Campus: CSU Long Beach -- December 2, 2005
Cal State Long Beach Professor Receives Joshua Tree National Park
Camille Holmgren, an assistant professor of geography at Cal State Long Beach, has been
awarded a $12,000 Joshua Tree National Park Research Grant for a project that will seek to
reconstruct thousands of years of climate and vegetation changes in the Joshua National
Holmgren will serve as the primary investigator for the project, which is titled "A
Long-Term Vegetation History of the Mojave-Colorado Desert Ecotone at Joshua Tree National
Monument." Julio L. Betancourt of the U.S. Geographical Survey and the University of Arizona
Desert Laboratory is the co-principal investigator. The start date for the grant is
To reconstruct those climate and vegetation changes, Holmgren and her team will study the
pollen and larger plant and animal materials embedded and fossilized in woodrat middens.
"We've got these rodents in the American southwest that exhibit the stereotypical packrat
behavior of collecting leaves, twigs, seeds and other materials from the landscape, which
they bring back to their nests," Holmgren explained. "The rats pee on parts of their nests,
and because their urine is very concentrated, it hardens around these materials, forming a
solid indurated mass, which is what we refer to as their 'midden.' We call the concentrated
pee 'amberat' because it looks like amber and is very hard. When middens are deposited in
a cave or under a rock shelter where they will stay dry, they may be preserved for tens of
thousands of years."
Holmgren noted that the grant was primarily written to get Cal State Long Beach geography
majors out in the field to hunt the nests of these prehistoric woodrats. These nests, or
middens, serve as a kind of time capsule for their environments. "We'll be using these
woodrat middens to reconstruct how vegetation and climate have changed in the region,"
Although woodrat urine may not have the romance of King Tut's golden mask, it offers a
record of its geological time that is every bit as accurate as its more glamorous cousin.
"When we find middens hidden in caves or rock shelters, they are usually very hard and we
need to use hammers and chisels to get them out. We bag them and take them back to the lab
where we throw them into buckets of water," Holmgren pointed out. "What we're left with are
all the loose plant parts and fecal matter. We can also process pollen from the middens.
Outside of these middens, pollen tends to be poorly preserved in arid environments. Middens
thus create a great record that we can easily radiocarbon date. What we end up with are
snapshots of the kinds of vegetation that existed and how the landscape looked through time."
What her research has revealed so far is that the American southwest was a much wetter place
in the era of the mastodon and giant sloth. Currently, the area is dominated by cacti and
creosote bushes, but the evidence left behind in the middens looks back to the Ice Age when
juniper bloomed and oak trees multiplied.
Holmgren has collected ancient oak leaves and acorns found where only cacti bloom today. One
of the samples she collected in Doubtful Canyon in the Chihuahuan Desert along the
Arizona-New Mexico border included samples of pinyon pine.
"They exist nowhere in the vicinity today," she said. "I can also look at various species
of grasses and annuals that respond to summer precipitation. Based on these species, I can
determine how precipitation seasonality has changed. Using what is known about the modern
ecology of these species, I can also estimate how much it rained in the summer and winter."
Her skill with detail allows her to recognize anything in the middens that does not belong
there. One helpful tool is her sense of smell. "The older the midden, the sweeter the smell,"
she said. "Older middens tend to smell like pipe tobacco. The younger middens however, smell
much more pungent. What these small woodrats left tells us as much, if not more, about the
ancient world as mammoth fossils."
The Joshua Tree National Park Research Grant is funded through generous contributions from
the Lee Family Foundation and the Joshua Tree National Park Association. The grant program
provides up to $12,000 to support field research in the physical, biological, ecological
and cultural sciences. Research proposals focus on answering questions about the important
natural and or cultural resources of Joshua Tree National Park, the Mojave and/or Colorado
deserts, and the peoples who have lived in the Joshua Tree region.
Holmgren earned her bachelor's degree from Macalester College in St. Paul, Minn., where
she was a double major in environmental studies and geology. She later went on to receive
a master's degree and a Ph.D. in geosciences, both from the University of Arizona.
Media Contacts: Rick Gloady, (562) 985-5454 or Shayne Schroeder, (562) 985-1727