Most Earthworms Are Invasive, What Does that Mean for Ecosystems?

An illustration of a mass of worms beneath a forest.

We generally think of earthworms as beneficial and essential to healthy soils–and in many ways they are! But did you know that much of the United States isn’t actually supposed to have any earthworms?

As the Atlantic reported,

“Until about 10,000 years ago, a vast ice sheet covered the northern third of the North American continent. Its belly rose over what is now Hudson Bay, and its toes dangled down into Iowa and Ohio. Scientists think it killed off the earthworms that may have inhabited the area before the last glaciation. And worms—with their limited powers of dispersal—weren’t able to recolonize on their own.”

So that means one thing: we’ve brought all sorts of earthworms to North America and not all of them are happy little soil creators. While gardeners love earthworms, they’re not quite so beneficial for forests, especially invasive jumping worms

What’s Happening: A globalized world means that earthworms have wound up all over the world–European earthworms now live on every continent except for Antarctica. But here’s the issue, as the Atlantic explained it: 

  • Although earthworms can be helpful for breaking up compacted soils and breaking down organic matter, worms can also cause trouble in agricultural fields.
  • Their burrows create channels that allow nutrients and pesticides to leak from fields into nearby waterways, and carbon dioxide and nitrous oxide to escape into the atmosphere.
  • In fact, a 2013 review of recent research found that worms likely increase greenhouse-gas emissions.

Jumping Worms: One the of most egregious invasive worm species are jumping worms, which are known for the violent way in which they wiggle. As Nature explained,

  • Jumping worms, consisting of various non-native species from multiple genera, have become established in a number of eastern and southeastern states. In 2013, species from the genus Amynthas were confirmed for the first time in the Upper Midwest, at the University of Wisconsin-Madison Arboretum.
  • In the forests and prairies of the Upper Midwest, the jumping worm could significantly alter habitats and decrease biodiversity.

What’s even more startling is that farmers are reporting that jumping worms are killing their crops in ways that European earthworms never did. 

Why This Matters: It’s still unclear about all the impacts that invasive earthworms might have on ecosystems. For one, there’s a chance they could speed up climate change as they speed up the process of decomposition in soil and release CO2 as a result. On the other hand, worm casings may be able to sequester carbon in the soil. We wrote earlier this week about the challenges we’ll face in managing nature and biodiversity in the climate change era, looks like we have to add worms to the list! 

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