Over the last two centuries, more than 180 have been found in the Great Lakes and the rivers that feed them. About 20% of those species are considered harmful either economically, ecologically or both.

A new study from researchers at McGill University in Montreal attempts to predict the future of invasive species in the lakes and what those species might be.

Predicting that future is more difficult than it sounds. What the future of the lakes looks like depends on what regulations are passed by the United States and Canada and how well those regulations are enforced. It also depends a great deal on the impact of climate change on the region.

In recent years, regulations have been put in place to protect the lakes against invasive species delivered by ship ballast.

As a ship takes on or drops off cargo, it takes on ballast water to mainntain a consistent weight. Regulations now require ships to take on ballast water in the Atlantic Ocean before entering the St. Lawrence Seaway and making their way to the Great Lakes. The enforcement of these regulations appears to have had a significant impact.

“No new species have been recorded since 2006. We may have closed the door on ballast water-mediated invasions. That remains to be seen.  But other doors are still open,” said Katie Pagnucco, PhD student at McGill and lead author of the study in a statement.

Still the researchers cannot make accurate predictions without knowledge of future regulation and enforcement. Instead the team came up with three different scenarios; optimistic, pessimistic and status-quo.

The status-quo scenario assumes that regulation and enforcement will remain at their current levels. It also envisions ballast regulations remain effective and that no new species make it into the Great Lakes in that way. Under this scenario the primary source of invasive species would be the trade in live animals as pets and a food source. The primary threat under this scenario would be Asian Carp, which are suited to the temperature conditions of the lakes and which could interrupt the food web with their voracious appetites.

The most pessimistic scenario assumes that ballast regulations will be ineffective in the long term and that the, largely unregulated, live trade continues to expand. In this possible future, many new invasive species would come from the Black Sea region, which is the source of many current invasive species in the great lakes. These could include the money goby and the killer shrimp.

Any of these hypothetical outcomes could be radically altered by the impact of climate change. As the water in the Great Lakes warm, they become hospitable to animals that could not have survived there previously.

“For example, the Great Lakes have already had all the invasive species from the Mississippi that could survive there, as a temperature barrier is protecting us from others” said Pagnucco.

The study will be published in a special issue of the Journal of Great Lakes Research which looks at the future as well as the recent history of the lakes. The study is also available online now.

It is also worth noting that it is difficult to tell how any of this will turn out for sure. In his recent book Where Do Camels Belong, Ken Thompson points out that species have been finding new homes for millions of years.

He mentions the Great Lakes invader zebra mussels in particular. While it is true that the animals attach themselves to boats and clog intake and drainage pipes, they have also become an important food source for many threatened bird and fish species and have made the water in the lakes clearer by eating algae.

“We’ve chopped down forests, built dams and turned the whole world into a giant cattle pasture, and then we’re surprised that some species quite like what we’ve done. We shouldn’t be surprised,” said Thompson in an interview with the CBC.