A bunch of threads to connect here:
Thread one: My own bias – invasive species are bad. The woods along the Rio Grande, my beloved bosque, are rich with native cottonwoods, but the riches are being inexorably choked out by the non-native salt cedar (Tamarix ramossisima). I am reasonably certain this is bad.
Thread two: Rudy Carillo’s battle with the London rocket (Sisymbrium irio), a Eurasian invader that is thriving on the back of our record-setting winter precipitation:
The plant is the winter home to a species of leafhopper that carries the dreaded curly top virus. When the weed dies out in mid-spring (it’s a winter annual from northern Europe, as the common name implies) it’s certain that those same insects will move on to a variety of garden favorites, including chile and tomato plants, transmitting the virus as they proceed. According to the big agricultural school down south, curly top virus is deadly to the state’s chile production: the last infestation, in 2001, destroyed between 40-50% of the crop.
My across-the-street neighbor, not noted for tidy gardening, has a front yard thick with London rocket. A couple of weeks ago, he mowed them. They’re already tall enough again for the neighborhood cats to hide in them. I am reasonably certain this is bad.
Thread three: The worldchanging Jennifer Forman Orth, author of the Invasive Species Weblog. ISW is one of those Internet treasures, the carefully assembled insights of a smart person with an odd but useful obsession. I am reasonably certain that Orth’s ISW motto – “It’s Time to Wipe Out Invasive Plants” – is good.
Thread four: The cover story in the May 2005 Discover Magazine, in which Alan Burdick argues that my conventional wisdom, that invasive species are bad, may be simply wrong. While there are individual cases in which invasive species have caused very specific kinds of damage, the case is not generalizable, Burdick argues. In many cases, he writes, what I would call “invasive species” are more like benign immigrants, sliding into an ecosystem while causing little displacement.
I’m not saying I’m convinced that Burdick is right, but it’s always fun to have one’s preconceptions well challenged. I eagerly await Orth’s review of Burdick’s observations.