Native vegetation makes a comeback on
Santa Cruz Island
17 September 2014, by Kathleen Wong
these ill-advised translocations. Step one is obvious:
eradicate the invaders. Step two, however, isn't so
clear. Experts argue over whether expensive, timeconsuming, and labor-intensive restoration is
necessary, or if simply removing non-natives is
enough.
Now a study set in California's Channel Islands
indicates eradication alone can jumpstart recovery.
Led by two UC Santa Cruz undergraduates, the
research shows native shrubs reclaiming the island
on their own nearly three decades after removal of
sheep and other grazers. The study is published in
the journal Restoration Ecology.
"Taking out those sheep triggered a large change in
the vegetation; it was going from grassland back to
coyote brush or California sage, to a more diverse
community," said Nissa Kreidler, one of the study's
student authors.
"People spend millions of dollars on restoring island
ecosystems. So it's a huge finding that passive
recovery can be sufficient and under certain
circumstances, active restoration is sometimes not
necessary," said Roxanne Beltran, the paper's lead
author.
Native vegetation on Santa Cruz Island is recovering
since grazers were removed nearly three decades ago.
Hillsides covered almost entirely in grasses in 1980 (top) Intensive supercourse
are now dotted with coyote brush and other shrubs in
2008 (bottom). Credit: Dirk Van Vuren
The paper grew out of an assignment in the
Conservation and Ecology in Practice
"supercourse" both students took in spring 2012.
Taught primarily by UCSC professors Don Croll
On islands, imported plants and animals can spell (ecology and evolutionary biology) and Erika
ecological disaster. The Aleutians, the Galápagos, Zavaleta (environmental studies), and UCSC
the Falklands, Hawaii, and countless other
Natural Reserve System Director Gage Dayton, the
archipelagoes have seen species such as rats,
class spends the entire quarter learning techniques
goats, brown tree snakes, and exotic grasses
for ecological and conservation research while
delivered by human visitors. Many of the
visiting the protected wildlands of the UC Natural
newcomers have flourished to the point of driving Reserve System. Students read previous research
unique island species extinct.
pertaining to local ecology and management, then
design and conduct their own short-term field
People are now trying to reverse the damage of
studies.
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On Santa Cruz Island Reserve, humans have had a Promising results
major impact on land conditions. The first sheep
arrived 150 years ago, to be joined by cattle,
The results were so promising that Beltran and
horses, and feral pigs. These large herbivores
Kreidler decided to develop them into a publishable
completely denuded some areas, and transformed paper.
others into non-native grassland.
"We said, we can do this," Kreidler recalls. "The
The effort to eradicate sheep, cattle, and horses
supercourse had given us the tools. We knew how
from the island began in 1981 and was largely
to design a project, run the statistics, talk with other
complete by 1999; feral pigs were eliminated by
people, and collaborate to write a paper."
2007. Then the land was left alone. At nearly 100
square miles in size, Santa Cruz Island is far too
That research confidence did not arrive by
large to actively replant native vegetation.
accident; it's what the supercourse was designed to
do. "We have them do study after study; when
Initially, removing grazers caused unforeseen
they're done with the quarter they've finished five,
consequences. Ten years on, non-native grasses one on each reserve they've visited. They are
had taken over a larger share of the island. Dirk
constantly writing up their work and getting more
Van Vuren, now an ecology professor at UC Davis, efficient at study design and data collection. It takes
documented that initial shift in the late 1980s and
the mystery out of doing research, and they're not
again in the 1990s. He compared the plants on
afraid to try things and make mistakes," instructor
either side of a sheep exclusion fence using photos Croll said.
and vegetation transects.
For her part, Beltran saw a chance to join the
While deciding on a class project for the island,
scientific community. "I had done a lot of learning
Beltran said, "we looked at his old black-and-white and practicing to be a scientist through lessons and
photos and saw herbivores had caused more
assignments. But Gage, Don, and Erika made it
damage than we could see currently. We decided really clear that we all had the capability to take the
to see exactly how much the island had recovered next step, to do research on our own, and to make
passively."
contributions in our field. They wanted us to find an
important question that had implications other
people would be interested in," Beltran said.
The students started by contacting Dirk Van Vuren,
the author of the earlier study. He shared
topographic maps of his photo and vegetation
transect locations as well as the historic photos
themselves.
The students and their fellow supercourse
participants, Mickie Tang, Zoe Wedel, and Jared
Anderson-Huxley, set out for the island that
summer to update Van Vuren's study. They
received research funding from UC Santa Cruz
through the Department of Ecology and
Evolutionary Biology, the STEM Diversity Program,
and the UCSC Natural Reserve System.
Reserve manager Lyndal Laughrin and student Roxanne Rugged terrain
Beltran plan the day's work on Santa Cruz Island. Credit:
Roxanne Beltran
Their week and a half on the island proved
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unexpectedly rocky. While the students had
translated Van Vuren's map locations into GPS
coordinates, they hadn't counted on how difficult it
would be to reach each site. "We could see the
places we needed to go in Google Earth, and the
route to each site looked fine from satellite images.
But one was in a huge ditch, another on top of the
mountain, and we didn't realize how crazy the
roads were," Beltran said.
Student researcher Roxanne Beltran clambers her way to
a study site on Santa Cruz Island. Credit: Roxanne
Beltran
The vegetation transects told a similar story. The
land area covered by grasses dropped by half, with
native coastal sage scrub making equivalent gains.
Reserve manager Lyndal Laughrin volunteered to Aerial surveys and vegetation maps of the island
drive the team around, allowing them to sidestep a from The Nature Conservancy, which manages the
rugged trek up 2,800-foot Diablo Peak. "He saved land, provided additional evidence of these
us," Beltran said. Even so, scrambling down cliffs changes.
and ducking around the barbed-wire sheep fence
"Thirty years after eradication, we've shown there is
left the students scraped and bloody.
enough resilience for the vegetation to restore
Back in Santa Cruz, the students compared photos itself," said Croll, a coauthor on the paper. "The
findings help set expectations on how long recovery
shot from the same island vantage points in the
can take. Funders want immediate results. But
early 1980s, late 1990s, and 2012. They found
large areas once occupied by grasses replaced by sometimes it's worthwhile to take the time to wait
rather than incur the huge expense of active
woody shrubs, a shift that nearly doubles the
restoration."
amount of carbon stored on the island. Places
grazed down to bare soil were being recolonized by
Both students say they gained a great deal from
plants, reducing soil erosion.
writing the paper. "It's very different than writing a
paper you think your teachers would like. I
developed a new appreciation for what it takes to
be a scientist," Kreidler said.
Go-getters
Publishing a paper based on supercourse research
is nearly unheard of, Croll said. "Roxanne and
Nissa have been really motivated across the board.
They're not your average undergraduates; they're
go-getters."
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"It has been my dream to go to Antarctica since I
can remember. One reason I worked so hard as an
undergraduate was to realize that goal," Beltran
said. Now she flies to McMurdo Station twice a
year, where she gets to see curious penguins
waddling around her equipment and minke whales
spyhopping on her from water holes in the ice.
"The field courses I took made me a much more
competitive applicant for graduate school, and
volunteering helped me find what I wanted to work
on," Beltran said. "It was a really fortunate
combination of identifying what I wanted to do and
making myself competitive enough to do it."
More information: Beltran, R. S., Kreidler, N.,
Van Vuren, D. H., Morrison, S. A., Zavaleta, E. S.,
Newton, K., Tershy, B. R. and Croll, D. A. (2014),
"Passive Recovery of Vegetation after Herbivore
Eradication on Santa Cruz Island, California."
Restoration Ecology. doi: 10.1111/rec.12144
Provided by University of California - Santa Cruz
UC Santa Cruz student researchers walk home after a
tough day of field work on the island. Credit: Roxanne
Beltran
Kreidler graduated from UCSC in 2012. She has
gone on to run Save The Bay's volunteer-based
restoration program. While replanting San
Francisco Bay shorelines with native plants, she
talks with thousands of local residents about issues
such as pollution and climate change in the region.
Kreidler plans to go to graduate school to study
conservation.
For her part, Beltran started volunteering at the
NRS's Año Nuevo Island Reserve working on
elephant seals alongside Dan Costa, professor of
ecology and evolutionary biology at UCSC. She
discovered her passion was marine mammals and,
after graduating in 2013, landed a coveted spot in
graduate school at the University of Alaska. She
now conducts her doctoral research on the world's
southernmost mammal, the Weddell seal.
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APA citation: Native vegetation makes a comeback on Santa Cruz Island (2014, September 17)
retrieved 18 June 2017 from https://phys.org/news/2014-09-native-vegetation-comeback-santa-cruz.html
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