Yep. Worms. Not the slimy invertebrates who write scurrilous, defamatory self-aggrandizing blogs and whine about free speech when they are taken to court over their lies, but actual earthworms. Nightcrawlers.
The little invertebrates we have in our gardens and at the end of fishhooks. They’re invading Canada. And they’re doing it rather quickly. For worms, that is. They’re actually being aided and abetted by us. Humans are the reason they’re here, and the main reason they are spreading at something slower than even a snail’s languid pace:
D. octaedra populations currently expand about 16 meters (around 52 feet) per year. At that rate, a single worm and its descendants—they reproduce asexually, so one worm reproduces on its own—could expand to cover the length of an American football field in six to seven years.
They spread thanks to hitching rides with humans, on cars, tires, shoes – and of course in fishing tackle boxes. Worm eggs and cocoons also travel as hitchhikers. Anglers who release their unused earthworms after a day’s fishing have helped the spread even more, so much so that PR campaigns are in full swing to stop anglers releasing them in the woods.
Non-native earthworms have been identified as a major threat to our forests:
…the impact of earthworms on forest vegetation was listed in 2011 as one of the top 15 emerging global conservation issues by the scholarly journal Trends in Ecology and Evolution.
The common everyday garden earthworm isn’t a native to North America. It’s a European invader, brought by settlers. Asian species have also been brought ashore more recently, and may even be destructive in your garden.