Selects: Plant Migration

Episode of Stuff You Should Know · July 25, 2026 · 46 min

Josh Clark and Chuck Bryant explain how plants migrate, why climate change is outpacing them, and the debate over human-assisted migration of trees.

Summary

In this rerun of an August 2023 episode, Josh Clark and Chuck Bryant discussed plant migration, the process by which sessile plant species shift their ranges over generations through seed and spore dispersal. Clark described the Tasmanian tree fern's long-distance spore dispersal and Reid's paradox, Clement Reid's 1899 observation that trees in the fossil record moved far faster than ordinary seed dispersal would allow, explained by rare long-distance events involving animals, wind, or water. The hosts described research methods including fossil pollen, permanent vegetation plots, historical records such as Alexander von Humboldt's survey of Chimborazo, and satellite imagery.

The hosts covered past climate-driven migrations, including Green Sahara periods and recolonization after the retreat of the Laurentide Ice Sheet, before turning to modern climate change. Bryant and Clark argued that current warming is far faster than post-glacial warming, and cited research showing New England trees moving a fraction of a mile per year while climate zones shift several miles annually. They discussed Songlin Fei's finding that eastern U.S. tree species are moving in different directions, the breakup of plant communities, species trapped on mountainsides or by unsuitable soils (such as sugar maples reaching Quebec's boreal forests), carbon and albedo feedback loops, and projections that much of the southern U.S. will become tropical by 2100.

In the final segment, the hosts discussed assisted migration, assisted range expansion, and assisted species migration; Clark argued that inaction is more destructive than intervention, while both noted the Monterey pine's invasiveness in Australia as a cautionary example. Tangents included Chuck's friendship with New Pornographers singer Kathryn Calder, the dungeon synth genre, digital sounds, and listener mail about numbers in the NATO phonetic alphabet.

Chapters

0:05
Introduction and migrating ferns
Josh introduces the Select rerun and the hosts discuss how far Tasmanian tree fern spores can travel.
6:59
Reid's paradox of rapid plant migration
The hosts explain Clement Reid's 1899 observation that trees migrated faster than expected and the role of rare dispersal events.
10:33
How scientists study plant migration
Fossil pollen, vegetation plots, historical records like Humboldt's Chimborazo survey, and satellite images are described.
15:05
Past migrations: Green Sahara and the Laurentide Ice Sheet
The hosts describe historical climate-driven plant movements and their influence on human migration.
18:08
Climate change outpacing plants
The accelerating rate of warming is compared with tree migration speeds and shifts in eastern U.S. forests.
22:37
Broken communities, trapped species, and feedback loops
The hosts discuss dissolving plant communities, mountaintop and soil traps, sugar maples, invasive species, and albedo effects.
29:26
Tropicalization of the southern U.S. and music tangent
Projections of a tropical southern U.S. lead into a tangent on Destroyer, the New Pornographers, Front Person, and dungeon synth.
34:35
Assisted migration
The hosts outline forest-assisted migration, assisted range expansion, and species rescue, including the Monterey pine example.
39:49
Digital sounds tangent and wrap-up
The hosts chat about phone voices and ringtones before closing the topic.
42:18
Listener mail on NATO phonetic numbers
A former Air Force pilot explains number pronunciations like niner in the NATO phonetic alphabet.

Key points

What was said, by whom, with the exact words. Timestamps jump to the moment.

Josh Clark
Clark stated that the Tasmanian tree fern can send spores 500 to 800 kilometers from the mother plant.
“the Tasmanian tree fern in particular, can send its spores 500 to 800 kilometers. That's 300 to 500 miles from the mother plant”
Listen from 1:55 · Plant migration
Chuck Bryant
Bryant explained that oaks in the British Isles traveled about 600 miles in roughly 10,000 years, a distance that ordinary dispersal would take about a million years to cover.
“They traveled about 600 miles and it would normally take about a million years to If the seeds were just dispersed in a typical way”
Listen from 8:29 · Reid's paradox
Josh Clark
Clark reported that a 2012 Danish team retracing Humboldt's survey of Chimborazo found species had moved up the mountain by about 500 meters on average.
“they found that everything, all species on average, had moved up the mountain by about an average of about 500 meters”
Listen from 12:55 · Chimborazo
Chuck Bryant
Bryant noted that moving 500 meters upslope can give a plant a more hospitable climate faster than moving 90 to 100 miles north.
“a plant can find more hospitable climbs going up 500 meters than they might by going, let's just say, north like 90 to 100 miles”
Listen from 13:15 · Plant migration
Josh Clark
Clark said Green Sahara periods recur about every 23,000 years, driven by the tilt of Earth's axis, with the next due in about 12,000 years.
“they figured out that they happen about every 23,000 years”
Listen from 16:11 · African humid period
Chuck Bryant
Bryant said Earth has warmed more than one degree Celsius since the Industrial Age began, with 0.37 of that since 2011.
“But 0.37 of that change over the past 200 years has come since 2011”
Listen from 18:59 · Climate change
Josh Clark
Clark contrasted current warming with post-glacial warming of one degree per 1,400 years and blamed Western industrialized nations for the acceleration.
“somebody's put their foot on the gas, and that somebody is Western industrialized nations, right?”
Listen from 19:54 · Climate change
Josh Clark
Clark cited University of Vermont research showing New England red oaks moving a tenth to three-tenths of a mile per year while climate moves four to six miles per year.
“The climate is moving something like four to six miles a year. So the climate is really kind of showing up as kind of the Usain Bolt of this race”
Listen from 20:56 · Plant migration
Chuck Bryant
Bryant described Songlin Fei's finding that eastern U.S. hardwoods are moving west and softwoods moving north at different rates.
“Different plants and trees are moving in different directions at different rates”
Listen from 22:14 · Plant migration
Josh Clark
Clark argued that palynologists view plant communities as always impermanent, but rapid climate change leaves migrating trees less time to form new connections.
“they're going to have far less time to develop new connections and networks with the new plants that they set up communities with”
Listen from 24:00 · Plant migration
Chuck Bryant
Bryant said researchers in Quebec found sugar maples migrating north cannot thrive in boreal forest soils because of differing pH and microbes.
“the soil pH and the microbe content in the soil is not what they're used to and not what they work well with”
Listen from 26:56 · Sugar maple
Josh Clark
Clark argued that boreal forests advancing into formerly icy regions will absorb more heat, creating a positive feedback loop of warming.
“there's more and more heat for them to trap, which is just going to heat the Earth up that much faster”
Listen from 28:58 · Boreal forest
Josh Clark
Clark relayed climatologists' expectation that by 2100 several southern U.S. states will become tropical.
“Alabama and Arizona are going to be like Guatemala by the end of the century”
Listen from 30:58 · Climate change
Josh Clark
Clark sided with ecologists who argue that assisted migration, though imperfect, is better than doing nothing.
“it's not a great, perfect solution, but it's way better than doing nothing”
Listen from 36:57 · Assisted migration
Josh Clark
Clark said ecologists consider assisted species migration the riskiest form because it can turn a benign plant into an invasive species.
“This is considered the riskiest of the three by ecologists because you can easily take something that's totally innocuous and benign”
Listen from 38:48 · Assisted migration
Chuck Bryant
Bryant noted that the Monterey pine is endangered in its native California but invasive in Australia.
“It's endangered in California. It is native to California. But they have introduced it in Australia”
Listen from 39:07 · Monterey pine

People

In the conversation

Josh ClarkCo-host of Stuff You Should Know
Chuck BryantCo-host of Stuff You Should Know

Discussed

Clement ReidBritish geologist who described the paradox of rapid plant migration in 1899
Alexander von HumboldtGerman naturalist who surveyed vegetation on Chimborazo in Ecuador
Anders SandbergOxford philosopher quoted on acorns
Andy SambergComedian and former 'Saturday Night Live' cast member
Songlin FeiPurdue researcher who studied tree migration in the eastern U.S.
Kathryn CalderSinger in the New Pornographers and Front Person
Joe RandazzoComedy writer, formerly of The Onion

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From the publisher

Climate change is having sweeping effects on our climate and this is changing the world, not just for humans and other animals, but plants too. Will the Earth’s flora manage to find safe refuge in time? Josh and Chuck run down the odds in this classic episode. See omnystudio.com/listener for privacy information.

Summary, chapters and key points were generated from the episode transcript on September 30, 2026. Quotes are checked word for word against the transcript.

Categories: Earth Sciences·Life Sciences·Nature