The zebra mussel has been a poster child for invasive species ever since it unleashed economic and ecological havoc on the Great Lakes in the late 1980s. Yet despite intensive efforts to control it and its relative, the quagga mussel, these fingernail-sized mollusks are spreading through U.S. rivers, lakes and bays, clogging water supply pipes and altering food webs.
As an environmental historian, I study how people’s attitudes toward nonindigenous species have changed over time. Like many other aquatic aliens, zebra and quagga mussels spread to new bodies of water when people move them, either accidentally or deliberately. Human-built structures, such as canals, and debris can also help invaders bypass natural barriers.
In my view, reducing the damage from these outbreaks – and preventing them if possible – requires understanding that human activities are the root cause of costly biological invasions.