Some people would say that dropping Asian elephants into nature reserves in North America is irresponsible. Those people clearly didn't consider A) the potentially hilarious and heart-warming results (see Operation Dumbo Drop) or B) that those elephants might have the ability to resuscitate ecosystems that disappeared over 13,000 years ago.

Believe it or not, serious conservation biologists have speculated that if living rough approximations of long-dead megafauna were introduced into appropriate North American ecosystems, they might have the ability to revert those ecosystems back to the state they were in 13,000 years ago. But why should we care about restore crazy ancient ecosystems? Well, the extinction of the original megafauna is attributed to over-hunting by ancient humans! Its our own fault that we're not all living in a prehistoric wonderland!

Humans: driving rare and beautiful animals to extinction since 11,000BC.

Further reading: "The Pleistocene re-wilding gambit" by Tim Caro in the June 2007 issue of Trends in Ecology and Evolution.