Flying Sheep and Swamp Pythons
In 2012, police caught a helicopter pilot flying axis deer from Maui to the Big Island of Hawaii. The flight was part of a smugglers’ scheme to improve hunting sport on each island by swapping the deer, found on Maui, for mouflon sheep from the Big Island. Both species are native to the Mediterranean, and both pose considerable threats to Hawaii’s native ecosystems.
The interrupted airlift is only one of the ways humans have transported exotic species to disparate parts of the globe. In 1884, a horticultural exposition in New Orleans included a water hyacinth (Eichornia crassipes) specimen from the Amazon. A hit with local gardeners, it quickly colonized aquatic ecosystems across the Southeastern United States. Though the full extent of its impact is unclear, water hyacinth sits on the surface, shielding other aquatic plants from sunlight and other resources. More recently, around 150,000 Burmese pythons (Python molurus bivittatus), native to Southeast Asia, have colonized the Florida everglades. They were probably introduced by the escape or purposeful release of pet pythons. With little competition for resources, the snakes are thriving on a diet of local aquatic birds and even alligators.
Every case of species invasion is unique. Some creatures were introduced by accident, stowaways aboard cargo ships or caravans. Others were human attempts to biologically control local pests or even other invasive species, like the cane toad in Australia. But the overall effect is a distinctively rapid movement—and sometimes removal—of species on Earth.