Podcast Summary: Unexplainable – "The Trees of Death"
Date: December 3, 2025
Host: Vox (Narrated by Meredith Hodnot)
Featured Guests: Dr. Lisa Amati (State Paleontologist), Dr. Chuck Ver Straeten (Geologist), Dr. Thomas Algeo (Geologist)
Overview of the Episode
In this episode, Unexplainable journeys to a quarry in Cairo, New York, exploring one of Earth's oldest fossil forests. The hosts and scientists unravel the mysteries behind the Devonian "plant explosion"—the moment when forests took over dry land. While these ancient trees transformed the planet into the green world we know today, they also triggered chaos, culminating in one of the largest mass extinctions in Earth’s history. The episode blends wonder, science, and caution, asking what it means when life radically changes the planet—then and now.
Key Discussion Points & Insights
1. Discovery of Ancient Forests
- Quarry in Cairo, NY: The episode opens with host Meredith Hodnot walking through a deserted quarry (01:18). Geologist Chuck Ver Straeten recounts how he recognized the fossilized root impressions of a 385-million-year-old tree, marking the remains of one of Earth's first full forests.
- “Just thinking about time, like geologists think about time in millions of years, hundreds of millions of years...” — Chuck Ver Straeten (02:28)
- “That is where a tree stood 385 million years ago.” — Chuck Ver Straeten (03:49)
- The root impressions are described as “like the footprints almost,” allowing scientists to envision the forest’s ancient layout (04:16).
2. Reconstructing the Devonian Era
- Setting the Scene: About 420 million years ago, Earth’s land was barren, save for tiny plants and the distant ancestors of insects. Landscapes were dominated by massive fungi like “Fungzilla” before trees appeared (08:05–09:04).
- “This thing’s 12ft tall...Turns out it’s a fungus.” — Lisa Amati (08:23)
- Age of Fishes: Meanwhile, oceans teemed with bizarre and diverse life—sharks, armored placoderms, and lobe-finned fishes, some of which would eventually walk on land (09:04–10:57).
3. The Devonian Plant Explosion
- Transformation: The Devonian plant explosion transformed Earth’s surface: plants rapidly evolved from a few inches tall to massive tree-like forms. The first full forests appeared, such as that in Cairo, NY (10:02–12:04).
- “By 35 million years later...everything had evolved through stages of those simple little plants to things...then by the middle of the Devonian, you had trees. You had trees.” — Chuck Ver Straeten (10:02)
- Strange Ancient Flora: The forests consisted of bizarre forms—broccoli-headed trees, palm-like trees, giant club moss, and tiny liverworts (10:39–11:10).
- “It’s like a furry telephone pole.” — Lisa Amati (10:57)
- Arrival of Vertebrates: These new habitats allowed some lobe-finned fishes to crawl onto land, marking the origins of amphibians, reptiles, birds, dinosaurs, and mammals—including humans (11:10–11:45).
4. Environmental Revolution—and Catastrophe
- Forests Reshape Planet: The expanding forests reshaped the land, air, and even the global climate. Through photosynthesis, they dramatically reduced atmospheric carbon dioxide and increased oxygen, enabling diverse terrestrial life to flourish (18:38–19:33).
- Triggering Mass Extinction: But the changes also had deadly consequences. The roots of forests broke down rocks, creating rich soils that eventually washed into rivers, fertilizing massive algal blooms in the oceans. As these blooms died and decomposed, they sucked oxygen from the water, creating vast marine "dead zones" and precipitating a mass extinction (20:41–21:46).
- “As those massive algal blooms died and decayed, it robbed the waters of dissolved oxygen.” — Dr. Thomas Algeo (21:19)
- Death Toll: Nearly three-quarters of Earth’s species died, especially in the oceans—ending the Age of Fishes (16:54).
5. The Elusive Cause—A Detective Story
- Indirect Evidence: Compared to dinosaur extinction (asteroid impact), the Devonian event’s cause is less direct; scientists look for indirect signals—climate change, soil chemistry, and plant fossils around the world (22:12–23:15).
- “But the Devonian plants are different because you’re looking, the evidence is indirect.”— Dr. Thomas Algeo (22:12)
- Mystery Remains: The episode underscores how much is still unknown: Did trees directly trigger the extinction, or did they set the stage for another disaster, like volcanic activity? It’s an ongoing puzzle for paleontologists and geologists.
6. Reflection and Connection to the Present
- Double-Edged Sword: The episode closes with Meredith wandering among ancient root fossils, marveling at how forests made modern life possible but also led to disaster—a “double-edged sword” metaphor for life’s impact on the planet (23:15–26:10).
- “There’s also a darkness here...A tombstone to the Age of Fishes marking a violent revolution that overturned the planet. Wow. Such a double-edged sword.” — Meredith Hodnot (25:15)
- Modern Echoes: The parallel to today is unmistakable: humans are now the living beings transforming Earth’s systems—this time, by releasing ancient, buried carbon and creating a new mass extinction. The question lingers: how will we be remembered?
Notable Quotes & Memorable Moments
- “That is where a tree stood 385 million years ago.” — Chuck Ver Straeten (03:49)
- “It’s a mystery novel. It’s an adventure novel. It’s a puzzle. It’s everything all in one. We don’t have the answers, which is what makes it fun.” — Lisa Amati (07:35)
- “It’s the oldest sense we have of first forests where you can actually look out across the forest floor and see where all these trees stood.” — Chuck Ver Straeten (12:35)
- “Trees basically remade the atmosphere, dropping carbon dioxide levels by maybe as much as 90% and doubling the oxygen.” — Meredith Hodnot (19:05)
- “But an ice age alone doesn’t necessarily lead to mass extinction. There was a second punch coming for the age of fishes. A wave of death spreading out from the land.” — Meredith Hodnot (19:47)
- “As those massive algal blooms died and decayed, it robbed the waters of dissolved oxygen.” — Dr. Thomas Algeo (21:19)
- “Such a double edged sword… to think about, like, life finding new homes to be as explosive, as violent as an asteroid.” — Meredith Hodnot (25:15)
Key Timestamps
- 01:18 — Meredith enters the quarry; Chuck describes discovery of fossil roots
- 02:28–03:49 — Chuck on geological timescales & discovery of the ancient tree
- 06:42–07:35 — In the museum: Lisa and Chuck on reconstructing ancient life
- 08:05–09:04 — Before trees: barren land and the “Fungzilla” fungus
- 09:04–10:57 — Age of Fishes and first hints of terrestrial life
- 10:57–12:04 — The strangeness and origins of Earth's first forests
- 13:10–14:14 — Devonian plant explosion changes everything
- 16:54–17:41 — Mass extinction begins: “The age of fishes was over.”
- 18:30–19:33 — Trees as planetary engineers, changing the atmosphere
- 20:41–21:26 — Nutrient runoff, algal blooms, and oceanic dead zones
- 23:15–23:50 — The search for more fossil evidence; mysteries remain
- 25:15–26:10 — Reflection on mass extinction; parallels to today
Conclusion
This episode of Unexplainable tells a story of deep time, ancient forests, and the unintended consequences of life's greatest innovations. Listeners are invited to marvel at our origins, confront the legacy of mass extinction, and grapple with the question of humanity’s present impact on the planet. The tone is both awe-filled and somber—a monument to life’s explosive power and the unpredictable paths it forges through history.