The climate change-weeds-herbicide efficacy nexus: A review of the complex interactions and emerging challenges

Abstract

Global climate change, characterized by elevated atmospheric CO₂ (eCO₂), rising temperatures, and altered precipitation regimes, poses a multifaceted and escalating threat to agricultural sustainability. While the direct impacts on crop yields are widely studied, a more insidious challenge is emerging at the nexus of climate change, weed biology, and the efficacy of chemical herbicides—the cornerstone of modern weed management. This comprehensive review synthesizes the current body of literature to meticulously examine this tripartite relationship. We detail how key climatic drivers—eCO₂, heat, and water availability—alter weed physiology, morphology, phenology, and competitive ability. Specifically, eCO₂ often disproportionately enhances the growth, biomass, and resource foraging capabilities of C₃ weeds, while concurrently inducing morphological changes, such as thicker leaf cuticles, increased trichome density, and altered stomatal architecture, that physically impede herbicide uptake. Concurrently, rising temperatures can accelerate weed life cycles, increasing propagule pressure, and paradoxically, can amplify the rate of metabolic detoxification of herbicides within the plant. Furthermore, the increasing frequency and intensity of drought stress leads to reduced herbicide translocation as weeds adopt a conservative, hardened-off physiological state, effectively shutting down the systemic transport pathways relied upon by many key herbicides. These climate-induced reductions in herbicide performance create a dangerous and self-reinforcing feedback loop: the increased survival of weeds following application of sublethal doses acts as a powerful and persistent selective force, dramatically accelerating the evolution of herbicide resistance. This review consolidates and integrates evidence from a diverse array of ecophysiological, agronomic, and molecular studies to construct a holistic and mechanistic understanding of this critical challenge. We conclude that a business-as-usual, herbicide-centric approach is fundamentally untenable and unsustainable in a rapidly changing climate. A paradigm shift towards proactive, climate-resilient Integrated Weed Management (IWM) systems—which prioritize ecological principles and are augmented by technological innovation, advanced genetic tools, and sophisticated predictive modeling—is not merely recommended, but imperative to mitigate this growing threat to global food security.