Moving Trees Uphill: The Bet and the Cost of Saving Forests
In high-elevation burn scars, seedlings moved up from lower ground survive at 80% to 90%; but seed banks are limited, and staking precious genetic material on unproven large-scale planting is itself a gamble.
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The argument · tap a timestamp to hear it
When the big trees die, the next generation has no seed
In places that burned at high intensity, large areas have no living trees left. Many conifers depend on the seed bank in the cones of living trees to regenerate the next generation; with no living trees, natural regeneration has nothing to work from. Scientists are seeing natural regeneration fall short of expectations more and more often in high-severity burn areas in the interior. Layer climate change on top and the seedlings themselves are sensitive; managers report that planted seedlings are not surviving the way they used to. The low-elevation Ponderosa pine belt is already at its ecological edge, with little natural regeneration and poor replanting survival, and some worry these places will degrade into grassland or shrubland.
— Katie LanganAssisted migration means moving seed somewhere warmer
The core worry is this: replant with local seed sources and the trees may be adapted to the past climate, not today's or the future's. Hence assisted migration — taking seed from somewhere slightly warmer (downslope or from a lower latitude) and planting it at higher elevation. In this burn scar, researchers planted 11,000 seedlings of 7 conifer species, putting high-elevation species down low and low-elevation species up high, with seed sources drawn from multiple elevation bands, to see how each performed.
— Katie LanganTrees live for centuries, so which climate do you aim for
A tree can live for centuries, and the climate when it germinates will not be the climate when it is 50 or 100 years old, so there is no simple answer to ‘which climate should we aim for’. British Columbia is relatively far ahead: in 2023 it implemented a planting regime that roughly plants at the quarter point of the so-called species rotation — that is, discounted to the point in the forestry cycle when they plan to come back and harvest, essentially a hedge, putting the tree at its optimum adaptation at about a quarter of its life cycle. Others can make different choices, but it is genuinely hard.
— Katie LanganHigh-elevation sites see 80% to 90% survival
The high-elevation site is about eight kilometres from the ignition point, and seedlings planted in 2022 have already grown to around half a metre, doing very well. The only poor performer was the low-elevation pinyon pine. Camille Stevens-Rumman says every high-elevation site looks like this, with survival across all species planted in 2022 at 80% to 90%. Ponderosa pine, Douglas fir and pinyon pine do not naturally grow at that elevation, but so far a good number of the Ponderosa and Douglas fir have survived there. The conclusion only goes as far as ‘the seedlings can live’; the long term remains unknown.
— Camille Stevens-RummanSeed is a scarce resource, not something to scatter
Maren Chambers says she is on the conservative side here: spending precious biological resources on large-scale implementation when you do not yet know whether it works strikes her as irresponsible, so she favours small-scale trials first. Seed collection itself is extremely labour-intensive — sending people out to stands that have seed, trucking it back to nurseries to grow seedlings, then returning the seedlings to the forest; every step of that pipeline faces a capacity problem, and the US currently cannot keep up. Enormous effort went into selecting multiple seed sources per species, with workers handling seedlings in near-freezer conditions just so the seedlings can get into the ground as soon as they reach the site, rather than dying before they are planted.
— Maren ChambersShort term you watch survival; long term you wait decades
The key metric is first survival: seedling roots are short in the first few years, and a dry spell in the soil or a cold snap can kill them. But long-term performance matters just as much. A study launching in 2028 will plant 40,000 seedlings in Colorado and track them for decades; the study Katie visited will probably be tracked for about 10 years, still not enough for long-lived tree species. Another study will space the trees further apart so their growth can be tracked as they mature and begin to reproduce.
— Katie LanganSnow is a protective layer for seedlings, not just a water source
These Christmas-tree-shaped conifers have long branches that shade the ground and delay spring snowmelt, which benefits downstream water users by avoiding an early melt pulse; but the roots also take up water, and snow sitting on the branches sublimates in winter, lost straight out of the system, so it is hard to quantify precisely. What surprised Katie is that snow is good for the seedlings themselves: scientists think high-elevation snowpack provides an insulating layer that helps seedlings ride out winter wind and cold. And as the climate changes, that layer of snow may be shrinking, making the whole equation more complicated.
— Katie LanganWhether there should be forest here is now a human choice
At the low-elevation Ponderosa pine site, scientists looked at rows of dead seedlings and started discussing almost philosophical questions: should the same genetic material be put back on this land? Is that the best investment? Or would those resources be better spent on another ecosystem? No one has an answer. Once you start intervening, you have to decide again at a very basic level: should there be forest here? Can forest survive here? And if so, who should its members be? Choices that nature used to make now fall to people.
— Katie LanganIn their own words · checked verbatim
Seedlings are very sensitive. And so a lot of managers are saying, you know, we're putting these seedlings out there, we're planting them, and they're just not surviving like they used to.
Katie Langan5:11
But it's really not easy because the climate that something germinates in today is not going to be the climate when it's 50 years old.
Katie Langan9:21
And that's what we're seeing across all of the, these high elevation sites is that none of them are not liking it. Like all of the species, we have like 80 to 90% survival of all of the species that we planted in 2022.
Camille Stevens-Rumman12:24
using that precious biological resource for larger scale implementation when we don't know that it's going to work feels to me like an irresponsibility.
Maren Chambers14:29
Because we put a lot of time and energy into selecting multiple seed sources for each species. It was a huge effort. I mean, I can't even describe what a huge effort it was.
Maren Chambers15:33
Do we want a forest here? Will a forest survive here? If we wanted to live here, what are the members of it going to be? It's just all of the decisions suddenly become something that humans have to decide, I guess.
Katie Langan18:40
You're kind of asking animals to have a concept of death that's as complex as our own when we have all these narratives and cultural manifestations of the concept of death and so on that they do not have.
Susanna Monso36:22
Figures
| Years of Colorado's three largest fires on record | 2020 | 1:03 |
| Typical winter snowfall in the subalpine zone | over 5 metres | 3:06 |
| Seedlings planted and species in the experiment | 11,000 seedlings, 7 conifer species | 7:19 |
| Survival rate of seedlings planted in 2022 at high-elevation sites | 80%–90% | 12:24 |
| Year British Columbia implemented its future planting regime | 2023 | 9:21 |
| Time discount point of British Columbia's planting regime | one quarter of the species rotation | 9:21 |
| Seedlings planned for the new Colorado study | 40,000 | 15:33 |
| Start year of the new Colorado study | 2028 | 15:33 |
| Tracking period of the study in this report | about 10 years | 15:33 |
Glossary
- assisted migration
- Moving seed or seedlings from warmer areas to warmer or higher-elevation sites to match future climate.
- subalpine forest
- The conifer belt below treeline and above the alpine zone.
- serotinous cones
- Cones whose seeds are sealed in resin, released only after fire melts the resin.
- species rotation
- A forestry term for the timespan over which a manager plans to come back and harvest a tree.
- theory of mind
- The ability to attribute mental states (thoughts, perceptions, emotions) to others.
- comparative cognition
- An interdisciplinary umbrella for the study of animal minds, covering comparative psychology, ethology and more.
How to listen
Practitioners in ecological restoration, forestry and climate-adaptation investment, and readers who care about science topics beyond AI; those interested in philosophy of science and animal cognition can listen to the second half.
The philosophy and animal cognition interview after 24:57 is more conceptual; skip it if you only want the forest reporting.