Economics and declining birthrates are pushing large swaths of Europe back to their primeval state, with wolves taking the place of people. Germans are getting used to a new kind of immigrant. In 1998, a pack of wolves crossed the shallow Neisse River on the Polish-German border. In the empty landscape of Eastern Saxony, the wolves found plenty of deer and rarely encountered humans. They multiplied so quickly that a second pack has since split off. Soon, says local wildlife biologist Gesa Kluth, a third pack will likely form, possibly heading northward in the direction of Berlin. Wolves returning to the heart of Europe? A hundred years ago, a burgeoning, land-hungry population killed off the last of Germany's wolves. Today, it's the local humans whose numbers are under threat. "Big parts of Europe will renaturalize," says Reiner Klingholz, head of the Berlin Institute for Population Development. Once the baby boomers start dying out around 2020, population will start to decline so sharply in many European countries that there simply won't be enough people for every town to reinvent itself as an exurbanite enclave or tourist resort. It's similarly unclear how long current government policies can stave off the inevitable.