FORT LAUDERDALE, Fla. -- Non-native iguanas are multiplying so rapidly in South Florida that a state wildlife agency is now encouraging people to kill them.

A Florida Fish and Wildlife Conservation Commission news release says people should exterminate the large green lizards on their properties as well as on 22 public lands areas across South Florida. It doesn't say just how civilians should try to kill them.

Iguanas aren't dangerous or aggressive, but they damage seawalls, sidewalks, landscape foliage and can dig lengthy tunnels. The males can grow to at least 5 feet (1.5 metres) long and weigh nearly 20 pounds (9 kilograms).

The commission says female iguanas can lay nearly 80 eggs a year. They are allowed to be kept as pets but are not protected by any law except anti-cruelty to animals.