Association of State Wetland Managers - Protecting the Nation's Wetlands.

The Compleat Wetlander: Rethinking the Role of Invasive Species in Wetlands

This week is “National Invasive Species Awareness Week” and a number of organizations around the country are holding workshops or distributing information to educate and inform the public about the threats invasive species pose to our natural resources including wetlands.

Not all non-native plants are invasive. An invasive species is a non-native plant or animal that has the following characteristics that help them out-compete native plants and animals.  They are

  • Aggressive spreaders and/or prolific reproducers
  • Adaptable  to a variety of conditions
  • Have few natural controls in their new habitat
  • Are difficult to control or eliminate once established.

The presence of invasive species has environmental and economic consequences.  These plants and animals have disrupted the landscape often with dramatic impacts on wetland resources.  Nutria eat emergent vegetation encouraging erosion and loss of coastal freshwater wetlands.  Purple loosestrife and phragmites (common or giant reed) establish extensive monocultures which crowd out native plants and provide little benefit to wildlife.  Many of these plants and animals are from other continents.  Some were brought here intentionally. Purple loosestrife was an ornamental plant that could be purchased from nurseries.  Others, such as the zebra snail, hitchhiked in the ballast of oceangoing ships.

There is an Executive Order on Invasive Species http://www.invasivespecies.gov/home_documents/EO%2013112.pdf which established the National Invasive Species Council http://www.invasivespecies.gov/

Wetlands seem especially vulnerable to invasions. Even though less than six percent of the earth’s land mass is wetland, more than 24 percent of the world’s most invasive plants are wetland species. (Causes and Consequences of Invasive Plants in Wetlands: Opportunities, Opportunists, and Outcomes http://www.globalrestorationnetwork.org/uploads/files/LiteratureAttachments/60_causes-and-consequences-of-invasive-plants-in-wetlands.pdf)

I was somewhat surprised and intrigued, therefore, when I came across “Invasive Plant Medicine:  The Ecological Benefits and Healing Ability of Invasive.”

In describing his purpose in writing a book about the benefits of invasive species, author  Timothy Lee Scott states:

I am here in defense of these plants, and I am set to demonstrate that the population of invasives is wrongly convicted.  I lay out evidence that these plants serve essential ecological functions and actually benefit the environment, with prospects to strengthen local economies and with their ways of stimulating our health and healing disease.

Included in the book is an analysis of the ecological and medicinal benefits of many well known invasive species.  For example the ecological benefits of phragmites include the plant’s ability to stabilize and rehabilitate severely damaged sites that have extreme pH, high salinity, and phytotoxins.  It accumulates soil organic matter to recreate natural habitat.  It can accomplish this much faster (30 years) than other pioneer species (120 years) and provides many of the wildlife benefits of natural cordgrass.  It has a long list of medicinal uses including scientific studies that quantify its antimicrobial and antiaging properties.

It is common knowledge that many invasive species colonize areas of human disturbance    where vegetation has been removed, soils damaged and compacted, and sometimes toxics have been added.  It’s possible that invasive species have much to tell us about what has happened on these sites and what is needed to fix them.  Viewing invasive species as nature’s pioneer rehabilitators may a productive approach and rather than eradicating these species, perhaps attention should be directed to understanding why they have colonized a particular site and how humans can help them help us restore and improve the natural landscape.

Additional Information on Invasive Species:

Ten Ways to Celebrate National Invasive Species Awareness Week: http://www.nisaw.org/2012/ways_to_observe.pdf

National Invasive Species Council White Papers: http://www.nisaw.org/InvasiveSpeciesWhitePapers.pdf

The Nature Conservancy Website on Invasive Species and Protecting Native Plants: http://www.nature.org/ourinitiatives/habitats/forests/howwework/protecting-native-plants-and-animals-taking-on-the-invaders.xml?src=CPC.AWG.CE2.AG177.CC59.CL2.MT2.KW923&gclid=CI3dqqX_u64CFQRN4Aodtmbc9g

USGS National Wetlands Research Center Website on Invasive Species http://www.nwrc.usgs.gov/invasive_species/nwrc_research.htm

USDA Website on Aquatic Invasive Species: http://www.invasivespeciesinfo.gov/aquatics/main.shtml

The United States National Arboretum Website on Invasive Plants (includes links to state websites) http://www.usna.usda.gov/Gardens/invasives.html

Citizen’s Guide to the Control of Invasive Plants in Wetland and

Riparian Areas, Chesapeake Bay http://www.dnr.state.md.us/irc/docs/00015763.pdf

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