Writing a policy brief

In 2006, a high profile outbreak of toxic E. coli in bagged spinach was traced to

California’s Central Coast, where >70% of the United States’ salad greens and

vegetables are produced. Though no definitive cause for the outbreak could be

determined, wildlife was implicated because some animals can harbor

pathogens. Growers were subsequently pressured, primarily through their

buyers and sometimes through regulatory mechanisms, to reduce perceived

risk by adopting practices to minimize potential wildlife intrusion onto their farm

fields. Specifically, growers were asked to remove surrounding non-crop

(natural) vegetation presumed to harbor wildlife. This practice is expensive for

growers to implement and has led to a significant loss of important natural

habitat in the region.

The authors of a study in the Proceedings of the National Academy of

Sciences assessed whether the presence of non-crop vegetation is associated

with foodborne pathogen prevalence on farms. They used a detailed

vegetation map and examined ~250,000 pathogen samples including

enterohemorrhagic E. coli (EHEC), generic E. coli, and Salmonella bacteria.

Although EHEC prevalence in produce was higher on farms near areas

suitable for livestock grazing, there was no evidence that EHEC, generic E.

coli, or Salmonella increased near non-grazed, semi-natural areas. Rather,

pathogen prevalence increased most on farms where non-crop vegetation was

removed.

The authors recommend that buyers, auditors, and regulators encourage

science-based approaches to co-manage for environmental quality and food

safety. The findings of this study suggest that the requirement for farmers to

clear non-crop vegetation is unnecessary, at best, and is damaging to the

natural environment. Government agencies and buyers can instead promote

both food safety and ecosystem benefits by funding and encouraging practices

such as vegetated buffers and wildlife-friendly fencing of riparian areas.

Practices to conserve vegetation and wildlife habitat will help sustain

agricultural productivity by providing natural benefits such as pest control,

water quality, groundwater recharge, and pollination services. These benefits

are urgently needed for agriculture, and will be increasingly valuable over time.

A diverse farming landscape, including non-crop vegetation on and near farms,

promotes these benefits.

California has long been a global leader in agriculture. By addressing the

serious issues of food safety and ecosystem benefits together, California has

the opportunity to demonstrate a path toward harmonizing environmental

quality, agricultural productivity and human health.

Healthy farms and nature are not at odds: Reducing environmental

impacts of food safety practices Karp DS, Gennet S, Kilonzo C, Partyka M, Chaumont N, Atwill ER, Kremen C. (2015) Co-managing fresh produce for nature

conservation and food safety. Proceedings of the National Academy of Sciences. August 10, 2015

http://www.pnas.org/content/early/2015/08/05/1508435112.abstract

Contacts: sgennet@tnc.org, danielsolkarp@gmail.com, or ckremen@berkeley.edu

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Schematic of farm environment

using co-management approach

for food safety and environment

KEY POINTS Produce growers in California

have been pressured to remove

non-crop vegetation and wildlife

habitat on farms for food safety

A new study shows this practice

of habitat removal around farms is

costly, damaging to the

environment, and is not effective

in reducing pathogens. In fact,

it may result in higher

prevalence of some pathogens.

Habitat removal should no longer

be encouraged. Buyers and

regulators should instead support

farming practices that enhance

nature for its beneficial functions.

Proximity of grazeable lands near

farm fields is correlated with

pathogens. However, practices

such as vegetated water quality

buffers and riparian fencing can

help mitigate associated risk.

California can be a global leader

in demonstrating sustainable

agriculture by solving this key

challenge to nature and human

health.