The Aliens Are Coming Consider, for example, the walking catfish, which is now colonising China, Thailand and the United States, after escaping from fish farms and ornamental ponds(6). It can move across land at night, reaching water that no other fish species has colonised. It slips into fish farms and quietly works through the stock. It can burrow into the mud when times are hard and lie without food for months, before exploding back into the ecosystem when conditions improve. It eats almost anything that moves.

..But in many parts of the world the policy appears to consist of staring dumbly at the problem while something can be done, then panicking when it’s too late.