Fern assault
An alien invader has taken over the cypress trees at Jonathan Dickinson State Park in Hobe Sound, just north of West Palm Beach in Florida, USA. The state has its share of botanical invaders but Lygodium microphyllum , popularly known as the Old World Climbing Fern, has beaten them all. The fern literally chokes its victims. A recent study by Cornell University researchers pegs the cost of the invading species at about US $123 billion annually. The fern has now spread all over southern Florida from the Atlantic Ocean to the Gulf of Mexico, its spores probably blown across by the prevailing winds ( Scientific America , Vol 281, No 5).