Last week millions of fish died in the river Rhine, victims of the worst case of pollution in the river’s history. Germans failed to sound the alarm sooner. The Dutch were furious.

The Rhine is one of the world’s most scenic and storied waterways. It was a commercial route before Christ, and Julius Caesar first spanned it with a bridge in 55 B.C. Along its picturesque banks, flanked by medieval castles, are Drachenfels, the cliff where Siegfried slew his dragon, and the…