Between the rhetoric and the reality — that’s where Great Lakes protection goes wrong.

The latest example is all over the news. It’s called the invasion of the Asian carp. Now somewhere within miles of Lake Michigan, two species of carp are a big threat to the $7 billion sport fishery of the entire Great Lakes system. They could displace the native and introduced species that are already here, and since North Americans have never really warmed to the taste of carp meat, the fish could turn the Lakes into an angler’s nightmare.

Michigan Attorney General Mike Cox has sued to force closure of the waterway that may give the carp access to Lake Michigan. Five states and Ontario have joined Michigan in the U.S. Supreme Court case. Illinois and the City of Chicago are fighting the closure, principally because they claim it would halt barge traffic on the Chicago Ship and Sanitary Canal, costing the regional economy millions. In a surprise and unwelcome move, the Obama administration’s solicitor general has intervened on the side of Chicago and Illinois on what is described as procedural grounds.

It’s good Cox and the other states are taking strong action, but the carp should never have gotten this far. The roots of this mess go back years, but it’s the last decade of government bumbling that deserves contempt.

Two human “improvements” are responsible for the carp threat. First, governments and fish farmers intentionally introduced the ravenous non-native carp into the lower Mississippi River in the 1970s to control weed growth. The carp escaped confinement during floods. They’ve been swimming north ever since. They can grow to 80 pounds and 6 feet in length and consume 40 percent of their body weight each day.

Second, when Chicago’s stinking sewage flowed into Lake Michigan in the late 1800s, it killed people who drank water from the city’s offshore intake, unleashing typhoid and cholera. In 1900, Illinois — over the objections of the other seven Great Lakes states — blasted a connection between the Chicago River and the Mississippi River, reversed the flow of the former, and sent the sewage toward St. Louis. Related improvements turned the canal into a profitable system for barge shipments of grain and other commodities.

The danger of the carp to the Great Lakes has been understood for at least a decade when the fish started swimming up the Illinois River. The solution proposed by the Army Corps of Engineers, responsible for commercial navigation, was an electric barrier that would shock the carp into turning back. The plan had plenty of skeptics and until recently was inadequately funded.

Then suddenly late last year evidence was found of carp DNA downstream of the electric barrier, and a decade-old emergency suddenly became a crisis. There is still no evidence that the carp are spawning in Lake Michigan, but they’ve got a fighting chance.

It says a lot that the mess has erupted within the 18 months since the Great Lakes States finished work on a Great Lakes water protection compact and just three months since Obama and Congress sent $475 million in new money to the Great Lakes for protection and restoration.

That was the easy part. Heralding commitment to the beauty and majesty of the Great Lakes comes easy for politicians. Accepting money from somebody else to protect them comes easy, too.

What comes harder is making politically difficult decisions and sacrifices to protect them. And Michigan’s record in this department is only marginally better than that of its neighbors. We’ve tolerated water raids by international companies, let toxic threats close to and in the Great Lakes languish, and failed to crack down invasive species in ballast water — each because a politically influential industry put its interests ahead of the Great Lakes and persuaded Michigan politicians to go along.

Detroit Free Press outdoor writer Eric Sharp, who has done an outstanding job of documenting the Great Lakes carp atrocity, has written that if Cox wins his lawsuit and also takes on the St. Lawrence Seaway, the chief route by which invasive species enter the Lakes, he “would be remembered as the equal of the greatest environmentalist in Michigan history: former Gov. William Milliken.”

Not quite. Mike Cox is no Milliken. But a win on the carp suit would at least put the reality of Michigan politics on Great Lakes protection temporarily back in line with the rhetoric.

(Dave Dempsey, who served as environmental adviser to Gov. James Blanchard, was the winner of the 2009 Author Award from the Michigan Center for the Book. His most recent book is “The Waters of Michigan.”)