ECOSYSTEM ENGINEERS
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THE GRAZERS OF OOSTVAARDERSPLASSEN
In 1968, a polder (a tract of lowland reclaimed from the sea and protected by dikes) in the Netherlands was drained to create a marshy nature reserve. Konik ponies, Heck cattle and red deer were introduced to mimic the grazing of extinct herbivores. They created enormous grasslands that provided habitat for geese and birds, but the reserve attracted controversy in 2016 when half its grazers had to be shot when they became malnourished after a harsh winter. There was not enough food to go around, prompting ecologists to highlight the need for predators to regulate herbivore numbers.
REWILDING AT THE KNEPP ESTATE
In 2002, the cows on a failing West Sussex dairy farm were replaced by free-roaming Longhorn cattle, Exmoor ponies, fallow and red deer, and Tamworth pigs. Since then, nature has taken over. The animals have created new habitat and the rewilding success story now boasts nightingales, turtle doves and peregrine falcons, not to mention Britain’s largest population of purple emperor butterflies.
THE WOLVES OF YELLOWSTONE
When wolves were reintroduced to Yellowstone National Park in 1995, after a 70-year absence, things changed radically. The elk they preyed on learned to avoid the steep-sided valleys where they could be trapped by the wolves, so these areas regenerated. Woody plants and trees shot up. Their roots stabilised riverbanks, so waterways became more fixed in their course. Songbirds came. Beavers returned, built dams and created ponds that provided habitat for fish, amphibians and reptiles. The wolves killed coyotes, leading to an increase in small mammals, which attracted weasels, foxes and birds of prey. From an ecological perspective, the wolves were a howling success.
species, also known as ‘ecosystem engineers’ have influenced local flora and fauna, not to mention geology. So the Zimovs chose their animals based on the ecological roles they perform. Sheep, for example, are good at eating weeds, horses mow the grass, while reindeer are partial to mosses and lichen. During the Pleistocene, mammoths were a keystone species. But the Zimovs haven’t had access to these hairy pachyderms… until now.
MAKE A MAMMOTH
Last year, Harvard University geneticist Dr George Church announced he was a few years off making a mammoth-like embryo. Church and his team are using CRISPR-Cas9, the system that enables scientists to edit DNA with pinpoint precision, to manoeuvre mammoth genes into elephant cells. Mammoth DNA, prised from Ice Age remains, has been decoded. By comparing the genomes of 23 individuals, Church has been able to pinpoint particular mammoth genes that were favoured by natural selection. “We have chosen 44 genetic changes based on this analysis,” says Church. These include genes that code for mammoths’ insulating fat and fur, as well as a unique version of the haemoglobin molecule that works well at low temperatures.
Once the edits are completed and checked, the cells will be used to create embryos. In an ideal world, these would be nurtured inside elephant surrogates, but with the world’s pachyderms so desperately endangered, their wombs are strictly off-limits. Instead, Church is pioneering the use of artificial wombs and last year made significant progress towards this goal when he nurtured a mouse embryo inside an artificial womb for 10 days; halfway through its normal gestation period. If Church succeeds, the result will not be a pure woolly mammoth, but a hybrid that is essentially a cold-adapted elephant. You could even call it a mammophant.
Later this year, the Zimovs expect Church to visit Pleistocene Park where he will see their newly created grasslands. When Church’s mammoth-like elephants are ready, the nature reserve could become the first of many places where the shaggy beasts roam. Sergey now spends most of his time at a second park they have created, Wildfield, 250km south of Moscow, and ultimately the duo envisage a network of similar reserves spanning Siberia and Alaska. “We need to take huge territories. This is a century-long plan,” says Nikita. Immense numbers of animals will need to be imported, including predators to keep the grazers in check. “We have bears, wolverines and polar foxes but we need wolves and maybe Siberian tigers,” says Nikita.
Crucially, experiments performed at Pleistocene Park have shown that where big herbivores graze, soil temperatures are, on average, several degrees cooler than where grazers are absent, which is tantalising evidence that the Zimovs’ approach could help keep the permafrost frozen. “Sergey Zimov is a remarkable character,” says permafrost scientist Max Holmes from the Woods Hole Research Center, Massachusetts. “He has big, crazy ideas and a lot of them turn out to be right.”
In the meantime, the permafrost is slowly, patchily starting to thaw, and in Siberia the consequences are
“THE RESULT WILL NOT BE A PURE WOOLLY MAMMOTH, BUT A HYBRID THAT IS A COLD-ADAPTED ELEPHANT”
all too apparent. Enormous sinkholes are appearing and huge chunks of land are falling away. Most buildings in the region rest on permafrost, but with their foundations slowly melting, entire houses are sinking into the mud. Nikita thinks that Pleistocene Park’s nearest town, Cherskii, will collapse in the next 30 years, displacing all of its 2,500 residents.
“We’re not losing a lot of carbon from the permafrost right now,” says Holmes, “but we are headed in that direction.” If we continue to burn fossil fuels at the
“LIKE WOOLLY MAMMOTHS, BISON ARE A KEYSTONE SPECIES. THEY CAN FASHION ENTIRE ECOSYSTEMS”
rate we do now, we stand to lose around 1.5 billion tonnes of carbon per year for the rest of the century. “That’s like adding another USA into the mix,” explains Holmes. Pleistocene Park, and its extended network of Ice Age nature reserves, could help slow the loss. “I think Pleistocene Park could make a difference,” says Holmes. “I don’t think it’s the solution to climate change, but I think it could be a small part of the solution.”
The Zimovs, however, aren’t putting things on hold to wait for the tens of thousands of mammoths that would be needed to help manage the region’s forests. They believe they can recreate the mammoth steppe ecosystem without the woolly beasts.
In the past, both Sergey and Nikita have been known to mimic the actions of mammoths by driving around in a battered Ukrainian tank they bought over a decade ago. It took them two months to drive it from the Russian border to the park. “We used it to knock down trees when we were building fences, and when we were entertaining journalists,” says Nikita. “But it’s broken now and we don’t want to change the ecosystem with a tank. It’s not efficient or sustainable. We want the animals to do it for themselves.”
So now they are turning to bison, rather than tanks. Like woolly mammoths, bison are a keystone species. They can fashion entire ecosystems by trampling, grazing and fertilising. And they kill trees, not by knocking them down, but by eating their bark. Until recently, Pleistocene Park had only one bison, a male that came from Europe, but according to Nikita, this sole animal was responsible for most of the major changes seen in the park. These encouraging findings made bison a number one priority for the Zimovs, and at the start of June a dozen baby bison from Alaska were put into crates and loaded onto a 74-year-old DC-4 aeroplane. Destination: Pleistocene Park. The hope now is that when they settle into their new home, these natural geoengineers will set to work doing what they do best – being bison – and turn their environment into a grassier, greener and colder place. So although the media love nothing more than a shaggy mammoth story, when it comes to sculpting ancient grasslands, it’s bison that are likely to be best.
Dr Helen Pilcher is a science writer and speaker. Her latest book is Bring Back The King: The New Science Of De-extinction (£16.99, Bloomsbury).