Levin: Aliens In The Compost

Oct 13, 2017

My compost pile sits west of the garden and consists of two ripening mounds of table scraps, grass clippings, and hand-pulled weeds that I turn from time to time.

When I do, sweet aromatic steam rises from an organic welter of interior blackness. Worms love it here and convene by the hundreds, maybe more. But none are native. All are exotic. And some dangerously so.

In fact, north of the southern boundary of the last glacier, which in Vermont scrubbed the bedrock bare, there are no native earthworms anywhere in North America. Every single earthworm in New England is an alien invasive. Of Vermont’s sixteen species, fourteen are from Europe, two from Asia.

The pedigree of every worm ever laced on a fishhook, every worm ever yanked by a robin from your front yard, can be traced to England or France. And even Japan. Several species arrived here in the seventeenth century, with the first European colonists. Others are more recent immigrants.

A Dutch study has determined that earthworms colonize approximately thirty feet of turf per year. And at that rate, we’d have had to wait fifty thousand years for earthworms to find us on their own.

The other day, I was helping a Pomfret friend stack wood, when I picked up a thin, four-inch- long worm off her driveway that twitched in my palm like a live wire. It was the “crazy snake worm,” a Japanese native that arrived in the northern United States in the 1980s. And it’s one of several species implicated in the elimination of the organic layer of soil in the northern hardwood forests.

Vermont woodlands evolved without earthworms, so our forests depend on soil fungus and invertebrates to slowly decompose organic matters into useful plant nutrients.

Invasive earthworms, however, digest the critically important leaf litter so rapidly that they threaten the very stability of hardwood forests. They also increase soil emission of two leading greenhouse gases - carbon dioxide and nitrous oxide - by more than one third.

So one might say earthworms have a starring role in the climate change drama - that sylvan “soap opera” with vast and negative implications across the Northeast.

With that in mind, I surrendered the hapless worm to a flock of hens scratching around in the yard nearby - where they made short work of it.