Our Publications

Hale, C.M. 2008. PERSPECTIVE: Evidence for human-mediated dispersal of exotic earthworms: support for exploring strategeis to limit further spread. Molecular Ecology 17: 1165-1169.

Hale, C.M. 1996. The nuts and bolts of Minnesota ecology, and beautiful too! Book Review of Minnesota's Natural Heritage: an ecological perspective, By John R. Tester. The Prairie Naturalist 28(1): 33-34. (no PDF available)

Hale, C.M. 2004. Ecological consequences of exotic invaders: interactions involving European earthworms and native plant communities in hardwood forests. PhD dissertation. University of Minnesota, Department of Forest Resources, St Paul, MN.

Hale, C. M., L. E. Frelich, P. B. Reich. 2006. Changes in cold-temperate hardwood forest understory plant communities in response to invasion by European earthworms. Ecology 87(7): 1637-1649.

Hale, C.M., J. Pastor, K. Rusterholz. 1999. Comparison of structural and compositional characteristics in old-growth versus mature hardwood forests of Minnesota, USA. Canadian Journal of Forest Research29: 1479-1489.

Hale, C.M. and J. Pastor. 1998. Nitrogen content and decay rates of hollow versus solid hardwood logs. Canadian Journal of Forest Research 28: 1276-1285.

Hale, C.M., L.E. Frelich, P.B. Reich, J. Pastor. 2008. Exotic earthworm effects on hardwood forest floor, nutrient availability and native plants: a mesocosm study. Oecologia 155:509-518.

Hale, C.M., L.E. Frelich, P.B. Reich, J. Pastor. 2005. Effects of European earthworm invasion on soil characteristics in northern hardwood forests of Minnesota, USA. Ecosystems 8:911-927.

Hale, C.M., L.E. Frelich, P.B. Reich. 2005. Exotic European earthworm invasion dynamics in northern hardwood forests of Minnesota, USA. Ecological Applications 15(3):848-860.

Hale, C.M. and G. E. Host. 2005. Assessing the impacts of European earthworm invasions in beechmaple hardwood and aspen-fir boreal forests of the western Great Lakes region. National Park Service Great Lakes Inventory and Monitoring Network Report GLKN/2005/11.

Hale, C.M., L.E. Frelich, P.B. Reich. 2004. Allometric equations for estimation of ash-free dry mass from length measurements for selected European earthworm species (Lumbricidae) in the western Great Lakes region. American Midland Naturalist 15(1):179-185.

Bohlen, P.J., S. Scheu, C.M. Hale, M.A. McLean, S. Migge, P.M. Groffman, D. Parkinson. 2004. Non-native invasive earthworms as agents of change in northern temperate forests. Frontiers in Ecology and the Environment 2(8):427-435.

Callaham, Mac A., Jr., Grizelle González, Cynthia M. Hale, Liam Heneghan, Sharon L. Lachnicht, and Xiaoming Zou. In press. Policy and management responses to earthworm invasions. Biological Invasions, online first DOI:10.1007/s10530-006-9016-6

Frelich, Lee E., Cindy M. Hale, Stefan Scheu, Andy Holdsworth, Liam Heneghan, Patrick J. Bohlen, and Peter B. Reich. 2006. Earthworm invasion into previously earthworm-free temperate and boreal forests. Biological Invasions, online first DOI:10.1007/s10530-006-9019-3

Holdsworth, A. R., L. E. Frelich, and P. B. Reich. 2007. Regional extent of an ecosystem engineer: earthworm invasion in northern hardwood forests. Ecological Applications 17:1666–1677.

Holdsworth, A. R., L. E. Frelich, and P. B. Reich. 2007. Effects of earthworm invasion on plant species richness in northern hardwood forests. Conservation Biology 21:997-1008.

Hobbie, Sarah E., Peter B. Reich, Jacek Oleksyn, Megan Ogdahl,  Roma Zytkowiak, Cynthia Hale, and Piotr Karolewski. 2006. Species effects on litter chemistry and microenvironment regulate litter decomposition and forest floor dynamics in a common garden experiment with fourteen tree species. Ecology 87(9): 2288-2297

Larson, E.R., K.F. Kipfmueller, C.M. Hale, L.E. Frelich, and P.B. Reich. (2010) Tree Rings Detect Earthworm Invasions and their Effects in Northern Hardwood Forests. Biological Invasions 12(5):1053-1067.

Loss, S. R., Hueffmeier, R. M., Hale, C. M., Host, G. E., Sjerven, G., & Frelich, L. E. (2013). Earthworm Invasions in Northern Hardwood Forests: a Rapid Assessment Method. Natural Areas Journal, 33(1), 21-30.

Proulx, N. 2003. Ecological Risk Assessment of Non-indigenous Earthworm Species. Minnesota Department of Natural Resources, 500 Lafayette Rd. St. Paul, MN 55155, Prepared for U.S. Fish and Wildlife Service, International Affairs, Division of Scientific Authority.

Reich, P.B., J. Oleksyn, J. Modrznyski, P. Mrozinski, S.E. Hobbie, D.M. Eissenstat, J. Chorover, OlA. Chadwick, C.M. Hale, and M.G. Tjoelker. 2005. Linking litter calcium, earthworms and soil properties: a common garden test with 14 tree species. Ecology Letters 8:811-818.

Reynolds, J.W., D.R. Linden, C.M. Hale. 2002. The earthworms of Minnesota (Oligochaeta: Acanthodrilidae, Lumbricidae and Megascolecidae). Megadrilogia 8(12):86-100.

Tiunov, A. V., C. M. Hale, A. R. Holdsworth, T. S. Perel. In press.  Invasion patterns of Lumbricidae into the previously earthworm-free areas of north-eastern Europe and the western Great Lakes region of North America. Biological Invasions, online first DOI:10.1007/s10530-006-9018-4

Extended Bibliography

Earthworm Identification keys

Dindal, D.L. (ed.) (1990) Soil Biology guide. John Wiley and Sons, New York.

James, S.W. Oligochaeta: Megascolecidae and other earthworms from southern and midwestern North America. pp. 370-386.

Schwert, D. P. 1990. Oligochaeta: Lumbricidae. p. 341-356.

Reynolds, J.W. 1977. The earthworms (Lumbricidae and Sparganophilidae) of Ontario. Life Sciences Miscellaneous Publications, Royal Ontario Museum, 100 Queen’s Park, Toronto, Canada, M5S 2C6

Sims R. W. and Gerard B. M. (1999) Earthworms: notes for the identification of British species. The Linnean Society of London and the Estuarine and Coastal Sciences Association.

Earthworms & Earthworm Ecology

Edwards, C. A. 1998. Earthworm Ecology. St. Lucie Press, New York.

Edwards, C. A. and P. J. Bohlen. 1996. Biology and ecology of earthworms. Third edition. Chapman & Hall, New York.

Hendrix, P.F. (ed.) 1995. Earthworm ecology and biogeography in North America, CRC Press, Boca Raton, FL.

Satchell, J.E. (ed.) 1983. Earthworm Ecology: from Darwin to vermiculture. Chapman and Hall, New York.

Plant and Animal Identification (taxonomic guides)

Gleason, H.A. & A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. New York Botanical Garden Bronx, NY, USA.

Voss, E.G. 1972. Michigan flora. Cranbrook Inst. of Science.

Barnes, B.V., W.H. Wagner and  C.H. Otis. 1981. Michigan Trees: A Guide to the Trees of Michigan and the Great Lakes Region. University of Michigan Press.

Tryon, R. 1980. Ferns of Minnesota. University of Minnesota Press.

Smith,W.R. 1993. Orchids of Minnesota. University of Minnesota Press.

Rathke, D.M. 1996. Minnesota trees. Minnesota Extension Service. St. Paul, MN.

Jannsen, J. Minnesota Moss Atlas

Field Guide to the Birds of North America. 2002. National Geographic Society. Washington, D.C.

Plants and Plant Ecology

Baskin, C. C. and J. M. Baskin (1998) Seeds: ecology, biogeography and evolution of dormancy and germination. Academic Press, San Diego.

Lakela, O. 1965. A flora of northeastern Minnesota. University of Minnesota Press, Minneapolis

Leck, M.A., V.T. Parker and R.L. Simpson (eds.). 1989. Ecology of soil seed banks. Academic Press, San Diego, CA.

Forest Ecology

Bormann, F. H. and G. E. Likens (1979) Pattern and process in a forested ecosystem. Springer-Verlag, New York.

Frelich, L.E. (2002) Forest Dynamics and Disturbance Regimes: studies from temperate evergreen-deciduous forests. Cambridge Studies in Ecology, Cambridge University Press.

Gilliam, F. S. and M. R. Roberts (eds.) (2003) The Herbaceous Layer in Forests of Eastern North America. Oxford University Press.

Green, J. C. (1995) Birds and Forests – a management and conservation guide. Publisher – Minnesota Department of Natural Resources, 500 Lafayette Road, St. Paul, MN

Tester, J. R. (1995) Minnesota's Natural Heritage: An Ecological Perspective. University of Minnesota Press.

Yahner, R. H. (2000) Eastern deciduous forest: ecology andwildlife conservation. University of Minnesota Press, Minneapolis, MN

Exotic Species Invasions

Mooney,H.A., H.L. Drake (1986) Ecology of biological invasions of North America and Hawaii. Springer-Verlag, New York.

 Drake,J.A., H.A. Mooney, F.di Castri, F.J.Groves, F.J.Kruger, M.Rejmanek, M. Williamson (1989) Biological Invasions: a global perspective. Wiley Press, on behalf of the Scientific Committee on Problems of the Environment of the International Council of Scientific Unions, Chichester, New York.

 Williamson,M. (1996) Biological invasions. Chapman-Hall, New York.

Habitat Classification

MN Department of Natural Resources (2006) Field Guide to the Native Plant Communities of Minnesota: the Eastern Broadleaf Forest Province. MN-DNR, 500 Lafayette Road, St. Paul, MN

MN Department of Natural Resources (2003) Field Guide to the Native Plant Communities of Minnesota: the Laurentian Mixed Forest Province. MN-DNR, 500 Lafayette Road, St. Paul, MN

Kotar, J. and T.L. Burger (1996) A guide to forest communities and habitat types of central and southern Wisconsin. Department of Forest Ecology and Management, University of Wisconsin - Madison, Madison, Wisconsin.

Kotar, J., J. A. Kovach and T.L. Burger (2002) A guide to forest communities and habitat types of northern Wisconsin., 2nd Edition. Department of Forest Ecology and Management, University of Wisconsin - Madison, Madison, Wisconsin.


Green, J.C. 1996. Geology on display: Geology and scenery of Minnesota’s North Shore state parks. Department of Natural Resources. St. Paul, MN.

Matsch, C. and R. Ojakangas. 1982. Minnesota’s Geology. University of Minnesota Press. Minneapolis, MN.

Popular Press: Books

Underground: how creatures of mud and dirt shape our world 

by Yvonne Baskin. A project of SCOPE, the Scientific Committee on Problems of the Environment. Island Press, Shearwater Books, Washington, 2005.

“Under Ground” explores the abundant life of the world beneath our feet, giving readers a closer look at soil and its diverse ecosystems. The author examines the roles that these organisms play in balancing the aboveground ecosystem as they make nutrients and minerals available for planktonic and plant life. We are invited to follow along as Baskin walks and talks with scientists and land managers who are pioneering ways to use our growing understanding of sediment and soil life to restore, sustain, or monitor the health of our lands and waters.

The Earth Moved – on the remarkable achievements of earthworms

by Amy Stewart. Algonquin Books of Chapel Hill, 2004.

Aristotle once called earthworms the intestines of the soil, and Darwin devoted the last years of his life to studying the humble worms in his backyard. But scientists still don't know very much about the prehistoric creatures that inhabit the soil beneath our feet.

Earthworms get a lot of credit for being gardener's helpers and great fishing bait. But these denizens of the dirt are more controversial than you would think. Some ecologists are sounding the alarm as foreign-born earthworms munch their way through the beds of pristine forests. Genetic researchers are studying worms to see if their spooky ability to regenerate may have applications for humans.

Amy Stewart who wrote a book about the little things that wriggle in her garden. They may be spineless, but she says, there's more than most of us know to the dark life of the earthworm

There’s A HAIR In My Dirt! A Worm’s Story

by Gary Larson. Harper Collins Publishers, 1998. Forward by renowned ecologist E.O. Wilson.

Gary Larson is at it again with a twisted natural history lesson told as a fairy tale. This story puts in print how naturalists talk about nature when children are not around. Side by side stories contrast the beautiful young maiden’s naive love of nature with the hard realities of how ecosystems function.


Popular Press: Articles

Print (2005)

Review of  Amy Stewart’s book “"The Earth Moved: On The Remarkable Achievements of Earthworms", San Francisco Chronicle: Jon Carroll, Tuesday, February 22, 2005 

“Non-native earthworms changing state’s forests”,  Prescott Journal (Wisconsin), Outdoors Section, Thursday May 12, 2005

“Diggin’ the Dirt on Earthworms” by Margo Retson Du Bernard, Midwest Gardening Magazine, March-April 2005

“Wiggling in the Woods – invasive worms disrupting forest ecosystems” by Megan Parker, The Country Today newspaper, Outdoors Section, Wednesday, June 22, 2005.

“Worming into new territory” by Sophia Estante, Wisconsin Natural Resources Magazine, August 2005, pages 24-28.

“Underground: how creatures of mud and dirt shape our world”, book by Yvonne Baskin. A project of SCOPE, the Scientific Committee on Problems of the Environment. Island Press, Shearwater Books, Washington, 2005.

Scholastic's Science World magazine, Jeanna Bryner
Assistant Editor, Science World
Scholastic Inc., 557 Broadway
New York, NY 10012
(212) 343-4538

Radio (2005)

NPR – Dick Gordon “The Connection”, Boston: call in show on earthworms, interview w/ Amy Stewart about her book. In was interviewed to give my perspective on the affects of earthworm in Minnesota and our educational efforts. March 16, 2005.

KDAL radio (Duluth), Dave Strandberg, on air interview, May 2005

Print (2004)

“Earthworms aren’t native to Minnesota”, Minneapolis Star Tribune, FIXIT column – January 4, 2004

“Attack of the alien earthworms”, National Geographic Magazine,  February 2004

“The Conqueror Earthworm”, Washington Post, by Kari Lydersen, March 29, 2004

Daily Oakland Press, Oakland, Michigan, early April 2004

“Invasion der Würmer”, bild der wissenschaft, pages 34-35, February 2004.

“Worm warfare: how exotic earthworms are wreaking havoc in North American forests”, Brooklyn Botanical Garden, Plant & Garden News, Volume 19, Number 1, Spring 2004

“Earthwormed Over” by Peter Friederici, Audubon Magazine, March 4, 2004.

“Earthworms – Eat, Excrete, Excavate, Repeat” By Margo du Bernard…some gardening magazine

"The Earth Moved: On The Remarkable Achievements of Earthworms", book by Amy Stewart. 2004 Algonquin Books of Chapel Hill, North Carolina.

Radio (2004)

“Killer Earthworms”, The Osgood File, WCBS Radio 880 AM, June 10, 2004

Newspaper and Magazines (prior to 2004)

“Foreign earthworm alert”, by Adele Conover. Smithsonian Magazine, August 2000

“A bad case of worms: slippery interlopers threaten Minnesota’s northern hardwoods”, by Norman Berlinger. Minneapolis Star & Tribune, St. Paul, MN, August 21, 2000

Audubon Magazine, article by Peter Friederici, spring 2001

Wildlife Conservation Society Magazine, article by Julie Maher, fall 2001

“About that bait bucket”, by Erik Ness. Wisconsin Trails Magazine, May/June 2002

“Exotic worms killing off North American plants”, by John Pickrell. National Geographic News Online, January 10, 2003

“The earthworm turns: off home turf, it’s down to no good”, by Ellen Byron. The Wall Street Journal, July 7, 2003

“An invasion of Hungrier, Bigger worms”, by Christopher West Davis. The New York Times, July  20, 2003

“Researchers build a case for earthworm’s slimy reputation”, by Anne Minard.

“Invasion of the killer worms”, by Eric Slater. Los Angeles Times, September 18, 2003

Radio & Television Interviews (prior to 2004)

Earth & Sky, public radio syndicated science program hosted by Deborah Byrd and Joel Block, spring 2001

Great Lakes Radio Consortium, Minnesota Public Radio, by Stephanie Hemphill, summer 2001

KARE11 NEWS, by Ken Speake, summer 2000

WDSE-TV, Duluth public television, Almanac North, fall 2001

Minnesota Public Radio, All Things Considered – spring 2002

Earthwatch Radio - University of Wisconsin Sea Grant Institute. by John Karl, summer 2002 (?)

Wisconsin Public Radio – September 2003

CBC Radio, As it Happens - October 2003

Video/Television (prior to 2004)

MN-DNR video press release

KDLH, Duluth, MN, Sunday morning outdoor program, author - Dave Carlson

“Evil Earthworms” Discovery Planet, Canadian TV program – November 4, 2003.