Book questions assumptions about earthworms
By Gary Sliworsky,
Ag rep, Emo
Earthworms are good, right?
Well, the following article by Anne Verhallen, soil management specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs, outlines that it may depend upon where they are found:
A new earthworm book by Dr. Cindy Hale of the University of Minnesota questions our assumptions about earthworms and the good they do.
Ontario farmers and gardeners recognize earthworms, particularly the dew worm, as a sign of healthy, active soil. However, our earthworms are not native to Ontario; the last glacier wiped them out.
The forested area of the Great Lakes developed without earthworms. Our current population of earthworms was brought here by pioneers and immigration, mostly from Europe.
Earthworms do help to decompose organic matter, cycle nutrients, stabilize aggregates, and, particularly in the case of dew worms, improve air and water drainage. These are all important for farm fields.
However, in the forested areas, their ability to feed on leaf litter and other organic residues on the soil surface is destructive.
Recreational fishing gets much of the blame. Leftover bait earthworms are dumped on the side of streams and rivers, allowing the earthworms access to the forested areas and the large amounts of leaf litter on the forest floor.
Hale’s book, “Earthworms of the Great Lakes,” looks at earthworms in the ecosystem and features beautiful colour pictures to help key out which earthworm you are looking at.
The book is an interesting discussion and a good reference on earthworm life cycle, feeding activity, and species.
For more information on invasive earthworms, check out http://greatlakeswormwatch.org/
Or if you are interested in getting a copy of the book, visit http://greatlakeswormwatch.org/educator/book.html
Some earthworm facts:
•Canadian bait worm exports to the U.S. are valued at roughly $110 million per year;
•There are no native earthworms in Ontario, the glaciers wiped out all the native earthworms about 10,000 years ago;
•Earthworms can move and colonize a field at the rate of just over 1.5 metres (five feet) a year;
•Earthworms were named the most successful species in the history of the world, based upon geographic spread, impact on ecology, and diversity;
•Once hatched, earthworms take 50-75 weeks to reach maturity; and
•Earthworms breathe through their skin.