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Does organic farming ironically lead to more pesticide use overall?

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Does organic farming ironically lead to more pesticide use overall?

Digging into the nuances of organic farming, a new study found that organic farms can actually boost insecticide use on nearby conventional farms. The fix: a shift from dispersed to clustered fields.
March 29, 2024

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New research adds to the increasingly nuanced picture of organic farming and how well it can meet both our food and ecological goals. The new study, published in Science, identifies one unintended consequence of organic agriculture: it seems to lead to the increased use of insecticides on neighboring fields. 

However, this uptick in chemical use can be entirely offset by grouping organic fields together at the landscape level, the researchers reveal.

What grabbed their interest to begin with was an unresolved concern about the interplay between organic farms and the insect life they harbor. One of the defining features of organic farming is a gentler approach to ‘pests’, either by recognising their value as natural predators, and as pollinators; or of managing them with lower amounts of chemicals, or with chemicals that have a kinder environmental footprint. 

But some say that a possible trade-off of this approach is that the abundant life on organic farms will spill over into conventional farmlands and trigger a more aggressive pest management response there. This dynamic remains little understood, but the new study sheds a bit of light on what might be going on. 

Its researchers chose to delve into this issue in Kern County, California, a famously productive and diverse agricultural region specializing in everything from almonds and grapes to citrus, stone fruits, and feed crops. The region produces $7.4 billion in farm goods each year, which also involves an estimated 13 million kilograms of pesticide, making it one of the biggest pesticide-applying counties in the US. It’s also home to dozens of organic fields.

 

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The scientists looked at a dataset of 14,000 farm fields, each of which included information about the crop types, pesticide-use, and organic certification of individual plots. This dataset, which spanned seven years, allowed them to compare fields with limited or no pesticide use—organic fields—with the application patterns on surrounding conventional fields (‘surrounding’ being those that fall within a 2.5 kilometer radius.) The large dataset also helped them to build a simulation to answer some other questions down the line. 

But first, from that huge dataset a notable pattern soon emerged. The researchers found that in cases where fields of conventional agriculture were surrounded by organic fields there was typically a small, but significant, increase in pesticide use there, driven mainly by an increase in the use of insecticides specifically. 

In fact, their analysis showed that a 10% increase in surrounding organic fields corresponded with a 0.3% increase in the application of pesticides. This effect was most obvious in conventional fields that were closest to the organic ones, within a 0.5 kilometer radius. The effect dimmed the further away the conventional fields were from the organic ones. 

But in organic fields surrounded by more organic plots, there was the reverse effect. Where there was a 10% increase in the acreage of organic fields, there was a parallel 3% decrease in the amount of pesticides applied on nearby organic lands. Similarly, here the effect was greatest at close range, between zero and 0.5 kilometers.

Across Kern county as a whole, “because there are so many more conventional fields, we see an increase [in insecticide use] overall,” explains Ashley Larsen, the study’s lead author and an associate professor at UC Santa Barbara. 

The researchers’ dataset wasn’t able to explain the reasons for these dynamics—why it is that conventional lands use more insecticide in the presence of organic fields, and why rates of use conversely drop on other organic fields. As the scientists note, there could be a range of overlapping factors at play: what crops the farmers are producing, the different management strategies they use to protect yields, and how insects move between farms. Unpicking these was beyond the study’s scope.

But, the data did reveal some other useful clues, when the researchers used the information they had gathered to build a simulation. In this simulation, they were able to test how things would look if they moved plots of organic and conventional agriculture around in the landscape. What they found here was that when many organic fields were clustered together instead of being dispersed across the landscape like they currently are, and the same occurred for conventional fields, this arrangement led to reduced levels of pesticide use on both organic and conventional fields. This new arrangement seemed to mitigate the previous negative effects of organic fields on insecticide use.

The researchers went a step further and ran a simulation using national data on organic and conventional fields, and found similar patterns here too. This suggests that reconfiguring our farmlands could have real and considerable benefits at even bigger scales—especially as the demand for certified organic food grows.

“We may see inadvertent increases in insecticide use if organic cropland expands haphazardly within landscapes otherwise dominated by conventional cropland,” Larsen says. To avoid this fate, she suggests “it may be worth considering policies that can incentivize spatial clustering of new organic fields.”

Larsen et. al. “Spillover effects of organic agriculture on pesticide use on nearby fields.” Science. 2024. 

Image: GoddessOfRocks via Flickr

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