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5 min readIn a 1980s rainforest in Washington state, ecologist Nalini Nadkarni was sitting a hundred feet up in a big leaf maple tree, cutting through a thick mat of moss on a branch. As she peeled back the moss, she found something she did not expect: soil. Not just a thin dusting, but a foot of dark, rich soil, formed over decades of moss and leaves decomposing right there on the branch. It held earthworms, invertebrates, and even fungi. She had essentially discovered a miniature forest floor floating in the air.
This Radiolab episode, a follow-up to their classic “From Tree to Shining Tree,” reveals that the hidden underground networks of trees are only half the story. The other half is happening above our heads, in the canopy. For decades, scientists assumed the treetops were mostly empty space. But starting with Nadkarni’s work, researchers have found that these canopies hold about fifty percent of all terrestrial life on the planet. In old-growth redwoods, they have found pockets of soil up to three feet deep, supporting berry bushes, flowers, salamanders that never touch the ground, and even tiny aquatic copepods—shrimp-like creatures normally found in the ocean—swimming around in mossy mats hundreds of feet in the air.
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What you'll learn
- 1 (02:01) **Introducing the Canopy as the New Frontier** - Latif Nasser sets up the episode as a follow-up to "From Tree to Shining Tree," which revealed underground tree networks. Now, producer Annie McEwen and host Robert Krulwich shift focus upward to the forest canopy.
- 2 (04:31) **The Queen of the Canopy** - Ecologist Nalini Nadkarni, known as the "Queen of the Canopy," describes her lifelong fascination with treetops, which began as a childhood refuge and led her to pioneer canopy research in the 1980s.
- 3 (06:48) **Discovering Soil in the Sky** - While perched on a branch 100 feet up, Nadkarni cuts through a thick layer of moss and is stunned to find a foot of rich, dark soil—a miniature replica of the forest floor.
- 4 (09:30) **A World of Life Hidden in the Redwoods** - Subsequent research in old-growth redwood forests reveals the canopy holds up to three feet of soil, supporting flowers, berry bushes, salamanders, and even tiny aquatic copepods living in mossy mats.
- 5 (11:23) **The Canopy Soil's Secret Power** - Ecologist Karina Mufune explains that canopy soils are not just a mirror of the ground below; they possess a critical resource that the forest desperately needs during lean times.
- 6 (13:45) **The Trees are Growing Roots into Their Own Hats** - The episode's central mystery is revealed: the trees themselves are actively tapping into these sky gardens.
- 7 (20:34) **A Fractal Forest of Endless Layers** - The episode concludes by emphasizing that canopy soil research is a new, wide-open field, with possibilities of trees growing on trees in infinite, fractal-like layers.
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Show Notes
For much of history, tree canopies were pretty much completely ignored by science. It was as if researchers said collectively, "It's just going to be empty up there, and we've got our hands full studying the trees down here! So why bother?"
But then around the mid-1980s, a few ecologists around the world got curious and started making their way up into the treetops using any means necessary (ropes, cranes, hot air dirigibles) to document all they could find. It didn't take long for them to realize not only was the forest canopy not empty, it was absolutely filled to the brim with life. You've heard of treehouses? How about tree gardens?!
This week, we bring you a story we first released in 2022. We journey up into the sky and discover forests above the forest. We learn about the secret powers of these sky gardens from ecologist Korena Mafune, and we follow Nalini Nadkarni as she makes a ground-breaking discovery that changes how we understand what trees are capable of.
P.S. This episode is a layer cake of arboreal surprises (including the reappearance of a certain retired host.
LATERAL CUTS:
From Tree to Shining Tree (https://zpr.io/4cHtDdYTuNxT): The episode that started this journey, where we look down instead of up.
EPISODE CREDITS:
Reported by - Annie McEwen
Produced by - Annie McEwen
EPISODE CITATIONS:
Videos -
Inside the Fight to Save an Ancient Forest (and the Secrets it Holds) (https://zpr.io/XKipP2z4NFiM), by Michael Werner, Joe Hanson, and the PBS Overview team. We first learned about the magical world of the canopy from this beautiful video. It features Korena Mafune’s research up in the treetops, as well as the people who have dedicated their lives to saving what’s left of the old growth forests. We highly recommend checking it out!
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