|The mosaic of oak woodland habitat and vineyards in Sonoma and Napa counties is rapidly changing. Photo © Mark Reynolds / The Nature Conservancy.|
In his provocative book Win-Win Ecology: How Earth's Species Can Survive in the Midst of the Human Enterprise, eminent scientist Michael Rosenzweig argues that the future of Earth's biodiversity will depend as much on redesigning human-dominated landscapes to support biodiversity as on traditional protected nature reserves. A committed group of private landowners, agency and NGO staff, and scientists including PRBO staff, are beginning to do just this in an unlikely place--California's vineyard landscapes in Napa and Sonoma counties.
The Mediterranean climate of cool wet winters and hot dry summers that sustains California's oak-dominated habitats and their rich biodiversity also creates ideal conditions for growing wine grapes, increasingly vital to the state's economy. Balancing the needs of a rapidly developing wine industry with the environmental and habitat values of oak woodlands is a growing challenge. More than 300 species of amphibians, reptiles, birds, and mammals and several thousand plant and invertebrate species thrive in oak habitats.
Oak woodlands occupy approximately ten million acres, or about ten percent, of California. Over 50 species of birds and mammals depend on the acorns produced by the five predominant oak species. Seven are focal species in the Oak Woodland Bird Conservation Plan (www.prbo.org/calpif/plans.html): Acorn, Lewis's and Nuttall's woodpeckers, Western Scrub Jay, Yellow-billed Magpie, and Oak Titmouse.
Residential development and urban sprawl, altered fire regimes, invasive species, and the recent spread of 'sudden oak death' have taken their toll on California's oak woodlands. In recent years, rapid development and expansion of vineyards in California oak woodlands have contributed to an increasingly fragmented and altered landscape for wildlife. Even though close to 75% of California's original area of oak woodlands remains, the vast majority is on privately owned land with an uncertain future and increasing pressure from development and agriculture (see map graphic at right).
Conserving these habitats will require not only an extensive network of protected lands but also that working landscapes, like ranches and vineyards, contribute to biodiversity protection. Setting priorities for land protection, and measuring restoration success, requires extensive baseline scientific data. Recent efforts to understand the biodiversity conservation potential of vineyard landscapes have included studies by PRBO, The Nature Conservancy, and other groups. Preliminary results show that when oak woodland habitat of sufficient size is retained in landscapes with a large amount of vineyard conversion, bird diversity is close to that for landscapes with a small amount of vineyard area. Retaining wide riparian habitat corridors enhances connectivity for movement of bobcats and other carnivores. Putting up nest boxes in vineyards shows promise for enhancing populations of Western Bluebirds and other cavity nesters.
These studies are timely. Recently there have been several efforts from within the winegrape growing community to develop more sustainable farming practices. Reducing pesticide use, increasing water-use efficiency, and reducing soil erosion are not only good for the environment: these practices make economic sense to grapegrowers. Although many questions remain--How much habitat to retain? In what configuration? What is the most effective way to restore habitat? How much will it cost?--the sustainable winegrape growing movement holds promise for valuing, retaining, and restoring wildlife habitat.
Rosensweig calls the search for environmentally sound ways to use land for human benefit 'reconciliation ecology'. Vineyard landscapes of Napa and Sonoma offer a hopeful place to practice reconciliation ecology. Appreciation of the rich bird diversity of California's oak woodlands is an aesthetic that values complexity--not unlike appreciating the nuances of fine wine.