In a remote corner of Siberia, a Russian geophysicist named Sergey Zimov, and his son, Nikita, are bringing back the Ice Age.

It isn’t like they have woolly mammoths and saber-toothed cats running around. Although they’d certainly be open to hosting some if anyone ever finds a solution  to that whole extinction thing.

Instead, the Zimovs are trying  to restore the ecosystem to the way it was 12,000 years ago. Back in the 90s, the Russian government  gifted them 160 square km of land to run their massive experiment, hich they named Pleistocene Park. And while it’s definitely eccentric,  the Zimovs’ “backyard” hobby could have huge implications for  the fate of the entire planet. [Intro music] Sergey Zimov has dedicated  the second half of his career to studying how grazing animals  affect grassland habitats.

He roped his son into joining the cause, and Nikita is now the  director of Pleistocene Park. They’re situated in a stark, frozen landscape, about a 4-hour flight away from the nearest city. If you lived out here, it wouldn’t be  hard to imagine the world frozen solid.

That’s probably how many of us imagine  the Earth looked 12,000 years ago at the end of the Pleistocene geological era, better known as the last Ice Age. But even in Siberia, that’s not how it was. Geological records indicate  that this shrubby tundra was once covered in lush  meadows with grazing megafauna.

That kind of ecosystem is called a mammoth steppe. Steppes are dry grassy plains  characterized by low amounts of rain. And mammoth is in the name because of, yanno, the mammoths.

But since the end of the Ice Age, Siberia has been a scrubby tundra. Tundras are basically cold  deserts, and in Siberia, the land is now covered  with small shrubs and trees, as well as mosses and lichen. For years, geologists’ reigning theory was that higher temperature and humidity at the end of the Ice Age converted  the mammoth steppe into a tundra.

Without grasses to eat, the megafauna would have been unable to survive. But Sergey challenges this theory. He believes that humans, with their recent invention of long-range weapons, over-hunted the steppe’s large game, eventually causing the  extinction of native grazers.

For reasons I’ll explain, grasslands disappear without animals  to graze and maintain the land. Because the climate in modern northern Siberia is actually very similar to the region’s  climate at the end of the Ice Age, Sergey is optimistic that the  mammoth steppe can be restored. Of course, they can’t actually  reintroduce mammoths to the steppe, and many other megafauna from  the Ice Age are likewise extinct.

So in their place, Zimov has  brought in large grazing animals   like reindeer, moose, muskoxen, and bison. But the Park isn’t a petting  zoo just for curiosity or fun. Grasslands could help save  a rapidly melting Siberia.

Most of Siberia is made of  permafrost that … ideally … remains frozen year-round. But given that the Arctic  is warming four times faster than the rest of the planet, that permafrost is in danger. Grasslands reflect more heat from  the sun than scrubby tundra,   which is important for keeping that  permafrost as frosty as possible.

Plus, in the winter, the animals have to eat whatever is leftover from the growing season. They dig through the snow and eat the old grass, leaving the ground more exposed to the cold air. That means a deeper freeze for the permafrost, so that it won’t melt as deeply  when the spring rolls back around.

The bottom line is that grassland could dramatically reduce the impact  of climate change on the Arctic. And grazing animals are the key  to the Zimovs’ plan to restore it. You might think that animals who eat grass would be the very last thing you’d want when you’re trying to grow more grass.

Overgrazing by huge livestock  herds is definitely a danger, and can seriously degrade grazing lands. But reasonable-sized herds of native grazers can actually improve a steppe ecosystem! This happens in a couple ways … First, herds trample the earth, breaking  up the tundra’s moss and shrubs, clearing space for more delicate grasses to grow.

Next, the grazers will quickly  eat the scrubby shrubby bits, which don’t grow back very  well after losing their leaves. On the other hand, some grasses  are quite resistant to grazing, and will regrow and spread as the scrub dies. The grasses that survive the grazing do so by diverting nutrients to their root systems.

Having their blades ripped off by a browsing bison  sends a signal to reinforce  and extend the root system, enriching the underground nutrient network and enhancing the amount of  carbon drawn into the ground. The final major benefit is that the  animals’ quick digestion of grasses means a fast fertilization cycle. In warmer biomes, bacteria  can break down organic matter and return those nutrients to the soil.

But in the frosty Arctic, a grazer’s gut microbes can do the job way faster than the ground, so that all the good stuff locked up in the plants can return to the ground in just a day or two. So watch your step if you ever take  a ramble through these meadows. All these benefits are being  tested at Pleistocene Park, but the Zimovs aren’t content to  let nature progress at its own rate.

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The owners view the Park as a  massive geoengineering experiment, so they’ve manually cleared trees and large shrubs to accelerate the conversion to grasslands. Their herds of large animals have done the rest. Bison knock down small trees  and shrubs as they pop up.

Muskoxen are uniquely capable  of digesting the tough scrub that blankets the tundra and  prevents grasses from growing. And where the larger animals  have already cleared the scrub, others graze the new grasses. But it’s hard to find cold-adapted fauna that can simulate the bygone grazers.

They have some native grazers in the Park, such as Yakutian horses,  yaks, moose, and reindeer. For the rest, they’ve turned to non-native species such as American Plains Bison and  Bactrian Camels from Mongolia. Because their goal is to recreate  the entire Ice Age ecosystem, the Zimovs eventually plan to add predators, like wolves, cougars, and Siberian tigers.

And while they aren’t in the  business of genetic engineering, the Park could be a potential home for cave lions or the recently “de-extincted” dire  wolves if those experiments succeed. Above all, they’d love to host  a herd of woolly mammoths, should they ever be resurrected. Because the role of those furry megafauna would have been to knock down large trees, the Zimovs have cheekily named their  tree-plowing vehicle “baby mammoth”.

So far, the experiment has had positive results. The Zimovs report that in just 20 years, the park has become a lusher  and more productive grassland. Visiting journalists have observed  that the grass density, coverage, and vitality is much stronger within the  Park’s fences than immediately outside.

The Zimovs are also constantly  measuring the air quality,  surface temperature, greenhouse gas levels, and permafrost thaw to conduct  quantitative studies on the Park. For example, upper layers of the un-grazed soils can be as much as 13°C warmer than grazed soils. AND ungrazed soils have been measured to thaw  more than 40 cm deeper than the grazed soils.

One study found that the  upper layers of grazed soils  held six times as much total organic carbon as samples from un-grazed soils. The researchers think that  over a longer amount of time, those benefits might extend to  lower layers of the soil, as well. Of course, Pleistocene Park isn’t the only  grassland ecosystem restoration project out there.

Programs across North America are bringing  bison back to the prairies and plains. Patagonia National Park is adding native grazers with hope of restoring their grasslands after decades of overgrazing by commercial herds. And steppe ecosystems in Kazakhstan are being restored to hopefully  save the native saiga antelopes.

Rewilding is a difficult process, but the importance of animals  in shaping and maintaining their landscapes has become clear. Sometimes, they just need a pair of  eccentric scientists and a “baby mammoth” to lead the way. [ outro ]