A grey wolf prowls through Yellowstone National Park near Mammoth Hot Springs in Montana. A group of 66 wolves was reintroduced to Idaho and Yellowstone in the late 1990s. They now total 2,800 ...

For decades, ecologists have puzzled over a mystery: Why do some natural habitats get overrun by invasive species while others seem to repel outside threats? In a classic 1958 book on the subject, the ...

A formula can be used to predict what happens when a new species is introduced into an ecosystem -- whether it will establish itself in the community or fail to gain a foothold and die out. When a new ...

If you liked this story, share it with other people. The forests of northern Europe provided Tim Christophersen with his first education. As a child in rural Germany he followed his grandfather, a ...