A take on my blog on Davis et al. 2011.
Connor Stedman blogs at Renewing the Commons, which discusses a potpourri of things on humans, nature and their intermingling. He decided to profile the same Nature article that I did last week, but did so with an eye on embracing the author's ideas. He took on my interpretation of Davis et al. 2011 about as much as he defended the article's authors...well, sort of.
While I respect Stedman's right to his own interpretation, I have several problems with how the author pulled me into his post that defended the article--even though it drives home my point on how the concepts of the non-native and invasive species are perceived in the public. Before I dive into the meat/tofurkey of Stedman's interpretation, the first of my quips is that Stedman chose to ignore several of my points and all of my references, focusing on a few of my tertiary items. I'm confident that had he looked at even the abstracts of the papers I cited, he wouldn't have focused on his perception that I was defending the home chemical industry, which I was absolutely not, and he wouldn't have proceeded to defend his view with a misinterpretation.
Stedman, has glaringly confused the roles and detrimental potential of the non-native and the invasive. Invasive species--not just species that are "non-native," but those that are actually harmful to local biodiversity and economies and possess traits that allow them to exert higher fitness in their non-native range--are the big problem. The opacity with which Stedman views non-natives is a bit alarming, but shows how Davis et al. may have needed more than two pages to build and clarify their concepts. In defending the uses of non-native species that may receive attention in Stedman's home range, Stedman cites Japanese knotweed (Polygonum sp.) as a beneficial non-native species.
Now, I'm no NRCS noxious weed scientist, but I'll be darned if Japanese knotweed isn't the invasive species responsible for the decline of riparia and forests across temperate zones worldwide, including the riparia that shade American Pacific Northwest rivers. You know, those rivers with names like Stillaguamish, Skagit, Snohomish and Snoqualmie. Yes, those rivers that once supported abundant salmon (Oncorrhynchus sp.), but are now too near their total daily maximum loads of temperature and dissolved oxygen due to riparian degradation, to support salmon into the indefinite future. I have a feeling that Davis and his co-authors would recognize that the Giant and Japanese knotweeds are more than just a "non-native," they're a trophic-level busting weed group that may reshape entire landscapes. But to most passive observers, is this "non-native" mostly harmless, a mere cash cow for the Monsanto man?
The fact that Stedman does not realize his example is in fact ironic, and offers only emotional rhetoric of his own making to support the article, shows how important it is for ecologists to clearly, proactively and effectively draw the line in defining non-native and invasive species when pitching big ideas in public forums. This is the confusion that Davis and his Nature co-authors have now inadvertently perpetuated, and one that Stedman illustrates in nearly real time.
To clarify, I'll offer an anecdote that is tied to some data. The Union Bay Natural Area (UBNA), a 74-acre former landfill that features novel hydrology, soils, vegetation, etc., illustrates that non-native species can fill roles in reclamation and provide temporary successional pathways in ecological restoration, but also inhibit native plant colonization and community succession. For example, nitrogen-fixing forbs like clover or vetch (naturalized non-natives) have maintained places within permanent plots across the UBNA where willows and cottonwoods have established, and perhaps benefitted from increased soil resources and advantageous microsites (Hough-Snee et al., unpublished data, submitted to Ecological Engineering). But for every UBNA site where a non-native has improved site conditions, there are five or six sites where even heavy site manipulation has not been able to move the plant community away from aggressive (invasive) pasture grasses that may be in a decade-long stalled successional state (Hough-Snee, Bakker and Ewing 2011). While this ruderal grassland may aid soil and nutrient retention (more so than say, bare ground), it is doing little more than farming more invasive plant seeds that can displace or invade local plant communities nearby. The plants in this latter example are not exactly making a great contribution to global biodiversity, local ecology or the potential uses for the site by humans.
Before anyone judges the rhetoric laced into my previous analysis of the article, I hope that they'll take the time to check out a few of the references that I cited--especially Lauren Urgenson's paper on knotweed.
Later this week I'll have less contentious items: an article alert on invasive species control and photos from the peatlands and forested wetlands around Fairbanks, Alaska. For now, here's a picture of a dog in a canoe:
Hope, the adventure dog.