Jim Lyles raises an interesting question that occurred me, too, when I
heard about the butterfly work on NPR. The evidence cited in the study of
Edith's Checkerspot is that populations have been disappearing and
appearing over a long time, but that on the average the populations are
moving farther north, and this is predicted by the global warming
hypothesis. Of course, evidence consistent with the hypothesis doesn't
prove that it's right, and what we really want is evidence that is
inconsistent with alternatives. Kelly's information is good evidence that
Edith's Checkerspot has probably become rare in this area for reasons
other than global warming.

Anyway, the related interesting question is about birds. Many species
are changing their ranges, and there's a lot of historical information
about just what changes have been occurring. Has anyone studied these
changes to see if there's an overall northward trend in the Northern
Hemisphere?

Burt Guttman guttmanb at elwha.evergreen.edu
The Evergreen State College Voice: 360-866-6000, x. 6755
Olympia, WA 98505 FAX: 360-866-6794

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