An invasion has been going on under our noses. It is multipronged, ruthless and very difficult to repel. It has been called an "ecological apocalypse."
If you look out your window you may be able to see evidence of it. That pigeon flying past? An invader. Likewise, the cat by the garbage. Most are so familiar we don't even think of them as invaders, but they are not native to Japan. There are many more, and most are far less obvious.
"Non-native invasive species have been popularly described as one of the four horsemen of the ecological apocalypse," says Nisha Owen, a conservation biologist at the Zoological Society of London. "They are a real and pressing danger to biodiversity and ecosystems."