Teaming up to save California's oaks

UCSC researchers use GIS technology to investigate declining populations

By Jennifer McNulty

Photo: Sleepy Hollow, oil on canvas, Kathleen Lipinski, B.A., Art, College Five (Porter College), 1977

Don't it always seem to go
That you don't know what you've got
Till it's gone
They paved paradise
And put up a parking lot.

Lyrics from "Big Yellow Taxi"
by Joni Mitchel

For three decades, the Endangered Species Act has helped conservationists fight for environmental protections. But ecologists now recognize that waiting to intervene until a species is endangered can be "too little, too late."

"Long before species go extinct, populations can decline to the point where they're not performing ecologically," says UCSC conservation biologist Erika Zavaleta.

"We lose a species functionally long before we lose it absolutely."

In a new trend, ecologists have begun documenting the plight of plants and animals as soon as they show signs of vulnerability. By heeding the early warning signs, ecologists hope to identify the sources of stress and inform policy makers about intervention and protection options.

Among the plants that are dwindling in number are two gems of the California landscape: the blue oak and the valley oak. These majestic trees, found only in the Central Valley and the foothills of the Coast Range and the Sierra Nevada, are not succumbing to the epidemic of Sudden Oak Death that is ravaging tanoaks, coast live oaks, and black oaks. Rather, something appears to be inhibiting their regeneration. Zavaleta is determined to find out what's causing the problem and how big a threat it poses.

"Almost all the trees we see today are 100 or more years old, and the concern is that as they die off, there won't be youngsters to replace them," says Zavaleta, an assistant professor of environmental studies and a rising star in conservation circles. "We know the conversion of oak woodlands to vineyards, croplands, and subdivisions is hurting them. If we lose them here, we're not going to have them anywhere else."

Blue and valley oaks serve an "incredibly important" ecological role, says Zavaleta. Their acorns are a major food source for birds, mammals, and insects, and they transform grasslands into the more biologically diverse California savannah, creating patches of shade, structure, and cooler temperature that provide habitat for many species.

The cultural value of oaks is evident in paintings, photography, and literature, and in the names of communities from Oakland to Oak Grove.

Conservation biologist Erika Zavaleta and Geographic Information Systems specialist Brian Fulfrost Photo: Jim MacKenzie

"These trees are not rare on the landscape yet," says Zavaleta, who received a prestigious David H. Smith Conservation Research Fellowship in 2001 from the Nature Conservancy that helped fund her oak research. "It's nice to do something at this early stage."

Working with graduate student researcher Kris Hulvey, Zavaleta discovered a treasure of information had been gathered about the two species of oaks. "I was amazed how much literature was out there," Zavaleta recalls. "There were about 100 different experiments looking at the regeneration of blue and valley oaks, and more than 30 surveys over the past 30 years."

With so much historical data, Zavaleta knew it would be foolish to launch yet another experiment without first compiling the existing results into a comprehensive profile of oaks in California. She turned to Brian Fulfrost, coordinator of UCSC's Geographic Information Systems (GIS) Laboratory, to collaborate with her on the project.

GIS software produces eye-catching maps, but it is also a powerful analytical tool, says Fulfrost. "A lot of people think you push a button and get a map, but it's the opposite of that," says Fulfrost, who teaches classes on the environmental applications of GIS technology. "GIS is a problem-solving and decision-making tool. Making a map is only one of the things you can do with it."

GIS enhances data analysis the way word processing facilitates the writing process. Fulfrost and Hulvey created multiple databases, plotting the presence of oak trees on maps and creating overlays for key variables like temperature, precipitation, elevation, longitude and latitude, and seedlings-per-adult. With all the information in one place, Zavaleta was able to analyze tree populations relative to different environmental variables.

Preliminary patterns showed some regeneration in almost 80 percent of blue oak sites studied but less than 50 percent of valley oak sites.

"That confirms there really is a statewide problem for the valley oak," says Zavaleta. The status of blue oaks will remain unclear until researchers learn more about the extent of regeneration taking place. "It might be enough, depending on the site, but if there's only one seedling per 300 adult trees, they'd definitely be in trouble," she says.

Poring over maps, Zavaleta was able to document that valley oaks statewide are more likely to regenerate on reserves than on land that is used more intensively. She also saw many sites with seedlings of about 12 inches in height that had no teenage trees, suggesting that the challenge for oaks isn't just germinating and surviving the first year or two, but making it into their 20s.

Zavaleta's next task is to enrich the database with details about specific reserves. She wants to map roads and development, north-and south-facing slopes, and land ownership classifications. Then she'll look at the maps again, searching for commonalities.

Despite the time-consuming nature of GIS analysis, a growing number of social scientists are embracing the technology, which can also be used to illuminate networks and relationships that don't have geographic links, like U.S. nonprofits dedicated to children's health, or the flow of corporate money to politicians. For Zavaleta, who enjoys bridging the gap between academia and policy, Fulfrost's maps will be the centerpiece of her outreach to conservation advocates and policy makers.

"I see science as part of a continuum of what I do as a person and a citizen," says Zavaleta. "I want to take our research findings and communicate them to conservation groups and government agencies that manage the land. That's my goal. Some scientists see getting published in journals as the end of their work. I'm too impatient to stop there. I want to get that information into the public arena where it can do some good."

—Jennifer McNulty