The spread of invasive species is more than an academic and scientific issue. Zebra mussels – which first arrived in the Great Lakes, then spread inland – cost the nation more than $250 million a year.

The Army Corps of Engineers is looking at ways to close a gateway just outside of Fort Wayne where unwanted fish can cross between the Great Lakes and Mississippi River watersheds – but the more tightly it is closed, the greater the financial, aesthetic and even environmental costs. Area residents should consider attending an early December meeting to learn more.

In 2010, the Indiana Department of Natural Resources installed a mesh fence in fear that the invasive Asian carp would cross from the Wabash River to the Great Lakes. The carp is a voracious eater of algae and other plankton that deprive other fish species of their nutrition. Already ubiquitous in the Wabash, the carp can even endanger people, leaping up to 10 feet and slamming their 20-pound bodies into boats and anglers. If they proliferate in the Great Lakes, scientists and others fear the carp could decimate the $7 billion Great Lakes fishing industry.

A report issued earlier this month by the Army Corps notes other aquatic nuisance species that could cause damage in a Wabash-Maumee River crossover. For example, VHSv – a fatal fish virus that attacks and breaks blood vessels of more than 50 species of fish – was discovered a decade ago in the Great Lakes. It threatens to cross over to the Wabash/Mississippi watersheds.

The Army Corps report offers nine options for reducing the threat of crossover. The most effective – but most damaging to Eagle Marsh – calls for building a $14 million concrete wall across the marsh. The report acknowledges the wall would “detrimentally alter the wetlands and aquatic habitat within and around Eagle Marsh.”

Other proposals emphasize higher berms along ditches and elsewhere, more fencing, riprap (a wall of stones), pumping stations and/or sluice gates, which can be raised and lowered.

Cost estimates for other options range from $2.8 million to $20 million.

“We don’t want invasive species to cross the Eagle Marsh,” said Betsy Yankowiak, director of preserves and programs for the Little River Wetlands Project, a 22-year-old non-profit that develops and preserves wetlands in the Little Wabash River watershed and owns Eagle Marsh. The group wants “a plan that doesn’t totally destroy all the hard work we’ve put into Eagle Marsh since 2005, while achieving the goal” of preventing crossover of invasive species.

Any project is most likely years – perhaps decades – away. One major question is funding: Even if Congress decides to spend the 65 percent federal share of a typical Army Corps project, no local funding exists. And the Army Corps may decide that Chicago waterways pose even bigger threats to crossover, especially of Asian carp, and should get first priority.

Area residents who care about the environment, are interested in fishing or simply want to see the tax dollars put to the best use should consider attending a Dec. 4 local meeting at the downtown library, where Army Corps representatives will explain the issue.