Beasts of burden

Hey there,

I’m stopping over in New York en route to Europe, and it is brick outside. Also, with gold back on top of the global monetary pecking order—at least vibes wise—feels like this is as good a day as any to discuss reasserting the old ways by reintroducing megafauna to the Arctic to prevent permafrost thaw and reap other benefits. Stay frosty out there.

DEEP DIVE

Luke Griswold-Tergis, a documentary filmmaker turned founder and Executive Director of the Alaska Future Ecology Institute (AFEI), is pursuing a lease for 7,000 acres of Alaskan wilderness to test whether reintroducing large herbivores (think bison, wild horses, muskox) can help avert permafrost thaw, enhance albedo effects, sequester gigatons of carbon, and close other precarious feedback loops that could otherwise drive significant releases of methane and carbon dioxide. The science suggests it could work; there’s plenty of precedent written into the geologic record. Perhaps the biggest near-term challenge lies in navigating bureaucracy, securing permits, and funding a landscape-scale physical experiment to test the proposed interventions, whose benefits predominantly lie in mitigating environmental externalities that often go unpriced. And then in building social licence to ecologically reshape the largest terrestrial biome on earth.

Luke’s journey into exploring this specific climate intervention strategy began in 2013, when he was working on a documentary film about Sergey Zimov, a Russian ecologist who’d spent decades trying to recreate ice-age ecosystems at Pleistocene Park in Siberia. “He was driving around in a tank saying ‘It is my synthetic woolly mammoth; only problem, it not make poop,’” Luke recalls. The story is irresistible: remote regions of Siberia, a mad scientist archetype, talk of woolly mammoths. Perfect documentary material.

There’s more than just entertainment value and science fiction at play here, however. In fact, after deciding to move on from Russia after Russia invaded Ukraine, Luke began to wonder whether and to what extent similar approaches could work stateside, specifically in Alaska.

An alternate stable state

The Arctic is what ecologists call an “alternate stable state system.” Imagine two holes with a ball sitting in one. Absent a push or pull, the ball “wants” to stay where it is. But if you push hard enough, it will roll into the other hole, in which it’s equally stable absent additional application of significant push or pull forces. That second hole represents the alternate state. The ball, or the ecosystem, remains stable once it’s in it until pushed or pulled towards the other state again.

One of Zimov’s core insights was that the Arctic similarly oscillates between two possible equilibria. It’s either a steppe grassland with Serengetti-like herds of large woolly herbivores, or a mossy tundra/boreal forest with very little wildlife. Which state it’s in matters considerably for the Earth’s climate. During the ice age, when the Arctic was a vibrant steppe ecosystem replete with much more flora and fauna, a 40-meter-deep frozen compost pile with extraordinary concentrations of organic carbon, which is today referred to as Yedoma, built up over tens of thousands of years. Permafrost thaw across Arctic regions threatens to release so much greenhouse gas that it risks massive-scale climate destabilization. In total, frozen Arctic soils contain twice as much carbon as the Earth’s atmosphere. Estimates of additional emissions from permafrost thaw also aren’t counted in most emission reduction targets (more than 80% don’t factor this dynamic in at all) or in modeling of future emissions pathways. The IPCC factored in permafrost feedback loops in its most recent assessment for the first time (previous assessments ignored it entirely), and did so in quite a conservative fashion, classifying exact amounts and projects as an “unresolved Earth system feedback.”

Further, most climate models assume linear rates of permafrost thaw, characterizing the impact thereof as a gradual, additional global warming contribution. But permafrosts don’t necessarily thaw linearly. When ground ice melts, the soil gives way, sinking and creating depressions that fill with water – a thermokarst lake. When those lakes warm and expand, they can accelerate ice melt and release stored carbon as methane, a more potent greenhouse gas pound for pound than carbon dioxide.

Other dynamics include the rate at which dwarf birch and willow are expanding northward, growing from ankle-high bushes to overhead thickets in mere years. Researchers who maintain field sites across the Arctic often find themselves bushwhacking through what used to be open tundra. Dark birch and willow branches absorb spring and summer radiation, reducing albedo and accelerating warming.

Considering the degree to which the alternate states of the Arctic ecosystem contribute differently to overarching global climate regulation, and the inherent risk of triggering reinforcing feedback loops elsewhere in Earth's climate systems as Arctic ecosystems change, the next important line of inquiry inherent to Zimov’s work focuses on identifying the levers and the leverage points to tip these ecosystems from state to state. Which brings us to bison.

Betting big on bison

Evidence for the importance of large herbivores to ecosystems like the Arctic is written into the earth itself, frozen in the ground, accumulated at millimeter per year rates for millions of years. Halfway up a 40-meter-high eroding permafrost cliff at a place called Duvanny Yar in Siberia, you can see sediment layers deposited during the height of the last ice age clearly.

You can also smell them, because they’re composed in no small part of mammoth dung (as well as rotting mammoth meat thawing out of permafrost after 20,000 years). To drive the point home, at the base of the cliff you’ll also find piles of bones, mostly from bison but also from mammoth, horse, and caribou, and the occasional lion, wolf, elk, or woolly rhinoceros.

All this is evidence that for two million years, through alternating glacial and interglacial periods, the ice-free Arctic was a vast grassland stretching from Spain across Eurasia, through Beringia, into Alaska, terminating in the Yukon where Canadian ice fields began. Then 12,000 years ago, animal populations diminished quickly—quite possibly due in large part to human hunting—and the Arctic shifted from its grassland steppe state into its mossy/shrubby/taiga state. What happened exactly is still debated, but there’s no doubt that the loss of large herbivore populations—whether attributable to hunting by humans and/or other drivers—contributed.

In short, too few animals meant less grass over time: Ruminants support grass by acting as “soil managers” through grazing, fertilization with manure, and by breaking up moss with their hooves that otherwise smothers grass growth, creating a symbiotic cycle that improves soil health, water retention, and plant resilience, making grasslands more productive. Less grass then likely also meant fewer animals could survive. This process likely repeated and reinforced itself until eventually you had neither grass nor large herbivores.

Is restoring Arctic ecosystems to the grassy steppe state as simple as bringing back large herbivores? In some senses, yes. The plan is to release 10,000 bison per year, for roughly ten years, and let their population grow naturally from there. The vision is that reintroducing bison at scale in the Arctic will help with:

1. Snow removal: The thermodynamic foundation

Hungry animals dig through snow looking for grass. In the winter, air temperatures are roughly -40°C, whereas permafrost ground temperatures average can be higher (-3°C on average in Zimov’s Pleistocene Park), because snow is a highly effective thermal insulator. By removing a meter of snow, you expose the ground to much colder temperatures, cooling it. As such, the feeding craters bison create (visualized below) offer thermodynamic benefits. A 2020 Nature publication estimated that increasing large herbivores in Arctic ecosystems could protect up to 80% of permafrost from thawing by reducing the insulating effect of snow.

2. Albedo restoration: Immediate and measurable

Nikita Zimov, Sergey’s son, ran an experiment with Bactrian camels, two-humped, giant, hairy goat-esque animals that eat almost anything, but particularly love willow. Over about two years, the camels ate head-high willow thickets down to ground level in Siberia. In late March, with complete snow cover but 12 hours of daylight, Nikita and a team from Moscow State flew thermal drone surveys along a fence line. The landscape outside the fence featured black leafless willow branches protruding from the snow. On the other side of the fence, ravenous camels had consumed all the willow. The willow-less snow-covered side remained 20% more reflective. De-”shrubyfing” the Arctic may not seem high tech, but it doesn’t have to be: Scaling this insight across the Arctic, especially in regions that are already rapidly shrubifying, and the impact could amount to gigatons of CO2-equivalent cooling. Albedo effects are also immediate and highly measurable from satellites. No complex accounting required.

3. Soil carbon sequestration: Gigatonne scale impact over a longer time horizon

Soil cores from Zimov’s Pleistocene Park in Siberia also suggest restored northern grassland ecosystems can sequester about 8 tons of additional CO2 per hectare annually. Beneficially, many arctic soils aren’t yet carbon-saturated, meaning they are primed to ingest more carbon provided with the right conditions. If you extrapolate roughly 8 tons per hectare across plausibly rewildable Arctic regions, and you’re removing gigatons of carbon from the atmosphere alongside the other gigaton-scale cooling benefits and avoided emissions from permafrost thaw, we’ve discussed.

4. Averting more emissions: Closing a methane loop

The smallest effect, but an important one no less, lies in preventing additional methane emissions to address potential objections. Ruminant animals, like bison, are one of the main drivers of anthropogenic methane emissions already. Rebuilding a population of many millions of ruminants in the Arctic would, of necessity, involve elevated methane emissions in the region. But waterlogged soils also emit methane, and if ruminants help shift an ecosystem to a state featuring drier soils, there could be a methane abatement benefit. Peer-reviewed research from Zimov’s Pleistocene Park showed reduced methane emissions from drier soils, which Zimov expected could compensate for ruminant emissions. Whether that’s the case, and to what extent it varies spatially and based on other factors, will require further study.

Beyond the thundering herd of bison

As above, making good on a version of the Zimov’s vision should offer four tenable and in some cases, readily visible and measurable, climate benefits across three timescales: Albedo effects and methane reduction from drier soils operates on a close to immediate timeline (and are satellite-measurable), soil carbon sequestration builds over decades, and permafrost protection prevents triggering reinforcing feedback loops that could otherwise dysregulate the Earth’s climate for millennia. Importantly, to all these solutions, bison and/or other large herbivores are a highly scalable “technology.” Luke described them as “the only self-replicating biotic factory that is going to impact really vast landscapes.” Solar panels don’t make more solar panels. But animals can make more animals. Plus, their track record from millions of years ago is sound.

While the main thrust of the plan may be simple, that doesn’t necessarily make it straightforward or foolproof. Whether large herbivores might drive climate and ecosystem benefits in general is not disputed. Where there is scientific skepticism, it focuses in large part on the feasibility of scalability, a concern Luke readily acknowledges and that we’ll discuss below, alongside concerns from some corners that invariably, climate systems like the Arctic are so complex that intervening in them is ultimately never simple or easy to model. On the latter, several ecologists have argued that climate and soil/moisture constraints, not just loss of herbivores, explain the transition from “mammoth steppe” to today’s tundra and forest, so adding grazers back may well not be enough to reinduce a Pleistocene-like grassland. None of which seems like sufficient reason not to try; not trying only guarantees all those questions remain opaque in perpetuity.

With respect to scale, there’s a chicken and egg challenge: High densities of animals are needed to push a state shift in the Arctic. Bison, released into the wild in the Yukon Territory, had a 4-year population doubling rate until Fish and Wildlife initiated hunting to stabilize the population (it continues growing, despite the best efforts of hungry Yukonners). Left to their own devices bison populations would double and double again, like grains of rice on a chess board, until they hit the carrying capacity of the ecosystem, then their growth would slow, limited by the rate of ecosystem state shift. This interplay of growing animal populations pushing against an alternate stable state system, with unknown thresholds and rates of change, is where many core uncertainties lie. Luke estimates that starting with 100,000 bison you could reach 20-million within 50 years, enough to achieve gigaton-scale carbon reduction, but admits that he is an optimist and nothing is guaranteed. Significant albedo changes might accelerate even at lower animal densities, but even that requires more research to state with confidence.

There’s also a lot more to be done beyond just reintroducing megafauna. Luke’s vision is to create a landscape-scale demonstration and experimental test bed to comprehensively test mega fauna reintroduction, and then, if early results are promising, establish a pragmatic “real world” pathway to actually doing it at larger scales (which involves navigating everything from the logistics to the politics, to ongoing research). At present, Luke and team are navigating a lease proposal with Alaska’s Department of Natural Resources. Suffice it to say it’s a rather unusual proposal that many agencies aren’t used to processing. If and when approved, a lot of baseline measurements will also be conducted concurrently with preparing to move megafauna. This will include plant surveys to catalog biodiversity and productivity, drone surveys correlating ground-truthing with remote sensing, and soil core sampling to establish baseline carbon levels (which is vastly more complicated than sticking a probe in the ground and getting a “clean” answer re: “how much carbon is there”). Ground-penetrating radar mapping would also be necessary to help understand permafrost distribution: In discontinuous permafrost zones, you genuinely don’t know what’s underground until you start looking.

Preparing for sound measurement will also require erecting eddy flux towers, each of which runs about $100,000+. These are the gold standard for real-time ecosystem carbon flux measurement. They work by sampling wind speed and direction in three dimensions at 15 hertz while simultaneously measuring carbon dioxide and methane with laser-based gas analyzers. Correlating airflow direction with carbon dioxide concentrations 15 times per second tells you whether the ecosystem is currently absorbing or releasing carbon. “They’re also really fussy,” Luke acknowledged. They often break, can get miscalibrated, are highly sensitive to wind conditions, and require continuous, careful analysis. Luke’s initial proposal would require two towers at a minimum, one for a control site and one for a grazed area.

Beasts of burden

Much of the world’s current approach to averting climate catastrophes is often construed as highly contingent on high tech solutions. Getting people excited about ecosystem restoration, especially when contingent on reintroducing megafauna, doesn’t square directly into traditional conservation frameworks (it’s altering an ecosystem state, not conservation) or geoengineering (it is an intervention in an ecosystem and ideally, in climate systems, but it’s not as high tech as most common conceptions of geoengineering). Really, there’s no reason we shouldn’t see bison as beasts of geoengineering burden. They’re a high-leverage, self-replication solution, and the burden of proof of their capacity to drive climate benefit is already written in the geologic record.

If the alteration vs. conservation dynamic is the hangup, those concerns can be assuaged by viewing the Arctic as both a fragile ecosystem we must preserve and protect, and one that’s already changed so much that there are significant benefits to turning back the clock. None of this will matter at planetary scales if people like Luke don’t start soon. Given the developing climate change prognoses, we really can’t afford not to investigate these types of interventions and scale them if early signals are promising.

— Nick