[Leps-l] Butterflies and climate change

David Gregg dgregg at rinhs.org
Thu Aug 23 17:10:04 EDT 2012

The release of this study has drawn a lot of public comment, mostcalling
out the study as either another argument for the existence of global
warming or another example of scientists rushing to wrong conclusions
because of their liberal biases.

I'm somewhat familiar with the species in question and the data gathering
efforts that went into the study. I read the original article, not just the
press releases. I have to say I don't find much that's political, or even
controversial. The authors state that the data indicate northern species
moving north out of Mass. and southern species moving north into Mass. They
say this is consistent with warming climate and therefore it may be
evidence of climate change. In fact, the only other main conclusion of the
study is that coherent trends can be extracted from volunteer-collected
data. This interesting and valuable demonstration has nothing to do with
climate change.

To Paul's point, I don't agree that monthly average temperature change in
Mass. is relevant. The authors cite some environmental factors that may be
related indirectly to temperature but they don't conclude anything about
what the range-limiting factors are in species shift in general or in the
cited shifts. We know that in wildlife biology range shifts can be related
to average temperature but also minimum winter temps, minimum frost free
days (not max temp), snow pack (which can actually be higher with increased
temperatures), timing of predators/parasites/pathogens, prevalence and
phenology of food plants, and a range of humidity parameters.

Scientists don't just make stuff up, and good science is hard to do. That's
why it's best left to professionals.

David W. Gregg, Ph.D., Executive Director
Rhode Island Natural History Survey
Kingston, RI

On Thu, Aug 23, 2012 at 4:08 PM, Paul Cherubini <monarch at saber.net> wrote:

> On Aug 23, 2012, at 8:22 AM, Jim Mason wrote:
> > Field data supports a species shift over the last
> >
> > two decades in Massachusetts.
> >
> The authors say:
> "The study outlines the growth and decline of butterfly species in
> Massachusetts during the past two decades. During this time,
> the study found that warm-climate-adapted butterfly species
> have grown by an estimated 1,000 percent, while
> cold-climate-adapted species, which have long been
> native to the Bay State, have declined -- some by up
> to 90 percent."
> But the authors don't tell the public or reporters what actually
> happened to temperatures in Massachusetts in recent
> decades vs the past.
> Here's a look at annual mean temperatures in MA
> between 1895-2011:
> http://i636.photobucket.com/albums/uu87/4ALC/maann.jpg
> I don't see anything in that graph that shows the 1990's
> and 2000's have been substantially warmer than some
> previous 20 year periods.   The graph also shows there
> have been some decades long cool periods during which
> warm-climate-adapted species could have declined in
> Massachusetts.
> Paul Cherubini
> El Dorado, Calif.
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