TWO species of beetle are credited with saving the economy of Benin in West Africa $260 million over 20 years. Between them, they have overpowered an aquatic super-weed that kills fish, interferes with boats and changes the ecology of lakes.
It is a familiar story. Foreign travellers develop a penchant for an exotic flower and take it home. There it escapes and runs amok, having no natural predators. In this case, the rampaging pest is the water hyacinth, which was transported from Brazil by 19th-century horticulturalists. It has now become a major problem in tropical waterways, having spread to 50…
