image: Schematic representation of the sensory mechanisms underlying CO2-induced oviposition behavior in Helicoverpa armigera. Abbreviations: LPO, labial pit organ; LPOG, labial pit organ glomerulus; CB, central body; Ca, calyx of the mushroom body; LH, lateral horn; AN, antennal nerve.
Credit: ©Science China Press
Climate change is rapidly reshaping ecosystems across the globe, and new research has identified a previously unrecognized consequence: disrupted insect reproductive behavior. A recent study published in National Science Review reveals that rising atmospheric carbon dioxide (CO2) levels are interfering with how agricultural pests choose egg-laying sites—posing significant risks to biodiversity, food security, and pest management strategies.
Insects, despite their adaptability, are especially sensitive to shifts in environmental conditions. As global temperatures rise and atmospheric composition changes, their behavior is changing in ways that ripple through ecosystems. CO2, the primary greenhouse gas driving global warming, has increased from 278 ppm in 1750 to approximately 420 ppm in 2023. Emerging evidence shows that elevated CO2 levels—alongside pollutants such as ozone and nitrogen oxides—are disrupting insects' ability to detect chemical cues essential for reproduction and survival. Until now, the underlying mechanisms remained poorly understood.
Now, an international collaborative study by scientists from the Chinese Academy of Agricultural Sciences, the Norwegian University of Science and Technology, and the Max Planck Institute has provided key insights. Focusing on Helicoverpa armigera—the cotton bollworm, a major global crop pest—the team discovered that females normally use plant-emitted CO2 to locate suitable egg-laying sites, particularly favoring younger leaves that emit higher CO2 gradients. These sites are critical for larval survival and development. However, under elevated atmospheric CO2 concentrations, this behavior is significantly disrupted. The study found that moths’ CO2-sensing ability is impaired, causing them to lay eggs in less suitable locations. “This disruption is akin to confusing a key olfactory cue from a GPS system,” said Prof. Guirong Wang, lead author of the study. “Without accurate CO2 signals, the insects struggle to find ideal egg-laying sites, which could affect pest population dynamics and agricultural damage.”
To understand the biological basis for this disruption, the researchers identified three CO2-detecting gustatory receptors—HarmGR1, HarmGR2, and HarmGR3. When any of these receptors were genetically deleted, the moths’ ability to detect CO2 impaired, resulting in disoriented egg-laying behavior.
The study’s simulations paint a worrying future: if atmospheric CO2 reaches 1000 ppm by 2100, moths’ preference for optimal egg-laying sites could drop by up to 75%. This would likely reduce larval survival, destabilize pest populations, and alter biodiversity and ecological balance.
Beyond the alarming ecological implications, these findings point to new opportunities. “By targeting the CO2 receptors, we can explore novel, eco-friendly pest control strategies,” said Dr. Qiuyan Cheng, first author of the paper. One promising approach is RNA interference (RNAi), a gene-silencing technique already used in mosquito control, which could disrupt pest reproduction without harmful chemicals.
The study adds to growing evidence that climate change is influencing insect behavior in complex and unexpected ways—not only through temperature shifts but also via direct changes to atmospheric chemistry. With global CO2 levels on track to exceed 1000 ppm by the end of the century, researchers stress the urgent need for both emissions reductions and innovative agricultural adaptation.