March 2007

Cheetahs originated in North America but are now found only in Africa or Southwestern Asia. Photo of Acinonyx jubatus. Source: Wikimedia Commons, photo by flickr member schani.

What do you mean by “rewilding” North America?

Barlow: Rewilding is a concept that works with restoration ecology and evolution combined. One type of rewilding deals with restoring lost biodiversity. Restoration ecology is when you look at a landscape and ask how we can bring it back to conditions that are more natural, say, before Europeans arrived in North America. Another type of rewilding has to do with climate change, for example, creating a park corridor from Yellowstone to the Yukon to give movement to animals as climate changes.

In 2005, a top science journal published an article by a dozen prominent conservation biologists proposing a shift in the benchmark that is commonly used for restoring lost wildlife to former habitats.¹ Most parklands and wilderness areas in North America will continue to be restored to conditions that prevailed just prior to the arrival of Columbus in 1492 [the “pre-Columbian” benchmark]. But what about rewilding a small portion of America’s natural heritage to conditions just prior to the first human incursion on the landscape some 13,000 years ago? This idea of rewilding from a deep time perspective is going back to a time before the first humans began to migrate to the Americas in the late Pleistocene [about 10,000 years ago] and asking how we can restore the ecological landscape.

Current trends in rewilding North America have to do with restoration of species displaced or endangered since the first European settlers arrived, for example, bringing back gray wolves to Yellowstone, reintroducing the lynx to Colorado, and bringing the peregrine falcon to the Midwest. That is standard practice restoration ecology. What I would like to address is the controversial subject of rewilding North America as proposed a few years ago by looking at a deep time perspective and saying lets not just stop with the wolves. What species were here before humans invaded the landscape, and is it still possible to bring them back?

Why restore animals from the Pleistocene era and not those that have disappeared since Columbus?

Barlow: This is a conservation question as well as an ethical one. Why should we do it? For several reasons:

• It was at the end of the Pleistocene that many large vertebrate [backboned] animals disappeared. The majority view in mainstream science now is that humans were the main cause of the extinction of these large animals, called megafauna. These large animals did not coevolve with humans in the way that large African and Asian animals did. So if humans were the cause for the loss of these animals, such as the mammoths, mastodons, and the big carnivores that depended on them, then it behooves us to do our best to restore them.

• I think it’s possible to manage rewilding efforts. A Pleistocene park, or an ecological history park, has been suggested, that is, some representative landscapes where we bring back these large creatures.

• The plants and the landscapes that we have here in North America lost their coevolved animal partners just 13,000 years ago. Plants take longer to adjust to environmental changes. By bringing back some of the big animals of the Pleistocene—the big browsers and the big carnivores—to control and evolve with plants, we would see what the American landscape really looks like.

• It is good for the economy. Tourists would visit the park and other rewilded areas, promoting the local economies, mostly in rural areas.

• Josh Donlan, one of the authors of the paper I mentioned, states that evidence shows when large animals disappear from ecosystems, the ecosystem biodiversity collapses and society is the lesser for this loss. The disappearance of megafauna had a domino affect on ecosystems.

Which large animals are suggested for rewilding?

Barlow: If one adopts an end-Pleistocene benchmark, then it is time to bring back the American cheetah, the American camel, the American plains lion, the American mastodons and mammoths, and other species by using proxies from the Old World to restart their evolution in the New, and to restore their vital roles as shapers of ecological landscapes.

Let’s take the camel as an example. Camels originated here in North America, not in the Old World, around 50 million years ago. They spent most of their time here, but then around 3 million years ago they crossed from Alaska to Siberia and moved down into Asia and into the African continent.

A Bactrian Camel in the Kyzyl Kum desert in Uzbekistan, Central Asia. Photo by Dmitriy Pitrimov.

If we were to bring back camels, the Bactrian camel for example, as well as elephants, these animals would probably do very well in controlling what is called shrub invasion of the arid West. Cattle and horses cannot eat mesquite, juniper, creocote, but the big browsers can. Camels are especially good at eating toxic shrubs. If you’re worried about your lawn, they cannot eat grass.

By introducing the Indian [Asian] elephant we have a replacement for the extinct mammoths. Indian elephants enjoy knocking over trees to browse, but when they leave an area, the grasses that grow after their departure will attract the grazers. You establish a dance between the grazers and the browsers. So the thought is that if we were to bring back some of the large browsers in particular, we would be able then to see the true ecological landscapes of North America.

Why choose megafauna over other animals; many animals have gone extinct.

Barlow: Whenever humans have set foot in a landscape, since the time when they could kill at a distance with stones and spears, they killed off megafauna. Humans hunted the megafauna to extinction. Spears were particularly lethal because you don’t even have to kill the animal. All you have to do is puncture its gut and wait till it dies of infection. The littler creatures could hide from humans; they also had the advantages of small populations and higher reproduction rates. Take the extinct moa of New Zealand. Its extinction is completely correlated to the arrival of the first Maoris. It’s the same with the elephant birds and the giant turtles of Madagascar.

Aren’t the animals that you are suggesting for rewilding genetically different from those extant species?

Barlow: Absolutely. The plan calls for rewilding proxies of native species in many cases. One of the closest genetic ties between today’s large animal and one that disappeared from North America would be the horse. Horses have already been rewilded. They originated in North America 50 million years ago and disappeared. Some horses went across into Alaska and Siberia, and down into Africa, and guess what they became? Zebras!

Przewalski’s horses numbered around 1500 in the wild in 2005. Creative Commons photo.

The Spaniards, as most schoolchildren know, brought back horses. Some escaped confinement and went wild. Plains Indians co-evolved a culture of hunting buffalo and riding horses. Our modern horses are the same genus as those of the Pleistocene, Equus caballus. The rewilding proposal suggests reintroducing modern horses as well as wild horses, such as Przewalski’s horse.

Let me give you an example of an elephant because an elephant is considered the most outrageous to some. Elephants evolved in the Old World, and then periodically some migrated from Africa into the western hemisphere millions of years ago. There were gomphotheres, mastodons, and several waves of mammoths that came in, most recently woolly mammoths. The mammoths that we had in North America, including in Florida, are more closely related to the Indian [Asian] elephant than the Indian elephant is related to the African elephant.

Why not work with the species you have in North America, such as the native puma, before they go extinct, instead of reintroducing the cheetah from Africa?

Barlow: We can do both. Sure, the pumas are close relatives to African cheetahs. Mountain lions, cougars, pumas, and cheetahs evolved from related lineages. All of them, except the cheetah, still roam various parts of the Americas. But did you know cheetahs originated here in North America? They are now found mainly in Africa. While they were here they coevolved with the fastest land herbivore on the planet—the American pronghorn. The American pronghorn runs 60 miles an hour, faster than any of the gazelles in Africa. Our wolves run 40 miles an hour. Evolution does not build in excess. The pronghorn that is running 60 miles an hour in Wyoming is still running from the American cheetah that went extinct here. So we are suggesting bringing back the cheetah because it not only belongs here but it is nature’s natural predator of the pronghorn.

How would these new megafauna survive, and would they destroy the native habitats that have evolved to be what they are now?

Barlow: The ecosystems haven’t evolved much in 13,000 years. You have different mixes of populations in different areas, but we have no new plant species other than exotic introductions and we didn’t lose most plant species. Thirteen thousand years to plants is nothing. It is just a question of how would things be reconfigured with the native species that we have. The point is that we are not suggesting repopulating all of North America. The natural history ecological park would be somewhere out in the great plains, say Nebraska or Kansas or perhaps in northern New Mexico, where we have some good grassland habitat and semiarid areas. It would be a scientific experiment to see if it works and how far we could go with the idea.

Some of the predators and other species considered for the park are migratory or need large areas to forage and to hunt. How could a park provide them with what they need and contain them as well?

Barlow: We’re not talking about a Hollywood-style Jurassic Park. Humans were not around at the time of the dinosaurs. The larger, more dangerous animals we propose to bring back would be contained in a big Texas-style ranch. Elephants would be the most difficult in that regard, but good grassland in eastern Texas is an ideal grazing area. These animals are all slow-reproducing megafauna, and they were once natives. It’s not like we are introducing an exotic, such as the troublesome Brazilian peppertree or the Cuban anole, that’s almost impossible to eradicate. If something goes wrong with the park and the new animals are destroying the landscape, we will be able to find them alternate arrangements.

Here’s an example of the imbalance that happens if you don’t manage rewilding well. Wild horses, introduced by the Spaniards after they disappeared from North America, are destroying a portion of the American west because people don’t want to have them shot and killed. These wild horses are breeding like fruit flies because this was always their native landscape. They have no natural predators here. All you need is to bring in the African lion. What is the primary food of the African lion in Africa? The zebra! Wolves can’t take down horses well, and neither can mountain lions. When you bring in the African lions to control the wild horses, you’ve actually created a balance of predator and prey.

Many American farmers and ranchers protested the recent reintroduction of wolves. What would you say to them about the introduction of large predators such as lions and cheetahs?

Barlow: First of all, this would not happen on public lands. They would be rewilded on private lands. Right now, the bolson tortoise is being reintroduced on Ted Turner’s private ranch in New Mexico. We are hoping to get to the point where a large private rancher, perhaps in Texas, will work with us on other efforts. There are already all kinds of African game in Texas ranches. There are more lions on Texas ranches than there are in all the zoos in the United States.

Do you view this park as a tourist attraction or solely a natural history experiment?

Barlow: The main idea is conservation and evolution. The proponents for this idea are thinking over the long term. Let’s say humans don’t go extinct in the next few million years, what sort of evolution is going to happen in North America if we bring back the species that were here before humans, or at least bring back founder populations that were here and give them a chance to evolve? Unless we do that we are going to just keep the same impoverished megafauna that we had when the Europeans arrived. We used to have as much megafauna here as we now see in Africa, for example, four species of camel, three species of horses, and five species of elephants. People were not native to North America. Even the ancient Clovis people from Siberia, the mammoth hunters, were native to the Asian landscape and not to this land, just as the ancestors of the Maori people who came to New Zealand were not native to New Zealand. These cultures crashed because the large creatures crashed. Out of the ashes came the indigenous peoples and the Native Americans. They were not the cause of the destruction of the Pleistocene megafauna. The frontier ancestors were the ones that did this.

A secondary advantage is the potential economic boon to areas where these megafauna would be rewilded. An ecological history park, say in Kansas, would bring in huge ecotourism benefits. Incidentally, there is already a ranch in Kansas that has camels. The camels are thriving just fine, even in winter. I personally foresee elephants and people working together. In the Old World, humans follow herds of elephants. You would let the elephants explore the landscape, even asking ranchers to open their gates and let the heard pass through. It could become a tourist activity where people follow elephants to see how they move to different landscapes seasonally to forage for food. Could be great for the economy, just like the buffalo commons.

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