9 Controversial Experiments In Rewilding

Strange as it is to imagine, at one point lions roamed Europe, horses galloped over Spain, and jaguars prowled parts of the United States. The reason these animals died out wasn’t climate change, but humans hunting or destroying their territory.

Rewilding is an effort to bring species back to their native habitats, even if they haven’t lived there for thousands of years. The idea isn’t just to preserve an ecosystem, but to go back in time.

1. Wolves in Yellowstone National Park

Wolves were all but extinct throughout the 20th century in Yellowstone, but between 1995 and 1997, 41 were released and re-introduced to the park. The effect on the ecosystem was dramatic. First, the wolves thinned out the deer population, which were overeating the vegetation. Eventually, valleys and gorges turned into forests. In some cases, trees grew five times their original size. The forests not only brought in more wildlife, but also changed the rivers, which saw less soil erosion due to the new vegetation. In 2011, the gray wolf was removed from the endangered species list in Idaho and Montana and was delisted in Wyoming.

2. Wild horses in Spain

For the first time in 2000 years, 48 Retuerta horses are roaming western Spain. The endangered Retuertas are the closest relatives to the wild Iberian horses that lived in the peninsula when the Romans were around. Prior to this experiment, the only remaining Retuerta horses—150 of them—were living in a national park in southern Spain. Releasing two groups of 24 horses in their native territory may prove to increase their odds of survival. As more people abandon rural Spain for the cities, conservationists hope to bring biodiversity to a region that has been historically used as farmland.

3. Tortoises in Ile Aux Aigrettes

Ile Aux Aigrettes in the Indian Ocean was once filled with exotic species—including the now-extinct dodo—until humans logged the trees and brought rats to the tiny island. In 2009, researchers introduced 19 Aldabra giant tortoises, which are similar to the extinct tortoise that used to live on Ile Aux Aigrettes. So far, the tortoises, which can get up to 660 pounds, are helping to reforest by eating the fruit of the ebony tree and depositing the seeds around the island. They also eat the nonnative plants and don’t seem bothered by the rats.

4. Trout in South London

At one time, London’s Wandle River was so polluted, locals said it would turn blue, pink, or red depending on what the tanneries were dumping at that moment. In 2003, the river, which connects to the Thames, was clean enough that trout could be released into it for the first time in 100 years. Today, you can even fish in the river, although the Wandle Valley Park says not to eat the trout “as they may hold high concentrations of heavy metals and other substances due to the river’s long industrial history.” 

5. Jaguars in Mexico

Jaguars once roamed the Southwest United States and Mexico, but these gorgeous animals (the largest cats in the Americas and the only ones that roar) have all but died out in the region. The Northern Jaguar Project is trying to change that. The bi-national nonprofit owns a 45,000-acre preserve in Sonora, Mexico that’s home to an estimated 80 to 120 jaguars. The preserve is located near Arizona, and in time these rare cats may be spotted in the U.S. once again.

6. Beavers in Wales

Beavers were hunted to extinction in Great Britain 500 years ago for their meat, fur, and scent glands. Blaeneinion, a 75-acre preserve in Wales, has introduced three beavers into the wild, and other parts of Wales may be following suit. In fact, the Welsh Beaver Project is considering releasing 30 to 40 beavers in River Rheidol sometime this year. The plan is controversial, with opponents worrying about how these dam-building animals will affect rural Welsh life.

7. Salmon in Washington

Speaking of dams, the Elwha River in Washington is a different kind of rewilding project. Instead of introducing species to the river, conservationists are removing dams so species can come back. Since 2011, dams have been removed and reservoirs have been drained and the river flows freely for the first time in a century. Not only are salmon resuming their historic swim, but the sighting of a Dungeness crab along the banks made front-page news.

8. Heck Cattle in Netherlands

Oostvaardersplassen, a 15,000-acre preserve in the Netherlands, has been stocked with animals that would have lived in the area during ancient times—or as close as you can get, anyway. For example, since aurochs went extinct in the 1600s, researchers brought in Heck cattle (which were developed, oddly enough, by the Nazis). Herds of Heck cattle now roam the preserve, as well as red deer, wild horses, and other animals. For $45, you can tour the preserve in a safari-like experience. But Oostvaardersplassen is far from perfect. Since the preserve has no top predators like wolves, rangers have to shoot animals deemed too weak to survive the winter—an issue that continues to be hotly debated in the news.

9. Wolves and bears in Scotland?

Alladale Wilderness Reserve in Scotland is a rewilding effort by multimillionaire Paul Lister. Since buying the 23,000-acre preserve, Lister has stocked it with deer, highland cattle, wild boar, and the first wild elk born in Scotland in 3000 years. There are also 800,000 indigenous trees, including Caledonian pine. (Scotland used to be so wooded that the Romans called it the “Great Wood of Caledon”—today only 1 percent of those forests survive.) Lister wants to reintroduce wolves and bears to the region, an idea that has been greeted with opposition. Despite this, Lister is moving ahead with a study on releasing two packs of 10 wolves in an enclosed 50,000-acre space. No doubt, he’s drawing on Yellowstone for inspiration.

BONUS: Horses in the Mongolian region

The Przewalski horse is the only surviving subspecies of the Asian wild horse. Stocky, with a thick neck and short mane, the horse used to roam from the Ural Mountains to Mongolia. For much of the 20th century, it was classified as “extinct in the wild.” However, these days there are herds of Przewalski’s horses in parks in Mongolia, Russia, Hungary, and China, according to Scientific American. There’s even a herd in the Chernobyl exclusion zone, which is now a wildlife refuge. The horse has been reclassified as “endangered.”

All images courtesy of Thinkstock.