Earthworms & Global Warming

Invasive, non-native earthworms (public domain photo)

Monday, May 20, 2019

This week, here in Central Oregon, you wouldn’t know it’s summer. Instead, it’s been so windy, rainy, and chilly that I pulled from storage cold-weather clothing. These mornings, while going down to feed horses, I’m really silly-looking, in a winter jacket that covers the upper part of my flapping bathrobe.

We had a couple of warm weeks, and fortunately, one while my visitor was here. Earlier, as the summer approached, I watched Robins multiplying and scouting for worms, Blue birds building a nest in my barn, California Jays diving for tossed peanuts, and Starlings returning to their summer lodging among the barn’s roof supports.

In our earliest rain, a big earthworm that wiggled into my garage appeared half-dead when I spotted it. I rushed it to the garden, covered it with dirt, and hoped it might survive. That was the only attention to the species that I paid, before seeing a New York Times article about an “earthworm dilemma”: https://www.nytimes.com/2019/05/20/science/earthworms-soil-climate.html?action=click&module=Discovery&pgtype=Homepage

According to the article, Canadian scientists are seeing in the boreal forest, the world’s most northerly forest, much evidence of earthworm activity–highly unusual, because native earthworms disappeared from most of northern America, 10,000 years ago, during the ice age. The current earthworms are an invasive species from Southern Europe, brought to Northern America by settlers centuries ago. They survived the ice age and are thriving.

This got to me: “As the worms feed, they release into the atmosphere much of the carbon stored in the forest floor [and] climate scientists are worried.” Worms speed decomposition, which releases carbon dioxide. Scientists calculate that earthworms currently occupy 9% of the Northeastern Alberta forest, and will occupy 50% by 2049. Worm feasting reduces the depth of leaf litter and reduces the forest’s native plants, so nonnative plants can enter and force out endemic plants. Scientists predict that the worm activity could eventually turn forest into prairie.

There’s evidence of earthworms also having spread to parts of Alaska’s boreal forest, where their biomass (total mass) is 500 times greater than that area’s moose population. Those earthworms on the edge of the northern boreal permafrost, will increase the pace of melt and the release of carbon.

There are no known methods of eradicating earthworms from boreal forests. Scientists are cautioning people to avoid transporting worms to unaffected parts of the forest. They’re also watching Asian earthworms–a new invader–moving toward Southern Quebec and Ontario.

Dear Friends, elements that affect climate include critters beneath our feet. Diana

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