifying it. One possibility is that on one of the first warm spring days of the year, thousands of years after the last ice age, a single Aspen seed floating 9,000 feet in the sky came to rest on the southeastern edge of the Fishlake Basin, a land littered with massive volcanic boulders, split apart along an active fault line, carved by glaciers, littered with mineral rich glacial till and shaped by landslides and torrential snow melts that continue to this day.
But what would appear to be a wasteland to the untrained eye made for a perfect home for the Pando seed. This was a prime location along the steep side of a spreading fault zone that provides water drainage to the lake below and a barren landscape with rich soil laid down by glaciers. Therefore this was a place where the light-hungry Pando seed would face no competition for sunlight. Underground, a tumultuous geologic landscape favored Pando’s sideways moving roots system over other native trees that prefer to dig down.
If we were to see the first branch of Pando, we might think nothing of it, not knowing what was in store for this organism with the ability to grow up to 3 feet per year. Those first years, any number of disasters could have destroyed the tree altogether.
In fact, for Pando to exist at all, at least one disaster likely set the tree on a new course that created the tree we know today. As a male tree, Pando only produces pollen so, to advance itself over the land, Pando has to replicate itself by sending up new stems from its root, a process called suckering. Probably at some time during those first 150 years of Pando’s life, something disrupted the growth hormones underground and within its trunk, creating an imbalance so Pando began to sucker. Although there’s no way to tell what that force was, we do know that was the moment Pando started to self-propagate, to spread both across the land and toward us in time. And today, that one tree has become a lattice-work of roots and stems that a rough field estimate indicates would conceivably be able to stretch as far as 12,000 miles or about halfway around the world.
Opinions do seem to vary on different estimates of Pando’s real weight and age. One source said Pando’s collective weight was 13 million pounds, double the estimate stated above, with the root system of these aspens believed to have been born from a single seed at the end of the last major ice age (about 2.6 million years ago). As we cannot measure Pando’s true age, we are left with intelligent guesses. This reminds me of what I often jestfully say might be an academic’s ideal state of mind, to be “unencumbered by facts or information and thus free to theorize”!
While Pando is the largest known aspen clone, other large and old clones exist, so Pando is not totally unique. According to a 2000 OECD report, clonal groups of Populus tremuloides in eastern North America are very common, but generally less than 0.1 hectare in size, while in areas of Utah, groups as large as 80 hectares have been observed. The age of this species is difficult to establish with any precision. In the western United States, some argue that widespread seedling establishment has not occurred since the last glaciation, some 10,000 years ago, but some biologists think these western clones could be as much as 1 million years old.
Pando encompasses 108 acres, weighs nearly 6,000 metric tons, and has over 40,000 stems or trunks, which die individually and are replaced by new stems growing from its roots. The root system is estimated to be several thousand years old with habitat modeling suggesting a maximum age of 14,000 years, but others estimate it as much older than that. Individual aspen stems typically do not live beyond 100–130 years and mature areas within Pando are approaching this limit. Indeed, the worry is that there are so few younger stems surviving that the whole organism is being placed at risk. This is why the scientists are trying to restrict herbivore access to this protected area.
A 72 year aerial photo chronosequence showing forest cover change within the Pando aspenclone. Base images courtesy of USDA Aerial Photography Field Office, Salt Lake City, Utah
This ancient giant, however, has been shrinking since the 1960s or 70s. This timing is no coincidence. As human activity has grown in the western United States, so has our impact on the surrounding ecosystems. The biggest factor behind this shrinking is a lack of “new recruits.” The shoots that form from Pando’s ancient rootstock are not making it to maturity. Instead, they are being eaten while they are still small, soft, and nutritious. Mule deer are the main culprits. Cattle are also allowed to browse in this forest for brief intervals every year, and the combined herbivory has thwarted Pando’s efforts to keep up with old dying trees.
These changes have led to a thinning of the forest. One study used aerial imagery to identify these changes, showing that Pando isn’t regenerating in the way that it should. Researchers assessed 65 plots that had been subjected to varying degrees of human efforts to protect the grove: some plots had been surrounded by a fence, some had been fenced in and regulated through interventions like shrub removal and selective tree cutting, and some were untouched. The team tracked the number of living and dead trees, along with the number of new stems. Researchers also examined animal feces to determine how species that graze in Fishlake National Forest might be impacting Pando’s health.
The problem is that with enough loss of old trees, the grove will lose its ability to regenerate. A dense forest can feed its roots with fuel from photosynthesis, and is able to send up new shoots regularly. But as it loses leaves and their photosynthetic capability, it can start to shrink.
A map showing the extent of Pando as well as recent fencing installations to protect its growth Image courtesy of Paul Rogers and Darren McAvoy, St. George News
As part of this new study, the team analyzed aerial photographs of Pando taken over the past 72 years (see previous image above with photos from 1939 to 2011). These impressions drive home the grove’s dire state. In the late 1930s, the crowns of the trees were touching. But over the past 30 to 40 years, gaps begin to appear within the forest, indicating that new trees aren’t cropping up to replace the ones that have died. And that isn’t great news for the animals and plants that depend on the trees to survive, researcher Paul C. Rogers said in a statement.
Fortunately, all is not lost. There are ways that humans can intervene to give Pando the time it needs to get back on track, among them culling voracious deer and putting up better fencing to keep the animals away from saplings. As Rogers says, “It would be a shame to witness the significant reduction of this iconic forest when reversing this decline is realizable should we demonstrate the will to do so.”
Though it seems easy to blame these changes on deer, the real blame still lies with us humans. Throughout the 20th century, deer populations have been hugely impacted by humans. Human impacts on ecosystems are complex and far-reaching. A major problem is the lack of apex predators in the area; in the early 1900s, humans aggressively hunted animals like wolves, mountain lions and grizzly bears, which helped keep mule deer in check. And much of the fencing that was erected to protect Pando isn’t working: mule deer, it seems, are able to jump over the fences. So we need to monitor all ecosystems to understand how they respond to human activity if we are to minimize damage, and take steps to compensate for the imbalances we create.
The aspen clone is one of the largest living organisms on the planet. (Lance Oditt/Friends of Pando)
Though it is hotly contested by ranchers wanting to protect their cattle, wolf reintroduction is ongoing in the West. Hunting is also regulated by federal and state agencies, which artificially adjust deer populations. The effects of these changes are not always immediately apparent. Forest managers do their best to replicate historical levels and manage new threats.
However, we lack good historical data on herbivory in Pando or many other surrounding areas. Controlling herbivory with more hunting is one remedial option. Reduced cattle grazing in the grove has also been suggested by researchers.
Reproduction and Threats
As mentioned, the asexual reproductive process for this entity is not like that of a regular forest. An individual stem sends out lateral roots that, under the right conditions, send up other erect stems which look just like individual trees. The process is then repeated until a whole stand, of what appear to be individual trees, forms. These collections of multiple stems, called ramets, all together form one, single, genetic individual, usually termed a clone. Thus, although it looks like a woodland of individual trees, with striking white bark and small leaves that flutter in the slightest breeze, they are one entity all linked together underground by a single complex system of roots.
Lance Oditt demonstrates how to use a 360-degree camerafor the Pando Photographic Survey. As of July, Oditt and his team had taken around 7,300 photos (Credit: Tonia Lewis)
A healthy aspen grove can replace dying trees with young saplings. As dying trees clear the canopy, more sunlight makes it to the forest floor, where young shoots can take advantage of the opening to rapidly grow. This keeps the forest eternally young, cycling through trees of all ages, as new clonal stems start growing, but when grazing animals eat the tops off newly forming stems, they die. This is why large portions of Pando have seen very little new growth.
The exception is one area that was fenced off a few decades ago to remove dying trees. This area excluded elk and deer from browsing and thus has experienced a successful regeneration of new clonal stems, with dense growth referred to as the “bamboo garden.”
Some other amazing features of Pando rise from the way aspens grow and develop. In Canada, aspen have earned the nickname “asbestos forests” as they have two unique characteristics that make them more fire tolerant. Aspen store massive quantities of water, allowing them to thwart low and medium intensity fires by simply being less flammable. They also do not create large quantities of flammable volatile oils that can make their conifer cousins so fire prone. Second, their branches reach high rather than spreading densely at the base, allowing them to avoid catching flame from fires that move over the land below.
Living where the growing season is short and winters are harsh, Pando features another advantage over other trees. It contains chlorophyll in its bark which allows it to create energy without leaves during the dark, cold winter months. Although this process is nowhere near as efficient as the energy production of the leaves in summer, this small energy boost allows Pando to get a head start by surging into bloom once temperatures reach 54 degrees for more than 6 days each spring.
However, the older stems in Pando are affected by at least three diseases: sooty bark canker, leaf spot, and conk fungal disease. While plant diseases have thrived in aspen stands for millennia, it is unknown what their ongoing ecosystemic effects might be, given Pando’s lack of new growth and an ever-increasing list of other pressures on the clonal giant, including that of climate change. Pando arose after the last ice age, so has had the benefit of a largely stable climate ever since, but that stability may be changing enough to endanger Pando’s long-term survival.
A scientist can plug in the metadata of a particular tree within the clone and be taken directly to that tree without having to navigate the entire forest virtually. (Intermountain Forest Service, USDA Region 4 Photography (Public domain via Wikimedia Commons)
Insects such as bark beetles and disease such as root rot and cankers attack the overstory trees, weakening and killing them. A lack of regeneration combined with weakening and dying trees, in time, could result in a smaller clone or a complete die-off. So the Forest Service in cooperation with partner organizations are working together to study Pando and address these issues. Over the years, foresters have tested different methods to stimulate the roots to encourage new sprouting. Research plots have been set up in all treated areas to track Pando’s progress, as foresters learn from Pando and adapt to their evolving understanding.
With regard to our changing climate, Pando inhabits an alpine region surrounded by desert, meaning it is no stranger to warm temperatures or drought. But climate change threatens the size and lifespan of the tree, as well as the whole complex ecosystem that it hosts. Aspen stands in other locations have struggled with climate-related pressures, such as reduced water supply and heat spells, all of which make it harder for these trees to form new leaves, which lead to declines in photosynthetic coverage and the continued viability of this amazing organism.
With more competition for ever-dwindling water resources (the nearby Fish Lake is just out of reach of the tree’s root system), with summertime temperatures expected to continue to reach record highs, and with the threat of more intense wildfires, Pando will certainly have to struggle to adjust to these fast-changing conditions while maintaining its full extent and size.
Age Estimates for Pando
Due to the progressive replacement of stems and roots, the overall age of an aspen clone cannot be determined from tree rings. In Pando’s case, ages up to 1 million years have therefore been suggested. An age of 80,000 years is often given for Pando, but this claim has not been verified and is inconsistent with the Forest Service‘s post ice-age estimate. Glaciers have repeatedly formed on the Fish Lake Plateau over the past several hundred thousand years and the Fish Lake valley occupied by Pando was partially filled by ice as recently as the last glacial maximum, about 20,000 to 30,000 years ago. Consequently, ages greater than approximately 16,000 years require Pando to have survived at least the Pinedale glaciation, something that appears unlikely under current genetic estimates of Pando’s age and the likely variation in Pando’s local climate.
Its longevity and remoteness have enabled a whole ecosystem of 68 plant species and many animals to evolve and be supported under its shade. However, this entire ecosystem relies on the aspen remaining healthy and upright. Though Pando is protected by the US National Forest Service and is not in danger of being cut down, it is in danger of disappearing due to several other factors and concerns, as noted above.
Estimates of Pando’s age have also been affected by changes in our understanding of aspen clones in western North America. Earlier sources argued germination and successful establishment of aspen on new sites was rare in the last 10,000 years, implying that Pando’s root system was likely over 10,000 years old. More recent observations, however, have disproved that view, showing seedling establishment of new aspen clones as a regular occurrence, especially on sites exposed to wildfire.
More recent research has documented post-fire quaking aspen seedling establishment following the 1986 and 1988 fires in Grand Teton and Yellowstone National Parks, respectively, where seedlings were concentrated in kettles and other topographic depressions, seeps, springs, lake margins, and burnt-out riparian zones. A few seedlings were widely scattered throughout the burns. Seedlings surviving past one season occurred almost exclusively on severely burned surfaces. While these findings haven’t led to a conclusive settling of Pando’s age, they do leave us with much to marvel over in this species’ longevity and history.
“Geologic Map of Fishlake Basin in Utah. Inset, an illustration of a Graben shows forces that continue to shape the land today.” (Friends of Pando)
Pando’s Uncertain Future
Pando is resilient; it has already survived rapid environmental changes, especially when European settlers arrived in the area in the 19th century, and after the rise of many intrusive 20th-century recreational activities. It has survived through disease, wildfires, and too much grazing before. Pando also remains the world’s largest single organism enjoying close scientific documentation. Thus, in spite of all these concerns, there is reason for hopefulness as scientists are working to unlock the secrets to Pando’s resilience, while conservation groups and the US Forest Service are working diligently to protect this tree and its associated ecosystem. A new group called the Friends of Pando is also making this tree accessible to virtually everyone through a series of 360˚ video recordings.
If you were able to visit Pando in summertime, you would walk under a series of towering mature stems swaying and “quaking” in the gentle breeze, between some thick new growth in the “bamboo garden,” and even venturing into charming meadows that puncture portions of the otherwise-enclosed center. You would see all sorts of wildflowers and other plants under the dappled shade canopy, along with lots of pollinating insects, birds, foxes, beaver, and deer, all using some part of the rich ecosystem created by Pando. In the summer the green, fluttering leaves symbolize the relief from summer’s heat that you get coming to the basin. In autumn the oranges and yellows of the leaves as they change color give a hint of the fall spectacular that is the Fish Lake Basin. All this can give us a renewed appreciation of how all these plants, animals, and ecosystems are well worth defending. And with respect to Pando, we can work to protect all three.
But attempts to do so have had some surprising consequences that were quite unexpected. When land managers, recognizing the stress that Pando was under from herbivores, fenced off one part of the stand to protect it from browsing, they split the grove into three parts: an unfenced control zone, an area with a fence erected in 2013, and another area that was first fenced in 2014. The 2014 fence was built from older materials to save money. This fence quickly fell into disrepair, such that mule deer could easily get around it until it was repaired in 2019. As a result, though they did not design it this way, managers had effectively created three treatment zones: a control area, a browse-free zone, and an area that experienced some browsing between 2014 and 2019. Unfortunately, these good intentions confused Pando. In 2021, it appeared that Pando was fracturing into three separate forests. With only 16 percent of the fenced area effectively keeping out herbivores, and over half of Pando without fencing, a single organism was effectively cut into 3 separate parts and exposed to varying ecological pressures.
The diverging ecologies of the world’s largest living organism, an aspen stand called Pando. Credit: Infographic Lael Gilbert
Bottom of Form
As Rogers explained, “Barriers appear to be having unintended consequences, potentially sectioning Pando into divergent ecological zones rather than encouraging a single resilient forest.” So not only does the stubborn trend of limited stand replacement persist in Pando, but by applying three treatments to a single organism, we also encouraged it to fracture into three distinct entities. The stumble makes sense; it is hard to understand whether fencing will work unless we compare the treatment to a control group. But the strategy does show our failing to understand Pando as one entity. After all, we would not apply three treatments to a single human. These surprising outcomes fuel vital learning experiences for researchers.
Furthermore, it may be that fencing Pando is not a solution to its regeneration problems. While unfenced areas are rapidly dying off, fencing alone is encouraging single-aged regeneration in a forest that has sustained itself over the centuries by varying growth. While this may not seem critical, aspen and understory growth patterns at odds from the past are already occurring, said Rogers. In Utah and across the West, Pando is iconic, and something of a canary in the coal mine.
As a keystone species, aspen forests support high levels of biodiversity—from chickadees to thimbleberry. As aspen ecosystems flourish or diminish, myriad dependent species follow suit. Long-term failure for new recruitment in aspen systems may have cascading effects on hundreds of species dependent on them.
Additionally, there are aesthetic and philosophical problems with a fencing strategy, said Rogers. “I think that if we try to save the organism with fences alone, we’ll find ourselves trying to create something like a zoo in the wild,” said Rogers. “Although the fencing strategy is well-intentioned, we’ll ultimately need to address the underlying problems of too many browsing deer and cattle on this landscape.”
Pando’s Songs?
“Microphones attached to Pando”. Photo Credit: Jeff Rice
Lance Oditt, Executive Director of Friends of Pando, is always searching for better ways to get his head around a tree this enormous. And he started wondering: “What would happen if we asked a sound conservationist to record the tree? What could a geologist, for example, learn from that, or a wildlife biologist?” So, Oditt invited sound artist Jeff Rice to visit Pando and record the tree.
“I just dove in and started recording everything I could in any way that I could,” says Rice, after making his pilgrimage to the mighty aspen. Rice says his sound recordings aren’t just works of art. “They also are a record of the place in time, the species and the health of the environment,” he says. “You can use these recordings as a baseline as the environment changes.” The wonders of science and curiosity never cease, do they?
In mid-summer, the aspen’s leaves are pretty much at their largest. “And there’s just a really nice shimmering quality to Pando when you walk through it,” says Rice. “It’s like a presence when the wind blows.” So that’s what Rice wanted to capture first — the sound of those bright lime green leaves fluttering in the wind. He then attached little contact microphones to individual leaves and was treated to a unique sound in return. The leaves had “this percussive quality,” he says. “And I knew that all of these vibrating leaves would create a significant amount of vibration within the tree.” Rice then set out to capture that tree-wide vibration in the midst of a thunderstorm. “I was hunkered down and huddling, trying to stay out of the lightning. When those storms come through Pando, they’re pretty big. They’re pretty dramatic.” All that wind blowing through the innumerable leaves offered Rice a sonic opportunity to record the tree.
A hydrophone was placed in contact with the roots of a tree (or “stem”) in the Pando aspen forest in south-central Utah. The sound captures vibrations from beneath the tree that may be emanating from the root system or the soil. The recording was made during a July 2022 thunderstorm and represents perhaps millions of aspen leaves trembling in the wind. It was made by Jeff Rice as part of an artist residency with the non-profit group Friends of Pando. Rice gives special thanks to Lance Oditt for his help in identifying recording locations, including the mysterious “portal to Pando.”
“We found this incredible opening in one of the [stems] that I’ve dubbed the Pando portal,” he says. Into that portal, he lowered a mic until it was touching the massive tangle of roots below. “As soon as the wind would blow and the leaves would start to vibrate,” Rice says, “you would hear this amazing low rumble.” The vibrations, he says, were passing through Pando’s branches and trunks into the ground. “It’s almost like the whole Earth is vibrating,” says Rice. “It just emphasizes the power of all of these trembling leaves, the connectedness, I think, of this as a single organism.” Rice and Oditt presented these recordings at an Acoustical Society of America meeting in Chicago.
“Field Technicians Rebekah Adams and Etta Crowley take vegetation measurement under Pando, the world’s largest living organism. A recent evaluation of the massive aspen stand in south-central Utah found that Pando seems to be taking three disparate ecological paths based on how the different segments are managed.” Credit: Paul Rogers
“This is the song of this ecosystem, this tree,” says Oditt. “So now we know sound is another way we can understand the tree.” In fact, the recordings have given Oditt research ideas, like using sound to map Pando’s labyrinth of roots. But above all, they’re a sonic snapshot of this leviathan at this moment in time. “We have to keep in mind,” says Oditt, “that it’s been changing shape and form for like 9000 years. I call it the David Bowie problem. It’s constantly reinventing itself!” And now, we’ve turned up the volume to hear Pando as the baritone soloist it has always been.
Pando as Teacher and Metaphor
Pando is seen as an inspiring symbol of our connectedness, in many engaging statements found here. I put just a few of them below, to give you the idea of how various people have reacted to Pando and its potential significance.
From The Rev. Ed Bacon, Former Senior Rector, All Saints Church, Pasadena, and Board Member, Pando Populus:
“‘We are already one but we imagine that we are not.’ Thomas Merton said those words just before his accidental death. A few months earlier in 1968, Dr. Martin Luther King in his last Sunday sermon notes that the ‘universe is constructed’ in an interdependent way: my destiny depends on yours. If there is one truth that will see us through whatever threats and chaos lie before us, it is that there will be no future without policies and attitudes based in the kind of Oneness we see in the one-tree Forest, Pando.”
FromJohn B. Cobb, Jr., Member, American Academy of Arts and Sciences, and Board Chair, Pando Populus:
“The one-tree forest we call Pando is a community. The health and well-being of every tree contributes to the whole of the root system and lives from it. But does it make sense today for Pando to be the symbol of what we aspire to in this country, when there are such intense political feelings and competing fears? Yes, it is in just such circumstances that seeking community is most important. If you are in any of the country’s opposing camps, you can begin by formulating the way people in other camps view the world and you. You do not have to agree. But if you understand why so many people feel so disturbed and even threatened by you and your values and beliefs, you have the beginning of community. Even that beginning might save us from the worst.”
From Paul Rogers, Chief Scientist for the Pando Aspen Clone and Director of the Western Aspen Alliance:
“In recent decades resource misuse – comorbid to a warming planet – have left a long-thriving colossus gasping for breath. In Pando, as in human societies, it is easy to forget vital relations between individuals and communities. Impulses are shared as mortality portends rebirth. Vast root networks maintain a single immense colony: e pluribus unum. Pando’s 47,000 stems with enumerable variation remain linked by DNA. Humans, though genetically distinct, are joined by need, desire, and innate dependence on Mother Earth. Pando’s paradox implores us to mutually foster communities and individuals. He is the trembling giant. She is the nurturing spring.”
From Devorah Brous, environmental consultant:
“To foster wholesale systems change, go to the roots. We gather in a sacred grove and branch out to feed shared roots – as descendants of colonizers and the colonized. We break bread as formerly enslaved peoples and enslavers, as immigrants, as indigenous peoples, as refugees. As ranchers and vegans. As scientists and spiritualists. As non-binary changemakers, and established clergy. As creatives, pioneers, and politicians. To study the known and unknown teachings of the trees – we sit still under a canopy of stark differences and harvest the nature of unity. We quest to feed and water a dying tree of life.”
* * * * *
I’ve written such a lengthy piece about Pando because it has so many fascinating and unusual characteristics. Who could ever imagine all the wondrous things that Nature creates? I think Her endless spontaneity in developing biodiverse life-forms is a truly intriguing phenomenon that motivates so many of our ‘Featured Creature’ essays. And exploring them is such an interesting process. We learn new aspects of Nature’s mysteries every time. Perhaps Pando has additional lessons for us as well!
So let us continue to root for this amazingly unified tree named Pando…
Fred
Fred is from Ipswich, MA, where he has spent most of his life. He is an ecological economist with a B.A. from Harvard and a Ph.D. from Stanford, both in economics. Fred is also an avid conservationist and fly fisherman. He enjoys the outdoors, and has written about natural processes and about economic theory. He has 40 years of teaching and research experience, first in academics and then in economic litigation. He also enjoys his seasonal practice as a saltwater fly fishing guide in Ipswich, MA. Fred joined Biodiversity for a Livable Climate in 2016.
What creature preys on ants and other insects, invading their bodies, seizing control of their minds, and killing them off to reproduce, all the while inspiring zombie stories that terrify us humans?
Welcome to Zombie Ant Fungus, or Ophiocordyceps Unilateralis!
Photo from Encyclopedia Britannica
One of the most amazing things about being in touch with the natural world is the uncontained sense of wonder that infuses us as we learn about the incredible range of biodiversity out there to be discovered. My recent pieces on Mantis Shrimp and Ghost Pipes are good examples of diversity and symbiosis, while this curious creature shows off the parasitic side of interspecies relationships. Ophiocordyceps unilateralis, commonly known as Zombie Ant Fungus, is an insect-pathogenic fungus, discovered by the British naturalist Alfred Russel Wallace in 1859, and currently found mostly in tropical forest ecosystems.
The Zombie Ant Fungus is like no other creature I know; it’s like a runaway horror movie that even ants shall encounter with fear, and try their best to avoid. Its story is intriguing and represents scary stuff. Indeed, this strange creature is featured in two books by M. R. Carey called The Girl with All the Gifts and The Boy on the Bridge, as well as in a video game and show, The Last of Us, which recently wrapped up its first season to critical acclaim. In that feature, humans struggle to survive after an infectious fungus turns us into zombies largely in the style of Ophiocordyceps.
Who knew that such an innocent seeming creature could become so devious and troublesome? Is there anywhere for us to hide? We need not worry. This pathogen can’t transfer to us, or at least to do so would take many millions of years. So I guess we can relax…
Photo from Shutterstock
There are some major differences between how the fungus is portrayed in shows like The Last of Us and in real life. Cordyceps does not typically infect other hosts through the mouth, and the infected aren’t connected to each other through a network.
Most importantly, the fungus cannot infect humans, because our body temperatures are too high for most of them. Phew! In fact, people have been eating Cordyceps for centuries now without turning into zombies. It’s a traditional Chinese medicine, used to treat kidney disease and other ailments. So let’s set aside these worries, and get back to the reality of these intriguing creatures.
Photo from the New York Times
A Sinister Cycle
These fungi live in jungle habitats, such as in tropical forests, where a species of carpenter ant, Camponotus Leonardi, lives in the high canopy and has an extensive network of aerial trails. But sometimes the canopy gaps are too far apart and difficult to cross, so the ants’ trails descend to the forest floor where they are exposed to Zombie Ant Fungus (Ophiocordyceps unilateralis) spores.
The spores attach to these ants’ exoskeletons and break through, invading its host’s body as a parasite. Like other fungi pathogenic to insects in the genus Ophiocordyceps, this fungus targets a specific host species, in this case the carpenter ant. However, this fungus may also parasitize other closely related species of ants or other insects, though these come with lesser degrees of host manipulation and reproductive success. Some of this fungus’ subspecies, such as Ophiocordycepssinensis, colonizes ghost moth caterpillars instead of carpenter ants and erupts from their head like a unicorn horn.
Check out the sprouting phenomenon taking place in an infected bullet ant:
As in zombie lore, there’s an incubation period where infected ants appear quite perfectly normal and go about their business undetected by the rest of the colony. First, the spore infects the ant and fungal cells start growing inside its body with no notable effects from the outside. But eventually, the infected ant stops participating in the foraging efforts of the colony and stops communicating well with its nest-mates. Then the ant becomes hyperactive and departs from the daily rhythms of the other ants.
Most carpenter ants, for example, forage during the nighttime, but the infected ant basically becomes active all the time. That’s unusual because social insects like ants usually have something called “social immunity”, where sick members get kicked out of the group to prevent the rest from becoming infected by them. Unfortunately, some ants don’t always employ this mechanism to effectively protect themselves from Ophiocordyceps.
While the infection is 100 percent lethal, the goal of this fungus isn’t to convert all the ants into the walking dead. For ecosystems to stay balanced, these fungi tend to keep host populations in check by usually only infecting a few ants in a local colony at any given time, though they also have been known to wipe out entire colonies of ants at times.
Dead Adult Calyptrate Fly by a fungus of the Genus Ophiocordyceps Photo from Getty Images / iStockphoto
This particular species of Zombie Ant Fungus drops its spores in the jungle on ants and takes sufficient control of them that they leave their nest and fellow ants to climb up off the jungle floor to a height of exactly 10 inches (25 cm) where the conditions are just right for the fungus to thrive and propagate.
The designated victim then attaches to the underside of a leaf with its mandibles while the fungus grows inside its host and sprouts a tiny mushroom-like growth. This fruiting body of fungus eventually distributes its spores to continue this cycle of propagation, infecting more ants in turn in a manner that is capable of infecting entire ant colonies.
Spread through Time and Space
This species shows some morphological variations due to its wide geographic range from Japan to the Americas. This may result from host-specific commitments to diverse species of ants in different areas, and helps avoid subspecies competition by occupying distinct ecological niches.
Photo from Wired
Ophiocordyceps also appears to be an ancient creature. In 2010, scientists identified a 48-million-year-old fossil of a Zombie Ant with a death grip on a leaf, verifying that zombifying fungi have been around for a while. But this fossil didn’t offer hints on how the fungus evolved.
Further work concluded that all Ophiocordyceps species descended from a common ancestor which started out by infecting the larvae of beetles that lived in rotting logs. When the beetle eggs hatched, the larvae crawled around alone inside the log, chewing on wood. When beetle larvae came into contact with a spore, the fungus would then invade the insect’s body to feed on its muscle, killing the beetle without any zombie drama. After that, the fungus would grow its stalk and spread spores around the dead body. Other larvae crawling inside the log were thus infected, prolonging this cycle of life and death.
Schematic representation of the ant behavioral manipulation caused by natural products secreted by Ophiocordyceps unilateralis from Wikipedia
The theory is that millions of years ago, the fungi got picked up by ants that also lived in logs. In their new ant hosts, the fungus had already acquired an ability to feed on muscles, grow stalks and spread.
But these ants brought a new challenge, because, unlike solitary beetles, ants live in crowded nests. Diseases can wipe out an entire colony, so the ants ruthlessly attack any individuals that show signs of sickness. This meant that Ophiocordyceps could not spread the way it had in beetles, just by killing its host and sending out spores. However, by keeping ant hosts healthy enough as they were being parasitized, the invasive fungus could zombify the ant host to move it out of the main nest of ants and climb up a nearby plant, from which it could spread its spores to other potential hosts.
This is how the fungi’s transition to ants set off an evolutionary explosion. Once Ophiocordyceps had evolved to live in one species of ant, it began hopping to other new species. It is also suspected that there are hundreds of other species of Ophiocordyceps still to be discovered, perhaps with a wider range of potentially infectious impact…
Photo from Live Science
Growth by Infection
When the fungus infects a carpenter ant, it grows through the insect’s body, draining it of nutrients and hijacking its mind and behavior. Over the course of a week, it compels the ant to leave the safety of its nest and ascend a nearby plant stem. When this fungus invades the ant, taking over its muscles and mandibles, there is apparently no intervention into the ant’s brain itself.
The invasive fungus forces the ant to permanently lock its mandibles around a major vein on the underside of a leaf to attach itself. The ant then loses control of its mandible and remains fixed in place, hanging upside-down on the leaf. This lockjaw trait is popularly known as the “death grip” and is essential in the fungus’s lifecycle. This “death grip” prevents the ant from falling as it dies hanging upside down, thus enabling the proper growth of the fungus’ fruiting body. The “death grip” is thought to be caused by a secretion of fungal compounds that atrophies the ant’s mandibular muscles, making it impossible for the ant to unclench.
Mandibular “Death Grip” (Photo by Katja Schultz from Flickr)
Once the ant is in place on the leaf’s underside, more fungal mycelia sprout, securely anchoring it to the plant substrate while secreting antimicrobials to ward off any other competitive fungi. Next, the fungus sends a lengthy growth through the ant’s head, growing into a bulbous capsule full of spores on a single, wiry yet pliant, darkly pigmented stalk rising through the back of the ant once it is dead.
This spore-bearing sexual structure appears as a bulge on the stalk, below its tip, which forms the fungus’ fruiting body. As the ant typically climbs onto a leaf that overhangs its colony’s foraging trails, its fungal spores will then rain down upon fellow ants below, ensuring that the cycle continues.
How to Create a Zombie: The View from the Inside
How this fungus takes over its host has been carefully analyzed. Once spores drop onto an ant, they attach to the ant’s exoskeleton and eventually break through it with mechanical pressure and the help of enzymes. Yeast stages of the fungus spread throughout the ant’s body and apparently produce compounds that affect the ant’s behavior such that it exhibits irregularly timed full-body convulsions that dislodge it from its canopy nest, dropping it to the forest floor. These infected behaviors work for the benefit of the fungus in terms of its own growth and transmission, increasing its fitness and survivability.
Photo by Andreas Kay
When the fungus first enters its host, it floats around the ant’s bloodstream as single cells, replicating copies of itself. Then, at some point, these single cells join together by building short tubes, which are only seen in fungi that infect plants. Hooked up together in this way, these cells in tubes successfully communicate and exchange nutrients with each other.
The next step is to invade the ant’s muscles, either by penetrating muscle cells or growing into interstitial spaces between these cells. The result is a muscle fiber encircled and drained by a network of interconnected fungal cells in a manner unique to this species, as shown in this brief simulation that represents the process quite clearly.
Zombies that don’t eat brains?
The Zombie Ant Fungus is often described as a single entity, which corrupts and subverts a host. But this fungus can also be seen as a colony, much like the ants it targets. Individual microscopic cells begin life alone but eventually come to cooperate, fusing into a superorganism.
Together, these brainless cells can take control of a much larger creature and manipulate its behavior. But perhaps surprisingly, they do that without ever physically entering or touching the brain itself, while infiltrating the ant’s body and muscles, including its head. Thus, this fungus can manipulate its host through a very precise sort of chemically-guided muscular control that does not affect the ant’s brain. This makes the intricacy of the fungal invasion even more compelling and disturbing, depending on how aware the ant is of this intrusive occupation.
Photo from Earthly Mission
Maintaining the Life Cycle
It is worth noting that throughout its lifecycle, the fungus must meet unique challenges in its metabolic activities. First, the fungal pathogen must attach securely to the arthropod exoskeleton and penetrate it – while avoiding or suppressing its host’s defenses – and then control its host’s behavior before killing it. Finally, it must protect the ant’s carcass from microbial and scavenger attack so that it can reproduce successfully.
This invasion process, leading up to the host ant’s mortality, takes 4–10 days, and includes a reproductive stage where fruiting fungal bodies emanate from the ant’s head, eventually rupturing to release fungal spores. However, the short viability of the fungal spores presents a challenge. The fungus uses its host’s vitality to sustain the growth of the fungus’s fruiting body and enable successful reproduction. To do so, this fungus fortifies the ant cadaver to prevent its decay, which consequently ensures the prolonged growth of the fruiting body.
But this composite creature of zombie-ant fungus is, in turn and ironically, susceptible to fungal infection itself. This can limit its impact on ant populations, when it might otherwise devastate entire ant colonies. Ophiocordyceps unilateralis suffers from an unidentified fungal hyperparasite, reported in the press as the “antizombie-fungus fungus,” that results in only 6–7% of the primary parasite’s spores being viable, limiting the damage this fungus can inflict on ant colonies. This hyperparasite attacks Zombie Ant Fungus just as the fungal stalk emerges from the ant’s body, thus stopping the stalk from generating and releasing its spores.
This suppressive effect is caused by the weakening of the fungus by the hyperparasite, which may limit the viability of its infectious spores. There are additional species of fungi that can grant beneficial and protective assistance to the ant colony, as well. A complicated picture indeed!
Dr. João Araújo of the New York Botanical Garden and his team discovered two new genera of fungus. (Photos by João Araújo)
For example, two novel lineages of fungi, each belonging to its own genus, were recently discovered infecting a species of Zombie Ant Fungus in Florida. One puts a fuzzy white coating on the Zombie Ant Fungus, while the other is harder to spot, with little black blobs that look like fleas. The fungi attacking the Zombie Ant Fungus don’t zombify their host, but they do feed on its tissues and appear to cause it harm by castrating the fungus so it cannot shoot its spores any longer. Then the attacker proceeds to grow and consume the entire fungus.
Though these new parasites are the first to be seen to infect the Zombie Ant Fungus, there could be others out there. Parasitism is a lucrative form of lifestyle, experts say; it might even be the most dominant one on the planet! (Maybe our politics illustrate that…)
Ants also can protect themselves by grooming each other to remove microscopic organisms that could potentially harm the colony. Consequently, in host–parasite dynamics, both the host and the parasite are under selective pressure: the fungal parasite evolves to increase its successful transmission for reproduction, while the ant host evolves to avoid or resist the infection by the parasite, in this case the Zombie Ant Fungus. And so an evolutionary battle continues…
A fuzzy white fungus grows on top of the parasitic Zombie Ant Fungus (Photo by João Araújo)
The principal carpenter ant hosts of Ophiocordyceps unilateralis have also evolved adaptive behaviors to limit the contact rate between uninfected and thus susceptible hosts and already infected hosts, thereby reducing the risk of transmission to their healthy fellow ants by evolving efficient behavioral forms of social immunity. As mentioned, the ants clean the exoskeletons of one another to decrease the presence of spores which are attached to their cuticles.
These ants also notice the abnormal behavior that indicates when a member of the colony is infected, resulting in healthy ants carrying infected individuals far away from the colony to avoid fungal spore exposure. Furthermore, since most worker ants remain inside the nest boundaries, only foragers who venture outside are at any significant risk of infection.
In addition, the fungus’s principal host species, the carpenter ant (or Camponotus Leonardi) tries to avoid the forest floor as a defense method by building its nests high in the canopy, with a broad network of aerial trails. These trails occasionally must move down to the ground level, where infection and graveyards occur, due to wide canopy gaps difficult for the ants to cross while staying safely high in the forest canopy. When these trails do by necessity descend to the forest floor, their length on the ground is as short as possible, only 10-18 feet (3-5 m) or so before climbing back up into the canopy. This shows that these ants avoid zones of infection wherever they can. This method of defense appears to be adaptive to this specific threat, as it is not observed in undisturbed forests where the Zombie Ant Fungus is absent.
Photo from the New York Times
When Ophiocordyceps unilateralis-infected ants die, they are generally found in regions containing a high density of ants which were previously manipulated and killed, which are termed “graveyards” of 70-100 feet (20-30 m.) in range. The density of dead ants within these graveyards can vary with climatic conditions, where humidity and temperature influence this fungus’s effects on the host population. It seems that large precipitation events at the beginning and end of the rainy season stimulate fungal development, which leads to more spores being released and ultimately to more individual ant hosts being infected and killed.
The Wide World of Insect Parasites
What we have here is a hostile takeover of a uniquely malevolent kind. Enemy forces invade a host’s body and use that body like a walkie-talkie to communicate with its fellows to influence the brain from afar, while exercising a more direct control over the ant’s muscles like a puppeteer. Once an infection is underway, the neurons in the ant’s body that give it control of its muscles start to die, as this fungus slowly takes over, effectively cutting the host ant’s limbs off from its brain, as it inserts itself in that place, releasing chemicals that control the ant’s muscles. After the fungus enters the ant, it propagates its invasive cells until they surround the host’s brain, at which point the fungus secretes compounds and takes over the ant’s central nervous system, enabling it to manipulate the ant to reach the forest floor and climb up the vegetation.
Photo from How Stuff Works
In this way, the ant ends its life as a prisoner in its own body, with its brain still in the driver’s seat while the fungus has seized control of the steering wheel in a cruel prolonging of the ant’s death in an agony of helpless surrender. The fungus survives and propagates successfully at the cost of these ants in this dark drama.
But not only ants can be infected with these creative parasites.
Much like the microbiome in our own guts, insects contain a whole array of fungal species, of which few have been closely studied, much less flagged for causing behavioral manipulations. Some are known, however.
One example is Entomophthora muscae, which literally means “insect destroyer of the fly” in Greek. It causes infected flies to climb a certain height, glue themselves at the mouth to a plant, and assume an abdomen-up “death pose” that’s optimal for spore dispersal. (Watch the flies turn into zombies here.)
And there’s Massospora cicadina, which pumps its cicada hosts full of hallucinogenic drugs and causes part of their abdomens to fall off. The bare-bottomed cicada then wiggles its way towards death – once again in the interest of spore dispersal.
Could this happen to us? Personally, this whole scenario gives me the willies, leaving me surprisingly sympathetic to these victimized ants and other infected insects, while also being enthralled by a sense of wonder about the endless variety of nature’s solutions to the reproductive urge of species to propagate themselves. Perhaps we humans should become more alert to all these striking opportunities for Mother Nature to assert her ultimate dominance over us. Some scientists believe that, by studying this Zombie Ant Fungus, we can learn a lot more about how the brain works – and how it might be taken over, which is surely some food for dystopian thought.
Photo from Utrecht University
Medicinal Properties
Ophiocordyceps are known in the pharmaceutical world to be a medically important group. These Zombie Ant Fungi (Ophiocordyceps unilateralis) and related species are known to engage in an active secondary metabolism to produce antibacterial substances that protect the fungus-host ecosystem against further pathogens during fungal reproduction.
Because of this secondary metabolism, chemists who study natural products have taken an interest in this species, discovering small molecule agents of potential interest for use as human anti-infective and anticancer agents. These natural products are reportedly being investigated as potential leads in discovery efforts toward the treatment of immune diseases, cancerous tumors, diabetes and high cholesterol levels.
Another species of fungus, Ophiocordycepssinensis, already mentioned above as a parasitic fungus-caterpillar husk combination, is prized in traditional Tibetan and Chinese medicine as an immune booster, cancer treatment, and aphrodisiac.
Moreover, red naphthoquinone pigments produced by Ophiocordyceps unilateralis are used as a dye for food, cosmetic, and pharmaceutical manufacturing processes. Curiously, naphthoquinone derivatives produced by the fungus also show a red color under acidic conditions, and a purple color under basic conditions. These pigments are stable under a wide variety of conditions as well as not being toxic, which makes them applicable both for food coloring and as a dye.
These attributes also make it a prime candidate for antituberculosis testing in TB patients, by alleviating symptoms and enhancing immunity joined with other chemotherapy drugs. So even this seemingly-nasty creature has some benefits for us humans, once we are able to look beyond its fearsome characteristics.
But this is so generally true of the wondrous variety of nature’s creatures such as featured in this series. We look at them through our human eyes, asking what they can do for us, when the whole natural world is swimming along quite well without our help or needing us for anything. The whole system should have our respect, just for including us in its amazing complexity of life forms and how it all works.
So here’s to a totally infectious and all-consuming curiosity!
This year I took two trips – one to Nashville, Tennessee and another to the Northeast, specifically to White Mountain National Forest in New Hampshire (Abenaki Penacook land). Both of these places have more trees than I’m used to in Southern California, so I was instantly amazed by everything that grew throughout these forest wonderlands, especially the turkey tails.
Turkey tails have three scientific names (depending on whom you ask): Trametes versicolor, Coriolus versicolor, and Polyporus versicolor. The common name, turkey tail, derives from the mushroom’s bands that resemble a wild turkey’s tail in color and shape. The ‘versicolor’ in the scientific names refers to the mushroom’s cap and its many colorations, from white, red, orange, to dark brown. This part of the mushroom has a fuzzy texture, almost as if it had tiny hairs all over, and is extremely flexible so you can bend it without breaking it. The ‘trametes’ in one of the scientific names refers to the genus, and the ‘polyporus’ refers to the placement of the pores. Turkey tails are a type of mushroom with pores on their undersides, in contrast to other mushrooms that have gills on their sides.
Polyporous mushrooms tend to grow on dead logs. Turkey tails can be found on fallen trees in nearly every forest worldwide. They grow year-round, but will be extra easy to spot when it’s time to release their spores (in North America, this happens between May and December). You can identify a family of turkey tails by their banding pattern – all the offspring of one individual will sport the same pattern as their ‘parent.’ It’s a fungal fingerprint!
Apart from their colors and tail-like shapes, turkey tails are extra intriguing for their health benefits. They contain numerous properties, including:
Antioxidants, such as phenols and flavonoids, which reduce inflammation and oxidative stress (an imbalance in our systems when we’re unable to detoxify).
Protein-bound polysaccharides (carbohydrates), one being Krestin which promotes immunity to toxins and regulates immune responses. It also activates white blood cells which protect our bodies from harmful bacteria.
Prebiotics, which foster beneficial bacteria. They also regulate our gut microbiome, leading to better digestion and lower cholesterol.
Fiber, found in many mushrooms, which also promotes better digestion.
People who consume turkey tail extract report better athletic performance, less fatigue, and when combined with chemotherapy, increased effectiveness of cancer treatments. By promoting our body’s natural production of beneficial compounds, and counteracting substances that harm us, turkey tails improve overall health when taken as a supplement.
There are some mushrooms you can eat right after foraging, but turkey tails are not one of those. To receive the many benefits from Trametes versicolor, you’ll need some prep work.
Due to the thick and woody structure of turkey tails, they’re extremely difficult to consume and, therefore, essentially inedible. However, when you dry them out and grind them to create a powder, you can reap their benefits in no time. After letting them dry, and cleaning them to ensure no dirt or insects remain, you can grind them up. The resulting powder can be put into capsules to be taken as a pill-based supplement, or you can brew some tea to extract the most beneficial compounds. Other mushrooms require a process that involves alcohol before eating, but not turkey tails!
If you’re feeling creative, you can also add the powder to your everyday meals. Since these mushrooms are relatively plain in flavor, people will add the extract to smoothies, oatmeal, or soup to add taste. The powder can be stored for years as long as it’s in an airtight container and kept in the pantry, away from the heat and sun.
We can thank ancient teachings for these turkey tail tips. Traditional Chinese medicine is the first documented time people practiced the art of extracting beneficial compounds from turkey tails. They originally used the extract to treat lung, liver, and spleen issues.
If you try any of these recipes, let us know your experience (you can email us at staff@bio4climate.org)!
A word of caution: If you do decide to forage, for turkey tails or any other organisms, please do so with consideration for the local ecosystem’s health. Only forage what you need, so as to not exploit natural resources.
It’s also best to forage with others when starting out (and it’s more fun this way!). You could join a local foraging group to gain access to resources regarding ecosystem health and potential contaminants in the area. This way, you can learn how to forage without causing harm to your body, other people, or the landscape.
Tea time, anyone?
Tania Roa
Tania graduated from Tufts University with a Master of Science in Animals and Public Policy. Her academic research projects focused on wildlife conservation efforts, and the impacts that human activities have on wild habitats. As a writer and activist, Tania emphasizes the connections between planet, human, and animal health. She is a co-founder of the podcast Closing the Gap, and works on outreach and communications for Sustainable Harvest International. She loves hiking, snorkeling, and advocating for social justice.
Slime molds are eukaryotic organisms (a type of organism with membrane bound organelles, like nuclei) that can live either as single-celled individuals or clumped together in large aggregates, called plasmodial slime molds. These strange creatures have long fascinated humans, and it’s no surprise why.
The individuals of the species Physarum polycephalum live as solitary cells for a period of time and then come together as plasmodial slime molds, before splitting again to reproduce. Because of this strange cellular structure across their life cycle, they have been a challenge to classify, and were previously grouped as fungi. There are over 900 different species of slime molds, which come in different shapes, sizes, and colors.
Since they are single-celled organisms, slime molds do not form nervous systems or organs like a brain. However, when they live as plasmodial slime molds, the many nuclei form a network within a single cell membrane that can process sensory information independently and share that information with each other. In this way, they have been shown to learn where displeasing or toxic substances are within an area and then avoid that area in the future, remembering such stimuli and passing it on. They can play the world’s most successful game of “telephone”!
How have slime molds become known for problem solving?
Because of their ability to group together and send out strands of slime, slime molds are adept problem solvers. They can sense the chemical traces of food sources in the air the way that we sniff out food with our senses of smell, and pulse out toward that signal.
Researchers have set up experiments where they placed oat flakes, a food greatly enjoyed by slime mold, at different points in a dish, and observed the slime mold find the shortest route between them. Slime molds can map out the most efficient network of pathways between dozens of different points of interest, organically figuring out the solution to a problem of tremendous computational complexity. In different experiments, they have mimicked the Tokyo train network, as well as British and Iberian road networks.
Take a look at their movement and decision making:
What else can slime molds do?
Scientists fascinated by slime molds’ power have wondered about the possibility of “computing” with slime molds. A graduate student in the UK has powered a microchip with a slime mold sample, and other British researchers have created a robot that is controlled by a slime mold at its center reacting to light, which it likes to avoid.
Perhaps strangest still is the decision by Hampshire College to give slime mold a faculty appointment. A sample of Physarum Polycephalum is the school’s resident non-human scholar, and it does research on problems posed to it by students modeling various policy questions.
Though their intelligence is quite different from our own, it is certainly worthy of respect, and can teach us a thing or two. For more interesting looks at slime mold, check out the work of Heather Barnett, who spoke at our Voices of Nature conference in 2018, and recorded a popular TED Talk on the subject. As research on this intriguing creature reminds us, intelligence comes in many life forms.
Off to learn some more, Maya
Maya Dutta is an environmental advocate and ecosystem restorer working to spread understanding on the key role of biodiversity in shaping the climate and the water, carbon, nutrient and energy cycles we rely on. She is passionate about climate change adaptation and mitigation and the ways that community-led ecosystem restoration can fight global climate change while improving the livelihood and equity of human communities. Having grown up in New York City and lived in cities all her life, Maya is interested in creating more natural infrastructure, biodiversity, and access to nature and ecological connection in urban areas.
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