Freshwater invasives get all the attention, but anybody look at our parks and highway land lately? Invasive species like garlic mustard, thistle and bindweed. And then there is the wild grape vine, which is a native species run amuck among its green brethren, crushing or blocking vital sunshine from reaching its victims.
There is a perfectly bad combination of things this year that is making the invasives situation worse.
1: The warm weather. Sustainable Story Hill held its annual Mitchell Blvd. Park weed-out on May 1, and the garlic mustard was as bad as I’ve ever seen it that early. The bindweed already is winding itself around native plants and trees, slowly killing them. (I’ve watched bindweed attack the same evergreens in Mitchell Blvd. Park every year, and am amazed at its tenacity. Bindweed kills over time. It wraps itself around branches in the spring, but goes dormant in the winter, making it appear the threat has passed. The cycle repeats itself the next year and the year after, though, and eventually overwhelming first a few branches and then the tree. I’ve pulled bindweed off the trees several times, but it keeps coming back).
Bindweed is overwhelming federal property along Gen. Mitchell Blvd.
2. Budget cuts in the Parks Department. No one left to fight invasives. The number of friends’ groups is way up, thanks to the efforts of Parks Director Sue Black, but friends’ groups can’t replace full-time staff. (Piles of twigs from the May 1 Mitchell Blvd. Park weedout are still sitting in the park. Maybe the Parks Department will pick them up by August?)
3. Our friends at the Wisconsin Department of Transportation, by far the most environmentally dangerous agency in state government. WisDOT stopped treating its thousands of miles of rights-of-way for invasives several years ago. It announced last year that it would reduce mowing to a once-a-year event. That means that WisDOT invasives are allowed to mature and go to seed and the seeds are ending up in parks and on private property. WisDOT creates the harm; we are left with the damage.
A variety of invasives along US Highway 41 in Milwaukee
Invasive species are a slow motion environmental disaster. Some of the damage, like that caused by the Japanese knotweed now making its way across the state, can be dramatic. According to the University of Wisconsin Extension:
Once established, this plant defies control, with roots that grow as deep as 9 feet and rhizomes (horizontal roots that send up shoots) that grow out to 60 feet. Though it dies to the ground with the first frost, every spring it sends up numerous early shoots along the whole length of these rhizomes. The rhizomes can also push their way under streets and up through pavement. In Bayfield, rhizomes have grown under streets to infest neighboring properties. A business in the United Kingdom spent over $600,000 to replace its parking lot after extensive damage from rhizomes, and one Welsh family even found the plant invading its living room as it pushed up from beneath the floor!
Other invasives do their damage with more subtlety. Bindweed, for example, has these bad attributes:
- Once established, nearly impossible to fully eradicate
- Out-competes native plant species
- Dense infestations can reduce crop yields by up to 60%
- Threatens restoration efforts by out-competing new plantings
Overall, invasives destroy diversity:
Invasive plants can replace the rich and diverse local flora with a monoculture consisting of only a single species. As the native plants are replaced by the invasive monoculture, many of the insects, birds, and other animal species that depend on the diversity of native plants for food, shelter, and reproduction decline rapidly or even become extinct.
An invasive species expert once warned me of another danger. If we allow an aggressive invasive to kill of plant diversity and establish a monoculture and then disease strikes the monoculture, what’s left?
Pretty scary to ponder.
