[Pollinator] Climate change and habitat destruction affect butterfly populations

[Scott Black]

Climate change and habitat destruction affect butterfly populations



Unique North American study authored by University of Nevada, Reno, biologist

RENO, Nev. – Butterfly populations in California 
are declining and, in some cases, moving to 
higher elevations in the Sierra Nevada due to 
climate change and loss of habitat, according to 
a study authored by biologist Matthew Forister, a 
University of Nevada, Reno assistant professor in the College of Science.

"Caterpillars are important herbivores as well as 
a food source for small mammals and birds," 
Forister said. "They play a significant role in 
an ecosystem. Butterflies are used as indicators 
of the health of the environment worldwide. 
What's happening here is a globally recognized 
pattern, though this study is unique in representing North America."

The study, to be published this week in the 
Proceedings of the National Academy of Sciences, 
is based on 35 years of data collected by Arthur 
Shapiro, professor of evolution and ecology at 
the University of California, Davis, and analyzed 
by a team headed by Forister, who was also a 
former doctoral student in Shapiro's lab.

The analysis of the data found that climate has 
changed over the past three decades, with an 
increase in both maximum and minimum daily 
temperatures, shifting some low-elevation 
butterfly populations to higher elevations.

For example, in recent years the field skipper 
butterfly seemed to react to global warming by 
expanding its range from northern California to 
central Washington State and Idaho. Now it's 
jumped the Sierra and invaded the western Great 
Basin, becoming established in California's 
Sierra Valley, and in the Carson Valley and near 
Verdi in Nevada. It also has been very responsive 
to spring temperatures, emerging nearly a month 
earlier than it did near Sacramento 30 years ago.

Forister has been working on analyzing the data 
for more than five years. For the data on 
butterflies to be meaningful, decades of 
consistent sampling is required with long-term data sets, he said.

The data are based on biweekly butterfly surveys 
taken at 10 sites in north-central California 
encompassing a variety of climates and habitats 
from sea level to tree line in the Sierra Nevada 
and including roughly 150 species­the largest 
data-set of its kind in North America and one of the two largest in the world.

"Art did an unusual thing with his career," 
Forister said. "He singlehandedly undertook this 
data collection, on his own, set a regular 
sampling schedule and held to it for 30-plus 
years. He had specific questions in collecting 
this data, but in a way it was impossible to have 
predicted what would be found after so many decades of data collection."

Using a battery of statistical approaches, 
Forister, Shapiro and their colleagues found that 
climate change alone cannot account in full for 
the deteriorating low-altitude fauna. They used 
information on land use to demonstrate that the 
declines also follow conversion of habitat from 
rural to urban and suburban types.

Their most significant findings:

    * Butterfly diversity (the number of 
different species present) is falling fast at all 
the sites near sea level. It is declining more 
slowly or holding roughly constant in the mountains, except at tree line.
    * At tree line, butterfly diversity is 
actually going up, as lower-elevation species 
react to the warming climate by moving upslope to higher, cooler elevations.
    * Diversity among the 
high-elevation-specialist butterflies is 
beginning to fall as temperatures become uncomfortably warm for them.

"It's a one-two punch, and a lot of lowland 
species are reeling from it," Shapiro said, 
noting that there has been much less habitat loss 
in the mountains than in the Central Valley and lower foothills so far.

###

The study, "Compounded effects of climate change 
and habitat alteration shift patterns of 
butterfly diversity," is online at 
<http://www.pnas.org>http://www.pnas.org. It was 
funded by the National Science Foundation.

Additional authors are James Thorne, Joshua 
O'Brien and David Waetjen at the UC Davis 
Department of Environmental Science and Policy; 
Andrew McCall at Denison University in Ohio; and 
Nathan Sanders and James Fordyce at the University of Tennessee at Knoxville.

Forister's Great Basin Bug Lab Web site can be 
found by clicking here and his department 
homepage is at 
<http://www.unr.edu/biology/forister.htm>http://www.unr.edu/biology/forister.htm. 
Shapiro's online database can be found at 
<http://butterfly.ucdavis.edu>http://butterfly.ucdavis.edu .

Nevada's land-grant university founded in 1874, 
the University of Nevada, Reno has an enrollment 
of nearly 17,000 students. The University is home 
to one the country's largest study-abroad 
programs and the state's medical school, and 
offers outreach and education programs in all 
Nevada counties. For more information, visit <http://www.unr.edu>www.unr.edu.



*************************
Scott Hoffman Black
Ecologist/Entomologist
Executive Director
The Xerces Society for Invertebrate Conservation
4828 SE Hawthorne
Portland, OR 97215
Direct line (503) 449-3792
sblack at xerces.org

The Xerces Society is an international, nonprofit 
organization that protects wildlife through the 
conservation of invertebrates and their habitat.

To join the Society, make a contribution, or read about our work,
please visit <http://www.xerces.org/>www.xerces.org.


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