California Vineyard Expansions Hurting Wildlife?

Stefan Lovgren
for National Geographic News
February 24, 2004
The cost of producing wine may be higher than what price tags on
bottles show. According to a recent conservation study, the rapid
expansion of California's vineyards also inflicts a serious cost on the
state's rich wildlife.

While the elimination of native oak forest habitats has already wiped out some animals, such as grizzly bears and wolves, researchers say that the survival of other native predators—among them, bobcats, foxes, and coyotes—could now be under threat.

In the report, which was published in the journal Conservation Biology, the scientists urge California wine growers to protect, and ideally expand, corridors of natural vegetation, especially along the many streams that run through the vineyards.

"If they're not careful about land-use planning and maintaining connectivity for wildlife that need large areas to survive, we're likely to see more species go extinct," said Jodi Hilty, a scientist at the Bozeman, Montana, office of the Wildlife Conservation Society, and the lead author of the report.

Connecting Wildlife

For the study, the researchers set remotely-triggered cameras in 21 areas in six California vineyards. Their goal: to find out if corridors of natural vegetation help maintain connectivity in wildlife populations.

Among the animals detected by the cameras were bobcats, coyotes, gray foxes, raccoons, and striped skunks as well as non-native species such as possums, domestic cats, and dogs.

The researchers found that wide streamside corridors are indeed very important for native predators, which were 11 times more likely to be found along streams than in the vineyards. Other native species primarily used wider streamside corridors and were not detected in narrower or denuded corridors.

In contrast, non-native species, especially domestic cats, were found primarily in wide expanses of vineyards and along denuded corridors.

"We found that not only do corridors help maintain connectivity in wildlife populations, but the width of the corridor also determines if species will use these zones," said Hilty, who was a graduate student at the University of California, Berkeley, when she conducted the field research.

Hilty found that non-native species were much more active, and perhaps more abundant, almost replacing some native species. The cameras never detected some species that are believed to still exist in the area, such as black bears, long-tailed weasels, ringtails, badgers, and spotted skunks.

"In a larger sense, the landscape configuration of natural areas and vineyards is going to impact what species are able to remain in that landscape," Hilty said.

Riparian Corridors

Most of the oak woodland in California's wine region is privately owned. Increased demand worldwide for wine has fueled a major expansion of vineyards. With the valleys already developed, much of that growth is taking place on hillsides. This, conservationists say, has led to increased watershed sedimentation and landscape changes across the ecosystem.

With the native forests gone, researchers believe the only way to ensure the survival of native mammalian species is to protect riparian, or riverbank, corridors.

The study says the size of these corridors is a crucial factor in saving the wildlife, with wider swaths of natural habitat attracting twice as many predator species as narrower ones.

"With the reduction in forests, particularly in agricultural systems like vineyards, often times the only remaining natural habitat is that which is retained along creeks," Hilty said.

Economic Benefits

The board of supervisors in Sonoma County, one of the main wine-growing areas north of San Francisco, is currently debating a riparian setback policy. Although Hilty applauds the move, she warns that the corridors considered by county officials may be too small to support larger native wildlife species.

One major challenge is to convince wine growers of the importance of the corridors. Hilty argues that there are economic benefits for retaining wildlife in the ecosystems.

"Wine growers have found out that it's really expensive to manage a creek once you remove the vegetation," she said. "Financially, it's a better decision for them to leave a buffer zone that will take care of itself so they don't have to actively burn the vegetation."

Although retaining wide streamside corridors may help some native species, the researchers concede that corridors cannot replace core habitat that is essential for wildlife conservation. Some species may not be able to survive at all.

Still, California's vineyards may provide an important lesson for the study of global habitat loss.

"Around the world they are talking about maintaining corridors to connect wildlife populations," Hilty said. "One of the things this study suggests is that it's really important to assess what kind of corridors, including the dimensions, that species are going to be willing to use. If the corridors are too narrow, there are some species that are not going to use them."

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