If a group of US researchers have their way, lions, cheetahs, elephants and camels could soon roam parts of North America, Nature magazine reports. The plan, which is called Pleistocene re-wilding, is intended to be a proactive approach to conservation.

Their disappearance left glaring gaps in the complex web of interactions, upon which a healthy ecosystem depends. The pronghorn, for example, has lost its natural predator and only its startling speed - of up to about 60mph - hints at its now forgotten foe.

By introducing living counterparts to the extinct animals, the researchers say, these voids could be filled. So, by introducing free-ranging African cheetahs to the Southwest, strong interactions with pronghorns could be restored, while providing cheetahs with a new habitat.

Other living species that could "stand in" for Pleistocene-era animals in North America include feral horses (Equus caballus), wild asses (E. asinus), Bactrian camels (Camelus bactrianus), Asian (Elephas maximus) and African (Loxodonta africana) elephants and lions (Panthera leo).

"Obviously, gaining public acceptance is going to be a huge issue, especially when you talk about reintroducing predators," said lead author Josh Donlan, of Cornell University. "There are going to have to be some major attitude shifts. That includes realising predation is a natural role, and that people are going to have to take precautions." {N.B. This could help cut down on illegal immigration crossing the border at night}

This idea is not as risky as it looks. After all, the HZ has already introduced Equus asinus to the web with no casualties. I see camels as making Arab immigrants more comfortable with their new home, Asian Indian software engineering immigrants will enjoy the familiar Asian elephants and african Americans will be reunited with familiar lions and elephants so that decendants will not lose their sprinting ability evolutionary adaptations. A win-win.