permaculture

[rafter sass <rafter@liberationecology.org>]

Food for thought, for the vermicomposters among us...

I do think we can rest assured that urban soils, in particular, stand  
to benefit from the introduction of just about *any*
life, even the "wrong" kind of earthworm...

~r



rafter sass
Liberation Ecology Project
liberationecology.org
518-567-7407
skype: raughter


Begin forwarded message:

> From: Deborah Neher <deborah.neher@uvm.edu>
> Date: November 18, 2009 5:27:31 PM EST
> To: PSSGRAD@LIST.UVM.EDU
> Subject: The Dirt on Worms
> Reply-To: deborah.neher@uvm.edu
>
> FYI - Some of you might be interested in this article. Our very own  
> Josef Gorres is conducting research on earthworms in maple forests.
>
> Cheers,
> Deb
>
>
>
> 11/17/2009 5:34:32 PM
> The Dirt on Worms
> by Pam Smith
>
>
>
> Most people don’t realize that many of the earthworms in our soils  
> are imports from Europe and Asia. Unearthing the truth behind them  
> is shedding new light on what we’ve perceived as old friends.
>
>
> The earthworm has long been considered the farmer’s friend. Their  
> burrowing has always been thought to aerate the soil while their  
> droppings provide fertilizer. No-till farmers count on these  
> tireless workers to improve soil tilth. And on their worst day,  
> earthworms sacrifice everything to land us a lunch from our favorite  
> fishing hole.
>
> So it may come as a surprise to learn that the beloved earthworm is  
> now getting a more slimy reputation. It turns out most earthworms  
> beneath our feet are exotic intruders from Europe or Asia. These sub- 
> terranean immigrants have moved farther into northern states and  
> Canada, where earthworms haven’t existed, and in some cases have  
> displaced the more beneficial native species in Southern states.
>
> “Soils with a lot of earthworms crawling around are generally  
> considered good in agricultural systems,” says Diane Stott, a  
> research soil scientist with USDA–Agricultural Research Service  
> located at Purdue University’s National Soil Erosion Research  
> Laboratory in Lafayette, Ind. “But all earthworms aren’t alike, and  
> the exotic species can have harmful effects even in agricultural  
> settings. Earthworms create macropores in the soil. A burrow that  
> reaches 6' deep might be good for drainage if you’ve got a lot of  
> water but bad if you don’t.
>
> “Also, the problem with earthworm channels is that recently applied  
> nutrients can be directly transported below the root zone during the  
> next rainfall,” she adds.
>
> Nuked forests. It is damage in hardwood forests that developed since  
> the last ice age that has gained the most attention. Without  
> earthworms, fallen leaves decompose slowly, creating a spongy layer  
> of organic “duff.” This duff layer is the natural growing envi- 
> ronment for native woodland wildflowers and tree seedlings, provides  
> habitat for ground-dwelling animals and prevents soil erosion.
>
> Invading earthworms eat the leaves that create the duff layer and  
> are capable of eliminating it entirely. Big trees survive, but young  
> seedlings and much of the understory plants perish.
>
> Cindy Hale, a University of Minnesota Duluth ecologist, spearheads  
> research and raises public awareness about the issue through the  
> Great Lakes Worm Watch. She says that unlike agricultural soils, the  
> soil in earthworm-free hardwood forests is naturally loose because  
> of the thick duff layer. When earthworms invade, they actually  
> increase the compaction of the soil, which can result in decreased  
> water infiltration and more surface runoff and erosion.
>
> Welcome to America. “We have no evidence that earthworms ever  
> inhabited Minnesota before European settlement,” Hale notes. “Even  
> if they did, the glaciers killed any native North American  
> earthworms in our region.” Scientists figure these European species  
> of earthworms were introduced on purpose or by accident by colonial  
> settlers—coming along for the ride in potted plants or in soil used  
> for ballast in ships.
>
> More recently, the widespread use of earthworms as fishing bait has  
> spread them to more remote regions of the country. Anglers—thinking  
> they are doing the world a favor—are famous for freeing their unused  
> bait in the forest or into the water.
>
> All common bait worms are non-native, including those known as night  
> crawlers, leafworms or angleworms. So are red wiggler earthworms,  
> which are sold and shipped all over the country for home compost  
> piles and vermi-composting (worm composting) operations. Hale says  
> red wigglers used in composting don’t like Northern winters and have  
> been shown to be more invasive in Southern regions if they escape  
> the composting operation.
>
>
> Night crawlers might be good for fishing, but they are robbing some  
> forests of nutrients. Scientists urge you not to introduce new  
> earthworms into the environment.
>
>
> Most recently, Asian varieties called Alabama jumpers, or jumping  
> worms, have been showing up as uninvited residents. They’re called  
> that because these worms have a very muscular and hyperactive  
> behavior that causes them to flip and jump.
>
> “Fisherman like them because of this activity,” Hale says. “The  
> scary thing is that they are able to live at high den-sities. We get  
> a lot of ‘nothing will grow here’ calls from these invasions. We are  
> concerned that these earthworms have the potential to have negative  
> consequences in ecosystems where you traditionally think of  
> earthworms being good, such as gardens and landscape,” she adds.
>
> Not all foreign earthworms are destructive, however. Of the  
> thousands of species around the globe, only approximately 15 of the  
> European and Asian varieties are considered to be bad guys. Hale  
> says that despite distinct differences in these worms’ anatomy,  
> color and behavior, most people never really notice and think “a  
> worm is a worm.” But research is showing that different species can  
> have very different environmental impacts.
>
> Perhaps the biggest challenge, Hale explains, is just getting people  
> to believe that earthworms are an issue. “There’s this mythology  
> that earthworms are always benevolent creatures that increase the  
> fertility and mix the soil for us,” she says.
>
> “It’s one of the ecological concepts people seem to really get. For  
> many people, earthworms are commonly known to be good—end of  
> discussion. That may be true in many agricultural systems, but not  
> necessarily so in native forests.”
>
>
> Contain Those Crawlers
>
> There’s not much to be done about earthworms that have already  
> invaded the landscape, says Cindy Hale, author of a book on  
> earthworms and an ecologist with the Natural Resources Research  
> Institute, University of Minnesota Duluth.
>
> “Controlling crawler introductions is the best way to contain the  
> problem,” Hale says. Scientists calculate that earthworms spread  
> only a short distance on their own. Here’s how you can help:
>
> Don’t dump extra worms in the woods or in or around ponds.
> Dispose of unwanted bait in the trash.
> If you use earthworms for composting (vermicomposting), freeze them  
> solid for at least one week (one month is better) to kill the  
> earthworms and their egg cases.
> Don’t transport leaves, mulch, compost or soil from one place to  
> another unless you are confident that there are no earthworms or  
> cocoons present in the mixture.
> Avoid planting non-native plants and shrubs. If you do, examine the  
> root balls and destroy any worms you find. Do not plant non-native  
> plants near woodlands or water.
>
>
> You can e-mail Pam Smith at psmith@farmjournal.com.
>
>
>
> © 2008 AgWeb.com. All Rights Reserved.
>
>
>
>
>
> Deborah Neher <deborah.neher@uvm.edu>
> Professor and Chairperson
> Plant and Soil Science
> University of Vermont