Earthworms Are Invasive - and Likely Hurting Insects - in Much of North America (nationalgeographic.com) 37
In the past five years, reports of staggering insect declines have stoked anxiety and debate concerning the fate of the "little things that run the world," as the late biologist E. O. Wilson once called them. As for the how and why of these declines, the prime culprits are habitat destruction, rampant use of pesticides, and climate change. But new research published March 30 in Biology Letters adds an unexpected suspect, at least for a large swath of North America: the earthworm. From a report: The study looked at 60 plots in an aspen and poplar forest in Alberta, Canada, and found that as the numbers of earthworms wriggling in the soil and leaf litter increased, the diversity and abundance of invertebrates aboveground decreased. These results might sound surprising, since earthworms are widely considered to be helpful garden residents. Worms earned their reputation by aerating and mixing soil with their burrows and releasing locked up nutrients in their castings, all of which can help certain plants thrive.
But this new study is part of a growing body of research suggesting that at least in the forests of northern North America, earthworms may not be the slimy angels of the underworld we tend to think they are. "When people talk about insect decline, they rarely talk about the soil," says Nico Eisenhauer, a soil ecologist at Leipzig University in Germany and one of the authors of the new study. "Many of the insects and invertebrates that are in decline have life phases in the soil. What you don't see flying around now has first disappeared from the soil, and earthworms can fundamentally alter soil conditions."
Earthworms' subterranean engineering isn't a problem in their native ecosystems, but in the northern half of North America, the glaciers of the last ice age wiped out virtually all soil-dwelling worms more than 10,000 years ago. The ice sheets covered nearly all of Canada, most of the northeast U.S., and much of the upper Midwest. When the ice receded, forests returned but the worms did not because they can only expand their range by a maximum of about 30 feet a year. These northerly ecosystems evolved for millennia in the absence of earthworms. Without worms munching through fallen foliage and churning the soil, these forests accumulated thick layers of leaf litter, which came to support a vast array of animals, fungi, and plants. Eisenhauer says even non-scientists can appreciate the difference.
But this new study is part of a growing body of research suggesting that at least in the forests of northern North America, earthworms may not be the slimy angels of the underworld we tend to think they are. "When people talk about insect decline, they rarely talk about the soil," says Nico Eisenhauer, a soil ecologist at Leipzig University in Germany and one of the authors of the new study. "Many of the insects and invertebrates that are in decline have life phases in the soil. What you don't see flying around now has first disappeared from the soil, and earthworms can fundamentally alter soil conditions."
Earthworms' subterranean engineering isn't a problem in their native ecosystems, but in the northern half of North America, the glaciers of the last ice age wiped out virtually all soil-dwelling worms more than 10,000 years ago. The ice sheets covered nearly all of Canada, most of the northeast U.S., and much of the upper Midwest. When the ice receded, forests returned but the worms did not because they can only expand their range by a maximum of about 30 feet a year. These northerly ecosystems evolved for millennia in the absence of earthworms. Without worms munching through fallen foliage and churning the soil, these forests accumulated thick layers of leaf litter, which came to support a vast array of animals, fungi, and plants. Eisenhauer says even non-scientists can appreciate the difference.
Groovy (Score:3)
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There is probably another correlation, like when earthwork are present, it means the surface plant life is in a restorative cycle and not conducive to above ground insects.
The study was done in the forest, not in disturbed regions. It really looks like earthworms are drastically altering the ground level ecology.
If I recall from reporting elsewhere one of the drivers of earthworm infestations was fishing cabins (escaped bait?) which is a nice randomization factor.
With the degree to which we're moving species around I do wonder what the planet it going to be like in a few hundred years.
Re: Maybe it's ad hoc fallacy (Score:2)
Perhaps we should just require everyone to leave their freezer door open so we can freeze the world and trigger a other ice age to kill off all the earthworms. /S for all the autists.
Evolve or die (Score:2)
It's nature's way.
Glaciers (Score:2)
in the northern half of North America, the glaciers of the last ice age wiped out virtually all soil-dwelling worms more than 10,000 years ago.
Apparently, this is just earthworms getting what is owed them. Everybody should be cool with that, right?
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... so what was the earthworm population like during the interglacial period? Maybe we're actually getting back to what should be normal, rather than the abnormalities / results from glaciation of the last 10K years.
I will wholeheartedly agree that humans have dramatically altered ecosystems all over the planet. And are responsible for and the cause of the climate change seen in the last 500 years.
North American forests are actually supposed to be a type of savana - not the dense thicket we have. We have
I welcome (Score:2)
our new below ground level overlords!
Oblig. (Score:2)
Not really invasive then (Score:2)
If the glaciers wiped them out in the north, aren't they just re-introducing themselves to their old habitat?
Man tries to do that sort of thing a lot. But it's bad if the worms are doing it on their own?
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If the glaciers wiped them out in the north, aren't they just re-introducing themselves to their old habitat?
It's an interesting question. A long time passed since they were wiped out by the glaciers. It may be fair to consider them invasive in today's world.
What if we were to genetically reproduce the woolly mammoth and reintroduce them to northern Asia. Would they be considered invasive?
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What if we were to genetically reproduce the woolly mammoth and reintroduce them to northern Asia. Would they be considered invasive?
No, because mammoths are way more cool than worms.
Re: Not really invasive then (Score:2)
And a whole lot more tasty. They'd be hunted to extinction within a week!
Huh? (Score:1)
10,000 years isn't enough time for significant "evolution" to occur that would make species intolerant of earthworms they previously lived amongst. This sounds like complete and utter (as Penn & Teller would say) "B-u-u-u-l-l-l-l Shit!"
Eisenhauer Is Calling for War on Earthworms (Score:2)
That is as far as I got the joke.
Earthworms get a lot of bad press lately (Score:2)
Is someone planning to invade them?
"in Much of North America" (Score:3)
Shouldn't that be "in Mulch of North America"?
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wait... which ones are we talkng about? (Score:2)
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Every since I was an angler in 1970's I'd dig earthworms near my home. Most had that light colored band 20% of the way from one end. the other end used to snap of an you'd get covered with worm junk. Yah. Gross. Are these the ones being called out? Not the Night Crawler with flat tail... and 50% larger size. Common Earthworm found in the black crumbly dirt in the trees?
Yeah, I live in Manitoba, a couple provinces over from Alberta and formerly the lakebed of glacial Lake Agassiz. I used to dig up earthworms for fishing in the 80s. I know for a fact people were digging up earthworms for many generations before that. Earthworms are not new here on human timescales. Maybe they are new on glacial timescales, but I'm having a hard time wondering why I should care.
Re: wait... which ones are we talkng about? (Score:2)
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Perspective (Score:2)
A millennium or so ago, glaciers wiped out the worm population. With the worms gone, waves of invasive insects and fungi moved into the worms' territory and prevailed there for thousands of year. Now that the worms are recovering their position in the ecosystem, they are being portrayed as villains for displacing the insects and fungi that have been squatting in the forests that were the worms' original habitat.
The important thing to note here is that the natural order of nature includes disasters and a l
Why would earthworms hurt anything? (Score:2)
I saw no explanation as to what damage the earthworms would do.
> "Without worms munching through fallen foliage and churning the soil, these forests accumulated thick layers of leaf litter, which came to support a vast array of animals, fungi, and plants."
So? What would happen if earthworms were there? How much would earthworms eat, and how fast? Maybe churning the soil, and leaving castings, would improve the soil, and thereby cause more trees to grow, and thereby create foliage?