It’s one thing to have evidence that the world is
experiencing an unprecedented period of warming, but quite
another to say for certain that this warming, subtle as it
is, will have a significant effect on the natural
world—on any species, let alone humans. Demonstrating
that the planet’s flora and fauna are indeed feeling
the effects of the warming trend has always been a critical
challenge in the research.
The first compelling evidence that this is indeed the
case began to appear in the mid-1990s. Leading the way was
a single-author paper in Nature by Camille Parmesan, who
completed much of the work as a graduate student, on the
northward range shift of a species of butterfly known as
Euphydryas editha or, more commonly, Edith’s
"What we need to do now is not just recreate the
ecosystems that existed 200 or 300 years ago, but create
systems that we believe will be most suited to a given area
for the next 100 to 200 years of climate change"
Since then, the evidence has grown from a trickle of papers to a river,
while Parmesan herself has become one of the leading figures in
climate-change research and has co-authored some of the most influential
and highly cited papers in the field. She is now ranked in the top 20 among
most-cited authors in the
Essential Science IndicatorsSM listing in the
field of Environment/Ecology for the last decade. Parmesan also ranked at
#2 among highly
cited authors in this publication’s recent survey based on papers
devoted expressly to
global warming and climate
change (November/December 2009).
These feats are amazing considering that Parmesan has only published a
couple dozen papers . One of those, however, is a 2003 Nature
report—"A globally coherent fingerprint of climate change impacts
across natural systems," co-authored with Wesleyan University economist
Gary Yohe—that has already racked up over 1,100 citations. That
report was originally selected as a
New Hot Paper at ScienceWatch.com, as was a
2006 paper in the Annual Review of Ecology, Evolution, and
Systematics (C. Parmesan, 37:637-69, 2006). Another Nature
paper, from 2002 —"Ecological responses to recent climate
change"—written with eight other authors, has collected more than
1,200 citations (see table below).
Parmesan, now 48, received her B.S. degree, summa cum laude, from the
University of Texas at Austin in 1984. She went back to UT Austin for her
Ph.D. in biological sciences in 1989 and received it in 1995. For the next
three years, she worked as a postdoctoral fellow at the National Center for
Ecological Analysis and Synthesis at the University of California at Santa
Barbara, and in 2000 returned to Texas to join the faculty at Austin, where
she’s now an associate professor in the Section of Integrative
Biology. In 2007, as a lead author, she shared in the Nobel Peace Prize
awarded to the Intergovernmental Panel on Climate Change.
Parmesan spoke to Science Watch
from her office in Austin.
The paper that launched you into climate-change
research was your original single-author paper in Nature in
1996 on the Edith’s Checkerspot butterfly. [Table, paper #6.]
How did that come about, considering how little research was being
pursued on climate change at the time when you were first studying the
When I started my graduate school, the bulk of my Ph.D. was very basic
research on Edith’s Checkerspot. I was not into climate change at
all. Then I got a NASA fellowship from the Planet Earth Program to study
possible biological impacts of climate change. I had been working with
Edith’s Checkerspot for several years by that time, and I knew that
if anything was responding to climate change it would be this butterfly.
People had been documenting for 40 years that it was very, very sensitive
to climate variability. We knew populations had gone extinct with severe
droughts or severe climate years in the past. At that time, 1991, climate
scientists were still not even sure there was a significant warming signal.
Everything was up in the air, so to speak. But this butterfly could be a
bio-indicator of climate change. It could be more sensitive than a
thermometer in some ways. So I got this fellowship funded for three years
and set out to gather all the historical records for the butterfly, to
visit as many sites as I could to determine whether the habitat was still
suitable and whether the butterfly still had a population there or whether
it had gone extinct.
How long did the research ultimately
It ended up taking me about four and a half years. It was very laborious. I
could have come up with absolutely nothing, but it didn’t matter
because I already had my Ph.D. in hand and I thought I would have a blast
camping out for all that time, which I did. I was tracking butterfly
populations, starting in March in Southern California and ending in August
when they emerge in Canada. I could track them across the seasons from site
What did you find?
When I put it all together, I found I had a much stronger signal than I
ever could have imagined. It wasn’t a matter of something complex,
with certain ecotypes showing subtle changes that might be tied to climate
change—it was a bloody obvious change. These butterflies were
shifting their entire range over the past century northward and upward,
which is the simplest possible link you could have with warming. I was
expecting some incredibly subtle, sophisticated response to warming, if at
all. What I got was 80% of the populations in Mexico and the Southern
California populations were extinct, even though there habitats still
looked perfectly fine.
After publishing this work in Nature in
1996, what response did you get?
You have to realize that there were two other studies published right about
that time, one a year earlier, on biological responses to climate change,
but that was it. One was on marine invertebrates, the other on Swiss
mountain plants, and then there was mine on this butterfly. So the response
was huge. The biological community was thrilled because of the amount of
data I had and the scale I was looking at—the entire geographical
range of a species, from Mexico to Canada. Typically in biology, people get
lots of data from a single field site. Biologists working on climate change
felt this was really the first convincing evidence that we were getting
responses in natural organisms to climate change. And they found it
convincing because the scale was so large. And the climate scientists were
thrilled because they were finally detecting a significant global warming
trend, but they were still kind of queasy about how real this was. My data
convinced them that their data was real, not just a statistically
significant fluctuation but a real signal that was already having an impact
on a completely different system.
Did you realize immediately that you were going to
be in climate change for life?
Cited Papers by Camille Parmesan and
Colleagues, Published Since
1996 (Ranked by
G.R. Walther, et al.,
"Ecological responses to recent
climate change,"Nature, 416(6879): 389-95,
C. Parmesan, G. Yohe, "A
globally coherent fingerprint of
climate change impacts across natural
421(6918): 37-42, 2003.
D.R. Easterling, et al.,
Observations, modeling, and
289(5487): 2068-74, 2000.
C. Parmesan, et al.,
"Poleward shifts in
geographical ranges of butterfly
species associated with regional
399(6736): 579-83, 1999.
C. Parmesan, "Ecological and
evolutionary responses to recent
climate change,"Ann. Rev.
Ecol. Evol. & System., 37:
Oh yes, it was pretty obvious that this was going to be what I’d be
doing. I’d just gotten my Ph.D. when that paper came out, and the
first response was not only a bunch of media, but an invitation to give a
talk at the White House. And while I was on my DC trip I was asked if
I’d like my name to be submitted as a nomination to the
Intergovernmental Panel on Climate Change. As a post-doc, here I am
suddenly on the international science circuit with silverbacks. It was
great. And while I was working at the IPCC, it was very clear why I was
catapulted so quickly. There were just very few biologists working on this
subject at all. Policymakers wanted to know what was happening with the
natural world, and there was an incredibly few people they could call upon
to help inform them.
Were you able to replicate the butterfly study
with other populations?
Actually, with many more species. To do that I had to start working in
Europe. It took me four and a half years to get sufficient data in the U.S.
on one butterfly, about which we knew quite a lot. I knew I couldn’t
ramp up the numbers, the sample size, very much by staying in the U.S. I
already had connections with lepidopterists in Europe, where they had
distributions starting from 1760 in Great Britain, Sweden, and Finland. In
northern countries, the first signs of spring are when the first
butterflies are out. So a lot of people were recording butterfly flight
seasons. We were then able to get down to the southern edge of these
species in Spain, France and North Africa. The data wasn’t as good on
the southern edge, so we had to do some fieldwork, but we ended up getting
data for 57 species, and it only took two years.
What was cool, in this case, was that the result was even stronger: 65% of
the species were colonizing northward at the northern range of the
boundary. They had jumped their historic ranges and were colonizing
northward by a lot—200 to 400 kilometers. It was very dramatic. On
the southern ranges, they had a tendency to be more stable, but still
something like 22% were contracting northward, going extinct at the
southern range boundary. We published that in Nature in 1999.
Did the IPCC find this data convincing, or were
there doubts that it was meaningful?
Well, the biologists at the IPCCC—about four of us total—wanted
to come out with a statement that we had high confidence that wild plants
and animals have responded to 20th-century climate change. But then the
economists at the meeting—four or five of them—thought we were
making too strong a claim. They wanted something much more watered
down—much more wimpy, in effect. I argued quite a bit about this
outside work hours with
Gary Yohe, who’s an economist at Wesleyan
University in Connecticut. I felt like I was having to teach him Biology
101, and he was having to teach me how the rest of the world thinks. We
just kept arguing and arguing. Finally the IPCC came up with a statement
in its third assessment report (2001) that was halfway between what the
biologists and the economists wanted. And Gary and I realized that we
needed a new analysis, something that would get directly at the key
issues that the economists had with the way the biologists were
interpreting the data.
What did you do?
I said, why not do a meta-analysis, but let’s be really careful to
deal with all the potential problems, specifically positive publishing
bias. If you’re working on a single species and you can link it to
climate change, that gets published. If you’re working on one species
and there’s no link, you don’t publish. So there’s a lot
of positive bias with people working on single species. You get around that
by only looking at multiple species. My European paper, for instance, had
57 butterfly species, so that went into the analysis. My Edith’s
Checkerspot paper, with one species, didn’t go in. By doing it this
way we found that about 50% of the species were being affected. I did that
analysis with Gary and we tried to think of some pattern of response that
could be uniquely attributed to change of climate, as opposed to all the
other things humans are always doing—habitat loss, nitrogen loading,
etc. We came up with something we called "sign shifting," in which the
species habitat or springtime appearance responds to the various changes in
temperature over the 20th century. You need long-term data for this, which
cuts out a lot of species, but if you don’t do it, you don’t
know if the changes you’re seeing are really due to climate change.
What do you think is the most important issue now,
regarding the effect of climate change on different species?
It’s one of the things I’m doing now that’s considered
very radical by most ecologists. We know a lot about ecological restoration
at this point; we’ve been doing it in a scientific fashion for 30
years. For certain habitat types, we can recreate functioning ecosystems
from fairly trashed-out land. We know we can do this. What I’m
suggesting we need to do now is not just recreate the ecosystem that
existed 200 or 300 years ago, which is what’s being done now, but to
create systems that we believe will be most suited to an area for the next
100 to 200 years of climate change. I think we have to pre-adapt habitats
to the climate that’s coming. I think that’s where ecology
needs to be going, where the science needs to be going.
How do you do this?
We have to use our existing knowledge of restoration and of species’
climate tolerances to create systems and communities that may not have
present analogs. This could mean putting species together that don’t
reasonably exist together right now, but will exist in the climates we can
expect to come. So, yes, the climate projections have to get better and
better on the scale that ecologists work on—a few kilometers.
That’s what’s needed in practical terms if we want to save
endangered species in the face of climate change. Right now 50 kilometers
is the resolution that gives high-confidence results. Technically we can
take it down to one kilometer, but we can’t have high confidence in
So your fellow ecologists are skeptical?
"We knew populations had gone extinct with severe
droughts or severe climate years in the past. At that time,
1991, climate scientists were still not even sure there was
a significant warming signal."
Yes. They think we don’t understand species interactions well enough
to be moving things out of their range, because we could cause invasions.
They’re also legitimately skeptical that climate projections are not
yet consistent enough for many areas. If we’re going to be creating
policy based on those predictions, we need climate models in high agreement
with each other. My response is, let’s focus on the areas where they
are in agreement—because there are those. And maybe we can continue
policy-as-usual in areas where the climate models are all over the board.
What do you think scientists have to do to get the
public and the policymakers to take the evidence for climate change
I think one of the problems is that climate-change science is moving so
rapidly that a lot is known that isn’t even out in the literature
yet. Results are presented at conferences and they take a couple of years
to be published. This is why it’s incredibly important for scientists
with knowledge of the latest science, scientists right on top of it, to be
talking directly with policymakers. As it is, there’s too many
intermediaries, too many people who either aren’t scientists at all
or aren’t up to date, and they’re getting the policymakers to
base decisions on ten-year old science. This is a very important role for
scientists and something we all should be doing, although there’s not
much positive feedback for doing it. The reward system in academia is just
not geared toward rewarding that kind of policy interaction and outreach.
Universities have to start recognizing that it’s part of the job of
professors in this field, rather than an add-on.
You’re one of the most highly cited
researchers in environment and ecology research, and yet you’ve
only published 24 papers. This may be unprecedented. Is there a
As you mentioned, it’s unusual to have so many citations for so few
publications. And I’ve just been talking about the reward system in
universities. It was actually an active decision in my career to spend my
research energy on a few really key papers where there was a major need for
this kind of information or this kind of analysis. I also use my time to do
outreach and speak to policymakers. I consciously chose to do these two
things instead of getting a lot of smaller papers out and just padding my
resume. So yes, it was a conscious trade-off that paid off in my case.
I’m not one of these people who can get by sleeping three hours a
night. Given that, I had to consider how best I can spend my waking hours.
I made the conscious decisions to participate in things like the IPCC,
which my department told me to drop when I was first hired. I told them
that I think the IPCC is more important than five more minor publications
in five minor journals.
You talked about how much you loved camping when
you first did the Edith’s Checkerspot paper. How much camping
have you managed to do since that came out?
Don’t ask me that. Since I became a professor nine years ago,
I’ve spent maybe a total of three weeks camping, mostly in visiting
my husband while he did his field work. I do a huge amount of traveling,
but it’s all conferences, meetings, giving outreach lectures to
policymakers, spending almost all the time in windowless