The widespread hypothesis that climate warming will result in unprecedented agricultural pest populations and cause food insecurity worldwide is oversimplified, according to a new study by a team led by Mia Lippey , an entomologist at the University of California, Davis. But the study does indicate that pests fare better in warmer temperatures than their natural enemies, which researchers identified as a cause for concern.
The study is published in the current issue of Proceedings of the National Academy of Sciences .
Globally, crop losses to arthropod pests exceed $470 billion annually, accounting for 20% of total crop production by value. Models based on laboratory experiments predict that insect pest population densities will rise along with temperatures.
The researchers studied 141,562 field-year observations of 43 arthropod populations (30 pest and 13 natural enemy populations, representing 28 pest and 11 natural enemy species) across five crops (rice, cotton, grapes, citrus and olives) in Andalusia, Spain, and in California, two temperate agricultural regions with uniquely extensive long-term monitoring data.
"We found that both pests and natural enemy insects exhibit highly diverse responses to warming, with about half of the populations increasing in size under warming and half decreasing," said Lippey, who holds a doctoral degree (2026) from UC Davis and studied with major professors Emily Meineke and Jay Rosenheim, co-authors of the paper. "While natural enemies did show some evidence of heightened vulnerability to warming compared to pests, we need more research to understand what drives these differences and how severe of an impact this difference would have on agriculture."
By challenging predictions of universal pest proliferation under warming conditions, the findings highlight the urgent need for species-specific monitoring approaches in agricultural climate adaptation, the authors said.
"Insect responses to climate are not predictable with the tools we have now, which means that though monitoring insect pests and natural enemies in crop fields is expensive, it is worth government investment as the climate warms," Meineke said. "Our study also indicates that pests appear to do slightly better in warmer climates than their natural enemies, which is cause for concern and further emphasizes the importance of monitoring both pests and the insects we rely on to control them."
Climate and other factors involved
Climate change is reshaping ecosystems worldwide and agriculture faces particular scrutiny, the researchers wrote. Models based on laboratory experiments warn that warming will boost crop pest populations while decimating their natural enemies, raising concern about food security and pesticide use. But in the real world, some species thrive with warming while others decline or show no response.
"We could not explain species' responses using traits that are currently thought to drive how species respond to temperature," Lippey said. "Our take-away message is that species, crop and location all contributed to the diversity of results we found, and traits alone cannot reliably be used to make predictions about how the changing world will shape agricultural arthropods in the coming years."
The research made use of two large, high-resolution datasets. The California dataset was assembled by co-principal investigator Jay Rosenheim, Distinguished Professor emeritus at the UC Davis Department of Entomology and Nematology, in collaboration with growers and pest control advisers across California's San Joaquin Valley.
Government technicians across Andalusia, Spain, collected the rest of the data, which was accessed through a Spanish collaborator, Daniel Paredes.
"Because these datasets are decentralized, they cover larger geographic areas and a longer timescale than most other insect field-collected datasets in existence," Lippey said.
Other co-authors are Daniel Karp, UC Davis; Rebecca Chaplin-Kramer of the University of Extremadura, Spain; Richard Sharp, World Wildlife Fund, San Francisco; Sara Emery, Cornell AgriTech; and Colleen Miller, University of Minnesota.
