Energetic criteria to predict biodiversity loss and keystone species in empirical agricultural food webs

Understanding how biodiversity loss propagates through food web networks is essential for managing ecosystem services in agricultural landscapes. Traditional binary-topological approaches often oversimplify extinction dynamics by assuming that species go extinct only after complete resource loss. Here, we applied energetic thresholds to model secondary extinctions in 504 empirical food webs from the Farm Scale Evaluations of conventional and genetically modified herbicide-tolerant (GMHT) crop systems. We simulated species removals under varying consumer sensitivity to resource loss to assess food web robustness across crop types and management regimes. Results show that food web fragility increases with energetic thresholds, especially in GMHT-managed beet fields. Beet fields exhibit the highest levels of secondary extinction, and GMHT treatments show slightly higher extinction rates than conventional ones, suggesting increased vulnerability to species loss. Secondary extinction after single-species removals is higher in food webs lacking carnivorous links from carabids to gastropods. Keystone species shift from autotrophs to gastropods as the extinction threshold rises. Omnivory, particularly carabid-gastropod links, enhances stability by reducing secondary extinctions. These findings highlight the value of incorporating quantitative dynamics to better predict biodiversity loss and identify key species in agroecosystems, offering insights for designing more resilient agricultural systems.