In California's 'salad bowl' – a landscape portioned into emerald fields of spinach, lettuce, kale, and other leafy vegetables, grown to satiate the nation's appetite for greens – hush-hush food safety standards are deforesting land and forcing wildlife out. These practices are unnecessary for ensuring safe food, say experts in a new study, and yet they spell marginalisation for a number of species.

The Californian Salinas Valley is the fertile, riverside floodplain where salad growing is concentrated in the state, and where 70% of America's greens are produced. It is also near to the site of one the most devastating bacterial outbreaks in recent American history. In 2006, E coli bacteria found nestling in the folds of spinach leaves killed five people, and sickened over 200 others.

Spinach was recalled across the United States, and producers suffered a major economic dent due to buyer concern and consumer boycotting. "Everyone wants to trust the food that they eat," says Lisa Schulte Moore, a landscape ecologist working to restore habitat around Iowa's farms, who commented on the new research.

Bacteria could have come from water sources contaminated with fecal matter from livestock farms upstream, bacteria-affected handlers, or from direct contact with wild animals like feral pigs, an investigation by the U.S. Food and Drug Administration later showed. Because of the variability of the threat, and the impact that single-source produce can have on people across the country, the industry dramatically ramped up its food safety standards.

The result was a number of industry-led groups intent on improving safety in salad-growing regions by imposing more stringent regulations on producers who voluntarily joined in. In the Salinas Valley, that industry collective is embodied by the California Leafy Green Products Handler Marketing Agreement (LGMA), which advertises science-based solutions to bacterial spread.

But in the wake of the E coli disaster, some corporate produce buyers have taken matters into their own hands, requiring producers to abide by apparently superfluous safety regulations. Ecologically, these translate into large chunks of land cleared of natural vegetation, and impermeable fencing designed to stave off wildlife, so restricting the movements of deer, coyote, and likely the endangered mountain lion says Sasha Gennet, a Central Coast ecologist with the Nature Conservancy, and an author on the study.

There's no proof that these rules make food any safer. If they did, they'd be included in official, third party-audited guidelines like those put forward by the LGMA, Schulte Moore says.

Maybe most problematically, these businesses are not required to make their dealings transparent, "and therefore even savvy consumers would not have any way to suspect this might be occurring," Gennet adds. "It's been an invisible issue."

Workers harvest iceberg lettuce at a Nunes Company farm on October 4, 2010 in Salinas, California. Photograph: Tony Avelar/Getty Images

What's in it for the buyers? Greens that they deem 'extra-safe', and therefore less likely to cause financial havoc. It's what Schulte Moore calls a "gut reaction", lacking a scientific base. But for farmers, these advances are hard to reject. "There are lots of businesses that enjoy a huge share of the food market," she says, including grocery stores and restaurants. "So by being a kingpin in the supply chain of a food between the producers and the consumers, [buyers] can say, we're not going to buy your product unless you do these things."

Most farmers must accept their land's fate. "Farmers care about their land. Many in this region had invested time and money in conservation, for example wetlands restoration," Gennet says. "I can't imagine it's been an easy choice to reverse all that."

Between 2005 (before the spinach E coli outbreak) and 2009 (three years afterwards) Sasha Gennet and her team took aerial photographs and analysed farmer surveys in the Salinas Valley, picked for its agricultural importance, but also because of its conservation value. The floodplain habitat is a stopover and feeding ground for migrating birds like the Great Blue Heron, its plains and river harbour a number of endangered species like the steelhead salmon, and the waterway connects with one of the country's largest marine sanctuaries.

But in that 2005-2009 period, the area lost 13% of its riverside and wetland habitat. Strips of land—some more than 100 meters wide—were completely cleared or degraded, says Gennet, apparently to create a suitable wildlife buffer, since animals are treated as potential carriers of bacteria.

If the destruction continues at its current rate, the researchers predict natural habitat losses of over 2000 square kilometers in California alone—which incorporates a 20% slash in riverside vegetation across nine Californian counties.

Bare ground also acts like a slipway between farm fields and nearby rivers for the pesticides and fertilizers showered over fresh produce. "Vegetation plays a key role in stabilising soils, in terms of uptake of nutrients and chemicals before it gets in the water way," Schulte Moore explains. Without natural cover to aid drainage, these contaminants sluice across the earth and into the water—bearing untold impacts on aquatic life.

There's the loss of ecosystem services to consider too: an intact system brings with it valuable pollinators, fertile soil, and unpolluted water. On fragmented lands, those features fade away.

Right now, it's not even clear who is instilling these hyper-safe reforms. Because private company activities aren't transparent, it's impossible to tie the changes to anyone in particular. Yet the researchers hold what they call "compelling evidence"—largely through bold farmer testimonies—that the degradation of the land and corporate paranoia are linked.

For consumers, the covert influence of some in the fresh produce industry makes it harder to weed out a good bag of greens from a questionable one. But, says Gennet, the more consumer pressure there is for information about food sources, the more likely big players are to feel the push.

"The health of the food we eat is tied directly to the health of the land it's grown on," she says—an overplayed sentiment to some perhaps, but one that holds true here.