Blogs and Reaching Out to the larger community

One of the things I like about blogs is that it's a quick way to make lots of connections. Sure, there is a lot of chaff, and finding those little kernels of value can take some serious sifting and winnowing, but the internets do have search functions, and it's not like one has to invest a great deal of time in things they don't find interesting.

I've been looking at my visit logs and I've seen a big uptick in activity - largely due to my adventure with Steve Austin. I think that points to a needed activity for this blog: more discussion of what the folks at "Answers in Genesis" are up to. This is even more important, IMO, given their attempts at "addressing" some of the standard geological facts that are used to demonstrate this diluvian model is hooey. It's no use trotting out standard arguments if the creationists feel like they have a perfectly valid counter. It's time to update our database of counter-counter-claims.

But parrying YEC's is tedious, and no fun if it's all that all the time. So it's time to bring things back to some snails. Particularly Ice Age snails and the modern snail fauna of the Upper Mississippi Valley. Consider the following two photos:

Some recent woodland snails from southwestern Wisconsin:



Common late Pleistocene (ca. 20ka) snails from southwestern Wisconsin and southeastern Minnesota:

Three important points - one of which requires some background info, which I've touched upon in much earlier posts (and we'll revisit in the future). The other two can be seen in the above photos. One is that the "modern" snail fauna is much more diverse and second, the modern fauna displays a very wide range in body shape and size with a much bigger "upper limit." Just from this observed fact, we can start to ask some questions:

• What was the timing of snail dispersal? Did the modern fauna appear before the ice age snails left?


• Was this faunal transition all-at-once, or did individual species expand/adjust their range according to their own needs?


• Do the changes in snail fauna (body size, range limits, etc.) imply something about climate change?


• How are fossil shells preserved in the sedimentary record, and how does this affect our ability to use their shells as clues to ancient conditions?

Okay, that's enough for now. A big hello to all my new visitors - feel free to peruse the archives, leave a message, or whatever.

Hendersonia occulta

Last year, Aydin over at Snail's Tales posted a note about an interesting land snail, Hendersonia occulta. This particular snail is one of the few operculate land snails in North America and represents an important evolutionary link between terrestrial and marine snails. It also is an important snail when one thinks about climate.

In the late Pleistocene (a mere 20,000 years ago), this snail roamed over a large portion of the interior of North America. Once the climate started warming, this snail started restricting its range, eventually becoming isolated in a few key regions today. One is in my field area - the Driftless Area of Wisconsin, Minnesota, Iowa, and Illinois. Another place was in eastern Wisconsin, where the dolomite bedrock is close to the surface. And finally, in the western Appalachian region including Pennsylvania.

Distribution map of H. occulta showing live (solid dots) and fossil (yellow dots) sites where it has been found.

What this tells us about climate is important when we think in terms of how organisms responded to past climate change, and how they might deal with future changes. In the late Pleistocene (i.e. Ice Age), much of North America had suitable habitat for this snail. They like relatively cool summers, but not intense winters. They often live near standing water, or places with plenty of moisture. A source of calcium is important (that makes sense, since they have pretty robust shells - with opercula - for land snails), and they need food. These snails generally live in dense leaf litter, probably feeding on Birch, Maple and other deciduous leaf material. So we can infer that many places in the Midwest had these conditions. As the climate warmed, however, the available moisture, temperature, and food/shelter sources disappeared throughout much of its previous habitat. Now, it is left in places that still have these conditions - refugia.

Suitable refugia exist in several locations - but what about future change? What would happen if these refugia disappeared? This snail has adjusted its range to stay in suitable areas, but now that we have drastically altered the landscape, there might not be a path for these snails to find refuge. A sad thought indeed.

So when people poo-poo climate change as just a "natural cycle" and that we shouldn't worry about it, they are ignoring an important point. We have created an artificial obstacle course that will interfere with organisms trying to adjust their ranges to match changes in climate. We may not be the sole cause of global warming, but we are actively placing many organisms at peril because of our existence. Food for thought...

Some H. occulta information:
MNFI (Michigan) zoological abstract

L. Watrous images of H. occulta and other land snails in Missouri