EDITOR'S NOTE: This is the final edition in a multi-part series looking at nonnative and invasive species and their impacts on Manistee County.
MANISTEE COUNTY — Northern Michigan is home to a wide variety of species, but few are as common as the earthworm.
There are roughly 25 grown earthworms per square foot of soil. That means as many as 81.8 billion worms could be right under our feet in Manistee County.
Earthworms play an important role in local gardens, compost piles and are sold as fishing bait throughout the region.
These crawlers have become so ubiquitous in Michigan that it may be surprising to find out they are not from here.
Elana Warsen previously told the News Advocate that “no worms are native to Michigan.”
Warsen, a Manistee worm farmer uses red wigglers to create vermicast, a nutrient rich soil amendment that she sells to other farmers and gardeners.
“All the worms that you find in your garden were imported by Europeans,” Warsen said in a prior interview. “Most of them have been here for a long time and most of the damage they caused has already happened.”
Several of northern Michigan’s most iconic species originated elsewhere, and many, like the coho and chinook salmon, were introduced intentionally.
By the 1960’s the Great Lakes were becoming an ecological disaster area, with invasive fish populations multiplying to the detriment of native species.
The alewife, a largely marine fish species, managed to bypass Niagara Falls through the Welland Canal arriving in Lake Michigan by 1949, according to Great Lakes Fishery Commission documents.
By the time the alewife gained a foothold in the Great Lakes, key predator species had already been decimated due to overfishing, habitat loss and the arrival of invasive sea lampreys in the 1830s.
Without natural predators to check the alewife, their populations grew rapidly, according to Scott Heintzelman, DNR fisheries unit supervisor. At their peak between 1950 and 1980, piles of rotting alewives were witnessed along Great Lakes shorelines, the Associate Press had reported.
Heintzelman said the decision was made to introduce the coho and chinook salmon to revitalize the Great Lakes Fisheries and “take advantage of the invasive alewife that exploded in population.”
Howard Tanner, the former head of the Michigan Department of Conservation Fish Division and director of the Michigan Department of Natural Resources is credited with introducing the non-native Pacific species into Great Lakes waterways.
Today, invasive alewife populations have decreased, and close to 10 million chinook and coho salmon swim in Lake Michigan, Lake Huron and Lake Superior, according to an AP report.
Descendants of these non-native salmon are still regularly stocked by state fishery officials like Heintzelman. DNR egg take operations at the Little Manistee River Weir in 2019 collected around 3 million chinook salmon and 4.4 million coho salmon eggs.
Related: Spring steelhead egg collection underway at Little Manistee River
Intentionally introduced non-native species like the coho and chinook salmon, as well as brown and steelhead trout make up a significant part of the region’s recreational fishing industry.
“These introduced species have adapted very well to Great Lake's ecosystem and tributaries. Most cold-water streams with good habitat support natural reproduction of all these species and many are no longer stocked,” Heintzelman said. “The Big Manistee, Little Manistee, Pere Marquette, Betsie and many area streams fall into this category. The stream characteristics and habitat are ideal for these species.”
Ironically, the biggest threat to these non-native fish may be other invasive species.
“The big issue today are quagga and zebra mussels that have drastically altered Great Lakes ecosystems by disrupting the food web,” Heintzeman said. “Their presence since the 1980’s has dramatically changed the productivity in the lakes from plankton to gamefish species and everything in-between. Sea lamprey are also still a major concern that cost millions of dollars every year to keep at bay by chemically treating streams they spawn in. With a major portion of Great Lakes energy tied up in mussel bio-mass the lakes now support fewer prey species and fewer predators."
But when does a non-native species, become an invasive one?
That answer is complicated, says Katie Grzesiak of the Northwest Michigan Invasive Species Network.
“There is a gray area between non-native and actually becoming invasive, depending on what lens you're looking through,” Grzesiak said. “As a food resource, parsnip is delicious. However, from a conservation standpoint, if it takes over a swamp in North America — which it can do — it can affect how the wetland deals with water and crowd out native plants. If it grows on a roadside or near sidewalks — which it does — its sap can hurt humans, causing chemical burns.”
The temptation to introduce a non-native species for their potential environmental benefits in the past has resulted in increased work for conservation groups today.
“Unfortunately, conservation groups have indeed introduced and even celebrated species that are now invasive, like autumn olive and kudzu,” Grzesiak said. “The major consequences have been reduced public trust and the seemingly-endless amounts of money and time lost responding to these invasive species.”
Kudzu was introduced from Japan to the United States in 1876. The Civilian Conservation Corps planted it to reduce soil erosion. Autumn olive, it was hoped could serve as a windbreak and to restore deforested lands.
Grzesiak said that similar questions can be raised about fish like the steelhead.
"They outcompete our native brook trout and damage stream ecosystems, but anglers really like how they fight on the line, and bring money to the state through fishing licenses," Grzesiak said, adding "My personal opinion, and even my opinion as an invasive species manager, may differ significantly from others.”
It is often a release from predation that allows invasive species to gain a foothold over their native counterparts.
“We have lots of species here that are so well-suited to our region, but we have the natural checks and balances of disease, parasites and predators to keep everything at a dull roar. When humans move a plant or animal somewhere else, we don't bring the predators, and things get out of hand because nothing eats them,” Grzesiak said.
These trends can also go in both ways, with several Michigan natives causing problems elsewhere. The common milkweed that is crucial for monarch butterflies is invasive in Europe, and field horse tail that is crucial for erosion control is invasive in New Zealand, according to Grzesiak.
Part one — Groups search for invasive bug in Manistee forests
Part two — Manistee's least wanted: Conservation group needs help tracking down these invasive plants
Part three — The impact of invasives: How conservation works in Manistee County
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Here's how invasive species were introduced to Manistee County - Manistee News Advocate
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