The view from 2015 is muddier. Like many modern wonders, Chicago’s canal solved the problem it was engineered to solve — the city’s sewage crisis — but it did so by sending the consequences downstream, to the Mississippi Valley and, in unanticipated ways, to all of us. In hindsight, it looks less like a triumph of the heroic age of civil engineering than like a prologue to the chastening age we live in now, the epoch geologists have proposed calling the Anthropocene, the age of the sixth extinction. One cause of this extinction: the trade routes and flight paths and navigable waterways with which we stitched continents and basins together. Thanks to us, species that evolved in isolation now collide, at times with devastating effects on ecosystems.

A hundred or so years after it opened, Chicago’s canal has been making news again. “Asian Carp DNA Found in Downtown Chicago, a Block From Lake Michigan” read a typical headline this past January. You’ve most likely seen footage of the slapstick scenes in which boaters motor through a storm of airborne fish. The aerialists in those videos are all silver carp, the only of the four invasive species of Asian carp that exhibits the entertaining fright response so popular on YouTube. Another of the four, the bighead carp, is constitutionally furtive, difficult to catch or detect. By the time the Asian carp footage went viral on the Internet, both species had already gone viral in the Mississippi watershed. Voracious planktivores, they reproduce quickly. Fully grown, they have no natural predators except humans. Commercial fishermen on the Illinois River now catch 25,000 pounds of Asian carp per day, with little discernible effect on the reproducing population.

Ecologists will tell you that it’s impossible to predict just how much havoc the Asian carp might wreak on the ecosystem of the Great Lakes, home to a $7 billion fishery; they will also tell you that we have more than carp to worry about. A 2011 report commissioned by the U.S. Army Corps of Engineers estimates that 87 species in the Great Lakes are at risk of invading the Mississippi and another 57 are threatening to travel in the other direction. They have colorful names: the spiny water flea, the bloody red shrimp, the northern snakehead, the red-rim melania. Those numbers do not include the 103 other species — the round goby, the zebra mussel — for which, according to the report, “any dispersal control mechanism is already too late.”

When dynamite and the steam-powered dredge breached the subcontinental divide in 1900, it also breached thousands of years of evolutionary history. Ecologists and political leaders in Great Lakes states downstream from Chicago argue that as long as the canal remains open, the invasions will continue. The best permanent solution, they say, is “hydroseparation.” In other words, we need to part the waters, restore the continental divide.

Last year, in a much-anticipated report with a misleadingly bland title, “The Great Lakes and Mississippi River Interbasin Study,” the U.S. Army Corps of Engineers affirmed the feasibility of hydroseparation but has yet to make a recommendation to Congress. Whatever recommendation it makes, the very prospect of re-engineering the canal suggests something about the ways our geographies and our own out-of-scale place in them have changed.

“The canal is the only remaining link wanting to complete the most stupendous chain of inland communications in the world,” one visitor to Chicago wrote in 1834. That use of the word “communications” sounds archaic to our ears, but there’s a furtive meaning bottom-dwelling in those etymological channels. Ideas, goods, images, species — everything is communicable now. In shortening distances, we’ve accelerated processes — climatological, evolutionary — to a pace even our own species, the most adaptable, invasive one on the planet, is struggling to keep up with.