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Michigan's Invasive Species Community

Treating Phrag-bit

Greg Norwood

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I recently started a new position with the Michigan DNR, working closely with Ryan Wheeler and Christina Baugher, as invasive species coordinator for the wildlife division. I thought I would try out the forum here and offer a topic for "discussion" that has been on my mind. The image shows proliferation of European frog-bit (Hydrocharus morsus-ranae) following broad-cast herbicide treatment via helicopter and marsh master of Phragmites along Lake Erie.

Certainly, some invasive species arrive and thrive whether or not an ecosystem is degraded or is changing enough to promote the invader (e.g., Emerald Ash Borer). A pristine black ash swamp is as susceptible to major impact from emerald ash borer just as much as street trees. Yet our community is talking about more than prevention. We actively manage invasive species once they arrive and establish, hopefully using principles of integrated pest management. But this simple example of treating one invasive to promote another does challenge us to ask tough questions about the invaded environment. Does the system have a physical environment (and processes) that will always favor the invasive? Are there root causes that need to be ameliorated while dealing with the invasive and are we willing to address them? Are we communicating too much about the invasive and not enough about overall ecological health?

I'd be interested in hearing what others think about this on the forum.



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  • 4 months later...

Hi Greg - I came across your post when looking for how to contact you at your new position. Thanks so much for sharing these thoughts here and I hope to see others respond - this is definitely a topic that needs to be discussed and explored as we are now several years into large investments in invasive species removal and can step back and see what is working on longer time scales. Where it is not working in a more sustained way (i.e. without constant removal or management efforts), we need to ask the tough question of what could we do differently to facilitate the system to move in the desired direction. Obviously these are complex systems with so much more to understand than simply the characteristics of the invasive species themselves (see, for example, news on microbial associations of invasive and native Phragmites: https://www.sciencedaily.com/releases/2017/09/170905145600.htm).

Other researchers are also noting how changed systems - e.g. hydrology, nutrients - may be the real issue to deal with vs. the invasive species themselves, as removal will only lead to return of that invasive or another that is also adapted to those altered conditions. Of course, systems are more difficult to manage than species presence/absence (reducing upstream nutrient loading vs. herbiciding Phragmites), but if we do not take this broader approach it seems that all of of our efforts may not, in the long-term, actually benefit the areas we aim to restore.

Interested to hear others thoughts on this.

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