Transoceanic freighters haul 80 percent of the world’s commercial goods. But those boats inadvertently carry destructive cargo as well. An empty ship can suck up more than 10 million gallons of water to stay balanced as it crosses the open ocean. Upon its arrival into another port, the crew pumps the ballast water and any small animals or plants living in that water—sometimes thousands of organisms per gallon—into foreign harbors, where they invade and damage local ecosystems.

First came the killer bees and now comes the crazy ants. Houston is home to a new invasive species of ant, thought to have arrived via a container ship in 2002. The as-of-yet unidentified species is colloquially referred to as the crazy rasberry ant for its erratic foraging habits, appearing to dart in every direction but straight ahead. The ant has quickly become a nuisance both to the local ecology and to the people living with them. They are omivorous and will eat everything from flora to other insects and even the hatchlings of a local grouse called the prarie chicken.