Responding to a pesky problem, a paper co-authored by PhD candidate Claire Powers offers a potential solution—clustering similar farming practices together

Organic agriculture may be as old as dirt, but that doesn’t mean its impact on pesticide use is fully understood. Claire Powers is doing her part to change that.  

Powers, a PhD candidate in environmental studies at the University of Colorado Boulder, has co-authored a paper published today in Science. Powers and co-authors Ashley E. Larsen of the University of California Santa Barbara (UCSB) and Frederik Noack of the University of British Columbia investigate how organic agriculture influences the pesticide use of neighboring farms. Does it increase it? Decrease it?   

The answer, they learned by analyzing thousands of field observations, is it depends.

Location, location, location 

“We found that conventional fields that are adjacent to organic fields tend to increase their pesticide use,” says Powers, “and organic fields that are adjacent to organic fields tend to decrease their pesticide use.”  

Precisely why this is the case is unclear, but Powers, Larsen and Noack suspect it has to do with how organic farms—many of which use pesticides, albeit organically approved ones—implicate the larger ecosystem.  

“Organic fields leverage the benefits of natural enemies that reduce the number of pests on their fields, like birds and bugs that eat smaller problematic pests,” says Powers.

These natural enemies and pests then venture onto neighboring fields for shelter and food. If those fields are conventional, farmers will likely have to increase their pesticide use, and if they’re organic, farmers will likely be able to decrease their pesticide use.

This may sound like a win for organic farmers, but not so fast.

When organic and conventional farms are distributed randomly across a landscape—meaning there’s no specific reason why one type of field sits next to another—it’s often both conventional and organic farmers who lose, Powers explains.

“I have not talked to farmers specifically, but I think that, from a conventional farmer’s perspective, it can be a bummer to be adjacent to organic fields, because it means that you will spend more on pesticides. Similarly, organic farmers with neighboring conventional fields may have smaller populations of natural enemies and so larger populations of pests to treat.”  

Yet thanks to Larsen, Noack and Powers’ paper, this predicament may someday be a thing of the past.

“The big takeaway from this research is to stack organic fields next to organic fields and conventional fields next to conventional fields,” says Powers. Doing so will likely reduce pesticide use overall and thereby benefit both the environment and farmers’ bank accounts.  

A data dilemma  

Completing this research was not without its challenges, says Powers. One was finding usable data.  

“You have to be able to identify specific fields in a spatial data format, link that spatial data to each field’s pesticide-use rates, and also determine which fields are organic and which are conventional,” says Powers, adding that this information comes from several sources that are tough to combine and that annual agricultural spatial data and pesticide use aren’t particularly well tracked, especially outside of California. 

But Powers, Larsen and Noack were able to find one county that kept such detailed records and made them publicly available: Kern County, California, an agricultural belt of land at the southern tip of the Central Valley and, as far as Powers and her co-authors were concerned, the golden ticket of the Golden State.  

“Kern County has annual spatial data for their agricultural fields that can be linked to the two other crucial datasets—pesticide use and organic-crop producer IDs—which is really rare,” says Powers. 

Yet the rareness of this data created a separate challenge: convincing the reviewers of the Science paper that it was enough. How reliable could data from just one county in just one state be?  

Pretty reliable, says Powers. For one thing, Kern is a high-crop-producing county with many farms, which gave her and her co-authors a lot of room to check for pesticide spillover across a decent sample size. For another, its mix of organic and conventional farms closely resembles that of the nation, making it a useful case study. 

Plus, Larsen and Noack put the data through a series of “robustness tests”—tests designed specifically to assess the data’s strength and generalizability—all of which it passed.  

Nevertheless, Powers admits that she would jump at the chance to expand the research from the Science paper outward to other counties in California as well as to other states.

“It would be awesome to be able to do that.”  

Past, present and future

Powers began this research while a master’s student at the Bren School at UCSB, where Larsen was one of her professors. Since coming to CU Boulder to pursue her doctorate, she has moved in a different direction, focusing on the impact of climate change on several species of alpine plants.  

Yet the thread holding all her work together, Powers believes, is her interest in land conservation and management.  

Growing up in Santa Paula, California—in “ag land,” as she calls it—Powers spent a lot of time on farms. She wasn’t a farmer herself, she’s quick to point out, but many of her family members and close friends were, and that gave her an appreciation for the outdoors.   

Her passion for conservation then crystalized while she worked for five years as a field instructor for NOLS, an outdoor education provider, which took her across the United States and around the globe, including to places like India and South America.  

“That got me interested in thinking about land management in a way that is inclusive and recognizes the need for working landscapes that support wildlife and native plants,” she says.

That interest drives her to this day, pushing her to ask questions, conduct research and publish papers like the one in Science, which she calls “a small step forward” on the long and winding path of scientific discovery.

“And there are lots more steps to take.”

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