Rideau Canal - Invaders
The Rideau Canal was built to defend Canada - but it also turned out to be a perfect avenue for invasion.
EPISODE NOTES
TRANSCRIPT
The Rideau Canal was built to help defend Canada. But what we didn’t know at the time is, we’d also built a perfect avenue for invasion.
The focus tends to be on the human achievement of the canal - which was incredible. But that tends to drown out its ecological impact.
And starting at the beginning - the construction of the canal totally reshaped the geography and ecology of these waterways. We cut down swaths of trees and drained marshland for settlement along the Rideau. And even though only 19 of its 202 kilometers were wholly man-made canals, sediment analysis shows that our impact went much further. Dams and mills transformed former wetland deltas into rivers and lowlands into lakes, permanently changing the landscape from Ottawa to Kingston.
And the rise in human activity started messing with some of the canal’s wildlife. Migrating species were used to moving through unimpeded but suddenly they were hitting walls, gates, or worse, boat propellers. The American eel, for example, a former canal resident, hasn’t been seen here since 2000.
But while individual species suffered, the net effect was actually homogenization. As the canal connected more bodies of water, naturally plants and animals would start to intermingle, and any uniqueness would get smoothed out.
That physical connection, along with the human activity, is the most dangerous combination in the canal. Because that is the avenue for invasion. Boats arriving at either end can carry invasive species with them. And once those species are in the canal, we’ve built them a freeway for colonization, hitching rides through the locks and expanding into each new body of water.
Eurasian watermilfoil, an obnoxiously tenacious water weed, is shading out native species and in some cases straight up sucking the oxygen out of the water in the fall. And there’s invasive fish like the round goby, and molluscs like these snails and the infamous zebra mussel - both of which we’ll get into later.
At this point the cat’s pretty much out of the bag - it’s not like we can reverse course, fill in the canals and invite the invasive species to vacate. But there is a new, rising consciousness around these ecological issues, and new technology is helping to track and combat them. You can even download a handy app for your phone to crowdsource sightings, and finally start to fight back against the invasion that’s been happening under our noses for decades.