Although the Great Lakes have more than 10,000 miles of shoreline—more than the United States’ Pacific and Atlantic Coasts combined—the region is uniquely positioned to stop biological invasions because of one incredible geographical fact: every overseas freighter that sails up from the East Coast into the lakes must pass through a single pinch point: the first lock on the St. Lawrence Seaway. It is 80 feet wide. That’s a little broader than some busy city streets and a little narrower than the distance between home plate and first base. There is a boat ramp at Lake Mead that is wider.
