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.
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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