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These above-ground benefits to hedgerows are easy to spot. But a few years ago, McNamara watched as a soil scientist dug into the dirt surrounding them. She scooped up rich, dark, compacted soil, mycelial strands tangled within. “I think we were in the middle of summer and the soil, even the topsoil, was moist,” he recalls. It was a memorable sight in drought-riddled California.

That scientist, Jessica Chiartas, was studying the soil around hedgerows. She selected a couple dozen farms in the Sacramento Valley, an area with plenty of well-established hedgerows thanks to a campaign initiated more than 20 years ago that sought to bring native vegetation back to local farms.

Chiartas’ study, published in late 2022, found that no matter the soil type, be it loam or clay, the soil below hedgerows stored significantly more carbon than the soil in the adjacent agricultural fields. While most of that carbon remained on the surface layer, an increase in soil carbon was detected down to the depth of 1 meter—where it’s more likely to remain. In fact, the study concludes that installing hedgerows on 50 to 80 percent of California’s farmland would capture so much carbon, it would help the state to reach up to 12 percent of its ambitious greenhouse gas reduction goals.

California farmers, who are contending with drought, flooding, and a long list of pests that can ruin fruits, nuts, and vegetables haven’t fully embraced planting native vegetation adjacent to fields. But as the state encourages and incentivizes climate-friendly agriculture practices, they might just start.

Hedgerows are straightforward strips of shrubs or trees roughly 15 feet wide, but they highlight nature’s complex work, says Chiartas. At the surface of the soil around them, “you have a buildup of litter: leaves, stems, dead insects, feces, whatever organic materials are deposited,” she explains. When it rains, the organic matter dissolves and moves deeper into the soil profile. That “litter layer” also protects soil temperature and moisture, creating a stable, thriving soil food web that pulls organic materials deeper into the ground. “We’re not fighting biology,” she says. “It’s efficient.”

Recognizing that, the USDA’s Natural Resources Conservation Service (NRCS) offers a program to farmers nationwide that provides technical assistance and some funding for hedgerow planting, and Xerces Society for Invertebrate Conservation has also focused on the expansion of pollinator habitat, including hedgerows. Individual states including Minnesota and Iowa have also encouraged the planting of native vegetation in the form of prairie strips.

Chiartas jokes that she’d like to start a campaign to “re-hedge California.” With millions of agricultural acres, she sees potential in otherwise long stretches of empty perimeter. “All these field edges are bare right now,” Chiartas says, adding that because hedgerows stay in place, the carbon benefits would last well into the future. “It’s a proxy for the potential of agroforestry,” she says. “We need shade in California. Not just for carbon sequestration but for farm laborers.”

During her research, growers told Chiartas farmworkers often gravitate toward the rows of native plants, including California redbud, Manzanita, or Blue Elderberry trees for a break. And she, along with others who prioritize conservation, applaud a farm system that can expand its scope beyond merely growing food to creating space for all living things.

A Woody History

In the U.S., efforts to introduce natural vegetation to agricultural land took a “huge hit,” Earnshaw says, in 2006, the year a serious E. coli outbreak was linked to fresh spinach grown in California’s central coast region. The outbreak sickened more than 200 people and caused three deaths.

“Since then, there has been tons of pressure on growers to do everything they can to keep wildlife off of their fields,” explains Daniel Karp, an associate professor at U.C. Davis in the Department of Wildlife, Fish, and Conservation Biology. “So, that’s meant killing all kinds of wildlife—putting out snap traps and rodenticides along field edges to kill off rodents.” It also often meant removing hedgerows.

Although a USDA investigation wasn’t able to definitively determine how E. coli wound up in bags of baby spinach, the outbreak strain was linked to specific fields where river water, cattle feces, and wild-pig feces all contained the bacteria. A grass-fed cattle operation was located on the ranch, less than a mile from the spinach field.

In the five years following the outbreak, a study found that 13 percent of the plants and trees growing along rivers in one of California’s leading produce-growing regions were eliminated out of fear that they would provide habitat for wildlife carrying pathogens. And a few years later, Karp says, a survey of California produce growers found that 40 percent were still removing habitat even a decade later.

Karp says it’s an understandable, albeit misguided, practice. A 2015 study co-authored by Karp found that, contrary to popular assumptions, the clearing of vegetation has been associated with increased prevalence of foodborne pathogens over time. “Shrubs, grasses, and trees (are) a well-known filter for nutrients and pathogens,” says Karp. “So, you might be able to prevent [pathogens] from getting onto your farm field by having those buffers.”

Karp’s research has also found that smaller, more diverse operations tend to attract species of birds that are less likely to carry foodborne pathogens, unlike monoculture operations that are more likely to have flocking birds that can deposit potentially harmful bacteria on produce.

Karp says many growers he speaks with acknowledge the benefits of hedgerows or riparian habitat, but companies who buy fresh produce often won’t engage with growers who have incorporated plants and wildlife into their operations.

This, says Chiartas, has led to a “scorched earth” mentality for those who grow produce that’s consumed raw. Karp notes, however, that the Food Safety Modernization Act signed into law in 2011 does not advise removing habitat. “The leverage point is definitely going to be big industry buyers and their auditors, and to really convince these folks that the science doesn’t support this idea that habitat removal is effective,” says Karp.

That Bustle in Your Hedgerow? Biodiversity.

Years later, she delights in walking past the various flowering plants. Doves and white-tailed kites sing. Come fall, her coyote bush hums with bees, flies, and other insects. Research shows native vegetation attract critters that can help devour pests harmful to crops. For example, a recent study showed that walnut orchards with hedgerows or riparian edges had more avian predators, like the white-breasted nuthatch and woodpeckers, gobbling up harmful codling moths, than orchards with only weeds growing. The more natural, woody vegetation, the more moth consumption occurred.

Long says that while many farmers have resisted planting hedgerows on their land out of fear the trees and shrubs would only draw harmful pests, studies have shown the opposite to be true. Several years ago, she and other researchers collected bugs in hedgerows during growing seasons over two years and found that 78 percent of the insects were beneficial, while only 22 percent were considered pests. “Hedgerows do bring in more natural enemies like ladybugs and parasitoid wasps that do move into adjacent crops,” she says. Her research has also shown that farmers who have hedgerows don’t have to spray as many insecticides as those farmers who have no habitat around their farm.

Insect biodiversity can also encourage more effective pollination in orchards, Long says, because more wild bees throw honeybees off their vertical, methodical paths. “The honeybee will kind of forget what it’s doing, and it will cross over rows; you get better pollination that way.”

Though establishing hedgerows can cost thousands of dollars, and, at least in the first few years, requires a dedicated water source (a big deal in parched California), Long’s research has found that once the habitat is established, the pollination and pest control that’s provided result in a return on investment that lasts between seven to 16 years.

The Importance of Incentives

Judith Redmond is one several founders of Full Belly Farm, 50 miles northwest of Sacramento; she and her co-founders have been using regenerative, organic farming practices for nearly 40 years. She’d like HSP to push hedgerows as a more attractive option, particularly in terms of carbon sequestration, even though planting them can be more labor intensive in the short-term than applying compost. “Compost has to be trucked around. It might not be as beneficial as hedgerows or cover crops,” she says.

Still, the HSP grants have enticed conventional and organic growers like Don Cameron, vice president and general manager of Terranova Ranch, a large, mostly conventional ag operation outside of Fresno that grows processing tomatoes, carrots, onions, nuts, and other crops, planted a half-mile hedgerow three years ago with an HSP grant.

Cameron has since noticed the presence of wild pollinators, as well as “hummingbirds all year,” he says, and around the hedgerows there’s stability in his otherwise sandy soil. “What we’ve found where we’ve done it is that we have no erosion,” he says. “There’s a lot of erosion without habitat established.”

Since receiving the grant, he’s worked with NRCS and other organizations to plant about two more miles of hedgerows. And he plans to put in another seven miles with funding help from the large companies he sells his produce to, including Nestlé. “We’re seeing major food companies wanting to promote increased sustainability on farms,” he says.

Cameron is well-known in California, particularly for his work around on-farm water recharge. He says that in a stretch of the San Joaquin Valley that is often dusty and void of natural vegetation, his hedgerows have gained attention. Other growers have taken notice and they’re curious about the more than 20 plant varieties that bloom around his crops.

If it works, this type of farmer-to-farmer education may help the state achieve Chiartas’ goal of re-hedging California and pulling more carbon into the soil at the same time. For now, though, Cameron can’t ignore the simple pleasure that comes from simply growing a wider array of plants. Hedgerows are “aesthetically pleasing,” he says. “I like that.”