Dave and others, I haven't read the Nature article yet, but I believe that tamarisk is actually one (or two) of the species about which there is some dispute. Not that it is a "boon to the environment," but that much of its reputation is exaggerated and effects might be site (and river regulation) specific (see Stromberg et al. 2009: http://onlinelibrary.wiley.com/doi/10.1111/j.1526-100X.2008.00514.x/full). The reasons for such things as cottonwood and willow displacement are sometimes complex, and may have as much to do with changes in hydrologic regime from flow regulation as any direct effects of tamarisk (although tamarisk itself could certainly be a contributing factor). I know that there was also some recent controversy over whether widespread tamarisk control (via biocontrol agents) could threaten nesting habitat for the endangered SW Willow Flycatcher.
Mark D. ________________________________________ From: Ecological Society of America: grants, jobs, news [[email protected]] On Behalf Of David L. McNeely [[email protected]] Sent: Friday, June 10, 2011 1:45 PM To: [email protected] Subject: Re: [ECOLOG-L] EcoTone: Speaking of species and their origins ---- Katie Kline <[email protected]> wrote: > An essay published in the June 8 issue of Nature is causing something of a > stir. Eighteen ecologists who signed the essay, titled "Don't judge species > on their origins," "argue that conservationists should assess organisms based > on their impact on the local environment, rather than simply whether they're > native," as described in a recent Scientific American podcast. > > In the essay, Mark Davis from Macalester College, St. Paul, Minnesota and > colleagues argue that adherence to the idea of non-natives as "the enemy" is > more a reflection of "prejudice rather than solid science," wrote Brandon > Keim in a Wired Science article. As the authors wrote, the "preoccupation > with the native-alien dichotomy" among scientists, land managers and > policy-makers is prohibitive to dynamic and pragmatic conservation and > species management in a 21st century planet that is forever altered by > climate change, land-use changes and other anthropogenic influences. As a > result of this misguided preoccupation, claim the authors, time and resources > are unnecessarily spent attempting to eradicate introduced species that > actually turn out to be a boon to the environment; the authors cite the > non-native tamarisk tree in the western U.S. as an example of this... > > Read more and comment at > http://www.esa.org/esablog/ecologist-2/speaking-of-species-and-their-origins/ Exactly how have tamarisks (there are two invasive species in the western U.S. unless I have been misinformed) been a "boon to the environment"? They have displaced native willows and cottonwoods. Their transpiration rates far exceed those of the native species they replace, lowering the water table in the area and drying streams, playas, and cienagas. By concentrating salts in their foliage, then dropping the foliage to the ground, they increase the salinity of surface soils. Animal species that depend on the riparian vegetation they displace lose out. So do those that depend on the streams and cienagas as aquatic habitat. mcneely
