Climate Change and Agroecosystem Pest Dynamics: A Critical Narrative Review of Impacts on Insect Pests, Their Natural Enemies, and Implications for Crop Protection

Abstract

Climate change is altering the physiology, phenology, distribution and interaction networks of agricultural insect pests and the natural enemies that regulate them, yet the literature addressing these changes remains fragmented across disciplines and taxa. This critical narrative review synthesises evidence on how rising temperatures, elevated atmospheric carbon dioxide, altered precipitation and increasing climatic variability affect insect pests and their predators, parasitoids and entomopathogens in agricultural systems, and evaluates the resulting implications for crop protection. Warming generally accelerates insect development, increases voltinism and extends the geographical range of many pest species, while its effects on natural enemies are more variable and frequently negative, owing to a combination of lower thermal optima among parasitoids relative to their hosts, disrupted phenological synchrony, and altered chemosensory cues that impair host or prey location. Elevated carbon dioxide most often reduces host-plant nitrogen content, prompting compensatory feeding by herbivores, with inconsistent consequences for third-trophic-level performance. Case evidence from the fall armyworm, Spodoptera frugiperda, bark beetle outbreaks in coniferous forests, desert locust plagues linked to Indian Ocean climate variability, and cereal aphid–parasitoid systems illustrates convergent patterns of pest release alongside marked context-dependency. Meta-analytic evidence indicates that predators continue to suppress pests and support yield across a range of climates, and that landscape complexity can buffer biological control against climatic variability, offering a partial counterweight to the more pessimistic single-species findings. Methodological heterogeneity, including short experimental durations, single-factor manipulations, and geographic concentration of research in temperate systems, limits confidence in generalising current findings to tropical and subtropical smallholder systems where food security risks are often greatest. Research priorities include multifactorial and multigenerational experiments, standardised reporting of thermal and moisture regimes, and expanded evidence from under-represented regions and cropping systems. The review concludes that climate change is reshaping the balance of tritrophic interactions in ways that generally favour pests over their natural enemies, but that this outcome is neither universal nor immutable, and that landscape-scale conservation of natural enemy diversity is among the more defensible adaptive strategies currently supported by evidence.