At 03:11 PM 8/29/96 -0700, Jim Lyles abstracted an Associated Press story:

> Global warming may well be redistributing populations of
> Edith's Checkerspot Butterflies northward and toward higher
> altitudes, says a researcher at the University of California
> at Santa Barbara.

As with virtually everything in the natural world, determining the causes of
an observed phenomenon is difficult. I would be interested in knowing how
the author addressed alternative explanations for the observed patterns in
population extinction. Edith's Checkerspot happens to be one of
Washington's rare butterflies, one that has probably suffered most from the
diminution of western Washington prairies. I am quite certain that
populations of this butterfly in Washington have been lost as their habitat
has changed but I doubt that anyone could build a strong case for global
warming as the cause. Instead, it's houses, pavement, Douglas-fir trees,
Scot's Broom and, possibly, a climate that is wetter now than it was several
thousand years ago.

Just the same, I can't think of a single plausible alternative factor that
would explain the observed pattern. I would, however, need to know more
about the other factors that bear upon the status of this butterflies'
populations before I would accept the global warming hypothesis.

Kelly McAllister







>
> UCSB's Camille Parmesan writes in the journal _Nature_ that
> of the 151 populations recorded in previous studies from
> western Mexico through the western US to western Canada,
> populations in Mexico are 4 times more likely to have died
> out than populations in Canada. And populations recorded
> above 7,900 feet have survived at a better rate than those
> at lower altitudes.
>
> Moreover, the sites of still-surviving populations are
> on average 2 degrees farther north than the sites of
> vanished populations.
>
> Parmesan's article in _Nature_ has been reported today
> (8/29/96) by the Associated Press.
>
> --cheers, Jim Lyles <jrlyles at usgs.gov>
> Tacoma, WA <jrlyles at eskimo.com>
>