September finds the invasive species discussion in full swing. As befits a wicked inconvenience, interested parties present their views, each in the bubble of indignation and subjective attack. We are expected to find a simple linear answer bereft of complexity and choose sides. The challenge of invasive species conversation prevents nuanced discussion. As a wicked problem, parties to the controversy are required to be right, in their particular world view, and then actually begin to have a discussion.
On September 7th, 2008 feralkevin stated for the record that there “There are no objective definitions of “invasive” and “native.”” I would have liked him to cite a source or sources for this claim, but none was forthcoming. Specifically, I wonder what an objective definition might be. How many people must be polled in order to decide a definition is objective, and is this how the scientific system is supposed to work? I rather thought that the idea was to posit a hypothesis and then subject the idea to multiple tests of the proposition until such a time as the theory is accepted by a majority of researchers, a majority being a rather broad aggregation of current work by specialists in their fields.
In the discussions of environmental issues, issues which are a wicked inconvenience, the choice of words is critical. However because of the complexity of the issue at hand, and because there are multiple stakeholders at the table, the precise meaning behind words is often assumed or presumed. Worse, words that have a scientific definition are most often appropriated out of context but the political discussion resulting in confusion to the end users who come to the table with preconceived notions based on internal definitions of the same terms. There is in some sense a hierarchy to terminology with fuzzy parameters; I propose that the Heisenberg Principle, as I understand it, most likely applies to definitions:
One can either KNOW the meaning in the limited specialized context of the moment, or one can understand the context surrounding the word or term actually having a precise definition at hand One cannot have both a precise meaning and a general context. If one is working in general context to broad audiences the definition of the word or term will be in motion and imprecise subject to immediate and constant redefinition.
Feralkevin states that “Modern ecology tells us that pretty much all ecosystems are recently evolved aggregates.” A friend wrote to me noting that “They (ecosystems) might be recent in terms of geological times scales, but so are humans. What (are) a couple of million years, compared to 4.5 billion years? However, systems are not "recent" in terms of human time scales and predate humans by thousands to tens of thousands of years. Invasions drive loss of biodiversity. Isolation drives speciation (sic) and biodiversity. Darwin's finches being prime examples. Islands (isolated areas) generate and contain the highest numbers of endemic species.”
I have written several times about the problem of scale in landscape and invasive species decision matrices. The blinders of the immediate obscure the choices of tomorrow. For better or worse we tend, for self preservation reasons, to focus on today and now in an endless series of small/fast dynamic choices, making our decisions without considering larger scale implications of the large/slow variety.
As I struggle to keep up with the author’s theses, Feralkevin writes that “… many people say it (Elaeagnus umbellate) dozen’t “belong” because it wasn’t there until very recently. What usually is not be considered here is the drastic changes the land has endured very recently. Now that the land has been catastrophically destroyed basically, does E. umbellata with its soil healing ability and massive edible abundance, really not “belong”?"
A contrarian view is presented in an interesting work on the subject by Cora Ann Johnston. “Habitat disturbance through anthropogenic development often leads to invasion by exotic species. While studies have examined the influence of non-native species on the breeding habitat of birds, little researched has looked at the importance of plant community composition change on the food resources available at stopover habitat used by migrating species. In order to examine the influence of land-use change, and especially species invasion, I analyzed the plant cover across forest, edge, and rural remnant habitat and assayed nutritional content of fruits from several common species of native and exotic plants in fruit in mid November near Falmouth, Massachusetts. I found that disturbed (edge and rural) habitat had higher total cover and exotic plant cover, while forests contained only native species. Assays of protein, carbohydrate, and lipid indicated that exotic fruits were sugary; natives were fatty. Studies of the preferred nutritional content used by resident and migratory birds indicate that only the lipid-rich natives are a suitable food source for migrating species. I also found that most fruiting plants were exotic, suggesting that they may fruit too late to be available during migration. Together, the availability and nutrition of exotic fruits suggests that they are not a suitable food replacement for migratory bird species. While this has conservation implications, further studies need to be completed in order to better analyze periods of bird migration and fruit production of all plant species in the area.”[i]
How can we square these two propositions? It seems that in the light of the present discussion we are faced with two seemingly opposed world views. The first strongly suggests that we are to mold the environment as we go adapting as we need in a series of best short term return option decisions, while the second thinks that we should attempt to integrate natural systems as best as we can with the knowledge of eco system services so that we can maximize the long term benefits as we understand them today. The former view seeks adaptation to a continuing use of natural systems a an infinite resource, the latter views a resource of systems which is finite and diminishing.
Feralkevin thinks that “Modern ecology tells us that pretty much all ecosystems are recently evolved aggregates. All species invade other places and have their ecosystems invaded. This is the drive of biological diversity. We don’t like certain species for certain reasons, some rational and others not. This points to the understanding that an “invasive” species is not a scientific phenomenon, but a cultural one.” This ties nicely with the next e-mail of the day, “Friendly Invaders” This article appeared in print on September 9, 2008, on page F1 of the New York edition.[ii] Mr. Zimmer writes, “But in a paper published in August in The Proceedings of the National Academy of Sciences, Dov Sax, an ecologist at Brown University, and Steven D. Gaines, a marine biologist at the University of California, Santa Barbara, point out that the invasion has not led to a mass extinction of native plants. The number of documented extinctions of native New Zealand plant species is a grand total of three.”
This rather interesting statement is off-set by an entry on the Wikipedia site: “The ecosystems of Lake Victoria and its surroundings have been badly affected by human influence. In 1954, the Nile perch (Lates niloticus) was first introduced into the lake's ecosystem in an attempt to improve fishery yields of the lake. Introduction efforts intensified during the very early-1960s. The species was present in small numbers until the early to mid-1980s, when it underwent a massive population expansion and came to dominate the fish community and ecology of the world's largest tropical lake. Also introduced was the Nile tilapia (Oreochromis niloticus), now an important food fish for local consumption. The Nile perch (Lates niloticus) proved ecologically and socioeconomically devastating. Together with pollution born of deforestation and overpopulation (of both people and domestic animals), the Nile perch has brought about a massive transformation in the lake's ecosystem and to the disappearance of hundreds of endemic haplochromine cichlid species. Many of these are now presumed to be entirely extinct. A number of other species are extinct in the wild, with populations being maintained in zoos and aquaria, e.g. as part of the Association of Zoos and Aquarium's Species Survival Plan for these species. Some species which were extirpated from Lake Victoria itself, are known to survive in nearby smaller so-called satellite lakes, such as Lake Kyoga, Lake Edward and Lake Albert.
Also vanished from Lake Victoria is one of two native species of tilapia (another kind of cichlid fish), the Singidia tilapia or ngege (Oreochromis esculentus). The ngege is superior in taste and texture to Nile tilapia, but it does not grow as fast or as large and produces fewer young. Ngege and some representatives of haplochromine diversity survive in minute swamp ponds and lakes that dot the Lake Victoria Basin. The initial good returns on Nile perch catches, at their peak delivering export revenues of several hundred million dollars a year, have diminished dramatically due to poor enforcement of fisheries regulations. The proceeds from Nile perch sales remain an important economic engine in the region, but the resulting wealth is very poorly distributed and the overall balance sheet on the Nile perch introduction to Lake Victoria is well into the red despite the enormous value of the perch landings as an export commodity.
Add to this conversation climate change and the addition of CO2 and the complexities quickly overwhelm the casual observer.
[i] Implications of land-use change on food resource availability for birds : Cora Ann Johnston, Hampshire College, Amherst, MA 01002, 18 December 2006, Advisor: Chris Neil, Collaborator: Brook Brouwer. http://courses.mbl.edu/SES/data/project/2006/johnston.pdf
[ii] CARL ZIMMER, Published: September 8, 2008. http://www.nytimes.com/2008/09/09/science/09inva.html?_r=2&8dpc&oref=slogin&oref=slogin