Sunday, May 31, 2009

Invasive species: The Great Green Divide

Some workhorses of traditional ornamental gardens, have jumped the fence, and become natural area terrorists. Uncompromisingly these invasive species dominate and change the shape and community around them. They destroy the web of weak ecological interactions creating a few strong relationships and depress the ability of the local ecosystem to sustain itself. They alter the culture of the place and overlay a new foreign structure bending the natives to their will. These ornamental invasive plants create biological deserts which negatively impact all the ecosystem services that were in the system, replacing some with new services while denying others especially those necessary relations in the food web. Ultimately the invasive while able to duplicate some of the regulating services such as CO2 sequestration begin to reduce the efficacy of genetic diversity through reduction of habitat services.

As all politics are local, so too any conversation about invasive species must at some point become a local discussion. Perforce my invasive plant discussion is centered in and on the Mid Atlantic’s Chesapeake Bay region where is not enough to simply remove the invasive plants, but rather, a plan of management including restoration or replacement needs to be created and followed; if not you will be enduring your own eternal Sisyphian chore.

An example of a foundational, dependable basic gardening solution plant in the Chesapeake Bay region of the Mid Atlantic is English ivy, Hedera helix. Solving many garden and landscape problems, English ivy used as a ground cover, covers the landscape with a uniform evergreen blanket. Ellen Russell writes:
Evergreen groundcovers can help hide a fence, fill in shady, bare spots on lawns and underneath trees, and provide interesting color and foliage to flowers and plants. Groundcovers climb over rocks and yard debris, and carpet an area in color where no other plant can grow. As an added benefit, evergreen groundcovers keep their foliage and color throughout the year, continuing to provide beauty and color without ever loosing the clean look of the planted area of yard.”
This monochromatic, pleasingly deep-green, living blanket smothers weeds and provides a feeling of a well kept property. The serenity and peacefulness that comes from an easily read and simplified garden design does not tax the landscape literacy of all who pass by.

On the other side of the great invasive species divide, the most attractive traits of a traditional garden setting are the ones that most offend. The very lack of species diversity, so prized along a drive or on a difficult to maintain embankment disturbs the sensibilities and desires of habitat and refugia creation. The lack of genetic diversity and the reduction of the available food from diverse host species send a message of environmental corruption and long term ecosystem destruction.. English ivy, shade kudzu, is an organic wild fire spreading through the local ecosystem. Even its evergreen trait is anathema in this geographic area and stand out as an violation of the syntax of the local native landscape where the color of winter is brown with hints of green randomly encountered, not an eternal carpet of green.

And so the partisans on each side of the green curtain contend with the issue of invasive species. Blithely certain that they are right, mostly unaware of the wicked inconvenience of the invasive species problem, entrenched behind their differing philosophies, the two sides dig in, talk past each other, and plan to stop the ideals and concepts of the other. Short term market preference is pitted against long term public values.

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