To help California combat climate change, air quality regulators would like to see this happen 20% of the state's agricultural land becomes organic by 2045. This means that approximately 65,000 hectares of conventional fields will have to be converted to organic farming every year.
But depending on how that transition takes place, the change can lead to an overall situation increase in the amount of pesticides used by growers across the state.
So suggests a new study in the journal Science that examined how organic farms influence the behavior of their neighbors. Researchers found that when new organic fields come into use, the associated insects can prompt conventional growers to increase their pesticide use by an amount large enough to offset the reduction in organic fields – and much more.
“We expect an increase in organic products in the future,” says research leader Ashley Larsen, professor of agricultural and landscape ecology at UC Santa Barbara. “How do we ensure that this doesn't cause unintended damage?”
Organic farming practices help combat climate change by producing healthier soil that can hold more carbon and by avoiding synthetic nitrogen fertilizers, which cause greenhouse gas emissions. Organic methods are also more sustainable for a warming world because, among other things, they ensure that the soil retains more water.
For their research, Larsen and her colleagues delved deep into the agricultural practices of California's Kern County, where growers regularly produce more. than $7 billion worth of grapes, citrus fruits, almonds, pistachios and other crops. Thanks to the county and state, there has been detailed data on how they're doing for years.
The researchers examined approximately 14,000 individual fields between 2013 and 2019. They could see the shape and location of these fields, as well as whether conventional or organic crops were grown and how much pesticides had been used.
A key difference between conventional and organic farming is their approach to dealing with unwanted pests. Traditional farms can use toxic chemicals such as organophosphates And organochlorine compoundswhile organic farms prefer to do so keep harmful bugs under control by encouraging the growth of their natural enemies, including mainly beetles, spiders and birds. They can also use certain pesticideswhich are typically made with natural rather than synthetic ingredients.
These contrasting strategies make for complicated neighbors. If destructive bugs migrate from an organic farm to a conventional farm, a grower can respond by using more pesticides. That, in turn, would undermine the helpful creatures that organic growers rely on. On the other hand, organic farms feed beneficial insects that migrate to other fields.
“Organic farms can be both a blessing and a curse if they are your neighbor,” he said David Havilandan entomologist with the integrative pest management program at the University of California, Bakersfield, who was not involved in the study.
In 2019, approximately 7.5% of permitted fields in Kern County were used to grow organic produce. They were scattered throughout the province's growing areas, although many were grouped in clusters.
An aerial view of farmland and orchards near Maricopa at the south end of Kern County's San Joaquin Valley.
(Al Seib / Los Angeles Times)
With their data in hand, the researchers created a statistical model to see if they could find a link between the use of pesticides in a given field and the presence of organic fields nearby.
In the case of organic fields, they found that a 10% increase in adjacent organic croplands was associated with a 3% decrease in pesticide use. For conventional fields, the same 10% increase in organic neighbors was accompanied by a 0.3% increase in pesticide use.
Because conventional fields far outpaced organic fields, the net effect in Kern County was a 0.2% increase in pesticide use. Most of that was caused by added insecticides rather than chemicals that targeted invasive weeds or harmful fungi, Larsen said.
“We think it really comes down to another reliance on natural pest control methods,” she said. More insects are bad for conventional farmers because it means more unwanted insects for them, she explained. But more insects are good for organic farmers because it means they have more natural enemies of those same pests.
The researchers also used their model to simulate different possible agricultural futures to see if this overall increase in pesticide use could be avoided. The answer, they found, was yes.
One way was to expand the amount of organically farmed land. In their model, the transition from no organic fields at all to 5% of cropland as organic was associated with a 9% increase in insecticide use in Kern County. However, if 20% of farmland contained organic crops – as the California Air Resources Board envisions – overall insecticide use dropped by 17%.
These figures were based on a simulation in which organic fields were spread out, maximizing pest control at the boundaries between organic and conventional fields. In a scenario where organic fields were clustered instead, increasing the combined footprint from 0% to 5% of the total area was associated with a 10% reduction in insecticide use, while going all the way to 20% of the total area was associated with a 36% drop in chemicals, the researchers reported.
“What we actually see in the simulation is that while there could be an increase in insecticide use at low biological rates, it can be completely mitigated by spatially clustering organic croplands,” Larsen said.
Making that happen in a simulation is one thing; doing it in the real world is another. An organic almond farmer whose orchard borders a conventional orchard cannot easily dig up his mature trees and replant them elsewhere. But as farmers switch more and more of their conventional fields to organic, these research results can help them decide where to focus their efforts to reap the biggest profits, Larsen said.
Similarly, policymakers could identify certain areas where they would like to see organic crops and offer incentives to encourage growers to make the leap. In principle, it would be similar to the subsidies offered by the California Department of Food and Agriculture Healthy Soils Programshe said.
Erik Lichtenbergan agricultural economist at the University of Maryland, said the study “provides compelling evidence” that organic farms impact their neighbors, but it would be important to know many more details before concluding that it is a good idea to divide organic and conventional farms to separate. .
Among other things: “I would like to know more about why the fields are where they are, what you plant where and how that relates to the pest control strategies that growers are following,” says Lichtenberg, who wrote a report. a comment that is part of the study.
Haviland said the idea of clustering organic farms makes sense in general because it reduces the boundaries between organic and conventional fields. However, he noted that there are cases where clustering could make matters worse.
Please take into account the glass-winged marksmanthat spreads a disease that kills vines. Conventional farmers have tools at their disposal to control this, but organic growers do not. When organic vines are more isolated, an insect is more likely to fly away from the field and “not come home” because it encounters a pesticide nearby, Haviland said. But if all organic fields were brought together, they would “dramatically increase their own problem by not taking advantage of conventional growers around them.”
Haviland also emphasized that “there is a misconception among the general public that all pesticides are created equal and all are bad, and that is absolutely not true.” Reducing overall pesticide use is valuable, but it's more important to consider the types of pesticides used, he said.
The statistical analysis alone does not prove that the addition of organic fields is responsible for the change in pesticide use, but Larsen said the indirect evidence for a causal relationship is compelling. The conventional fields that had acquired an organic neighbor previously showed the same pattern of pesticide use as their other conventional fields, and they only began to diverge after the nearby field switched to organic.
“This is, in our view, quite strong evidence,” she said.
Milt McGiffen, a cooperative extension specialist in UC Riverside's Department of Botany and Plant Sciences, was less sure. He said growers make it a point to plant organic crops in places where they know pest control won't be a major problem because they can't use conventional pesticides.
“The reason you have a group of organic farms is mainly because that's where you have the fewest pests, not the other way around,” says McGiffen, who was not involved in the study.
He said there are many examples of governments trying to accelerate the transition to organic food production, but he is not aware of any effort to encourage growers to locate organic fields in specific places.
“This study raises some interesting ideas,” McGiffen said, but “an experimentalist has to go out and test it all.”
