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Protecting Soils in Sonoma: A Moratorium on Hillside Vineyard Development

The Department of Terroir Security

A forest cleared for vineyard planting in Sonoma County
A forest cleared for vineyard planting in Sonoma County

On January 31, the Sonoma County Board of Supervisors imposed a four-month moratorium on the development of vineyards on forested slopes and hilltops. This halt on new vines is meant to buy the County time to update the existing regulations that allow for some development on hillsides. The existing Vineyard Erosion and Sediment Control Ordinance, or VESCO rules passed in 2000 were touted as a hard-won consensus on vineyard development, but the omission of tree removal from the rules immediately led some environmental advocates to question their strength.

Sonoma County Agricultural Commissioner Tony Linegar was just three weeks on the job in January when he proposed this moratorium on slopes with more than a 15 percent grade. Officials are concerned about applications for vineyard development that would result in tree removal that would result in erosion into adjacent waterways. In the short-term, the moratorium would affect seven pending vineyard projects covering 341 acres in western and northern Sonoma County, including a 122-acre project put forward on Skaggs Springs Road by Healdsburg vinters Ken and Diane Wilson of Wilson Winery and a 40-acre proposal off Bodega Highway outside of Sebastopol by Kistler Vineyards.

While some projects may be small and the ultimate impact of tree removal might be limited in magnitude, the same might not be said for two Annapolis area proposals: Napa’s Artesa Vineyards wants to develop 146 acres, and Premier Pacific Vineyards’ “Preservation Ranch,” hopes to convert 1,769 of its 20,000 acres to vineyards. Tony Linegar has made statements about the proposed rules that indicate a clear orientation towards precaution:

We’ve seen proposals that would remove a significant number of trees on steep slopes. I don’t think it takes a rocket scientist to know that that is going to affect erosion …. Some of the projects that we have in front of us now are proposing to remove large amount of trees. We’re not talking about small acreages …. Rather than let these projects go forward and cause a problem with sedimentation, we’d rather be proactive.

Russian River Winegrowers President and Healdsburg-area attorney John Holdredge of Holdredge Winery noted that “[t]he vast majority of Sonoma County winegrowers … farm sustainably, sensibly, respectfully and with a view toward passing things down to the next generation.” However, Holdredge ceded that “even the best rules over time need to be adjusted.” The proposed regulations are due back to the board April 24.

There can be no “soil profile” indicative of terroir where there is no soil. Certainly, slopes are destabilized when trees are removed on any surface – but when those surfaces are sloping, the likelihood of soil loss is significantly increased. Taking into consideration the increased probability and magnitude of storm events due to climate change, the probability of soil loss is further magnified. Is this new news? In 2003, the Soil and Water Conservation Society published a report entitled “Conservation Implications of Climate Change: Soil Erosion and Runoff from Cropland” warning:

Conservationists should be seriously concerned about the implications of climate change–as expressed by changes in precipitation patterns–for the conservation of soil and water resources in the United States. The magnitude and extent of increased rates of soil erosion and runoff that could occur under simulated future precipitation regimes are large. More importantly, analyses of the climate record in the United States show that changes in precipitation patterns are occurring now. In fact, the magnitude of observed trends in precipitation and the bias toward more extreme precipitation events are, in some cases, larger than simulated by global climate change models, particularly since 1970.

Extrapolating those relationships to the changes in precipitation observed over the past century suggests increases in soil erosion ranging from 4 percent to 95 percent and increases in runoff from 6 percent to 100 percent could already be evident on cropland in some locations …. Unless additional protective measures are taken, such increases in soil erosion and runoff from cropland–if widespread–could reverse much of the progress that has been made in reducing soil degradation and water pollution from cropland in the United States.

Forests play an important role in the hydrogeologic cycle. They quickly absorb and water during storms and release it slowly into streams and rivers while recharging aquifers. In effect, they mitigate the possibility of flooding events and the sedimentation of streams and rivers that could choke off aquatic life in our waterways. As a matter of watershed protection, deforestation on slopes for vineyard development should be reviewed for its deleterious effects. However, as a matter of terroir security, we should ensure that vineyards are established and managed only where they might be sufficiently sustainable for their terroir to be understood over the long-term.