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Managing wild birds for improved strawberry production, pest control, and food safety outcomes in the California Central Coast

Karp, Daniel
University of California - Davis
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A critical challenge for this century is transitioning towards sustainable food systems that are productive and secure for nature and people. Diversified agriculture--a production system that maintains and enhances on-farm biodiversity-- shows great promise for accomplishing this goal (Kremen & Miles 2012; Kremen et al. 2012). However, farmers recognize tradeoffs involved in practicing diversified agriculture. For example, non-crop habitats may enhance or depress pest populations, depending on interactions among pests and their predators (Chaplin-Kramer et al. 2011). Perceptions among growers of how biodiversity impacts yields may drive farm management decisions. Therefore, advancing multifunctional agriculture requires collaborating with growers to quantify not only ecosystem services but also disservices and trade-offs involved in farm management (Zhang et al. 2007; Karp et al. 2015c). Wild bird management on farms is particularly fraught with tradeoffs. Birds are beloved in the U.S, evidenced by the US$85 billion bird watching industry (La Rouche 2001). Birds can also benefit farmers directly by limiting insect pest infestations (Maas et al. In Press; Karp et al. 2013; Karp & Daily 2014). Yet birds are also pests themselves, responsible for a billion dollars of annual crop damage in the U.S. (Peer et al. 2003; Pimentel et al. 2005). Also, as disease outbreaks trigger sweeping reforms to farming practices (LGMA 2013; FDA 2014), the role of birds in transmitting illnesses such as Salmonella enterica and enterohemorrhagic Escherichia coli (EHEC) is being seriously considered (Carlson et al. 2011; Callaway et al. 2014). Now, birds are often perceived as hazards to fresh produce and buyers regularly force growers to manage them accordingly.Our work broadly seeks to elucidate the socio-ecological conditions that determine bird biodiversity, associated ecosystem services and disservices, and bird management strategies on strawberry farms throughout the Central Coast of California. As a valuable crop with strict quality controls, strawberries are highly susceptible to pest damage (Swezey et al. 2007). Also, strawberries are potential carriers of foodborne diseases, and wildlife have been implicated in foodborne disease outbreaks originating from strawberries in the past (Laidler et al. 2013).Our core goal is to develop and popularize science-based strategies for co-managing birds for conservation, food safety, and profitability goals in strawberry crops. Specifically, our ecological research will identify best practices for enhancing bird services and mitigating disservices. First, we will study farms that vary in diversification and bird management practices to elucidate how practices such as deterring birds (with sound cannons, whistles, or flags) and removing non-crop vegetation (in grass strips, hedgerows, or forest patches) affect birds' net economic impact on strawberry production. Additionally, we will identify which species act as strawberry pests, pest predators, and/or disease vectors, as well as where they nest, to help provide growers with strategies for reducing nest site availability for problem species and enhancing availability for beneficial species.Our broad goal for our behavioral research is to provide strategies for transitioning from science to practice. First, we will elucidate how values and identities correlate with attitudes towards birds-- and how values and identities vary among grower groups (e.g., diversified vs. monoculture growers)-- can aid outreach. Multiple communication strategies could be designed and deployed to reach growers with varied identities/values. Second, we will determine whether growers with similar identities influence each other's behaviors. If they do, then piloting practices with a few growers that each exemplifies a different identity, and then empowering them as advocates, could help provoke behavior change across the wider grower community. Finally, we will determine how external constraints shape grower attitudes and practices so that we can target outreach materials to appropriate decision-makers. For example, if growers reluctantly engage in severe bird management practices after being pressured by their buyers, then sharing our work with buyers could reduce pressure on growers.
Funding Source
Nat'l. Inst. of Food and Agriculture
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Bacterial Pathogens
Escherichia coli