Fertilizers Fuel, Insecticides Stabilize: Resolving the Paradox of Enrichment in Agriculture

The Paradox of Enrichment (PoE) predicts that increasing resources, such as nutrient inputs like fertilizers or food availability, should destabilize ecological systems, such as crop-pest dynamics, leading to population cycles that can increase the risk of crop failure during environmental shocks. Yet, since the Green Revolution, fertilizer use has surged without widespread evidence of yield instability, challenging the PoE's relevance to modern agriculture. Here, we propose and test a novel resolution: that insecticides, frequently co-applied with fertilizers, act as stabilizing agents that counterbalance enrichment-induced instability. Using a modified PoE model with empirically grounded parameters for three major crop-pest systems-soybean-aphid, wheat-aphid, and cabbage-diamondback moth-we find that fertilizer increases yields, but destabilizes dynamics, whereas insecticides restore stability and ensure more predictable harvests. These findings reveal that insecticides may suppress pests but also play a critical role in stabilizing crop yields in nutrient-enriched agroecosystems, with implications for ecosystem management, eutrophication, conservation biology, and pesticide policy.