Re: NANFA-L-- Old story, new twist? Old twist new story. Long.
Michael Sandel (kwksand-in-yahoo.com)
Mon, 15 May 2006 15:12:23 -0700 (PDT)
Normally I look forward to reading your posts, because they are witty and well-informed. However, I must disagree with you as strongly as possible on this issue, because it has such a persuasive tone. Here goes.
". . . the Mississippi River . . . is starved for ecological specialists."
"Lets face it, the Mississippi has a definite disparity of fish along with it's lack of diversity."
"Yes, we as humans can rase both the diversity and reverse the disparity of the life forms in the Mississippi."
"The Mississippi doesn't even come close to the diversity of most big tropical rivers around the world."
These comments are ill-founded and simply incorrect. You are operating under a human construct, that directly equates species richness with ecosystem integrity. Biodiversity cannot be viewed simply as a "more the merrier" phenomenon. In many situations, adding species to a given ecosystem is destabilizing.
Anyone who has conducted an index of biotic integrity (IBI) would agree that, even-in-much smaller scales, assessing community integrity by way of diversity is not always accurate. I think your rationale may be based on personal observations of human disturbance, and the resulting loss of local diversity. We must keep in mind that only anthropogenic environmental disturbance (and resulting loss of biodiversity) is unnatural. Therefore, only anthropogenic sources of disturbance should be viewed negatively. Glaciers, high seastands, hurricanes, and continental drift account for huge losses in biodiversity, but through time evolution steps in to return the balance. We should not attempt to "repair" the disturbances that occured in prehistory.
While our personal observations make it easy to associate damaged ecosystems with low diversity, this is only a one-way relationship. Look-in-species richness within the Arctic Circle, the Sahara, and even Western Europe. These systems can be described as depauperate because they are do not contain as many species as other systems-in-the same latitude. However, this is primarily a natural situation. By such standards, the Mississippi River is not-in-all depauperate. Europeans could look-in-the Mississippi the same way you view the Amazon.
"The Mississippi is a very large river system and as such can support a
large variety of fish. Unfortunately these are all fish that are closely related to each other and in a million years they will still be closely related to each other. In other words the disparity of the fish in the Mississippi is unlikely to change on it's own."
This is also incorrect. At one time, the Mississippi was part of a very warm, environmentally consistant ecosystem. Like most of eastern North America, it had much greater biodiversity than it does now, perhaps rivaling or exceeding the modern-day Amazon. What we have now are relics of that ancient community, like the Paddlefish, Alligator Gar, and Bowfin, and species that are of a more recent radiation, like most of the darters and minnows. The fact that some species within the Mississippi River are closely related (undergoing a recent radiation) is not "unfortunate". If anything, it is exciting. Our species are actually DOING something. Look-in-the work Dr. Hank Bart does with Buffalos and Carpsuckers, or even look-in-the Alabama sturgeon. Some suggest the Alabama sturgeon is actually a recent species within an ancient lineage. Imagine that, the relic sturgeon could still be keeping pace and speciating after all the changes that have occurred since the Miocene. It
reminds me of Mr. Miaggi or something.
"Lets say that some unimaginable disaster rendered the Mississippi
lifeless. Could we bring back the river with a diversity and with a disparity
of organisms on a par with tropical rivers?"
Most of us are familiar with the concept of forest succession, where disturbance and colonization occur-in-varying frequencies, resulting in a patchwork of communities that are kept in equilibrium through time. Continents and biomes are not dissimilar on a much grander scale. We can view a continent the way foresters view a particular tree stand. The glaciers and high seastands have effected the eastern United States the same way fires or floods wipe out a tree stand. What we have now is a number of lineages that are evolving, in real-time, and therefore are presently closely related. Millions of years from now, the Mississippi River may actually contain a level of biodiversity that far exceeds what we see in the Amazon today (inversely, the Amazon may look like the present-day Rhine). This is the way it works without our meddling.
Using the forest analogy, the eastern United States is recovering from a devastating series of "forest fires". Therefore, introducing any outside species directly interferes with the natural evolutionary radiation, through competition, predation etc. To put it straight, (I like thinking long-term) introducing Psuedoscaphirhynchus to eastern North America could preclude the evolution of new species within Scaphirhynchus, and even cause some to go extinct (through competition, hybridization?).
"How would we raise the diversity of the Mississippi, increase the disparity and as
much as possible preserve what little native live is still there?"
The "disparity" between the Mississippi and the Amazon has existed for hundreds of thousands, if not millions of years. However, we still maintain a native community of considerable diversity, that is threatened with every introduction of a nonindigenous species.
"Actually there is evidence that cool water rivers support less fish in diversity and the disparity of these fish is very low."
Google "latitudinal diversity gradient".
"I love the Amazon, mostly because of the incredible variety of fish and other animals that inhabit it's waters. Many of these fish compete for the same food and space as the others do, surviving by tiny differences in some part of their survival strategy."
I whole-heartedly agree man, diversity is beautiful. This is why we should allow our species to continue to evolve and diversify as they would without us (which does require considerable effort). The complexity you admire in the Amazon River has evolved there in a much more consistent environment, over very long periods of time.
In short, you are downplaying the significance of evolutionary and ecological processes occurring in the Mississippi, and nature in general. This idea is like throwing a bunch of iron beams in a pile and hoping it will form the Eiffel Tower.
Because these ideas are of the best intentions, and are passion-fueled, they are the most dangerous. I would really like to emphasize that the Mississippi River (or any other river) does not benefit from the introduction of any non-indigenous species. Less diverse systems should not be viewed as "starved" or unfilled. The aquatic fauna of the Big Muddy (read eastern United States) is unique, from the alligator gar, to the johnny darter, to the amphiuma, to the blue catfish; and just as deserving of protection as the other great rivers. That should be enough information for conservation-minded folks, like you and me, to value the integrity of the present community; keeping native species around and non-natives out. Our rivers are not aquariums.
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