by Chris Benz
Published in the Napa Valley Register

Biodiversity is the variety of life on Earth, from genes and bacteria to entire ecosystems such as forests and coral reefs. Biodiversity is being reduced by climate change as temperatures warm and habitats disappear. Modern agriculture with its practice of monoculture—large plantings of a single crop—has played a role in habitat loss, but this is starting to change in the Napa Valley as growers explore ways to bring nature back to the vineyard.

These new practices were on display at a field day at Honig Vineyard & Winery in Rutherford on May 30, organized by Wild Farm Alliance. As a national group the Alliance provides resources to help farmers farm in ways that are compatible with preservation of a broad range of native plants and animals. Jo Ann Baumgartner, Executive Director, described the group’s laudable goals for U.S. farms by 2050: plant 500,000 miles of hedgerows, install one million nest boxes or bird perches, and restore 100,000 miles of riparian habitat.

Hedgerows provide many ecosystem benefits and increase biodiversity.

Honig Vineyard planted a hedgerow of native plants along a drainage ditch in 2002 and saw a reduction of Pierce’s disease, a vine disease transmitted by sharpshooter and leafhopper insects. Sam Earnshaw of Hedgerows Unlimited explained that hedgerows can provide habitat for beneficial insects (predators and parasites of the pests). Hedgerows also provide habitat for birds and wildlife and function as movement corridors. The plants in a hedgerow stabilize banks of waterways, increase groundwater infiltration, and sequester carbon. Hedgerows provide many ecosystem benefits and increase biodiversity.

Coyote brush, a common scrubland plant in Napa County, is the hedgerow superstar. It’s a hardy survivor that serves as an overwintering host for the parasitoid wasps that attack the Grape Leafhopper pest.

Entomologist Stephen Pryor described how plants used in cover crops (planted between the vine rows) or in perennial borders, such as hedgerows, can enhance the habitat for beneficial insects. Flowers of these plants provide nectar, a flight fuel source, and pollen, a protein source.

Birds can also play a role in pest control. Songbirds (western bluebirds and tree swallows) are insect eaters and cavity nesters. They are losing much of their native habitat as oak woodlands disappear from the Valley. Barn owls are rodent eating machines—a family of five can eat over 3400 gophers, mice, and voles per year. Bluebird boxes and larger owl boxes encourage these birds to return to the vineyard for nesting and raising young. Honig has over 100 bluebird boxes, three barn owl nest boxes, and has recently installed three kestrel nest boxes. A research group based at Cal Poly Humbolt, UC Davis, and UC Riverside showed how adult songbirds are (gently) captured and fitted with GPS backpack trackers. The flight paths mapped so far show that the birds spend most of their insect foraging time in the vineyards (86% of the time for bluebirds and 77% of the time for swallows). This season’s research will look at the birds’ diet through genetic analysis of bird poop to see if they are eating the pests.

Kristin Belair, winemaker at Honig for 25 years and now Director of Winegrowing and Sustainability, showed off a pollinator garden she designed for planting underneath ground-based solar panels. “This had been all weeds, but here was another location to bring in more biodiversity. A good pollinator habitat can help beneficial insects be more resilient to farming stresses.” Belair chose plants that would bloom throughout the season and have different flower colors and shapes. Some plants will provide seeds for bird food, others will become shrubs and provide shelter for quail.

Belair noted that more biodiversity equals more resiliency. She framed her commitment this way: “How can we have a more reciprocal relationship with our farm community, rather than an extractive one? How can we give back? It will be fun to see what happens.”

Contributor Chris Benz is a retired winemaker and co-founder of Napa Climate NOW!

Napa Climate NOW! is a local nonprofit citizens’ group advocating for smart climate solutions based on the latest climate science, part of 350 Bay Area.