Wednesday, July 25, 2007


Trophic Cascade

Trophic cascade. Such a lovely term for a not-so-lovely phenomenon. A trophic cascade is a domino effect in the natural world, wherein if one part of an ecosystem is taken away, the others around it eventually fail. According to "The Sixth Extinction" by Terry Glavin, deforestation has been a major cause of trophic cascades around the world. Once the trees are gone, the plants and animals dependent upon the trees tend to go extinct if they can't find another area to move into. Trouble is that it's not only the plants and animals that suffer, but human beings, too. Once a trophic cascade really gets going, its eventual outcome is to take human culture with it as well.

Political upheaval can also cause a trophic cascade. Witness Iraq. Did you know that Iraqi farmers are not allowed to save agricultural seeds from year to year? Or that the U.S. government ordered Iraqi seed stocks to be destroyed during the war? Neither did I, until someone mentioned it at my writers group. I looked it up. Unfortunately, 'tis true under Order 81 of The Coalition Provisional Authority. There is a more intelligible discussion of the issue at CorpWatch. While I had no idea this was going on, I've been well aware of the cultural destruction in Iraq, having heard quite a bit about the looting of Iraqi museums.

According to Glavin, the current extinction cycle, the sixth in the earth's history that we're aware of, is by far the most destructive of all the extinction cycles because we have twice the average biological diversity of any other period on earth. The other extinctions were the Ordovician, Devonian, Permian (most destructive before this one), Triassic, and Cretaceous, which took the dinosaurs.

Although the entire subject is incredibly depressing if you're paying attention (and we all should be paying attention, because our necks are on the line), Glavin's book is not depressing, but quite hopeful. Along with pointing out the complex interplay between species and the causes of extinction, he regularly discusses the ways that humans have attempted to stem the bleed of species extinctions, in some cases even reversing extinctions. Bald eagles, which I rarely ever saw in central Minnesota as a child, now often fly over the area where I work. We've even seen flocks of them in area fields. They've made such a comeback that they've been removed from the Endangered Species list. Wild turkeys are also returning in force, as are timber wolves.

Human beings can be a wondrous force for change, if we put our minds to it.

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