Tip of the Week: Invasives Create Monocultures, Kill Diversity

Posted in Gardening Tips on October 4 2010, by Sonia Uyterhoeven

Sonia Uyterhoeven is Gardener for Public Education. Join her each weekend for home gardening demonstrations on a variety of topics in the Home Gardening Center.

Years ago, I returned home to Massachusetts after living in England for 10 years and drove around my old neighborhood with a friend. I commented on a pretty purple flower I saw growing in a wetland area. When I asked her what it was, she cringed and told me it was purple loosestrife (Lythrum salicaria, pictured. Photo by Wikipedia user Meggar). At first I thought her reaction was severe until, continuing our drive, I realized it had taken over many wetland areas. Where were the native cattails (Typha), the sedges (Carex), and the swamp milkweed (Asclepias incarnata) that I had grown up with?

Ecosystems are by definition complex, and the lives of their inhabitants are interconnected. When an ecosystem is thrown out of balance by an invasive intruder, more than the flora suffers.

Insects, birds, amphibians, and mammals all depend on the native flora for food, shelter, and nesting sites and materials. An area stripped of its native vegetation creates a sterile environment that is no longer inhabitable to many creatures.

As we know from the examples of purple loosestrife and Japanese stilt grass, which I wrote about previously, once the invasive species gets established, it can overrun an area by out-competing the existing flora and turning rich diversity into a monoculture.

While it may be virtually impossible to completely get rid of invasive species, it is worth preserving and re-creating native landscapes so that large pockets of indigenous and ecologically diverse habitats exist in the environment.

Over the summer I read Douglas Tallamy’s book Bringing Nature Home and found many good reasons why it is worth preserving natural habitats. Next week I will write about some of Tallamy’s arguments.