In 2006, a deadly Escherichia coli O157:H7 outbreak in bagged spinach was traced to California's Central Coast region, where >70% of the salad vegetables sold in the United States are produced. Although no definitive cause for the outbreak could be determined, wildlife was implicated as a disease vector. Growers were subsequently pressured to minimize the intrusion of wildlife onto their farm fields by removing surrounding noncrop vegetation. How vegetation removal actually affects foodborne pathogens remains unknown, however. We combined a fine-scale land use map with three datasets comprising ∼250,000 enterohemorrhagic E. coli (EHEC), generic E. coli, and Salmonella tests in produce, irrigation water, and rodents to quantify whether seminatural vegetation surrounding farmland is associated with foodborne pathogen prevalence in California's Central Coast region. We found that EHEC in fresh produce increased by more than an order of magnitude from 2007 to 2013, despite extensive vegetation clearing at farm field margins. Furthermore, although EHEC prevalence in produce was highest on farms near areas suitable for livestock grazing, we found no evidence of increased EHEC, generic E. coli, or Salmonella near nongrazed, seminatural areas. Rather, pathogen prevalence increased the most on farms where noncrop vegetation was removed, calling into question reforms that promote vegetation removal to improve food safety. These results suggest a path forward for comanaging fresh produce farms for food safety and environmental quality, as federal food safety reforms spread across ∼4.5 M acres of US farmland.agriculture | biodiversity | disease ecology | E. coli | foodborne pathogens

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Interest in land application of organic amendments—such as biosolids, composts, and manures—is growing due to their potential to increase soil carbon and help mitigate climate change, as well as to support soil health and regenerative agriculture. While organic amendments are predominantly applied to croplands, their application is increasingly proposed on relatively arid rangelands that do not typically receive fertilizers or other inputs, creating unique concerns for outcomes such as native plant diversity and water quality. To maximize environmental benefits and minimize potential harms, we must understand how soil, water, and plant communities respond to particular amendments and site conditions. We conducted a global meta‐analysis of 92 studies in which organic amendments had been added to arid, semiarid, or Mediterranean rangelands. We found that organic amendments, on average, provide some environmental benefits (increased soil carbon, soil water holding capacity, aboveground net primary productivity, and plant tissue nitrogen; decreased runoff quantity), as well as some environmental harms (increased concentrations of soil lead, runoff nitrate, and runoff phosphorus; increased soil CO2 emissions). Published data were inadequate to fully assess impacts to native plant communities. In our models, adding higher amounts of amendment benefitted four outcomes and harmed two outcomes, whereas adding amendments with higher nitrogen concentrations benefitted two outcomes and harmed four outcomes. This suggests that trade‐offs among outcomes are inevitable; however, applying low‐N amendments was consistent with both maximizing benefits and minimizing harms. Short study time frames (median 1–2 years), limited geographic scope, and, for some outcomes, few published studies limit longer‐term inferences from these models. Nevertheless, they provide a starting point to develop site‐specific amendment application strategies aimed toward realizing the potential of this practice to contribute to climate change mitigation while minimizing negative impacts on other environmental goals.

Summary1. Over the past decade, several foodborne disease outbreaks provoked widespread reforms to the fresh produce industry. Subsequent concerns about wildlife vectors and contaminated manures created pressure on growers to discontinue use of manure-based composts and remove nearby semi-natural vegetation. Despite widespread adoption, impacts of these practices on ecosystem services such as pest control have not been assessed. 2. We used a landscape-scale field experiment to quantify associations between compost applications, semi-natural vegetation, pest control services and lettuce yields on organic farms throughout California's Central Coast, a region experiencing food safety reforms. 3. We found that farms with surrounding semi-natural vegetation supported a diverse arthropod assemblage, whereas a herbivore-dominated assemblage occupied farms in simplified landscapes. Moreover, predatory arthropods consumed more herbivores at sites with more surrounding non-crop vegetation and reduced aphid pest infestations in lettuce. 4. Compost improved lettuce yields by increasing soil nutrients and organic matter, but affected neither pest control nor Escherichia coli prevalence. 5. Synthesis and applications. Food safety concerns are prompting practices that simplify farms and landscapes. Our results demonstrate that two practices -elimination of manurebased composts and removal of non-crop vegetation -are likely having negative impacts on arthropod biodiversity, pest control and soil quality. Critically, our findings and previous research suggest that compost can be applied safely and that habitat removal is likely ineffective at mitigating food safety risk. There is thus scope for co-managing fresh produce fields for food safety, ecosystem services, and biodiversity through applying appropriately treated composts and stopping habitat removal.

Floodplain and riparian ecosystems are noteworthy for their biodiversity conservation value as well as for their widespread conversion to agriculture. Recent evidence indicates that the conversion of remaining habitat may be accelerating because of a new threat: on‐farm practices meant to promote food safety. Nationwide, US fruit and vegetable farmers report being pressured by commercial produce buyers to engage in land‐use practices that are not conducive to wildlife and habitat conservation, in a scientifically questionable attempt to reduce food‐borne illness risk. We measured the extent of impacts from some of these practices in a leading produce‐growing region of California. Over a 5‐year period following an outbreak of toxic Escherichia coli from spinach, a crop grown extensively in the region, 13.3% of remaining riparian habitat was eliminated or degraded. If these practices were implemented statewide, across all crops, up to 40% of riparian habitat and 45% of wetlands in some counties would be affected. This study highlights the importance of managing farms for both food safety and ecological health through the use of an evidence‐based, adaptive management approach. Ongoing biodiversity loss and global integration of the food supply make these findings relevant wherever produce is grown.

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Controlling human pathogens on fresh vegetables, fruits and nuts is imperative for California growers. A range of rules and guidelines have been developed since 2006, when a widespread outbreak of E. coli O157:H7 was linked to bagged spinach grown in California. Growers face pressure from industry and government sources to adopt specific control measures on their farms, resulting in a complex, shifting set of demands, some of which conflict with environmental stewardship. We surveyed 588 California produce growers about on-farm practices related to food safety and conservation. Nearly all respondents considered both food safety and environmental protection to be important responsibilities for their farms. Responses indicate that clearing vegetation to create buffers around cropped fields, removing vegetation from ditches and ponds, and using poison bait and wildlife fences are commonly used practices intended to reduce wildlife movements onto farm fields. The survey also revealed that on-farm practices vary substantially even among farms with similar characteristics. This variability suggests inconsistencies in food safety requirements, auditors' interpretations or growers' perception of the demands of their buyers. Although site-specific considerations are important and practices should be tailored to local conditions, our findings suggest growers, natural resources and food safety would benefit from clearer, more consistent requirements. C alifornia leads the nation in production of vegetables, fruits and nuts (CDFA 2014) and its fresh produce industry is composed of an exceptional diversity of crops and farm types. Beginning in the late 1990s and accelerating after prominent incidents such as the 2006 outbreak of E. coli O157:H7 linked to bagged spinach, new rules and best practice guidelines to mitigate foodborne pathogen contamination propagated rapidly through the fresh produce industry (Stuart 2010). The multiple layers of rules and guidance developed over the past decade present growers with a complex landscape of pressures to adopt and intensify on-farm practices intended to improve food safety, some of which may conflict with efforts to conserve natural resources.Alongside continually developing expectations for food safety, growers are also expected to conserve water and soil and are legally obligated to protect water quality as well as wildlife and its habitat. Many of the state's major agricultural regions, such as the San Joaquin, Sacramento, Santa Clara and Salinas River valleys are located in or near ecologically sensitive river corridors and floodplains. These ecosystems host fertile soils, are sources of fresh water, and also provide habitat for many species of birds, amphibians and other wildlife. On-farm practices, including those related to food safety, can have direct and indirect consequences to the benefits provided from these ecosystems Karp et al. 2016;Karp, Baur et al. 2015;Letourneau et al. 2015). Food safety measures and impactsEarly evidence suggested that pressures to improve food ...

1. Bird conservation in agricultural settings can be controversial. While some bird species damage some crops, others suppress insect pests. Few studies have simultaneously compared bird services and disservices to assess their net impact.2. Using an exclusion experiment in six California strawberry farms, we show that bird suppression of berry damage by insect pests (about 3.8% of berries) is similar in magnitude to the damage birds inflict on strawberries (about 3.2% of berries).3. Across 27 farms, we found that bird species richness and the relative abundance of insectivorous birds increased, while the relative abundance of strawberry-eating birds and bird damage decreased on farms with more semi-natural land cover in the surrounding landscapes (1000 m radius).4. Relative to homogeneous farms, those that implemented diversification practices, such as hedgerows, flower strips or increased crop diversity, had greater bird species richness, total relative abundance, insectivore abundance and strawberryeating bird abundance. Synthesis and applications.Conserving semi-natural land cover in the surrounding landscape benefits bird species richness locally and aids farmers through reduced abundance of strawberry-eating birds and bird damage. These results highlight the need to consider both the services and disservices of birds when making management decisions. K E Y W O R D Sagriculture, agroecology, bird, diversified farming systems, ecosystem services, humanwildlife conflict, pest suppression, strawberry