Anchorage Daily News

Who would have thought that earthworms could be considered bad, exotic or invasive? Certainly not me, and I bet you didn't think so either.

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Both Organic Gardening and Horticulture magazines recently printed almost identical items on the dangers of earthworms in the forest. Both cite studies done by scientists at the University of Minnesota (without mentioning the source) that point to a decline in the health of Minnesota hardwood forests and some loss of species.

"For over 12,000 years, Minnesota's forests developed without the influence of earthworms. If North American earthworm species ever inhabited Minnesota, they were extirpated during the last glaciation. Without earthworms, forests' fallen leaves accumulated and developed a thick duff layer that provided an excellent rooting zone for herbs and tree seedlings. ...

"Over the last 150 years, European earthworms were likely accidentally and intentionally introduced with the importation of plant materials and soils from Europe and the use of worms as fishing bait across the region. Ongoing studies suggest that invasive European earthworms have a notable effect on forest understory plant diversity and composition, nutrient cycling and soil properties.

"Since the 1980s, forest managers in the Chippewa National Forest have been concerned about the loss of understory plant cover and diversity in areas with high earthworm populations. Exotic earthworms are considered a major factor in the population decline of the threatened goblin fern."

Popular thought is that earthworms are gardeners' friends. They help loosen the soil, providing aeration and drainage, help compost kitchen waste and leave behind nourishing castings. They feed birds. But because they are not native in the northern wild, they could disturb the delicate balance of the forest ecosystem.

Think of other accidentally introduced species, like the spruce bark beetle and the birch leaf miner. Even though they are above-the-ground insects and worked their damage swiftly, they are also arguably easier to combat and control.

Consideration should be given when transplanting plant materials in areas close to the forest edge. Worms move slowly, so any damage they might do may not be noticed for a long time. And since they can burrow far into the ground, and they can reproduce fairly rapidly, if they begin to cause any damage in the ecosystem, they would be difficult to eradicate.

Professor John Yarie of the UAF Forestry Experiment Station said that as far as he knows, there are no earthworms in Interior Alaska and no studies are being done.

Michele Hébert, land resources agent with the Fairbanks District Office of the Cooperative Extension Service, said, "No one has even done a look at what species are in Alaska. We have no data. No one has even had a good look at what we have. It's hard for me to think that there may not be native earthworms (somewhere in Alaska). Not all Alaska was glaciated. ... There were some grasslands."

She wondered if there is anyone in Alaska who could even identify different species of earthworms. Maybe the subject for a speaker at a future garden conference?

So think twice the next time you want to bring a piece of your favorite fern or a new shrub or tree from the nursery to your remote cabin in the woods. If you can, make them native to the area, bring them bare-root and keep them as close to the cabin as you can.

Who knew?

Fran Durner writes the Talk Dirt to Me blog at adn.com/talkdirt.

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